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      5  1.2    lneto <title>Lua 5.3 Reference Manual</title>
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     14  1.1  mbalmer <h1>
     15  1.1  mbalmer <a href="http://www.lua.org/"><img src="logo.gif" alt="" border="0"></a>
     16  1.2    lneto Lua 5.3 Reference Manual
     17  1.1  mbalmer </h1>
     18  1.1  mbalmer 
     19  1.1  mbalmer by Roberto Ierusalimschy, Luiz Henrique de Figueiredo, Waldemar Celes
     20  1.1  mbalmer <p>
     21  1.1  mbalmer <small>
     22  1.3    lneto Copyright &copy; 2015 Lua.org, PUC-Rio.
     23  1.1  mbalmer Freely available under the terms of the
     24  1.2    lneto <a href="http://www.lua.org/license.html">Lua license</a>.
     25  1.1  mbalmer </small>
     26  1.1  mbalmer <hr>
     27  1.1  mbalmer <p>
     28  1.1  mbalmer 
     29  1.1  mbalmer <a href="contents.html#contents">contents</A>
     30  1.1  mbalmer &middot;
     31  1.1  mbalmer <a href="contents.html#index">index</A>
     32  1.1  mbalmer 
     33  1.1  mbalmer <!-- ====================================================================== -->
     34  1.1  mbalmer <p>
     35  1.1  mbalmer 
     36  1.3    lneto <!-- Id: manual.of,v 1.146 2015/01/06 11:23:01 roberto Exp  -->
     37  1.1  mbalmer 
     38  1.1  mbalmer 
     39  1.1  mbalmer 
     40  1.1  mbalmer 
     41  1.2    lneto <h1>1 &ndash; <a name="1">Introduction</a></h1>
     42  1.1  mbalmer 
     43  1.1  mbalmer <p>
     44  1.1  mbalmer Lua is an extension programming language designed to support
     45  1.1  mbalmer general procedural programming with data description
     46  1.1  mbalmer facilities.
     47  1.3    lneto Lua also offers good support for object-oriented programming,
     48  1.1  mbalmer functional programming, and data-driven programming.
     49  1.2    lneto Lua is intended to be used as a powerful, lightweight,
     50  1.2    lneto embeddable scripting language for any program that needs one.
     51  1.2    lneto Lua is implemented as a library, written in <em>clean C</em>,
     52  1.2    lneto the common subset of Standard&nbsp;C and C++.
     53  1.1  mbalmer 
     54  1.1  mbalmer 
     55  1.1  mbalmer <p>
     56  1.3    lneto As an extension language, Lua has no notion of a "main" program:
     57  1.1  mbalmer it only works <em>embedded</em> in a host client,
     58  1.1  mbalmer called the <em>embedding program</em> or simply the <em>host</em>.
     59  1.2    lneto The host program can invoke functions to execute a piece of Lua code,
     60  1.1  mbalmer can write and read Lua variables,
     61  1.1  mbalmer and can register C&nbsp;functions to be called by Lua code.
     62  1.1  mbalmer Through the use of C&nbsp;functions, Lua can be augmented to cope with
     63  1.1  mbalmer a wide range of different domains,
     64  1.1  mbalmer thus creating customized programming languages sharing a syntactical framework.
     65  1.1  mbalmer The Lua distribution includes a sample host program called <code>lua</code>,
     66  1.2    lneto which uses the Lua library to offer a complete, standalone Lua interpreter,
     67  1.2    lneto for interactive or batch use.
     68  1.1  mbalmer 
     69  1.1  mbalmer 
     70  1.1  mbalmer <p>
     71  1.1  mbalmer Lua is free software,
     72  1.1  mbalmer and is provided as usual with no guarantees,
     73  1.1  mbalmer as stated in its license.
     74  1.1  mbalmer The implementation described in this manual is available
     75  1.1  mbalmer at Lua's official web site, <code>www.lua.org</code>.
     76  1.1  mbalmer 
     77  1.1  mbalmer 
     78  1.1  mbalmer <p>
     79  1.1  mbalmer Like any other reference manual,
     80  1.1  mbalmer this document is dry in places.
     81  1.1  mbalmer For a discussion of the decisions behind the design of Lua,
     82  1.1  mbalmer see the technical papers available at Lua's web site.
     83  1.1  mbalmer For a detailed introduction to programming in Lua,
     84  1.2    lneto see Roberto's book, <em>Programming in Lua</em>.
     85  1.1  mbalmer 
     86  1.1  mbalmer 
     87  1.1  mbalmer 
     88  1.2    lneto <h1>2 &ndash; <a name="2">Basic Concepts</a></h1>
     89  1.1  mbalmer 
     90  1.1  mbalmer <p>
     91  1.2    lneto This section describes the basic concepts of the language.
     92  1.1  mbalmer 
     93  1.1  mbalmer 
     94  1.1  mbalmer 
     95  1.2    lneto <h2>2.1 &ndash; <a name="2.1">Values and Types</a></h2>
     96  1.1  mbalmer 
     97  1.1  mbalmer <p>
     98  1.1  mbalmer Lua is a <em>dynamically typed language</em>.
     99  1.1  mbalmer This means that
    100  1.1  mbalmer variables do not have types; only values do.
    101  1.1  mbalmer There are no type definitions in the language.
    102  1.1  mbalmer All values carry their own type.
    103  1.1  mbalmer 
    104  1.1  mbalmer 
    105  1.1  mbalmer <p>
    106  1.1  mbalmer All values in Lua are <em>first-class values</em>.
    107  1.1  mbalmer This means that all values can be stored in variables,
    108  1.1  mbalmer passed as arguments to other functions, and returned as results.
    109  1.1  mbalmer 
    110  1.1  mbalmer 
    111  1.1  mbalmer <p>
    112  1.1  mbalmer There are eight basic types in Lua:
    113  1.1  mbalmer <em>nil</em>, <em>boolean</em>, <em>number</em>,
    114  1.1  mbalmer <em>string</em>, <em>function</em>, <em>userdata</em>,
    115  1.1  mbalmer <em>thread</em>, and <em>table</em>.
    116  1.1  mbalmer <em>Nil</em> is the type of the value <b>nil</b>,
    117  1.1  mbalmer whose main property is to be different from any other value;
    118  1.1  mbalmer it usually represents the absence of a useful value.
    119  1.1  mbalmer <em>Boolean</em> is the type of the values <b>false</b> and <b>true</b>.
    120  1.1  mbalmer Both <b>nil</b> and <b>false</b> make a condition false;
    121  1.1  mbalmer any other value makes it true.
    122  1.2    lneto <em>Number</em> represents both
    123  1.3    lneto integer numbers and real (floating-point) numbers.
    124  1.2    lneto <em>String</em> represents immutable sequences of bytes.
    125  1.1  mbalmer 
    126  1.1  mbalmer Lua is 8-bit clean:
    127  1.2    lneto strings can contain any 8-bit value,
    128  1.2    lneto including embedded zeros ('<code>\0</code>').
    129  1.3    lneto Lua is also encoding-agnostic;
    130  1.3    lneto it makes no assumptions about the contents of a string.
    131  1.2    lneto 
    132  1.2    lneto 
    133  1.2    lneto <p>
    134  1.2    lneto The type <em>number</em> uses two internal representations,
    135  1.2    lneto one called <em>integer</em> and the other called <em>float</em>.
    136  1.2    lneto Lua has explicit rules about when each representation is used,
    137  1.2    lneto but it also converts between them automatically as needed (see <a href="#3.4.3">&sect;3.4.3</a>).
    138  1.2    lneto Therefore,
    139  1.3    lneto the programmer may choose to mostly ignore the difference
    140  1.2    lneto between integers and floats
    141  1.3    lneto or to assume complete control over the representation of each number.
    142  1.2    lneto Standard Lua uses 64-bit integers and double-precision (64-bit) floats,
    143  1.2    lneto but you can also compile Lua so that it
    144  1.2    lneto uses 32-bit integers and/or single-precision (32-bit) floats.
    145  1.3    lneto The option with 32 bits for both integers and floats 
    146  1.3    lneto is particularly attractive
    147  1.3    lneto for small machines and embedded systems.
    148  1.3    lneto (See macro <code>LUA_32BITS</code> in file <code>luaconf.h</code>.)
    149  1.1  mbalmer 
    150  1.1  mbalmer 
    151  1.1  mbalmer <p>
    152  1.1  mbalmer Lua can call (and manipulate) functions written in Lua and
    153  1.3    lneto functions written in C (see <a href="#3.4.10">&sect;3.4.10</a>).
    154  1.3    lneto Both are represented by the type <em>function</em>.
    155  1.1  mbalmer 
    156  1.1  mbalmer 
    157  1.1  mbalmer <p>
    158  1.1  mbalmer The type <em>userdata</em> is provided to allow arbitrary C&nbsp;data to
    159  1.1  mbalmer be stored in Lua variables.
    160  1.3    lneto A userdata value represents a block of raw memory.
    161  1.2    lneto There are two kinds of userdata:
    162  1.3    lneto <em>full userdata</em>,
    163  1.3    lneto which is an object with a block of memory managed by Lua,
    164  1.3    lneto and <em>light userdata</em>,
    165  1.3    lneto which is simply a C&nbsp;pointer value.
    166  1.2    lneto Userdata has no predefined operations in Lua,
    167  1.1  mbalmer except assignment and identity test.
    168  1.2    lneto By using <em>metatables</em>,
    169  1.2    lneto the programmer can define operations for full userdata values
    170  1.2    lneto (see <a href="#2.4">&sect;2.4</a>).
    171  1.1  mbalmer Userdata values cannot be created or modified in Lua,
    172  1.1  mbalmer only through the C&nbsp;API.
    173  1.1  mbalmer This guarantees the integrity of data owned by the host program.
    174  1.1  mbalmer 
    175  1.1  mbalmer 
    176  1.1  mbalmer <p>
    177  1.1  mbalmer The type <em>thread</em> represents independent threads of execution
    178  1.2    lneto and it is used to implement coroutines (see <a href="#2.6">&sect;2.6</a>).
    179  1.3    lneto Lua threads are not related to operating-system threads.
    180  1.1  mbalmer Lua supports coroutines on all systems,
    181  1.3    lneto even those that do not support threads natively.
    182  1.1  mbalmer 
    183  1.1  mbalmer 
    184  1.1  mbalmer <p>
    185  1.1  mbalmer The type <em>table</em> implements associative arrays,
    186  1.1  mbalmer that is, arrays that can be indexed not only with numbers,
    187  1.3    lneto but with any Lua value except <b>nil</b> and NaN.
    188  1.3    lneto (<em>Not a Number</em> is a special numeric value used to represent
    189  1.3    lneto undefined or unrepresentable results, such as <code>0/0</code>.)
    190  1.1  mbalmer Tables can be <em>heterogeneous</em>;
    191  1.1  mbalmer that is, they can contain values of all types (except <b>nil</b>).
    192  1.2    lneto Any key with value <b>nil</b> is not considered part of the table.
    193  1.2    lneto Conversely, any key that is not part of a table has
    194  1.2    lneto an associated value <b>nil</b>.
    195  1.2    lneto 
    196  1.2    lneto 
    197  1.2    lneto <p>
    198  1.3    lneto Tables are the sole data-structuring mechanism in Lua;
    199  1.2    lneto they can be used to represent ordinary arrays, sequences,
    200  1.1  mbalmer symbol tables, sets, records, graphs, trees, etc.
    201  1.1  mbalmer To represent records, Lua uses the field name as an index.
    202  1.1  mbalmer The language supports this representation by
    203  1.1  mbalmer providing <code>a.name</code> as syntactic sugar for <code>a["name"]</code>.
    204  1.1  mbalmer There are several convenient ways to create tables in Lua
    205  1.2    lneto (see <a href="#3.4.9">&sect;3.4.9</a>).
    206  1.2    lneto 
    207  1.2    lneto 
    208  1.2    lneto <p>
    209  1.2    lneto We use the term <em>sequence</em> to denote a table where
    210  1.3    lneto the set of all positive numeric keys is equal to {1..<em>n</em>}
    211  1.3    lneto for some non-negative integer <em>n</em>,
    212  1.2    lneto which is called the length of the sequence (see <a href="#3.4.7">&sect;3.4.7</a>).
    213  1.1  mbalmer 
    214  1.1  mbalmer 
    215  1.1  mbalmer <p>
    216  1.1  mbalmer Like indices,
    217  1.2    lneto the values of table fields can be of any type.
    218  1.1  mbalmer In particular,
    219  1.1  mbalmer because functions are first-class values,
    220  1.1  mbalmer table fields can contain functions.
    221  1.2    lneto Thus tables can also carry <em>methods</em> (see <a href="#3.4.11">&sect;3.4.11</a>).
    222  1.2    lneto 
    223  1.2    lneto 
    224  1.2    lneto <p>
    225  1.2    lneto The indexing of tables follows
    226  1.2    lneto the definition of raw equality in the language.
    227  1.2    lneto The expressions <code>a[i]</code> and <code>a[j]</code>
    228  1.2    lneto denote the same table element
    229  1.2    lneto if and only if <code>i</code> and <code>j</code> are raw equal
    230  1.2    lneto (that is, equal without metamethods).
    231  1.2    lneto In particular, floats with integral values
    232  1.2    lneto are equal to their respective integers
    233  1.2    lneto (e.g., <code>1.0 == 1</code>).
    234  1.2    lneto To avoid ambiguities,
    235  1.2    lneto any float with integral value used as a key
    236  1.2    lneto is converted to its respective integer.
    237  1.2    lneto For instance, if you write <code>a[2.0] = true</code>,
    238  1.2    lneto the actual key inserted into the table will be the
    239  1.2    lneto integer <code>2</code>.
    240  1.3    lneto (On the other hand,
    241  1.3    lneto 2 and "<code>2</code>" are different Lua values and therefore
    242  1.3    lneto denote different table entries.)
    243  1.1  mbalmer 
    244  1.1  mbalmer 
    245  1.1  mbalmer <p>
    246  1.1  mbalmer Tables, functions, threads, and (full) userdata values are <em>objects</em>:
    247  1.1  mbalmer variables do not actually <em>contain</em> these values,
    248  1.1  mbalmer only <em>references</em> to them.
    249  1.1  mbalmer Assignment, parameter passing, and function returns
    250  1.1  mbalmer always manipulate references to such values;
    251  1.1  mbalmer these operations do not imply any kind of copy.
    252  1.1  mbalmer 
    253  1.1  mbalmer 
    254  1.1  mbalmer <p>
    255  1.1  mbalmer The library function <a href="#pdf-type"><code>type</code></a> returns a string describing the type
    256  1.2    lneto of a given value (see <a href="#6.1">&sect;6.1</a>).
    257  1.2    lneto 
    258  1.1  mbalmer 
    259  1.1  mbalmer 
    260  1.1  mbalmer 
    261  1.2    lneto 
    262  1.2    lneto <h2>2.2 &ndash; <a name="2.2">Environments and the Global Environment</a></h2>
    263  1.1  mbalmer 
    264  1.1  mbalmer <p>
    265  1.2    lneto As will be discussed in <a href="#3.2">&sect;3.2</a> and <a href="#3.3.3">&sect;3.3.3</a>,
    266  1.3    lneto any reference to a free name
    267  1.3    lneto (that is, a name not bound to any declaration) <code>var</code>
    268  1.3    lneto is syntactically translated to <code>_ENV.var</code>.
    269  1.2    lneto Moreover, every chunk is compiled in the scope of
    270  1.3    lneto an external local variable named <code>_ENV</code> (see <a href="#3.3.2">&sect;3.3.2</a>),
    271  1.3    lneto so <code>_ENV</code> itself is never a free name in a chunk.
    272  1.1  mbalmer 
    273  1.1  mbalmer 
    274  1.2    lneto <p>
    275  1.2    lneto Despite the existence of this external <code>_ENV</code> variable and
    276  1.3    lneto the translation of free names,
    277  1.2    lneto <code>_ENV</code> is a completely regular name.
    278  1.2    lneto In particular,
    279  1.2    lneto you can define new variables and parameters with that name.
    280  1.3    lneto Each reference to a free name uses the <code>_ENV</code> that is
    281  1.2    lneto visible at that point in the program,
    282  1.2    lneto following the usual visibility rules of Lua (see <a href="#3.5">&sect;3.5</a>).
    283  1.1  mbalmer 
    284  1.1  mbalmer 
    285  1.2    lneto <p>
    286  1.2    lneto Any table used as the value of <code>_ENV</code> is called an <em>environment</em>.
    287  1.1  mbalmer 
    288  1.1  mbalmer 
    289  1.2    lneto <p>
    290  1.2    lneto Lua keeps a distinguished environment called the <em>global environment</em>.
    291  1.2    lneto This value is kept at a special index in the C registry (see <a href="#4.5">&sect;4.5</a>).
    292  1.3    lneto In Lua, the global variable <a href="#pdf-_G"><code>_G</code></a> is initialized with this same value.
    293  1.3    lneto (<a href="#pdf-_G"><code>_G</code></a> is never used internally.)
    294  1.1  mbalmer 
    295  1.1  mbalmer 
    296  1.1  mbalmer <p>
    297  1.3    lneto When Lua loads a chunk,
    298  1.3    lneto the default value for its <code>_ENV</code> upvalue
    299  1.3    lneto is the global environment (see <a href="#pdf-load"><code>load</code></a>).
    300  1.2    lneto Therefore, by default,
    301  1.3    lneto free names in Lua code refer to entries in the global environment
    302  1.3    lneto (and, therefore, they are also called <em>global variables</em>).
    303  1.2    lneto Moreover, all standard libraries are loaded in the global environment
    304  1.3    lneto and some functions there operate on that environment.
    305  1.2    lneto You can use <a href="#pdf-load"><code>load</code></a> (or <a href="#pdf-loadfile"><code>loadfile</code></a>)
    306  1.2    lneto to load a chunk with a different environment.
    307  1.2    lneto (In C, you have to load the chunk and then change the value
    308  1.2    lneto of its first upvalue.)
    309  1.1  mbalmer 
    310  1.1  mbalmer 
    311  1.1  mbalmer 
    312  1.1  mbalmer 
    313  1.1  mbalmer 
    314  1.2    lneto <h2>2.3 &ndash; <a name="2.3">Error Handling</a></h2>
    315  1.1  mbalmer 
    316  1.1  mbalmer <p>
    317  1.2    lneto Because Lua is an embedded extension language,
    318  1.2    lneto all Lua actions start from C&nbsp;code in the host program
    319  1.3    lneto calling a function from the Lua library.
    320  1.3    lneto (When you use Lua standalone,
    321  1.3    lneto the <code>lua</code> application is the host program.)
    322  1.2    lneto Whenever an error occurs during
    323  1.2    lneto the compilation or execution of a Lua chunk,
    324  1.2    lneto control returns to the host,
    325  1.2    lneto which can take appropriate measures
    326  1.2    lneto (such as printing an error message).
    327  1.1  mbalmer 
    328  1.1  mbalmer 
    329  1.1  mbalmer <p>
    330  1.2    lneto Lua code can explicitly generate an error by calling the
    331  1.2    lneto <a href="#pdf-error"><code>error</code></a> function.
    332  1.2    lneto If you need to catch errors in Lua,
    333  1.2    lneto you can use <a href="#pdf-pcall"><code>pcall</code></a> or <a href="#pdf-xpcall"><code>xpcall</code></a>
    334  1.2    lneto to call a given function in <em>protected mode</em>.
    335  1.1  mbalmer 
    336  1.1  mbalmer 
    337  1.1  mbalmer <p>
    338  1.2    lneto Whenever there is an error,
    339  1.2    lneto an <em>error object</em> (also called an <em>error message</em>)
    340  1.2    lneto is propagated with information about the error.
    341  1.3    lneto Lua itself only generates errors whose error object is a string,
    342  1.2    lneto but programs may generate errors with
    343  1.3    lneto any value as the error object.
    344  1.3    lneto It is up to the Lua program or its host to handle such error objects.
    345  1.1  mbalmer 
    346  1.1  mbalmer 
    347  1.1  mbalmer <p>
    348  1.2    lneto When you use <a href="#pdf-xpcall"><code>xpcall</code></a> or <a href="#lua_pcall"><code>lua_pcall</code></a>,
    349  1.2    lneto you may give a <em>message handler</em>
    350  1.2    lneto to be called in case of errors.
    351  1.2    lneto This function is called with the original error message
    352  1.2    lneto and returns a new error message.
    353  1.2    lneto It is called before the error unwinds the stack,
    354  1.2    lneto so that it can gather more information about the error,
    355  1.2    lneto for instance by inspecting the stack and creating a stack traceback.
    356  1.2    lneto This message handler is still protected by the protected call;
    357  1.2    lneto so, an error inside the message handler
    358  1.2    lneto will call the message handler again.
    359  1.3    lneto If this loop goes on for too long,
    360  1.3    lneto Lua breaks it and returns an appropriate message.
    361  1.1  mbalmer 
    362  1.1  mbalmer 
    363  1.1  mbalmer 
    364  1.1  mbalmer 
    365  1.1  mbalmer 
    366  1.2    lneto <h2>2.4 &ndash; <a name="2.4">Metatables and Metamethods</a></h2>
    367  1.1  mbalmer 
    368  1.2    lneto <p>
    369  1.2    lneto Every value in Lua can have a <em>metatable</em>.
    370  1.2    lneto This <em>metatable</em> is an ordinary Lua table
    371  1.2    lneto that defines the behavior of the original value
    372  1.2    lneto under certain special operations.
    373  1.2    lneto You can change several aspects of the behavior
    374  1.2    lneto of operations over a value by setting specific fields in its metatable.
    375  1.2    lneto For instance, when a non-numeric value is the operand of an addition,
    376  1.2    lneto Lua checks for a function in the field "<code>__add</code>" of the value's metatable.
    377  1.2    lneto If it finds one,
    378  1.2    lneto Lua calls this function to perform the addition.
    379  1.1  mbalmer 
    380  1.1  mbalmer 
    381  1.1  mbalmer <p>
    382  1.2    lneto The keys in a metatable are derived from the <em>event</em> names;
    383  1.2    lneto the corresponding values are called <em>metamethods</em>.
    384  1.2    lneto In the previous example, the event is <code>"add"</code>
    385  1.2    lneto and the metamethod is the function that performs the addition.
    386  1.1  mbalmer 
    387  1.1  mbalmer 
    388  1.2    lneto <p>
    389  1.2    lneto You can query the metatable of any value
    390  1.2    lneto using the <a href="#pdf-getmetatable"><code>getmetatable</code></a> function.
    391  1.1  mbalmer 
    392  1.1  mbalmer 
    393  1.1  mbalmer <p>
    394  1.2    lneto You can replace the metatable of tables
    395  1.2    lneto using the <a href="#pdf-setmetatable"><code>setmetatable</code></a> function.
    396  1.2    lneto You cannot change the metatable of other types from Lua
    397  1.3    lneto (except by using the debug library (<a href="#6.10">&sect;6.10</a>));
    398  1.2    lneto you must use the C&nbsp;API for that.
    399  1.1  mbalmer 
    400  1.1  mbalmer 
    401  1.1  mbalmer <p>
    402  1.2    lneto Tables and full userdata have individual metatables
    403  1.2    lneto (although multiple tables and userdata can share their metatables).
    404  1.2    lneto Values of all other types share one single metatable per type;
    405  1.2    lneto that is, there is one single metatable for all numbers,
    406  1.2    lneto one for all strings, etc.
    407  1.2    lneto By default, a value has no metatable,
    408  1.2    lneto but the string library sets a metatable for the string type (see <a href="#6.4">&sect;6.4</a>).
    409  1.1  mbalmer 
    410  1.1  mbalmer 
    411  1.1  mbalmer <p>
    412  1.2    lneto A metatable controls how an object behaves in
    413  1.3    lneto arithmetic operations, bitwise operations,
    414  1.2    lneto order comparisons, concatenation, length operation, calls, and indexing.
    415  1.2    lneto A metatable also can define a function to be called
    416  1.3    lneto when a userdata or a table is garbage collected (<a href="#2.5">&sect;2.5</a>).
    417  1.1  mbalmer 
    418  1.1  mbalmer 
    419  1.1  mbalmer <p>
    420  1.2    lneto A detailed list of events controlled by metatables is given next.
    421  1.2    lneto Each operation is identified by its corresponding event name.
    422  1.2    lneto The key for each event is a string with its name prefixed by
    423  1.2    lneto two underscores, '<code>__</code>';
    424  1.2    lneto for instance, the key for operation "add" is the
    425  1.2    lneto string "<code>__add</code>".
    426  1.2    lneto Note that queries for metamethods are always raw;
    427  1.2    lneto the access to a metamethod does not invoke other metamethods.
    428  1.2    lneto You can emulate how Lua queries a metamethod for an object <code>obj</code>
    429  1.2    lneto with the following code:
    430  1.1  mbalmer 
    431  1.2    lneto <pre>
    432  1.3    lneto      rawget(getmetatable(obj) or {}, "__" .. event_name)
    433  1.2    lneto </pre>
    434  1.1  mbalmer 
    435  1.2    lneto <p>
    436  1.2    lneto For the unary operators (negation, length, and bitwise not),
    437  1.2    lneto the metamethod is computed and called with a dummy second operand,
    438  1.2    lneto equal to the first one.
    439  1.2    lneto This extra operand is only to simplify Lua's internals
    440  1.2    lneto (by making these operators behave like a binary operation)
    441  1.2    lneto and may be removed in future versions.
    442  1.2    lneto (For most uses this extra operand is irrelevant.)
    443  1.1  mbalmer 
    444  1.1  mbalmer 
    445  1.1  mbalmer 
    446  1.2    lneto <ul>
    447  1.1  mbalmer 
    448  1.2    lneto <li><b>"add": </b>
    449  1.2    lneto the <code>+</code> operation.
    450  1.1  mbalmer 
    451  1.2    lneto If any operand for an addition is not a number
    452  1.2    lneto (nor a string coercible to a number),
    453  1.2    lneto Lua will try to call a metamethod.
    454  1.2    lneto First, Lua will check the first operand (even if it is valid).
    455  1.2    lneto If that operand does not define a metamethod for the "<code>__add</code>" event,
    456  1.2    lneto then Lua will check the second operand.
    457  1.3    lneto If Lua can find a metamethod,
    458  1.2    lneto it calls the metamethod with the two operands as arguments,
    459  1.2    lneto and the result of the call
    460  1.2    lneto (adjusted to one value)
    461  1.2    lneto is the result of the operation.
    462  1.3    lneto Otherwise,
    463  1.3    lneto it raises an error.
    464  1.2    lneto </li>
    465  1.1  mbalmer 
    466  1.2    lneto <li><b>"sub": </b>
    467  1.2    lneto the <code>-</code> operation.
    468  1.1  mbalmer 
    469  1.2    lneto Behavior similar to the "add" operation.
    470  1.2    lneto </li>
    471  1.1  mbalmer 
    472  1.2    lneto <li><b>"mul": </b>
    473  1.2    lneto the <code>*</code> operation.
    474  1.1  mbalmer 
    475  1.2    lneto Behavior similar to the "add" operation.
    476  1.2    lneto </li>
    477  1.1  mbalmer 
    478  1.2    lneto <li><b>"div": </b>
    479  1.2    lneto the <code>/</code> operation.
    480  1.1  mbalmer 
    481  1.2    lneto Behavior similar to the "add" operation.
    482  1.2    lneto </li>
    483  1.1  mbalmer 
    484  1.2    lneto <li><b>"mod": </b>
    485  1.2    lneto the <code>%</code> operation.
    486  1.1  mbalmer 
    487  1.2    lneto Behavior similar to the "add" operation.
    488  1.2    lneto </li>
    489  1.1  mbalmer 
    490  1.2    lneto <li><b>"pow": </b>
    491  1.2    lneto the <code>^</code> (exponentiation) operation.
    492  1.1  mbalmer 
    493  1.2    lneto Behavior similar to the "add" operation.
    494  1.2    lneto </li>
    495  1.1  mbalmer 
    496  1.2    lneto <li><b>"unm": </b>
    497  1.2    lneto the <code>-</code> (unary minus) operation.
    498  1.1  mbalmer 
    499  1.2    lneto Behavior similar to the "add" operation.
    500  1.2    lneto </li>
    501  1.1  mbalmer 
    502  1.2    lneto <li><b>"idiv": </b>
    503  1.3    lneto the <code>//</code> (floor division) operation.
    504  1.1  mbalmer 
    505  1.3    lneto Behavior similar to the "add" operation.
    506  1.2    lneto </li>
    507  1.1  mbalmer 
    508  1.2    lneto <li><b>"band": </b>
    509  1.2    lneto the <code>&amp;</code> (bitwise and) operation.
    510  1.1  mbalmer 
    511  1.3    lneto Behavior similar to the "add" operation,
    512  1.3    lneto except that Lua will try a metamethod
    513  1.3    lneto if any operator is neither an integer
    514  1.3    lneto nor a value coercible to an integer (see <a href="#3.4.3">&sect;3.4.3</a>).
    515  1.2    lneto </li>
    516  1.1  mbalmer 
    517  1.2    lneto <li><b>"bor": </b>
    518  1.2    lneto the <code>|</code> (bitwise or) operation.
    519  1.1  mbalmer 
    520  1.2    lneto Behavior similar to the "band" operation.
    521  1.2    lneto </li>
    522  1.1  mbalmer 
    523  1.2    lneto <li><b>"bxor": </b>
    524  1.2    lneto the <code>~</code> (bitwise exclusive or) operation.
    525  1.1  mbalmer 
    526  1.2    lneto Behavior similar to the "band" operation.
    527  1.2    lneto </li>
    528  1.1  mbalmer 
    529  1.2    lneto <li><b>"bnot": </b>
    530  1.2    lneto the <code>~</code> (bitwise unary not) operation.
    531  1.1  mbalmer 
    532  1.2    lneto Behavior similar to the "band" operation.
    533  1.2    lneto </li>
    534  1.1  mbalmer 
    535  1.2    lneto <li><b>"shl": </b>
    536  1.2    lneto the <code>&lt;&lt;</code> (bitwise left shift) operation.
    537  1.1  mbalmer 
    538  1.2    lneto Behavior similar to the "band" operation.
    539  1.2    lneto </li>
    540  1.1  mbalmer 
    541  1.2    lneto <li><b>"shr": </b>
    542  1.2    lneto the <code>&gt;&gt;</code> (bitwise right shift) operation.
    543  1.1  mbalmer 
    544  1.2    lneto Behavior similar to the "band" operation.
    545  1.2    lneto </li>
    546  1.1  mbalmer 
    547  1.2    lneto <li><b>"concat": </b>
    548  1.2    lneto the <code>..</code> (concatenation) operation.
    549  1.1  mbalmer 
    550  1.2    lneto Behavior similar to the "add" operation,
    551  1.2    lneto except that Lua will try a metamethod
    552  1.2    lneto if any operator is neither a string nor a number
    553  1.2    lneto (which is always coercible to a string).
    554  1.2    lneto </li>
    555  1.2    lneto 
    556  1.2    lneto <li><b>"len": </b>
    557  1.2    lneto the <code>#</code> (length) operation.
    558  1.2    lneto 
    559  1.2    lneto If the object is not a string,
    560  1.2    lneto Lua will try its metamethod.
    561  1.2    lneto If there is a metamethod,
    562  1.2    lneto Lua calls it with the object as argument,
    563  1.2    lneto and the result of the call
    564  1.2    lneto (always adjusted to one value)
    565  1.2    lneto is the result of the operation.
    566  1.2    lneto If there is no metamethod but the object is a table,
    567  1.2    lneto then Lua uses the table length operation (see <a href="#3.4.7">&sect;3.4.7</a>).
    568  1.2    lneto Otherwise, Lua raises an error.
    569  1.2    lneto </li>
    570  1.1  mbalmer 
    571  1.2    lneto <li><b>"eq": </b>
    572  1.2    lneto the <code>==</code> (equal) operation.
    573  1.1  mbalmer 
    574  1.2    lneto Behavior similar to the "add" operation,
    575  1.2    lneto except that Lua will try a metamethod only when the values
    576  1.2    lneto being compared are either both tables or both full userdata
    577  1.2    lneto and they are not primitively equal.
    578  1.2    lneto The result of the call is always converted to a boolean.
    579  1.2    lneto </li>
    580  1.1  mbalmer 
    581  1.2    lneto <li><b>"lt": </b>
    582  1.2    lneto the <code>&lt;</code> (less than) operation.
    583  1.1  mbalmer 
    584  1.2    lneto Behavior similar to the "add" operation,
    585  1.2    lneto except that Lua will try a metamethod only when the values
    586  1.2    lneto being compared are neither both numbers nor both strings.
    587  1.2    lneto The result of the call is always converted to a boolean.
    588  1.2    lneto </li>
    589  1.2    lneto 
    590  1.2    lneto <li><b>"le": </b>
    591  1.2    lneto the <code>&lt;=</code> (less equal) operation.
    592  1.2    lneto 
    593  1.2    lneto Unlike other operations,
    594  1.2    lneto The less-equal operation can use two different events.
    595  1.2    lneto First, Lua looks for the "<code>__le</code>" metamethod in both operands,
    596  1.2    lneto like in the "lt" operation.
    597  1.2    lneto If it cannot find such a metamethod,
    598  1.2    lneto then it will try the "<code>__lt</code>" event,
    599  1.2    lneto assuming that <code>a &lt;= b</code> is equivalent to <code>not (b &lt; a)</code>.
    600  1.2    lneto As with the other comparison operators,
    601  1.2    lneto the result is always a boolean.
    602  1.2    lneto </li>
    603  1.1  mbalmer 
    604  1.2    lneto <li><b>"index": </b>
    605  1.2    lneto The indexing access <code>table[key]</code>.
    606  1.1  mbalmer 
    607  1.2    lneto This event happens when <code>table</code> is not a table or
    608  1.2    lneto when <code>key</code> is not present in <code>table</code>.
    609  1.2    lneto The metamethod is looked up in <code>table</code>.
    610  1.1  mbalmer 
    611  1.1  mbalmer 
    612  1.1  mbalmer <p>
    613  1.2    lneto Despite the name,
    614  1.2    lneto the metamethod for this event can be either a function or a table.
    615  1.2    lneto If it is a function,
    616  1.2    lneto it is called with <code>table</code> and <code>key</code> as arguments.
    617  1.2    lneto If it is a table,
    618  1.2    lneto the final result is the result of indexing this table with <code>key</code>.
    619  1.2    lneto (This indexing is regular, not raw,
    620  1.2    lneto and therefore can trigger another metamethod.)
    621  1.2    lneto </li>
    622  1.2    lneto 
    623  1.2    lneto <li><b>"newindex": </b>
    624  1.2    lneto The indexing assignment <code>table[key] = value</code>.
    625  1.1  mbalmer 
    626  1.2    lneto Like the index event,
    627  1.2    lneto this event happens when <code>table</code> is not a table or
    628  1.2    lneto when <code>key</code> is not present in <code>table</code>.
    629  1.2    lneto The metamethod is looked up in <code>table</code>.
    630  1.1  mbalmer 
    631  1.1  mbalmer 
    632  1.1  mbalmer <p>
    633  1.3    lneto Like with indexing,
    634  1.2    lneto the metamethod for this event can be either a function or a table.
    635  1.2    lneto If it is a function,
    636  1.2    lneto it is called with <code>table</code>, <code>key</code>, and <code>value</code> as arguments.
    637  1.2    lneto If it is a table,
    638  1.2    lneto Lua does an indexing assignment to this table with the same key and value.
    639  1.2    lneto (This assignment is regular, not raw,
    640  1.2    lneto and therefore can trigger another metamethod.)
    641  1.1  mbalmer 
    642  1.1  mbalmer 
    643  1.2    lneto <p>
    644  1.3    lneto Whenever there is a "newindex" metamethod,
    645  1.2    lneto Lua does not perform the primitive assignment.
    646  1.2    lneto (If necessary,
    647  1.2    lneto the metamethod itself can call <a href="#pdf-rawset"><code>rawset</code></a>
    648  1.2    lneto to do the assignment.)
    649  1.2    lneto </li>
    650  1.1  mbalmer 
    651  1.2    lneto <li><b>"call": </b>
    652  1.2    lneto The call operation <code>func(args)</code>.
    653  1.1  mbalmer 
    654  1.2    lneto This event happens when Lua tries to call a non-function value
    655  1.2    lneto (that is, <code>func</code> is not a function).
    656  1.2    lneto The metamethod is looked up in <code>func</code>.
    657  1.2    lneto If present,
    658  1.2    lneto the metamethod is called with <code>func</code> as its first argument,
    659  1.2    lneto followed by the arguments of the original call (<code>args</code>).
    660  1.2    lneto </li>
    661  1.1  mbalmer 
    662  1.2    lneto </ul>
    663  1.1  mbalmer 
    664  1.1  mbalmer 
    665  1.1  mbalmer 
    666  1.1  mbalmer 
    667  1.2    lneto <h2>2.5 &ndash; <a name="2.5">Garbage Collection</a></h2>
    668  1.1  mbalmer 
    669  1.1  mbalmer <p>
    670  1.2    lneto Lua performs automatic memory management.
    671  1.2    lneto This means that
    672  1.3    lneto you do not have to worry about allocating memory for new objects
    673  1.3    lneto or freeing it when the objects are no longer needed.
    674  1.2    lneto Lua manages memory automatically by running
    675  1.2    lneto a <em>garbage collector</em> to collect all <em>dead objects</em>
    676  1.2    lneto (that is, objects that are no longer accessible from Lua).
    677  1.2    lneto All memory used by Lua is subject to automatic management:
    678  1.2    lneto strings, tables, userdata, functions, threads, internal structures, etc.
    679  1.1  mbalmer 
    680  1.2    lneto 
    681  1.2    lneto <p>
    682  1.2    lneto Lua implements an incremental mark-and-sweep collector.
    683  1.2    lneto It uses two numbers to control its garbage-collection cycles:
    684  1.2    lneto the <em>garbage-collector pause</em> and
    685  1.2    lneto the <em>garbage-collector step multiplier</em>.
    686  1.2    lneto Both use percentage points as units
    687  1.2    lneto (e.g., a value of 100 means an internal value of 1).
    688  1.1  mbalmer 
    689  1.1  mbalmer 
    690  1.1  mbalmer <p>
    691  1.2    lneto The garbage-collector pause
    692  1.2    lneto controls how long the collector waits before starting a new cycle.
    693  1.2    lneto Larger values make the collector less aggressive.
    694  1.2    lneto Values smaller than 100 mean the collector will not wait to
    695  1.2    lneto start a new cycle.
    696  1.2    lneto A value of 200 means that the collector waits for the total memory in use
    697  1.2    lneto to double before starting a new cycle.
    698  1.2    lneto 
    699  1.1  mbalmer 
    700  1.2    lneto <p>
    701  1.2    lneto The garbage-collector step multiplier
    702  1.2    lneto controls the relative speed of the collector relative to
    703  1.2    lneto memory allocation.
    704  1.2    lneto Larger values make the collector more aggressive but also increase
    705  1.2    lneto the size of each incremental step.
    706  1.2    lneto You should not use values smaller than 100,
    707  1.3    lneto because they make the collector too slow and
    708  1.2    lneto can result in the collector never finishing a cycle.
    709  1.2    lneto The default is 200,
    710  1.2    lneto which means that the collector runs at "twice"
    711  1.2    lneto the speed of memory allocation.
    712  1.1  mbalmer 
    713  1.1  mbalmer 
    714  1.2    lneto <p>
    715  1.2    lneto If you set the step multiplier to a very large number
    716  1.2    lneto (larger than 10% of the maximum number of
    717  1.2    lneto bytes that the program may use),
    718  1.2    lneto the collector behaves like a stop-the-world collector.
    719  1.2    lneto If you then set the pause to 200,
    720  1.2    lneto the collector behaves as in old Lua versions,
    721  1.2    lneto doing a complete collection every time Lua doubles its
    722  1.2    lneto memory usage.
    723  1.1  mbalmer 
    724  1.1  mbalmer 
    725  1.2    lneto <p>
    726  1.2    lneto You can change these numbers by calling <a href="#lua_gc"><code>lua_gc</code></a> in C
    727  1.2    lneto or <a href="#pdf-collectgarbage"><code>collectgarbage</code></a> in Lua.
    728  1.2    lneto You can also use these functions to control
    729  1.2    lneto the collector directly (e.g., stop and restart it).
    730  1.1  mbalmer 
    731  1.1  mbalmer 
    732  1.1  mbalmer 
    733  1.2    lneto <h3>2.5.1 &ndash; <a name="2.5.1">Garbage-Collection Metamethods</a></h3>
    734  1.1  mbalmer 
    735  1.2    lneto <p>
    736  1.2    lneto You can set garbage-collector metamethods for tables
    737  1.2    lneto and, using the C&nbsp;API,
    738  1.2    lneto for full userdata (see <a href="#2.4">&sect;2.4</a>).
    739  1.2    lneto These metamethods are also called <em>finalizers</em>.
    740  1.2    lneto Finalizers allow you to coordinate Lua's garbage collection
    741  1.2    lneto with external resource management
    742  1.2    lneto (such as closing files, network or database connections,
    743  1.2    lneto or freeing your own memory).
    744  1.1  mbalmer 
    745  1.1  mbalmer 
    746  1.1  mbalmer <p>
    747  1.2    lneto For an object (table or userdata) to be finalized when collected,
    748  1.2    lneto you must <em>mark</em> it for finalization.
    749  1.1  mbalmer 
    750  1.2    lneto You mark an object for finalization when you set its metatable
    751  1.2    lneto and the metatable has a field indexed by the string "<code>__gc</code>".
    752  1.2    lneto Note that if you set a metatable without a <code>__gc</code> field
    753  1.2    lneto and later create that field in the metatable,
    754  1.2    lneto the object will not be marked for finalization.
    755  1.3    lneto However, after an object has been marked,
    756  1.2    lneto you can freely change the <code>__gc</code> field of its metatable.
    757  1.1  mbalmer 
    758  1.1  mbalmer 
    759  1.2    lneto <p>
    760  1.2    lneto When a marked object becomes garbage,
    761  1.2    lneto it is not collected immediately by the garbage collector.
    762  1.2    lneto Instead, Lua puts it in a list.
    763  1.2    lneto After the collection,
    764  1.3    lneto Lua goes through that list.
    765  1.3    lneto For each object in the list,
    766  1.3    lneto it checks the object's <code>__gc</code> metamethod:
    767  1.3    lneto If it is a function,
    768  1.3    lneto Lua calls it with the object as its single argument;
    769  1.3    lneto if the metamethod is not a function,
    770  1.3    lneto Lua simply ignores it.
    771  1.1  mbalmer 
    772  1.1  mbalmer 
    773  1.2    lneto <p>
    774  1.2    lneto At the end of each garbage-collection cycle,
    775  1.2    lneto the finalizers for objects are called in
    776  1.3    lneto the reverse order that the objects were marked for finalization,
    777  1.2    lneto among those collected in that cycle;
    778  1.2    lneto that is, the first finalizer to be called is the one associated
    779  1.2    lneto with the object marked last in the program.
    780  1.2    lneto The execution of each finalizer may occur at any point during
    781  1.2    lneto the execution of the regular code.
    782  1.1  mbalmer 
    783  1.1  mbalmer 
    784  1.2    lneto <p>
    785  1.2    lneto Because the object being collected must still be used by the finalizer,
    786  1.3    lneto that object (and other objects accessible only through it)
    787  1.2    lneto must be <em>resurrected</em> by Lua.
    788  1.2    lneto Usually, this resurrection is transient,
    789  1.2    lneto and the object memory is freed in the next garbage-collection cycle.
    790  1.2    lneto However, if the finalizer stores the object in some global place
    791  1.2    lneto (e.g., a global variable),
    792  1.3    lneto then the resurrection is permanent.
    793  1.2    lneto Moreover, if the finalizer marks a finalizing object for finalization again,
    794  1.2    lneto its finalizer will be called again in the next cycle where the
    795  1.2    lneto object is unreachable.
    796  1.2    lneto In any case,
    797  1.2    lneto the object memory is freed only in the GC cycle where
    798  1.2    lneto the object is unreachable and not marked for finalization.
    799  1.1  mbalmer 
    800  1.1  mbalmer 
    801  1.2    lneto <p>
    802  1.2    lneto When you close a state (see <a href="#lua_close"><code>lua_close</code></a>),
    803  1.2    lneto Lua calls the finalizers of all objects marked for finalization,
    804  1.2    lneto following the reverse order that they were marked.
    805  1.2    lneto If any finalizer marks objects for collection during that phase,
    806  1.2    lneto these marks have no effect.
    807  1.1  mbalmer 
    808  1.1  mbalmer 
    809  1.1  mbalmer 
    810  1.1  mbalmer 
    811  1.1  mbalmer 
    812  1.2    lneto <h3>2.5.2 &ndash; <a name="2.5.2">Weak Tables</a></h3>
    813  1.2    lneto 
    814  1.2    lneto <p>
    815  1.2    lneto A <em>weak table</em> is a table whose elements are
    816  1.2    lneto <em>weak references</em>.
    817  1.2    lneto A weak reference is ignored by the garbage collector.
    818  1.2    lneto In other words,
    819  1.2    lneto if the only references to an object are weak references,
    820  1.2    lneto then the garbage collector will collect that object.
    821  1.2    lneto 
    822  1.2    lneto 
    823  1.2    lneto <p>
    824  1.2    lneto A weak table can have weak keys, weak values, or both.
    825  1.2    lneto A table with weak keys allows the collection of its keys,
    826  1.2    lneto but prevents the collection of its values.
    827  1.2    lneto A table with both weak keys and weak values allows the collection of
    828  1.2    lneto both keys and values.
    829  1.2    lneto In any case, if either the key or the value is collected,
    830  1.2    lneto the whole pair is removed from the table.
    831  1.2    lneto The weakness of a table is controlled by the
    832  1.2    lneto <code>__mode</code> field of its metatable.
    833  1.2    lneto If the <code>__mode</code> field is a string containing the character&nbsp;'<code>k</code>',
    834  1.2    lneto the keys in the table are weak.
    835  1.2    lneto If <code>__mode</code> contains '<code>v</code>',
    836  1.2    lneto the values in the table are weak.
    837  1.1  mbalmer 
    838  1.1  mbalmer 
    839  1.2    lneto <p>
    840  1.2    lneto A table with weak keys and strong values
    841  1.2    lneto is also called an <em>ephemeron table</em>.
    842  1.2    lneto In an ephemeron table,
    843  1.2    lneto a value is considered reachable only if its key is reachable.
    844  1.2    lneto In particular,
    845  1.2    lneto if the only reference to a key comes through its value,
    846  1.2    lneto the pair is removed.
    847  1.1  mbalmer 
    848  1.1  mbalmer 
    849  1.2    lneto <p>
    850  1.2    lneto Any change in the weakness of a table may take effect only
    851  1.2    lneto at the next collect cycle.
    852  1.2    lneto In particular, if you change the weakness to a stronger mode,
    853  1.2    lneto Lua may still collect some items from that table
    854  1.2    lneto before the change takes effect.
    855  1.1  mbalmer 
    856  1.1  mbalmer 
    857  1.2    lneto <p>
    858  1.2    lneto Only objects that have an explicit construction
    859  1.2    lneto are removed from weak tables.
    860  1.2    lneto Values, such as numbers and light C functions,
    861  1.2    lneto are not subject to garbage collection,
    862  1.2    lneto and therefore are not removed from weak tables
    863  1.3    lneto (unless their associated values are collected).
    864  1.2    lneto Although strings are subject to garbage collection,
    865  1.2    lneto they do not have an explicit construction,
    866  1.2    lneto and therefore are not removed from weak tables.
    867  1.1  mbalmer 
    868  1.1  mbalmer 
    869  1.1  mbalmer <p>
    870  1.2    lneto Resurrected objects
    871  1.2    lneto (that is, objects being finalized
    872  1.2    lneto and objects accessible only through objects being finalized)
    873  1.2    lneto have a special behavior in weak tables.
    874  1.2    lneto They are removed from weak values before running their finalizers,
    875  1.2    lneto but are removed from weak keys only in the next collection
    876  1.2    lneto after running their finalizers, when such objects are actually freed.
    877  1.2    lneto This behavior allows the finalizer to access properties
    878  1.2    lneto associated with the object through weak tables.
    879  1.1  mbalmer 
    880  1.1  mbalmer 
    881  1.1  mbalmer <p>
    882  1.2    lneto If a weak table is among the resurrected objects in a collection cycle,
    883  1.2    lneto it may not be properly cleared until the next cycle.
    884  1.1  mbalmer 
    885  1.1  mbalmer 
    886  1.1  mbalmer 
    887  1.1  mbalmer 
    888  1.1  mbalmer 
    889  1.1  mbalmer 
    890  1.1  mbalmer 
    891  1.2    lneto <h2>2.6 &ndash; <a name="2.6">Coroutines</a></h2>
    892  1.1  mbalmer 
    893  1.1  mbalmer <p>
    894  1.2    lneto Lua supports coroutines,
    895  1.2    lneto also called <em>collaborative multithreading</em>.
    896  1.2    lneto A coroutine in Lua represents an independent thread of execution.
    897  1.2    lneto Unlike threads in multithread systems, however,
    898  1.2    lneto a coroutine only suspends its execution by explicitly calling
    899  1.2    lneto a yield function.
    900  1.1  mbalmer 
    901  1.1  mbalmer 
    902  1.1  mbalmer <p>
    903  1.2    lneto You create a coroutine by calling <a href="#pdf-coroutine.create"><code>coroutine.create</code></a>.
    904  1.2    lneto Its sole argument is a function
    905  1.2    lneto that is the main function of the coroutine.
    906  1.2    lneto The <code>create</code> function only creates a new coroutine and
    907  1.2    lneto returns a handle to it (an object of type <em>thread</em>);
    908  1.2    lneto it does not start the coroutine.
    909  1.1  mbalmer 
    910  1.1  mbalmer 
    911  1.1  mbalmer <p>
    912  1.2    lneto You execute a coroutine by calling <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>.
    913  1.2    lneto When you first call <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>,
    914  1.2    lneto passing as its first argument
    915  1.2    lneto a thread returned by <a href="#pdf-coroutine.create"><code>coroutine.create</code></a>,
    916  1.2    lneto the coroutine starts its execution,
    917  1.2    lneto at the first line of its main function.
    918  1.3    lneto Extra arguments passed to <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> are passed
    919  1.3    lneto as arguments to the coroutine's main function.
    920  1.2    lneto After the coroutine starts running,
    921  1.2    lneto it runs until it terminates or <em>yields</em>.
    922  1.1  mbalmer 
    923  1.1  mbalmer 
    924  1.1  mbalmer <p>
    925  1.2    lneto A coroutine can terminate its execution in two ways:
    926  1.2    lneto normally, when its main function returns
    927  1.2    lneto (explicitly or implicitly, after the last instruction);
    928  1.2    lneto and abnormally, if there is an unprotected error.
    929  1.3    lneto In case of normal termination,
    930  1.3    lneto <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> returns <b>true</b>,
    931  1.2    lneto plus any values returned by the coroutine main function.
    932  1.2    lneto In case of errors, <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> returns <b>false</b>
    933  1.2    lneto plus an error message.
    934  1.1  mbalmer 
    935  1.1  mbalmer 
    936  1.1  mbalmer <p>
    937  1.2    lneto A coroutine yields by calling <a href="#pdf-coroutine.yield"><code>coroutine.yield</code></a>.
    938  1.2    lneto When a coroutine yields,
    939  1.2    lneto the corresponding <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> returns immediately,
    940  1.2    lneto even if the yield happens inside nested function calls
    941  1.2    lneto (that is, not in the main function,
    942  1.2    lneto but in a function directly or indirectly called by the main function).
    943  1.2    lneto In the case of a yield, <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> also returns <b>true</b>,
    944  1.2    lneto plus any values passed to <a href="#pdf-coroutine.yield"><code>coroutine.yield</code></a>.
    945  1.2    lneto The next time you resume the same coroutine,
    946  1.2    lneto it continues its execution from the point where it yielded,
    947  1.2    lneto with the call to <a href="#pdf-coroutine.yield"><code>coroutine.yield</code></a> returning any extra
    948  1.2    lneto arguments passed to <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>.
    949  1.1  mbalmer 
    950  1.1  mbalmer 
    951  1.1  mbalmer <p>
    952  1.2    lneto Like <a href="#pdf-coroutine.create"><code>coroutine.create</code></a>,
    953  1.2    lneto the <a href="#pdf-coroutine.wrap"><code>coroutine.wrap</code></a> function also creates a coroutine,
    954  1.2    lneto but instead of returning the coroutine itself,
    955  1.2    lneto it returns a function that, when called, resumes the coroutine.
    956  1.2    lneto Any arguments passed to this function
    957  1.2    lneto go as extra arguments to <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>.
    958  1.2    lneto <a href="#pdf-coroutine.wrap"><code>coroutine.wrap</code></a> returns all the values returned by <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>,
    959  1.2    lneto except the first one (the boolean error code).
    960  1.2    lneto Unlike <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>,
    961  1.2    lneto <a href="#pdf-coroutine.wrap"><code>coroutine.wrap</code></a> does not catch errors;
    962  1.2    lneto any error is propagated to the caller.
    963  1.1  mbalmer 
    964  1.1  mbalmer 
    965  1.2    lneto <p>
    966  1.2    lneto As an example of how coroutines work,
    967  1.2    lneto consider the following code:
    968  1.1  mbalmer 
    969  1.1  mbalmer <pre>
    970  1.2    lneto      function foo (a)
    971  1.2    lneto        print("foo", a)
    972  1.2    lneto        return coroutine.yield(2*a)
    973  1.2    lneto      end
    974  1.2    lneto      
    975  1.2    lneto      co = coroutine.create(function (a,b)
    976  1.2    lneto            print("co-body", a, b)
    977  1.2    lneto            local r = foo(a+1)
    978  1.2    lneto            print("co-body", r)
    979  1.2    lneto            local r, s = coroutine.yield(a+b, a-b)
    980  1.2    lneto            print("co-body", r, s)
    981  1.2    lneto            return b, "end"
    982  1.2    lneto      end)
    983  1.2    lneto      
    984  1.2    lneto      print("main", coroutine.resume(co, 1, 10))
    985  1.2    lneto      print("main", coroutine.resume(co, "r"))
    986  1.2    lneto      print("main", coroutine.resume(co, "x", "y"))
    987  1.2    lneto      print("main", coroutine.resume(co, "x", "y"))
    988  1.1  mbalmer </pre><p>
    989  1.2    lneto When you run it, it produces the following output:
    990  1.1  mbalmer 
    991  1.2    lneto <pre>
    992  1.2    lneto      co-body 1       10
    993  1.2    lneto      foo     2
    994  1.2    lneto      main    true    4
    995  1.2    lneto      co-body r
    996  1.2    lneto      main    true    11      -9
    997  1.2    lneto      co-body x       y
    998  1.2    lneto      main    true    10      end
    999  1.2    lneto      main    false   cannot resume dead coroutine
   1000  1.2    lneto </pre>
   1001  1.1  mbalmer 
   1002  1.2    lneto <p>
   1003  1.2    lneto You can also create and manipulate coroutines through the C API:
   1004  1.2    lneto see functions <a href="#lua_newthread"><code>lua_newthread</code></a>, <a href="#lua_resume"><code>lua_resume</code></a>,
   1005  1.2    lneto and <a href="#lua_yield"><code>lua_yield</code></a>.
   1006  1.1  mbalmer 
   1007  1.1  mbalmer 
   1008  1.1  mbalmer 
   1009  1.1  mbalmer 
   1010  1.1  mbalmer 
   1011  1.2    lneto <h1>3 &ndash; <a name="3">The Language</a></h1>
   1012  1.1  mbalmer 
   1013  1.1  mbalmer <p>
   1014  1.2    lneto This section describes the lexis, the syntax, and the semantics of Lua.
   1015  1.2    lneto In other words,
   1016  1.2    lneto this section describes
   1017  1.2    lneto which tokens are valid,
   1018  1.2    lneto how they can be combined,
   1019  1.2    lneto and what their combinations mean.
   1020  1.1  mbalmer 
   1021  1.1  mbalmer 
   1022  1.1  mbalmer <p>
   1023  1.2    lneto Language constructs will be explained using the usual extended BNF notation,
   1024  1.2    lneto in which
   1025  1.2    lneto {<em>a</em>}&nbsp;means&nbsp;0 or more <em>a</em>'s, and
   1026  1.2    lneto [<em>a</em>]&nbsp;means an optional <em>a</em>.
   1027  1.2    lneto Non-terminals are shown like non-terminal,
   1028  1.2    lneto keywords are shown like <b>kword</b>,
   1029  1.2    lneto and other terminal symbols are shown like &lsquo;<b>=</b>&rsquo;.
   1030  1.2    lneto The complete syntax of Lua can be found in <a href="#9">&sect;9</a>
   1031  1.2    lneto at the end of this manual.
   1032  1.1  mbalmer 
   1033  1.1  mbalmer 
   1034  1.1  mbalmer 
   1035  1.2    lneto <h2>3.1 &ndash; <a name="3.1">Lexical Conventions</a></h2>
   1036  1.1  mbalmer 
   1037  1.1  mbalmer <p>
   1038  1.2    lneto Lua is a free-form language.
   1039  1.2    lneto It ignores spaces (including new lines) and comments
   1040  1.2    lneto between lexical elements (tokens),
   1041  1.2    lneto except as delimiters between names and keywords.
   1042  1.1  mbalmer 
   1043  1.1  mbalmer 
   1044  1.1  mbalmer <p>
   1045  1.2    lneto <em>Names</em>
   1046  1.2    lneto (also called <em>identifiers</em>)
   1047  1.2    lneto in Lua can be any string of letters,
   1048  1.2    lneto digits, and underscores,
   1049  1.2    lneto not beginning with a digit.
   1050  1.2    lneto Identifiers are used to name variables, table fields, and labels.
   1051  1.1  mbalmer 
   1052  1.1  mbalmer 
   1053  1.2    lneto <p>
   1054  1.2    lneto The following <em>keywords</em> are reserved
   1055  1.2    lneto and cannot be used as names:
   1056  1.1  mbalmer 
   1057  1.1  mbalmer 
   1058  1.2    lneto <pre>
   1059  1.2    lneto      and       break     do        else      elseif    end
   1060  1.2    lneto      false     for       function  goto      if        in
   1061  1.2    lneto      local     nil       not       or        repeat    return
   1062  1.2    lneto      then      true      until     while
   1063  1.2    lneto </pre>
   1064  1.1  mbalmer 
   1065  1.2    lneto <p>
   1066  1.2    lneto Lua is a case-sensitive language:
   1067  1.2    lneto <code>and</code> is a reserved word, but <code>And</code> and <code>AND</code>
   1068  1.2    lneto are two different, valid names.
   1069  1.2    lneto As a convention,
   1070  1.2    lneto programs should avoid creating 
   1071  1.2    lneto names that start with an underscore followed by
   1072  1.2    lneto one or more uppercase letters (such as <a href="#pdf-_VERSION"><code>_VERSION</code></a>).
   1073  1.1  mbalmer 
   1074  1.1  mbalmer 
   1075  1.1  mbalmer <p>
   1076  1.2    lneto The following strings denote other tokens:
   1077  1.1  mbalmer 
   1078  1.1  mbalmer <pre>
   1079  1.2    lneto      +     -     *     /     %     ^     #
   1080  1.2    lneto      &amp;     ~     |     &lt;&lt;    &gt;&gt;    //
   1081  1.2    lneto      ==    ~=    &lt;=    &gt;=    &lt;     &gt;     =
   1082  1.2    lneto      (     )     {     }     [     ]     ::
   1083  1.2    lneto      ;     :     ,     .     ..    ...
   1084  1.2    lneto </pre>
   1085  1.1  mbalmer 
   1086  1.1  mbalmer <p>
   1087  1.2    lneto <em>Literal strings</em>
   1088  1.2    lneto can be delimited by matching single or double quotes,
   1089  1.2    lneto and can contain the following C-like escape sequences:
   1090  1.2    lneto '<code>\a</code>' (bell),
   1091  1.2    lneto '<code>\b</code>' (backspace),
   1092  1.2    lneto '<code>\f</code>' (form feed),
   1093  1.2    lneto '<code>\n</code>' (newline),
   1094  1.2    lneto '<code>\r</code>' (carriage return),
   1095  1.2    lneto '<code>\t</code>' (horizontal tab),
   1096  1.2    lneto '<code>\v</code>' (vertical tab),
   1097  1.2    lneto '<code>\\</code>' (backslash),
   1098  1.2    lneto '<code>\"</code>' (quotation mark [double quote]),
   1099  1.2    lneto and '<code>\'</code>' (apostrophe [single quote]).
   1100  1.2    lneto A backslash followed by a real newline
   1101  1.2    lneto results in a newline in the string.
   1102  1.2    lneto The escape sequence '<code>\z</code>' skips the following span
   1103  1.2    lneto of white-space characters,
   1104  1.2    lneto including line breaks;
   1105  1.2    lneto it is particularly useful to break and indent a long literal string
   1106  1.2    lneto into multiple lines without adding the newlines and spaces
   1107  1.2    lneto into the string contents.
   1108  1.1  mbalmer 
   1109  1.1  mbalmer 
   1110  1.1  mbalmer <p>
   1111  1.3    lneto Strings in Lua can contain any 8-bit value, including embedded zeros,
   1112  1.3    lneto which can be specified as '<code>\0</code>'.
   1113  1.3    lneto More generally,
   1114  1.3    lneto we can specify any byte in a literal string by its numerical value.
   1115  1.3    lneto This can be done
   1116  1.3    lneto with the escape sequence <code>\x<em>XX</em></code>,
   1117  1.2    lneto where <em>XX</em> is a sequence of exactly two hexadecimal digits,
   1118  1.2    lneto or with the escape sequence <code>\<em>ddd</em></code>,
   1119  1.2    lneto where <em>ddd</em> is a sequence of up to three decimal digits.
   1120  1.3    lneto (Note that if a decimal escape sequence is to be followed by a digit,
   1121  1.2    lneto it must be expressed using exactly three digits.)
   1122  1.1  mbalmer 
   1123  1.1  mbalmer 
   1124  1.2    lneto <p>
   1125  1.2    lneto The UTF-8 encoding of a Unicode character
   1126  1.2    lneto can be inserted in a literal string with
   1127  1.2    lneto the escape sequence <code>\u{<em>XXX</em>}</code>
   1128  1.2    lneto (note the mandatory enclosing brackets),
   1129  1.2    lneto where <em>XXX</em> is a sequence of one or more hexadecimal digits
   1130  1.2    lneto representing the character code point.
   1131  1.1  mbalmer 
   1132  1.1  mbalmer 
   1133  1.2    lneto <p>
   1134  1.2    lneto Literal strings can also be defined using a long format
   1135  1.2    lneto enclosed by <em>long brackets</em>.
   1136  1.2    lneto We define an <em>opening long bracket of level <em>n</em></em> as an opening
   1137  1.2    lneto square bracket followed by <em>n</em> equal signs followed by another
   1138  1.2    lneto opening square bracket.
   1139  1.2    lneto So, an opening long bracket of level&nbsp;0 is written as <code>[[</code>, 
   1140  1.2    lneto an opening long bracket of level&nbsp;1 is written as <code>[=[</code>, 
   1141  1.2    lneto and so on.
   1142  1.2    lneto A <em>closing long bracket</em> is defined similarly;
   1143  1.2    lneto for instance,
   1144  1.2    lneto a closing long bracket of level&nbsp;4 is written as  <code>]====]</code>.
   1145  1.2    lneto A <em>long literal</em> starts with an opening long bracket of any level and
   1146  1.2    lneto ends at the first closing long bracket of the same level.
   1147  1.3    lneto It can contain any text except a closing bracket of the same level.
   1148  1.2    lneto Literals in this bracketed form can run for several lines,
   1149  1.2    lneto do not interpret any escape sequences,
   1150  1.2    lneto and ignore long brackets of any other level.
   1151  1.2    lneto Any kind of end-of-line sequence
   1152  1.2    lneto (carriage return, newline, carriage return followed by newline,
   1153  1.2    lneto or newline followed by carriage return)
   1154  1.2    lneto is converted to a simple newline.
   1155  1.1  mbalmer 
   1156  1.1  mbalmer 
   1157  1.2    lneto <p>
   1158  1.2    lneto Any byte in a literal string not
   1159  1.2    lneto explicitly affected by the previous rules represents itself.
   1160  1.2    lneto However, Lua opens files for parsing in text mode,
   1161  1.2    lneto and the system file functions may have problems with
   1162  1.2    lneto some control characters.
   1163  1.2    lneto So, it is safer to represent
   1164  1.2    lneto non-text data as a quoted literal with
   1165  1.2    lneto explicit escape sequences for non-text characters.
   1166  1.1  mbalmer 
   1167  1.1  mbalmer 
   1168  1.2    lneto <p>
   1169  1.2    lneto For convenience,
   1170  1.2    lneto when the opening long bracket is immediately followed by a newline,
   1171  1.2    lneto the newline is not included in the string.
   1172  1.2    lneto As an example, in a system using ASCII
   1173  1.2    lneto (in which '<code>a</code>' is coded as&nbsp;97,
   1174  1.2    lneto newline is coded as&nbsp;10, and '<code>1</code>' is coded as&nbsp;49),
   1175  1.2    lneto the five literal strings below denote the same string:
   1176  1.1  mbalmer 
   1177  1.1  mbalmer <pre>
   1178  1.2    lneto      a = 'alo\n123"'
   1179  1.2    lneto      a = "alo\n123\""
   1180  1.2    lneto      a = '\97lo\10\04923"'
   1181  1.2    lneto      a = [[alo
   1182  1.2    lneto      123"]]
   1183  1.2    lneto      a = [==[
   1184  1.2    lneto      alo
   1185  1.2    lneto      123"]==]
   1186  1.1  mbalmer </pre>
   1187  1.1  mbalmer 
   1188  1.1  mbalmer <p>
   1189  1.3    lneto A <em>numerical constant</em> (or <em>numeral</em>)
   1190  1.3    lneto can be written with an optional fractional part
   1191  1.2    lneto and an optional decimal exponent,
   1192  1.2    lneto marked by a letter '<code>e</code>' or '<code>E</code>'.
   1193  1.2    lneto Lua also accepts hexadecimal constants,
   1194  1.2    lneto which start with <code>0x</code> or <code>0X</code>.
   1195  1.2    lneto Hexadecimal constants also accept an optional fractional part
   1196  1.2    lneto plus an optional binary exponent,
   1197  1.2    lneto marked by a letter '<code>p</code>' or '<code>P</code>'.
   1198  1.2    lneto A numeric constant with a fractional dot or an exponent 
   1199  1.2    lneto denotes a float;
   1200  1.2    lneto otherwise it denotes an integer.
   1201  1.2    lneto Examples of valid integer constants are
   1202  1.1  mbalmer 
   1203  1.1  mbalmer <pre>
   1204  1.2    lneto      3   345   0xff   0xBEBADA
   1205  1.1  mbalmer </pre><p>
   1206  1.2    lneto Examples of valid float constants are
   1207  1.1  mbalmer 
   1208  1.1  mbalmer <pre>
   1209  1.2    lneto      3.0     3.1416     314.16e-2     0.31416E1     34e1
   1210  1.2    lneto      0x0.1E  0xA23p-4   0X1.921FB54442D18P+1
   1211  1.1  mbalmer </pre>
   1212  1.1  mbalmer 
   1213  1.1  mbalmer <p>
   1214  1.2    lneto A <em>comment</em> starts with a double hyphen (<code>--</code>)
   1215  1.2    lneto anywhere outside a string.
   1216  1.2    lneto If the text immediately after <code>--</code> is not an opening long bracket,
   1217  1.2    lneto the comment is a <em>short comment</em>,
   1218  1.2    lneto which runs until the end of the line.
   1219  1.2    lneto Otherwise, it is a <em>long comment</em>,
   1220  1.2    lneto which runs until the corresponding closing long bracket.
   1221  1.2    lneto Long comments are frequently used to disable code temporarily.
   1222  1.2    lneto 
   1223  1.1  mbalmer 
   1224  1.1  mbalmer 
   1225  1.1  mbalmer 
   1226  1.1  mbalmer 
   1227  1.2    lneto <h2>3.2 &ndash; <a name="3.2">Variables</a></h2>
   1228  1.1  mbalmer 
   1229  1.2    lneto <p>
   1230  1.2    lneto Variables are places that store values.
   1231  1.2    lneto There are three kinds of variables in Lua:
   1232  1.2    lneto global variables, local variables, and table fields.
   1233  1.1  mbalmer 
   1234  1.1  mbalmer 
   1235  1.2    lneto <p>
   1236  1.2    lneto A single name can denote a global variable or a local variable
   1237  1.2    lneto (or a function's formal parameter,
   1238  1.2    lneto which is a particular kind of local variable):
   1239  1.1  mbalmer 
   1240  1.1  mbalmer <pre>
   1241  1.2    lneto 	var ::= Name
   1242  1.1  mbalmer </pre><p>
   1243  1.2    lneto Name denotes identifiers, as defined in <a href="#3.1">&sect;3.1</a>.
   1244  1.1  mbalmer 
   1245  1.1  mbalmer 
   1246  1.1  mbalmer <p>
   1247  1.2    lneto Any variable name is assumed to be global unless explicitly declared
   1248  1.2    lneto as a local (see <a href="#3.3.7">&sect;3.3.7</a>).
   1249  1.2    lneto Local variables are <em>lexically scoped</em>:
   1250  1.2    lneto local variables can be freely accessed by functions
   1251  1.2    lneto defined inside their scope (see <a href="#3.5">&sect;3.5</a>).
   1252  1.2    lneto 
   1253  1.1  mbalmer 
   1254  1.2    lneto <p>
   1255  1.2    lneto Before the first assignment to a variable, its value is <b>nil</b>.
   1256  1.1  mbalmer 
   1257  1.1  mbalmer 
   1258  1.1  mbalmer <p>
   1259  1.2    lneto Square brackets are used to index a table:
   1260  1.1  mbalmer 
   1261  1.1  mbalmer <pre>
   1262  1.2    lneto 	var ::= prefixexp &lsquo;<b>[</b>&rsquo; exp &lsquo;<b>]</b>&rsquo;
   1263  1.1  mbalmer </pre><p>
   1264  1.2    lneto The meaning of accesses to table fields can be changed via metatables.
   1265  1.2    lneto An access to an indexed variable <code>t[i]</code> is equivalent to
   1266  1.2    lneto a call <code>gettable_event(t,i)</code>.
   1267  1.2    lneto (See <a href="#2.4">&sect;2.4</a> for a complete description of the
   1268  1.2    lneto <code>gettable_event</code> function.
   1269  1.2    lneto This function is not defined or callable in Lua.
   1270  1.2    lneto We use it here only for explanatory purposes.)
   1271  1.1  mbalmer 
   1272  1.1  mbalmer 
   1273  1.1  mbalmer <p>
   1274  1.2    lneto The syntax <code>var.Name</code> is just syntactic sugar for
   1275  1.2    lneto <code>var["Name"]</code>:
   1276  1.1  mbalmer 
   1277  1.1  mbalmer <pre>
   1278  1.2    lneto 	var ::= prefixexp &lsquo;<b>.</b>&rsquo; Name
   1279  1.2    lneto </pre>
   1280  1.1  mbalmer 
   1281  1.1  mbalmer <p>
   1282  1.2    lneto An access to a global variable <code>x</code>
   1283  1.2    lneto is equivalent to <code>_ENV.x</code>.
   1284  1.2    lneto Due to the way that chunks are compiled,
   1285  1.2    lneto <code>_ENV</code> is never a global name (see <a href="#2.2">&sect;2.2</a>).
   1286  1.1  mbalmer 
   1287  1.1  mbalmer 
   1288  1.1  mbalmer 
   1289  1.1  mbalmer 
   1290  1.1  mbalmer 
   1291  1.2    lneto <h2>3.3 &ndash; <a name="3.3">Statements</a></h2>
   1292  1.1  mbalmer 
   1293  1.1  mbalmer <p>
   1294  1.2    lneto Lua supports an almost conventional set of statements,
   1295  1.2    lneto similar to those in Pascal or C.
   1296  1.2    lneto This set includes
   1297  1.2    lneto assignments, control structures, function calls,
   1298  1.2    lneto and variable declarations.
   1299  1.2    lneto 
   1300  1.2    lneto 
   1301  1.1  mbalmer 
   1302  1.2    lneto <h3>3.3.1 &ndash; <a name="3.3.1">Blocks</a></h3>
   1303  1.1  mbalmer 
   1304  1.1  mbalmer <p>
   1305  1.2    lneto A block is a list of statements,
   1306  1.2    lneto which are executed sequentially:
   1307  1.1  mbalmer 
   1308  1.1  mbalmer <pre>
   1309  1.2    lneto 	block ::= {stat}
   1310  1.1  mbalmer </pre><p>
   1311  1.2    lneto Lua has <em>empty statements</em>
   1312  1.2    lneto that allow you to separate statements with semicolons,
   1313  1.2    lneto start a block with a semicolon
   1314  1.2    lneto or write two semicolons in sequence:
   1315  1.1  mbalmer 
   1316  1.1  mbalmer <pre>
   1317  1.2    lneto 	stat ::= &lsquo;<b>;</b>&rsquo;
   1318  1.2    lneto </pre>
   1319  1.2    lneto 
   1320  1.2    lneto <p>
   1321  1.2    lneto Function calls and assignments
   1322  1.2    lneto can start with an open parenthesis.
   1323  1.2    lneto This possibility leads to an ambiguity in Lua's grammar.
   1324  1.2    lneto Consider the following fragment:
   1325  1.1  mbalmer 
   1326  1.1  mbalmer <pre>
   1327  1.2    lneto      a = b + c
   1328  1.2    lneto      (print or io.write)('done')
   1329  1.1  mbalmer </pre><p>
   1330  1.2    lneto The grammar could see it in two ways:
   1331  1.1  mbalmer 
   1332  1.1  mbalmer <pre>
   1333  1.2    lneto      a = b + c(print or io.write)('done')
   1334  1.2    lneto      
   1335  1.2    lneto      a = b + c; (print or io.write)('done')
   1336  1.1  mbalmer </pre><p>
   1337  1.2    lneto The current parser always sees such constructions
   1338  1.2    lneto in the first way,
   1339  1.2    lneto interpreting the open parenthesis
   1340  1.2    lneto as the start of the arguments to a call.
   1341  1.2    lneto To avoid this ambiguity,
   1342  1.2    lneto it is a good practice to always precede with a semicolon
   1343  1.2    lneto statements that start with a parenthesis:
   1344  1.1  mbalmer 
   1345  1.1  mbalmer <pre>
   1346  1.2    lneto      ;(print or io.write)('done')
   1347  1.2    lneto </pre>
   1348  1.2    lneto 
   1349  1.2    lneto <p>
   1350  1.2    lneto A block can be explicitly delimited to produce a single statement:
   1351  1.1  mbalmer 
   1352  1.1  mbalmer <pre>
   1353  1.2    lneto 	stat ::= <b>do</b> block <b>end</b>
   1354  1.1  mbalmer </pre><p>
   1355  1.2    lneto Explicit blocks are useful
   1356  1.2    lneto to control the scope of variable declarations.
   1357  1.2    lneto Explicit blocks are also sometimes used to
   1358  1.2    lneto add a <b>return</b> statement in the middle
   1359  1.2    lneto of another block (see <a href="#3.3.4">&sect;3.3.4</a>).
   1360  1.2    lneto 
   1361  1.2    lneto 
   1362  1.2    lneto 
   1363  1.2    lneto 
   1364  1.2    lneto 
   1365  1.2    lneto <h3>3.3.2 &ndash; <a name="3.3.2">Chunks</a></h3>
   1366  1.2    lneto 
   1367  1.2    lneto <p>
   1368  1.2    lneto The unit of compilation of Lua is called a <em>chunk</em>.
   1369  1.2    lneto Syntactically,
   1370  1.2    lneto a chunk is simply a block:
   1371  1.1  mbalmer 
   1372  1.1  mbalmer <pre>
   1373  1.2    lneto 	chunk ::= block
   1374  1.2    lneto </pre>
   1375  1.1  mbalmer 
   1376  1.2    lneto <p>
   1377  1.2    lneto Lua handles a chunk as the body of an anonymous function
   1378  1.2    lneto with a variable number of arguments
   1379  1.2    lneto (see <a href="#3.4.11">&sect;3.4.11</a>).
   1380  1.2    lneto As such, chunks can define local variables,
   1381  1.2    lneto receive arguments, and return values.
   1382  1.2    lneto Moreover, such anonymous function is compiled as in the
   1383  1.2    lneto scope of an external local variable called <code>_ENV</code> (see <a href="#2.2">&sect;2.2</a>).
   1384  1.2    lneto The resulting function always has <code>_ENV</code> as its only upvalue,
   1385  1.2    lneto even if it does not use that variable.
   1386  1.1  mbalmer 
   1387  1.1  mbalmer 
   1388  1.1  mbalmer <p>
   1389  1.2    lneto A chunk can be stored in a file or in a string inside the host program.
   1390  1.2    lneto To execute a chunk,
   1391  1.3    lneto Lua first <em>loads</em> it,
   1392  1.3    lneto precompiling the chunk's code into instructions for a virtual machine,
   1393  1.3    lneto and then Lua executes the compiled code
   1394  1.2    lneto with an interpreter for the virtual machine.
   1395  1.1  mbalmer 
   1396  1.1  mbalmer 
   1397  1.1  mbalmer <p>
   1398  1.2    lneto Chunks can also be precompiled into binary form;
   1399  1.2    lneto see program <code>luac</code> and function <a href="#pdf-string.dump"><code>string.dump</code></a> for details.
   1400  1.2    lneto Programs in source and compiled forms are interchangeable;
   1401  1.2    lneto Lua automatically detects the file type and acts accordingly (see <a href="#pdf-load"><code>load</code></a>).
   1402  1.2    lneto 
   1403  1.2    lneto 
   1404  1.2    lneto 
   1405  1.1  mbalmer 
   1406  1.1  mbalmer 
   1407  1.2    lneto <h3>3.3.3 &ndash; <a name="3.3.3">Assignment</a></h3>
   1408  1.1  mbalmer 
   1409  1.1  mbalmer <p>
   1410  1.2    lneto Lua allows multiple assignments.
   1411  1.2    lneto Therefore, the syntax for assignment
   1412  1.2    lneto defines a list of variables on the left side
   1413  1.2    lneto and a list of expressions on the right side.
   1414  1.2    lneto The elements in both lists are separated by commas:
   1415  1.1  mbalmer 
   1416  1.1  mbalmer <pre>
   1417  1.2    lneto 	stat ::= varlist &lsquo;<b>=</b>&rsquo; explist
   1418  1.2    lneto 	varlist ::= var {&lsquo;<b>,</b>&rsquo; var}
   1419  1.2    lneto 	explist ::= exp {&lsquo;<b>,</b>&rsquo; exp}
   1420  1.1  mbalmer </pre><p>
   1421  1.2    lneto Expressions are discussed in <a href="#3.4">&sect;3.4</a>.
   1422  1.1  mbalmer 
   1423  1.1  mbalmer 
   1424  1.1  mbalmer <p>
   1425  1.2    lneto Before the assignment,
   1426  1.2    lneto the list of values is <em>adjusted</em> to the length of
   1427  1.2    lneto the list of variables.
   1428  1.2    lneto If there are more values than needed,
   1429  1.2    lneto the excess values are thrown away.
   1430  1.2    lneto If there are fewer values than needed,
   1431  1.2    lneto the list is extended with as many  <b>nil</b>'s as needed.
   1432  1.2    lneto If the list of expressions ends with a function call,
   1433  1.2    lneto then all values returned by that call enter the list of values,
   1434  1.2    lneto before the adjustment
   1435  1.2    lneto (except when the call is enclosed in parentheses; see <a href="#3.4">&sect;3.4</a>).
   1436  1.1  mbalmer 
   1437  1.1  mbalmer 
   1438  1.1  mbalmer <p>
   1439  1.2    lneto The assignment statement first evaluates all its expressions
   1440  1.3    lneto and only then the assignments are performed.
   1441  1.2    lneto Thus the code
   1442  1.1  mbalmer 
   1443  1.1  mbalmer <pre>
   1444  1.2    lneto      i = 3
   1445  1.2    lneto      i, a[i] = i+1, 20
   1446  1.1  mbalmer </pre><p>
   1447  1.2    lneto sets <code>a[3]</code> to 20, without affecting <code>a[4]</code>
   1448  1.2    lneto because the <code>i</code> in <code>a[i]</code> is evaluated (to 3)
   1449  1.2    lneto before it is assigned&nbsp;4.
   1450  1.2    lneto Similarly, the line
   1451  1.1  mbalmer 
   1452  1.1  mbalmer <pre>
   1453  1.2    lneto      x, y = y, x
   1454  1.2    lneto </pre><p>
   1455  1.2    lneto exchanges the values of <code>x</code> and <code>y</code>,
   1456  1.2    lneto and
   1457  1.1  mbalmer 
   1458  1.2    lneto <pre>
   1459  1.2    lneto      x, y, z = y, z, x
   1460  1.2    lneto </pre><p>
   1461  1.2    lneto cyclically permutes the values of <code>x</code>, <code>y</code>, and <code>z</code>.
   1462  1.1  mbalmer 
   1463  1.1  mbalmer 
   1464  1.2    lneto <p>
   1465  1.2    lneto The meaning of assignments to global variables
   1466  1.2    lneto and table fields can be changed via metatables.
   1467  1.2    lneto An assignment to an indexed variable <code>t[i] = val</code> is equivalent to
   1468  1.2    lneto <code>settable_event(t,i,val)</code>.
   1469  1.2    lneto (See <a href="#2.4">&sect;2.4</a> for a complete description of the
   1470  1.2    lneto <code>settable_event</code> function.
   1471  1.2    lneto This function is not defined or callable in Lua.
   1472  1.2    lneto We use it here only for explanatory purposes.)
   1473  1.1  mbalmer 
   1474  1.1  mbalmer 
   1475  1.2    lneto <p>
   1476  1.3    lneto An assignment to a global name <code>x = val</code>
   1477  1.2    lneto is equivalent to the assignment
   1478  1.2    lneto <code>_ENV.x = val</code> (see <a href="#2.2">&sect;2.2</a>).
   1479  1.1  mbalmer 
   1480  1.1  mbalmer 
   1481  1.1  mbalmer 
   1482  1.1  mbalmer 
   1483  1.1  mbalmer 
   1484  1.2    lneto <h3>3.3.4 &ndash; <a name="3.3.4">Control Structures</a></h3><p>
   1485  1.2    lneto The control structures
   1486  1.2    lneto <b>if</b>, <b>while</b>, and <b>repeat</b> have the usual meaning and
   1487  1.2    lneto familiar syntax:
   1488  1.1  mbalmer 
   1489  1.1  mbalmer 
   1490  1.1  mbalmer 
   1491  1.1  mbalmer 
   1492  1.1  mbalmer <pre>
   1493  1.2    lneto 	stat ::= <b>while</b> exp <b>do</b> block <b>end</b>
   1494  1.2    lneto 	stat ::= <b>repeat</b> block <b>until</b> exp
   1495  1.2    lneto 	stat ::= <b>if</b> exp <b>then</b> block {<b>elseif</b> exp <b>then</b> block} [<b>else</b> block] <b>end</b>
   1496  1.1  mbalmer </pre><p>
   1497  1.2    lneto Lua also has a <b>for</b> statement, in two flavors (see <a href="#3.3.5">&sect;3.3.5</a>).
   1498  1.1  mbalmer 
   1499  1.1  mbalmer 
   1500  1.2    lneto <p>
   1501  1.2    lneto The condition expression of a
   1502  1.2    lneto control structure can return any value.
   1503  1.2    lneto Both <b>false</b> and <b>nil</b> are considered false.
   1504  1.2    lneto All values different from <b>nil</b> and <b>false</b> are considered true
   1505  1.2    lneto (in particular, the number 0 and the empty string are also true).
   1506  1.1  mbalmer 
   1507  1.1  mbalmer 
   1508  1.1  mbalmer <p>
   1509  1.2    lneto In the <b>repeat</b>&ndash;<b>until</b> loop,
   1510  1.2    lneto the inner block does not end at the <b>until</b> keyword,
   1511  1.2    lneto but only after the condition.
   1512  1.2    lneto So, the condition can refer to local variables
   1513  1.2    lneto declared inside the loop block.
   1514  1.1  mbalmer 
   1515  1.1  mbalmer 
   1516  1.1  mbalmer <p>
   1517  1.2    lneto The <b>goto</b> statement transfers the program control to a label.
   1518  1.2    lneto For syntactical reasons,
   1519  1.2    lneto labels in Lua are considered statements too:
   1520  1.1  mbalmer 
   1521  1.1  mbalmer 
   1522  1.1  mbalmer 
   1523  1.2    lneto <pre>
   1524  1.2    lneto 	stat ::= <b>goto</b> Name
   1525  1.2    lneto 	stat ::= label
   1526  1.2    lneto 	label ::= &lsquo;<b>::</b>&rsquo; Name &lsquo;<b>::</b>&rsquo;
   1527  1.2    lneto </pre>
   1528  1.1  mbalmer 
   1529  1.1  mbalmer <p>
   1530  1.2    lneto A label is visible in the entire block where it is defined,
   1531  1.2    lneto except
   1532  1.2    lneto inside nested blocks where a label with the same name is defined and
   1533  1.2    lneto inside nested functions.
   1534  1.2    lneto A goto may jump to any visible label as long as it does not
   1535  1.2    lneto enter into the scope of a local variable.
   1536  1.1  mbalmer 
   1537  1.1  mbalmer 
   1538  1.1  mbalmer <p>
   1539  1.2    lneto Labels and empty statements are called <em>void statements</em>,
   1540  1.2    lneto as they perform no actions.
   1541  1.1  mbalmer 
   1542  1.1  mbalmer 
   1543  1.1  mbalmer <p>
   1544  1.2    lneto The <b>break</b> statement terminates the execution of a
   1545  1.2    lneto <b>while</b>, <b>repeat</b>, or <b>for</b> loop,
   1546  1.2    lneto skipping to the next statement after the loop:
   1547  1.1  mbalmer 
   1548  1.1  mbalmer 
   1549  1.2    lneto <pre>
   1550  1.2    lneto 	stat ::= <b>break</b>
   1551  1.2    lneto </pre><p>
   1552  1.2    lneto A <b>break</b> ends the innermost enclosing loop.
   1553  1.1  mbalmer 
   1554  1.1  mbalmer 
   1555  1.1  mbalmer <p>
   1556  1.2    lneto The <b>return</b> statement is used to return values
   1557  1.3    lneto from a function or a chunk
   1558  1.3    lneto (which is an anonymous function).
   1559  1.1  mbalmer 
   1560  1.2    lneto Functions can return more than one value,
   1561  1.2    lneto so the syntax for the <b>return</b> statement is
   1562  1.1  mbalmer 
   1563  1.2    lneto <pre>
   1564  1.2    lneto 	stat ::= <b>return</b> [explist] [&lsquo;<b>;</b>&rsquo;]
   1565  1.2    lneto </pre>
   1566  1.1  mbalmer 
   1567  1.1  mbalmer <p>
   1568  1.2    lneto The <b>return</b> statement can only be written
   1569  1.2    lneto as the last statement of a block.
   1570  1.2    lneto If it is really necessary to <b>return</b> in the middle of a block,
   1571  1.2    lneto then an explicit inner block can be used,
   1572  1.2    lneto as in the idiom <code>do return end</code>,
   1573  1.2    lneto because now <b>return</b> is the last statement in its (inner) block.
   1574  1.1  mbalmer 
   1575  1.1  mbalmer 
   1576  1.1  mbalmer 
   1577  1.1  mbalmer 
   1578  1.1  mbalmer 
   1579  1.2    lneto <h3>3.3.5 &ndash; <a name="3.3.5">For Statement</a></h3>
   1580  1.1  mbalmer 
   1581  1.2    lneto <p>
   1582  1.1  mbalmer 
   1583  1.2    lneto The <b>for</b> statement has two forms:
   1584  1.2    lneto one numeric and one generic.
   1585  1.1  mbalmer 
   1586  1.1  mbalmer 
   1587  1.2    lneto <p>
   1588  1.2    lneto The numeric <b>for</b> loop repeats a block of code while a
   1589  1.2    lneto control variable runs through an arithmetic progression.
   1590  1.2    lneto It has the following syntax:
   1591  1.1  mbalmer 
   1592  1.2    lneto <pre>
   1593  1.2    lneto 	stat ::= <b>for</b> Name &lsquo;<b>=</b>&rsquo; exp &lsquo;<b>,</b>&rsquo; exp [&lsquo;<b>,</b>&rsquo; exp] <b>do</b> block <b>end</b>
   1594  1.2    lneto </pre><p>
   1595  1.2    lneto The <em>block</em> is repeated for <em>name</em> starting at the value of
   1596  1.2    lneto the first <em>exp</em>, until it passes the second <em>exp</em> by steps of the
   1597  1.2    lneto third <em>exp</em>.
   1598  1.2    lneto More precisely, a <b>for</b> statement like
   1599  1.1  mbalmer 
   1600  1.1  mbalmer <pre>
   1601  1.2    lneto      for v = <em>e1</em>, <em>e2</em>, <em>e3</em> do <em>block</em> end
   1602  1.1  mbalmer </pre><p>
   1603  1.2    lneto is equivalent to the code:
   1604  1.1  mbalmer 
   1605  1.1  mbalmer <pre>
   1606  1.2    lneto      do
   1607  1.2    lneto        local <em>var</em>, <em>limit</em>, <em>step</em> = tonumber(<em>e1</em>), tonumber(<em>e2</em>), tonumber(<em>e3</em>)
   1608  1.2    lneto        if not (<em>var</em> and <em>limit</em> and <em>step</em>) then error() end
   1609  1.2    lneto        <em>var</em> = <em>var</em> - <em>step</em>
   1610  1.2    lneto        while true do
   1611  1.2    lneto          <em>var</em> = <em>var</em> + <em>step</em>
   1612  1.2    lneto          if (<em>step</em> &gt;= 0 and <em>var</em> &gt; <em>limit</em>) or (<em>step</em> &lt; 0 and <em>var</em> &lt; <em>limit</em>) then
   1613  1.2    lneto            break
   1614  1.1  mbalmer          end
   1615  1.2    lneto          local v = <em>var</em>
   1616  1.2    lneto          <em>block</em>
   1617  1.1  mbalmer        end
   1618  1.1  mbalmer      end
   1619  1.2    lneto </pre>
   1620  1.2    lneto 
   1621  1.2    lneto <p>
   1622  1.2    lneto Note the following:
   1623  1.1  mbalmer 
   1624  1.2    lneto <ul>
   1625  1.1  mbalmer 
   1626  1.2    lneto <li>
   1627  1.2    lneto All three control expressions are evaluated only once,
   1628  1.2    lneto before the loop starts.
   1629  1.2    lneto They must all result in numbers.
   1630  1.1  mbalmer </li>
   1631  1.1  mbalmer 
   1632  1.2    lneto <li>
   1633  1.2    lneto <code><em>var</em></code>, <code><em>limit</em></code>, and <code><em>step</em></code> are invisible variables.
   1634  1.2    lneto The names shown here are for explanatory purposes only.
   1635  1.1  mbalmer </li>
   1636  1.1  mbalmer 
   1637  1.2    lneto <li>
   1638  1.2    lneto If the third expression (the step) is absent,
   1639  1.2    lneto then a step of&nbsp;1 is used.
   1640  1.2    lneto </li>
   1641  1.1  mbalmer 
   1642  1.2    lneto <li>
   1643  1.2    lneto You can use <b>break</b> and <b>goto</b> to exit a <b>for</b> loop.
   1644  1.1  mbalmer </li>
   1645  1.1  mbalmer 
   1646  1.2    lneto <li>
   1647  1.2    lneto The loop variable <code>v</code> is local to the loop body.
   1648  1.2    lneto If you need its value after the loop,
   1649  1.2    lneto assign it to another variable before exiting the loop.
   1650  1.1  mbalmer </li>
   1651  1.1  mbalmer 
   1652  1.2    lneto </ul>
   1653  1.1  mbalmer 
   1654  1.2    lneto <p>
   1655  1.2    lneto The generic <b>for</b> statement works over functions,
   1656  1.2    lneto called <em>iterators</em>.
   1657  1.2    lneto On each iteration, the iterator function is called to produce a new value,
   1658  1.2    lneto stopping when this new value is <b>nil</b>.
   1659  1.2    lneto The generic <b>for</b> loop has the following syntax:
   1660  1.1  mbalmer 
   1661  1.2    lneto <pre>
   1662  1.2    lneto 	stat ::= <b>for</b> namelist <b>in</b> explist <b>do</b> block <b>end</b>
   1663  1.2    lneto 	namelist ::= Name {&lsquo;<b>,</b>&rsquo; Name}
   1664  1.2    lneto </pre><p>
   1665  1.2    lneto A <b>for</b> statement like
   1666  1.1  mbalmer 
   1667  1.2    lneto <pre>
   1668  1.2    lneto      for <em>var_1</em>, &middot;&middot;&middot;, <em>var_n</em> in <em>explist</em> do <em>block</em> end
   1669  1.2    lneto </pre><p>
   1670  1.2    lneto is equivalent to the code:
   1671  1.1  mbalmer 
   1672  1.1  mbalmer <pre>
   1673  1.2    lneto      do
   1674  1.2    lneto        local <em>f</em>, <em>s</em>, <em>var</em> = <em>explist</em>
   1675  1.2    lneto        while true do
   1676  1.2    lneto          local <em>var_1</em>, &middot;&middot;&middot;, <em>var_n</em> = <em>f</em>(<em>s</em>, <em>var</em>)
   1677  1.2    lneto          if <em>var_1</em> == nil then break end
   1678  1.2    lneto          <em>var</em> = <em>var_1</em>
   1679  1.2    lneto          <em>block</em>
   1680  1.1  mbalmer        end
   1681  1.1  mbalmer      end
   1682  1.1  mbalmer </pre><p>
   1683  1.2    lneto Note the following:
   1684  1.2    lneto 
   1685  1.2    lneto <ul>
   1686  1.2    lneto 
   1687  1.2    lneto <li>
   1688  1.2    lneto <code><em>explist</em></code> is evaluated only once.
   1689  1.2    lneto Its results are an <em>iterator</em> function,
   1690  1.2    lneto a <em>state</em>,
   1691  1.2    lneto and an initial value for the first <em>iterator variable</em>.
   1692  1.1  mbalmer </li>
   1693  1.1  mbalmer 
   1694  1.2    lneto <li>
   1695  1.2    lneto <code><em>f</em></code>, <code><em>s</em></code>, and <code><em>var</em></code> are invisible variables.
   1696  1.2    lneto The names are here for explanatory purposes only.
   1697  1.2    lneto </li>
   1698  1.1  mbalmer 
   1699  1.2    lneto <li>
   1700  1.2    lneto You can use <b>break</b> to exit a <b>for</b> loop.
   1701  1.2    lneto </li>
   1702  1.1  mbalmer 
   1703  1.2    lneto <li>
   1704  1.2    lneto The loop variables <code><em>var_i</em></code> are local to the loop;
   1705  1.2    lneto you cannot use their values after the <b>for</b> ends.
   1706  1.2    lneto If you need these values,
   1707  1.2    lneto then assign them to other variables before breaking or exiting the loop.
   1708  1.1  mbalmer </li>
   1709  1.1  mbalmer 
   1710  1.2    lneto </ul>
   1711  1.2    lneto 
   1712  1.2    lneto 
   1713  1.1  mbalmer 
   1714  1.1  mbalmer 
   1715  1.2    lneto <h3>3.3.6 &ndash; <a name="3.3.6">Function Calls as Statements</a></h3><p>
   1716  1.2    lneto To allow possible side-effects,
   1717  1.2    lneto function calls can be executed as statements:
   1718  1.2    lneto 
   1719  1.1  mbalmer <pre>
   1720  1.2    lneto 	stat ::= functioncall
   1721  1.1  mbalmer </pre><p>
   1722  1.2    lneto In this case, all returned values are thrown away.
   1723  1.2    lneto Function calls are explained in <a href="#3.4.10">&sect;3.4.10</a>.
   1724  1.2    lneto 
   1725  1.2    lneto 
   1726  1.2    lneto 
   1727  1.1  mbalmer 
   1728  1.1  mbalmer 
   1729  1.2    lneto <h3>3.3.7 &ndash; <a name="3.3.7">Local Declarations</a></h3><p>
   1730  1.2    lneto Local variables can be declared anywhere inside a block.
   1731  1.2    lneto The declaration can include an initial assignment:
   1732  1.1  mbalmer 
   1733  1.1  mbalmer <pre>
   1734  1.2    lneto 	stat ::= <b>local</b> namelist [&lsquo;<b>=</b>&rsquo; explist]
   1735  1.1  mbalmer </pre><p>
   1736  1.2    lneto If present, an initial assignment has the same semantics
   1737  1.2    lneto of a multiple assignment (see <a href="#3.3.3">&sect;3.3.3</a>).
   1738  1.2    lneto Otherwise, all variables are initialized with <b>nil</b>.
   1739  1.2    lneto 
   1740  1.2    lneto 
   1741  1.2    lneto <p>
   1742  1.2    lneto A chunk is also a block (see <a href="#3.3.2">&sect;3.3.2</a>),
   1743  1.2    lneto and so local variables can be declared in a chunk outside any explicit block.
   1744  1.1  mbalmer 
   1745  1.1  mbalmer 
   1746  1.2    lneto <p>
   1747  1.2    lneto The visibility rules for local variables are explained in <a href="#3.5">&sect;3.5</a>.
   1748  1.2    lneto 
   1749  1.1  mbalmer 
   1750  1.1  mbalmer 
   1751  1.1  mbalmer 
   1752  1.1  mbalmer 
   1753  1.1  mbalmer 
   1754  1.1  mbalmer 
   1755  1.2    lneto <h2>3.4 &ndash; <a name="3.4">Expressions</a></h2>
   1756  1.1  mbalmer 
   1757  1.2    lneto <p>
   1758  1.2    lneto The basic expressions in Lua are the following:
   1759  1.1  mbalmer 
   1760  1.1  mbalmer <pre>
   1761  1.2    lneto 	exp ::= prefixexp
   1762  1.2    lneto 	exp ::= <b>nil</b> | <b>false</b> | <b>true</b>
   1763  1.3    lneto 	exp ::= Numeral
   1764  1.3    lneto 	exp ::= LiteralString
   1765  1.2    lneto 	exp ::= functiondef
   1766  1.2    lneto 	exp ::= tableconstructor
   1767  1.2    lneto 	exp ::= &lsquo;<b>...</b>&rsquo;
   1768  1.2    lneto 	exp ::= exp binop exp
   1769  1.2    lneto 	exp ::= unop exp
   1770  1.2    lneto 	prefixexp ::= var | functioncall | &lsquo;<b>(</b>&rsquo; exp &lsquo;<b>)</b>&rsquo;
   1771  1.2    lneto </pre>
   1772  1.2    lneto 
   1773  1.2    lneto <p>
   1774  1.3    lneto Numerals and literal strings are explained in <a href="#3.1">&sect;3.1</a>;
   1775  1.2    lneto variables are explained in <a href="#3.2">&sect;3.2</a>;
   1776  1.2    lneto function definitions are explained in <a href="#3.4.11">&sect;3.4.11</a>;
   1777  1.2    lneto function calls are explained in <a href="#3.4.10">&sect;3.4.10</a>;
   1778  1.2    lneto table constructors are explained in <a href="#3.4.9">&sect;3.4.9</a>.
   1779  1.2    lneto Vararg expressions,
   1780  1.2    lneto denoted by three dots ('<code>...</code>'), can only be used when
   1781  1.2    lneto directly inside a vararg function;
   1782  1.2    lneto they are explained in <a href="#3.4.11">&sect;3.4.11</a>.
   1783  1.2    lneto 
   1784  1.1  mbalmer 
   1785  1.2    lneto <p>
   1786  1.2    lneto Binary operators comprise arithmetic operators (see <a href="#3.4.1">&sect;3.4.1</a>),
   1787  1.2    lneto bitwise operators (see <a href="#3.4.2">&sect;3.4.2</a>),
   1788  1.2    lneto relational operators (see <a href="#3.4.4">&sect;3.4.4</a>), logical operators (see <a href="#3.4.5">&sect;3.4.5</a>),
   1789  1.2    lneto and the concatenation operator (see <a href="#3.4.6">&sect;3.4.6</a>).
   1790  1.2    lneto Unary operators comprise the unary minus (see <a href="#3.4.1">&sect;3.4.1</a>),
   1791  1.2    lneto the unary bitwise not (see <a href="#3.4.2">&sect;3.4.2</a>),
   1792  1.3    lneto the unary logical <b>not</b> (see <a href="#3.4.5">&sect;3.4.5</a>),
   1793  1.2    lneto and the unary <em>length operator</em> (see <a href="#3.4.7">&sect;3.4.7</a>).
   1794  1.1  mbalmer 
   1795  1.1  mbalmer 
   1796  1.2    lneto <p>
   1797  1.2    lneto Both function calls and vararg expressions can result in multiple values.
   1798  1.2    lneto If a function call is used as a statement (see <a href="#3.3.6">&sect;3.3.6</a>),
   1799  1.2    lneto then its return list is adjusted to zero elements,
   1800  1.2    lneto thus discarding all returned values.
   1801  1.2    lneto If an expression is used as the last (or the only) element
   1802  1.2    lneto of a list of expressions,
   1803  1.2    lneto then no adjustment is made
   1804  1.2    lneto (unless the expression is enclosed in parentheses).
   1805  1.2    lneto In all other contexts,
   1806  1.2    lneto Lua adjusts the result list to one element,
   1807  1.2    lneto either discarding all values except the first one
   1808  1.2    lneto or adding a single <b>nil</b> if there are no values.
   1809  1.1  mbalmer 
   1810  1.1  mbalmer 
   1811  1.2    lneto <p>
   1812  1.2    lneto Here are some examples:
   1813  1.1  mbalmer 
   1814  1.1  mbalmer <pre>
   1815  1.2    lneto      f()                -- adjusted to 0 results
   1816  1.2    lneto      g(f(), x)          -- f() is adjusted to 1 result
   1817  1.2    lneto      g(x, f())          -- g gets x plus all results from f()
   1818  1.2    lneto      a,b,c = f(), x     -- f() is adjusted to 1 result (c gets nil)
   1819  1.2    lneto      a,b = ...          -- a gets the first vararg parameter, b gets
   1820  1.2    lneto                         -- the second (both a and b can get nil if there
   1821  1.2    lneto                         -- is no corresponding vararg parameter)
   1822  1.2    lneto      
   1823  1.2    lneto      a,b,c = x, f()     -- f() is adjusted to 2 results
   1824  1.2    lneto      a,b,c = f()        -- f() is adjusted to 3 results
   1825  1.2    lneto      return f()         -- returns all results from f()
   1826  1.2    lneto      return ...         -- returns all received vararg parameters
   1827  1.2    lneto      return x,y,f()     -- returns x, y, and all results from f()
   1828  1.2    lneto      {f()}              -- creates a list with all results from f()
   1829  1.2    lneto      {...}              -- creates a list with all vararg parameters
   1830  1.2    lneto      {f(), nil}         -- f() is adjusted to 1 result
   1831  1.2    lneto </pre>
   1832  1.2    lneto 
   1833  1.2    lneto <p>
   1834  1.2    lneto Any expression enclosed in parentheses always results in only one value.
   1835  1.2    lneto Thus,
   1836  1.2    lneto <code>(f(x,y,z))</code> is always a single value,
   1837  1.2    lneto even if <code>f</code> returns several values.
   1838  1.2    lneto (The value of <code>(f(x,y,z))</code> is the first value returned by <code>f</code>
   1839  1.2    lneto or <b>nil</b> if <code>f</code> does not return any values.)
   1840  1.2    lneto 
   1841  1.1  mbalmer 
   1842  1.1  mbalmer 
   1843  1.2    lneto <h3>3.4.1 &ndash; <a name="3.4.1">Arithmetic Operators</a></h3><p>
   1844  1.2    lneto Lua supports the following arithmetic operators:
   1845  1.1  mbalmer 
   1846  1.3    lneto <ul>
   1847  1.3    lneto <li><b><code>+</code>: </b>addition</li>
   1848  1.3    lneto <li><b><code>-</code>: </b>subtraction</li>
   1849  1.3    lneto <li><b><code>*</code>: </b>multiplication</li>
   1850  1.3    lneto <li><b><code>/</code>: </b>float division</li>
   1851  1.3    lneto <li><b><code>//</code>: </b>floor division</li>
   1852  1.3    lneto <li><b><code>%</code>: </b>modulo</li>
   1853  1.3    lneto <li><b><code>^</code>: </b>exponentiation</li>
   1854  1.3    lneto <li><b><code>-</code>: </b>unary minus</li>
   1855  1.3    lneto </ul>
   1856  1.1  mbalmer 
   1857  1.2    lneto <p>
   1858  1.3    lneto With the exception of exponentiation and float division,
   1859  1.2    lneto the arithmetic operators work as follows:
   1860  1.2    lneto If both operands are integers,
   1861  1.2    lneto the operation is performed over integers and the result is an integer.
   1862  1.2    lneto Otherwise, if both operands are numbers
   1863  1.2    lneto or strings that can be converted to
   1864  1.2    lneto numbers (see <a href="#3.4.3">&sect;3.4.3</a>),
   1865  1.2    lneto then they are converted to floats,
   1866  1.2    lneto the operation is performed following the usual rules
   1867  1.2    lneto for floating-point arithmetic
   1868  1.2    lneto (usually the IEEE 754 standard),
   1869  1.2    lneto and the result is a float.
   1870  1.1  mbalmer 
   1871  1.1  mbalmer 
   1872  1.1  mbalmer <p>
   1873  1.3    lneto Exponentiation and float division (<code>/</code>)
   1874  1.2    lneto always convert their operands to floats
   1875  1.2    lneto and the result is always a float.
   1876  1.3    lneto Exponentiation uses the ISO&nbsp;C function <code>pow</code>,
   1877  1.2    lneto so that it works for non-integer exponents too.
   1878  1.1  mbalmer 
   1879  1.1  mbalmer 
   1880  1.1  mbalmer <p>
   1881  1.3    lneto Floor division (<code>//</code>) is a division 
   1882  1.3    lneto that rounds the quotient towards minus infinite,
   1883  1.3    lneto that is, the floor of the division of its operands.
   1884  1.1  mbalmer 
   1885  1.1  mbalmer 
   1886  1.1  mbalmer <p>
   1887  1.2    lneto Modulo is defined as the remainder of a division
   1888  1.3    lneto that rounds the quotient towards minus infinite (floor division).
   1889  1.1  mbalmer 
   1890  1.1  mbalmer 
   1891  1.1  mbalmer <p>
   1892  1.2    lneto In case of overflows in integer arithmetic,
   1893  1.2    lneto all operations <em>wrap around</em>,
   1894  1.2    lneto according to the usual rules of two-complement arithmetic.
   1895  1.3    lneto (In other words,
   1896  1.3    lneto they return the unique representable integer
   1897  1.3    lneto that is equal modulo <em>2<sup>64</sup></em> to the mathematical result.)
   1898  1.2    lneto 
   1899  1.2    lneto 
   1900  1.2    lneto 
   1901  1.2    lneto <h3>3.4.2 &ndash; <a name="3.4.2">Bitwise Operators</a></h3><p>
   1902  1.2    lneto Lua supports the following bitwise operators:
   1903  1.1  mbalmer 
   1904  1.3    lneto <ul>
   1905  1.3    lneto <li><b><code>&amp;</code>: </b>bitwise and</li>
   1906  1.3    lneto <li><b><code>&#124;</code>: </b>bitwise or</li>
   1907  1.3    lneto <li><b><code>~</code>: </b>bitwise exclusive or</li>
   1908  1.3    lneto <li><b><code>&gt;&gt;</code>: </b>right shift</li>
   1909  1.3    lneto <li><b><code>&lt;&lt;</code>: </b>left shift</li>
   1910  1.3    lneto <li><b><code>~</code>: </b>unary bitwise not</li>
   1911  1.3    lneto </ul>
   1912  1.1  mbalmer 
   1913  1.1  mbalmer <p>
   1914  1.2    lneto All bitwise operations convert its operands to integers
   1915  1.2    lneto (see <a href="#3.4.3">&sect;3.4.3</a>),
   1916  1.2    lneto operate on all bits of those integers,
   1917  1.2    lneto and result in an integer.
   1918  1.1  mbalmer 
   1919  1.1  mbalmer 
   1920  1.1  mbalmer <p>
   1921  1.2    lneto Both right and left shifts fill the vacant bits with zeros.
   1922  1.2    lneto Negative displacements shift to the other direction;
   1923  1.2    lneto displacements with absolute values equal to or higher than
   1924  1.2    lneto the number of bits in an integer
   1925  1.3    lneto result in zero (as all bits are shifted out).
   1926  1.2    lneto 
   1927  1.2    lneto 
   1928  1.2    lneto 
   1929  1.2    lneto 
   1930  1.2    lneto 
   1931  1.2    lneto <h3>3.4.3 &ndash; <a name="3.4.3">Coercions and Conversions</a></h3><p>
   1932  1.2    lneto Lua provides some automatic conversions between some
   1933  1.2    lneto types and representations at run time.
   1934  1.3    lneto Bitwise operators always convert float operands to integers.
   1935  1.3    lneto Exponentiation and float division
   1936  1.3    lneto always convert integer operands to floats.
   1937  1.3    lneto All other arithmetic operations applied to mixed numbers
   1938  1.2    lneto (integers and floats) convert the integer operand to a float;
   1939  1.2    lneto this is called the <em>usual rule</em>.
   1940  1.2    lneto The C API also converts both integers to floats and
   1941  1.2    lneto floats to integers, as needed.
   1942  1.2    lneto Moreover, string concatenation accepts numbers as arguments,
   1943  1.2    lneto besides strings. 
   1944  1.1  mbalmer 
   1945  1.1  mbalmer 
   1946  1.1  mbalmer <p>
   1947  1.2    lneto Lua also converts strings to numbers,
   1948  1.2    lneto whenever a number is expected.
   1949  1.1  mbalmer 
   1950  1.1  mbalmer 
   1951  1.2    lneto <p>
   1952  1.2    lneto In a conversion from integer to float,
   1953  1.2    lneto if the integer value has an exact representation as a float,
   1954  1.2    lneto that is the result.
   1955  1.2    lneto Otherwise,
   1956  1.3    lneto the conversion gets the nearest higher or
   1957  1.3    lneto the nearest lower representable value.
   1958  1.2    lneto This kind of conversion never fails.
   1959  1.1  mbalmer 
   1960  1.1  mbalmer 
   1961  1.2    lneto <p>
   1962  1.2    lneto The conversion from float to integer
   1963  1.3    lneto checks whether the float has an exact representation as an integer
   1964  1.3    lneto (that is, the float has an integral value and
   1965  1.3    lneto it is in the range of integer representation).
   1966  1.3    lneto If it does, that representation is the result.
   1967  1.2    lneto Otherwise, the conversion fails.
   1968  1.1  mbalmer 
   1969  1.1  mbalmer 
   1970  1.1  mbalmer <p>
   1971  1.2    lneto The conversion from strings to numbers goes as follows:
   1972  1.2    lneto First, the string is converted to an integer or a float,
   1973  1.2    lneto following its syntax and the rules of the Lua lexer.
   1974  1.2    lneto (The string may have also leading and trailing spaces and a sign.)
   1975  1.2    lneto Then, the resulting number is converted to the required type
   1976  1.2    lneto (float or integer) according to the previous rules.
   1977  1.1  mbalmer 
   1978  1.1  mbalmer 
   1979  1.1  mbalmer <p>
   1980  1.3    lneto The conversion from numbers to strings uses a
   1981  1.3    lneto non-specified human-readable format.
   1982  1.2    lneto For complete control over how numbers are converted to strings,
   1983  1.2    lneto use the <code>format</code> function from the string library
   1984  1.2    lneto (see <a href="#pdf-string.format"><code>string.format</code></a>).
   1985  1.2    lneto 
   1986  1.2    lneto 
   1987  1.2    lneto 
   1988  1.2    lneto 
   1989  1.2    lneto 
   1990  1.2    lneto <h3>3.4.4 &ndash; <a name="3.4.4">Relational Operators</a></h3><p>
   1991  1.2    lneto Lua supports the following relational operators:
   1992  1.3    lneto 
   1993  1.3    lneto <ul>
   1994  1.3    lneto <li><b><code>==</code>: </b>equality</li>
   1995  1.3    lneto <li><b><code>~=</code>: </b>inequality</li>
   1996  1.3    lneto <li><b><code>&lt;</code>: </b>less than</li>
   1997  1.3    lneto <li><b><code>&gt;</code>: </b>greater than</li>
   1998  1.3    lneto <li><b><code>&lt;=</code>: </b>less or equal</li>
   1999  1.3    lneto <li><b><code>&gt;=</code>: </b>greater or equal</li>
   2000  1.3    lneto </ul><p>
   2001  1.2    lneto These operators always result in <b>false</b> or <b>true</b>.
   2002  1.1  mbalmer 
   2003  1.1  mbalmer 
   2004  1.1  mbalmer <p>
   2005  1.2    lneto Equality (<code>==</code>) first compares the type of its operands.
   2006  1.2    lneto If the types are different, then the result is <b>false</b>.
   2007  1.2    lneto Otherwise, the values of the operands are compared.
   2008  1.2    lneto Strings are compared in the obvious way.
   2009  1.2    lneto Numbers follow the usual rule for binary operations:
   2010  1.2    lneto if both operands are integers,
   2011  1.3    lneto they are compared as integers;
   2012  1.2    lneto otherwise, they are converted to floats
   2013  1.2    lneto and compared as such.
   2014  1.1  mbalmer 
   2015  1.1  mbalmer 
   2016  1.1  mbalmer <p>
   2017  1.2    lneto Tables, userdata, and threads
   2018  1.2    lneto are compared by reference:
   2019  1.2    lneto two objects are considered equal only if they are the same object.
   2020  1.2    lneto Every time you create a new object
   2021  1.2    lneto (a table, userdata, or thread),
   2022  1.2    lneto this new object is different from any previously existing object.
   2023  1.2    lneto Closures with the same reference are always equal.
   2024  1.2    lneto Closures with any detectable difference
   2025  1.2    lneto (different behavior, different definition) are always different.
   2026  1.1  mbalmer 
   2027  1.1  mbalmer 
   2028  1.1  mbalmer <p>
   2029  1.2    lneto You can change the way that Lua compares tables and userdata
   2030  1.2    lneto by using the "eq" metamethod (see <a href="#2.4">&sect;2.4</a>).
   2031  1.1  mbalmer 
   2032  1.1  mbalmer 
   2033  1.2    lneto <p>
   2034  1.3    lneto Equality comparisons do not convert strings to numbers
   2035  1.2    lneto or vice versa.
   2036  1.2    lneto Thus, <code>"0"==0</code> evaluates to <b>false</b>,
   2037  1.2    lneto and <code>t[0]</code> and <code>t["0"]</code> denote different
   2038  1.2    lneto entries in a table.
   2039  1.1  mbalmer 
   2040  1.1  mbalmer 
   2041  1.1  mbalmer <p>
   2042  1.2    lneto The operator <code>~=</code> is exactly the negation of equality (<code>==</code>).
   2043  1.1  mbalmer 
   2044  1.1  mbalmer 
   2045  1.2    lneto <p>
   2046  1.2    lneto The order operators work as follows.
   2047  1.2    lneto If both arguments are numbers,
   2048  1.2    lneto then they are compared following
   2049  1.2    lneto the usual rule for binary operations.
   2050  1.2    lneto Otherwise, if both arguments are strings,
   2051  1.2    lneto then their values are compared according to the current locale.
   2052  1.2    lneto Otherwise, Lua tries to call the "lt" or the "le"
   2053  1.2    lneto metamethod (see <a href="#2.4">&sect;2.4</a>).
   2054  1.2    lneto A comparison <code>a &gt; b</code> is translated to <code>b &lt; a</code>
   2055  1.2    lneto and <code>a &gt;= b</code> is translated to <code>b &lt;= a</code>.
   2056  1.2    lneto 
   2057  1.2    lneto 
   2058  1.2    lneto 
   2059  1.2    lneto 
   2060  1.2    lneto 
   2061  1.2    lneto <h3>3.4.5 &ndash; <a name="3.4.5">Logical Operators</a></h3><p>
   2062  1.2    lneto The logical operators in Lua are
   2063  1.2    lneto <b>and</b>, <b>or</b>, and <b>not</b>.
   2064  1.2    lneto Like the control structures (see <a href="#3.3.4">&sect;3.3.4</a>),
   2065  1.2    lneto all logical operators consider both <b>false</b> and <b>nil</b> as false
   2066  1.2    lneto and anything else as true.
   2067  1.2    lneto 
   2068  1.2    lneto 
   2069  1.2    lneto <p>
   2070  1.2    lneto The negation operator <b>not</b> always returns <b>false</b> or <b>true</b>.
   2071  1.2    lneto The conjunction operator <b>and</b> returns its first argument
   2072  1.2    lneto if this value is <b>false</b> or <b>nil</b>;
   2073  1.2    lneto otherwise, <b>and</b> returns its second argument.
   2074  1.2    lneto The disjunction operator <b>or</b> returns its first argument
   2075  1.2    lneto if this value is different from <b>nil</b> and <b>false</b>;
   2076  1.2    lneto otherwise, <b>or</b> returns its second argument.
   2077  1.2    lneto Both <b>and</b> and <b>or</b> use short-circuit evaluation;
   2078  1.2    lneto that is,
   2079  1.2    lneto the second operand is evaluated only if necessary.
   2080  1.2    lneto Here are some examples:
   2081  1.2    lneto 
   2082  1.2    lneto <pre>
   2083  1.2    lneto      10 or 20            --&gt; 10
   2084  1.2    lneto      10 or error()       --&gt; 10
   2085  1.2    lneto      nil or "a"          --&gt; "a"
   2086  1.2    lneto      nil and 10          --&gt; nil
   2087  1.2    lneto      false and error()   --&gt; false
   2088  1.2    lneto      false and nil       --&gt; false
   2089  1.2    lneto      false or nil        --&gt; nil
   2090  1.2    lneto      10 and 20           --&gt; 20
   2091  1.2    lneto </pre><p>
   2092  1.2    lneto (In this manual,
   2093  1.2    lneto <code>--&gt;</code> indicates the result of the preceding expression.)
   2094  1.2    lneto 
   2095  1.2    lneto 
   2096  1.2    lneto 
   2097  1.2    lneto 
   2098  1.2    lneto 
   2099  1.2    lneto <h3>3.4.6 &ndash; <a name="3.4.6">Concatenation</a></h3><p>
   2100  1.2    lneto The string concatenation operator in Lua is
   2101  1.2    lneto denoted by two dots ('<code>..</code>').
   2102  1.2    lneto If both operands are strings or numbers, then they are converted to
   2103  1.2    lneto strings according to the rules described in <a href="#3.4.3">&sect;3.4.3</a>.
   2104  1.2    lneto Otherwise, the <code>__concat</code> metamethod is called (see <a href="#2.4">&sect;2.4</a>).
   2105  1.2    lneto 
   2106  1.2    lneto 
   2107  1.2    lneto 
   2108  1.2    lneto 
   2109  1.2    lneto 
   2110  1.2    lneto <h3>3.4.7 &ndash; <a name="3.4.7">The Length Operator</a></h3>
   2111  1.2    lneto 
   2112  1.2    lneto <p>
   2113  1.2    lneto The length operator is denoted by the unary prefix operator <code>#</code>.
   2114  1.2    lneto The length of a string is its number of bytes
   2115  1.2    lneto (that is, the usual meaning of string length when each
   2116  1.2    lneto character is one byte).
   2117  1.2    lneto 
   2118  1.2    lneto 
   2119  1.2    lneto <p>
   2120  1.2    lneto A program can modify the behavior of the length operator for
   2121  1.2    lneto any value but strings through the <code>__len</code> metamethod (see <a href="#2.4">&sect;2.4</a>).
   2122  1.2    lneto 
   2123  1.2    lneto 
   2124  1.2    lneto <p>
   2125  1.2    lneto Unless a <code>__len</code> metamethod is given,
   2126  1.2    lneto the length of a table <code>t</code> is only defined if the
   2127  1.2    lneto table is a <em>sequence</em>,
   2128  1.2    lneto that is,
   2129  1.2    lneto the set of its positive numeric keys is equal to <em>{1..n}</em>
   2130  1.2    lneto for some non-negative integer <em>n</em>.
   2131  1.2    lneto In that case, <em>n</em> is its length.
   2132  1.2    lneto Note that a table like
   2133  1.2    lneto 
   2134  1.2    lneto <pre>
   2135  1.2    lneto      {10, 20, nil, 40}
   2136  1.2    lneto </pre><p>
   2137  1.2    lneto is not a sequence, because it has the key <code>4</code>
   2138  1.2    lneto but does not have the key <code>3</code>.
   2139  1.2    lneto (So, there is no <em>n</em> such that the set <em>{1..n}</em> is equal
   2140  1.2    lneto to the set of positive numeric keys of that table.)
   2141  1.2    lneto Note, however, that non-numeric keys do not interfere
   2142  1.2    lneto with whether a table is a sequence.
   2143  1.2    lneto 
   2144  1.2    lneto 
   2145  1.2    lneto 
   2146  1.2    lneto 
   2147  1.2    lneto 
   2148  1.2    lneto <h3>3.4.8 &ndash; <a name="3.4.8">Precedence</a></h3><p>
   2149  1.2    lneto Operator precedence in Lua follows the table below,
   2150  1.2    lneto from lower to higher priority:
   2151  1.2    lneto 
   2152  1.2    lneto <pre>
   2153  1.2    lneto      or
   2154  1.2    lneto      and
   2155  1.2    lneto      &lt;     &gt;     &lt;=    &gt;=    ~=    ==
   2156  1.2    lneto      |
   2157  1.2    lneto      ~
   2158  1.2    lneto      &amp;
   2159  1.2    lneto      &lt;&lt;    &gt;&gt;
   2160  1.2    lneto      ..
   2161  1.2    lneto      +     -
   2162  1.2    lneto      *     /     //    %
   2163  1.2    lneto      unary operators (not   #     -     ~)
   2164  1.2    lneto      ^
   2165  1.2    lneto </pre><p>
   2166  1.2    lneto As usual,
   2167  1.2    lneto you can use parentheses to change the precedences of an expression.
   2168  1.2    lneto The concatenation ('<code>..</code>') and exponentiation ('<code>^</code>')
   2169  1.2    lneto operators are right associative.
   2170  1.2    lneto All other binary operators are left associative.
   2171  1.2    lneto 
   2172  1.2    lneto 
   2173  1.2    lneto 
   2174  1.2    lneto 
   2175  1.2    lneto 
   2176  1.2    lneto <h3>3.4.9 &ndash; <a name="3.4.9">Table Constructors</a></h3><p>
   2177  1.2    lneto Table constructors are expressions that create tables.
   2178  1.2    lneto Every time a constructor is evaluated, a new table is created.
   2179  1.2    lneto A constructor can be used to create an empty table
   2180  1.2    lneto or to create a table and initialize some of its fields.
   2181  1.2    lneto The general syntax for constructors is
   2182  1.2    lneto 
   2183  1.2    lneto <pre>
   2184  1.2    lneto 	tableconstructor ::= &lsquo;<b>{</b>&rsquo; [fieldlist] &lsquo;<b>}</b>&rsquo;
   2185  1.2    lneto 	fieldlist ::= field {fieldsep field} [fieldsep]
   2186  1.2    lneto 	field ::= &lsquo;<b>[</b>&rsquo; exp &lsquo;<b>]</b>&rsquo; &lsquo;<b>=</b>&rsquo; exp | Name &lsquo;<b>=</b>&rsquo; exp | exp
   2187  1.2    lneto 	fieldsep ::= &lsquo;<b>,</b>&rsquo; | &lsquo;<b>;</b>&rsquo;
   2188  1.2    lneto </pre>
   2189  1.2    lneto 
   2190  1.2    lneto <p>
   2191  1.2    lneto Each field of the form <code>[exp1] = exp2</code> adds to the new table an entry
   2192  1.2    lneto with key <code>exp1</code> and value <code>exp2</code>.
   2193  1.2    lneto A field of the form <code>name = exp</code> is equivalent to
   2194  1.2    lneto <code>["name"] = exp</code>.
   2195  1.2    lneto Finally, fields of the form <code>exp</code> are equivalent to
   2196  1.3    lneto <code>[i] = exp</code>, where <code>i</code> are consecutive integers
   2197  1.2    lneto starting with 1.
   2198  1.2    lneto Fields in the other formats do not affect this counting.
   2199  1.2    lneto For example,
   2200  1.2    lneto 
   2201  1.2    lneto <pre>
   2202  1.2    lneto      a = { [f(1)] = g; "x", "y"; x = 1, f(x), [30] = 23; 45 }
   2203  1.2    lneto </pre><p>
   2204  1.2    lneto is equivalent to
   2205  1.2    lneto 
   2206  1.2    lneto <pre>
   2207  1.2    lneto      do
   2208  1.2    lneto        local t = {}
   2209  1.2    lneto        t[f(1)] = g
   2210  1.2    lneto        t[1] = "x"         -- 1st exp
   2211  1.2    lneto        t[2] = "y"         -- 2nd exp
   2212  1.2    lneto        t.x = 1            -- t["x"] = 1
   2213  1.2    lneto        t[3] = f(x)        -- 3rd exp
   2214  1.2    lneto        t[30] = 23
   2215  1.2    lneto        t[4] = 45          -- 4th exp
   2216  1.2    lneto        a = t
   2217  1.2    lneto      end
   2218  1.2    lneto </pre>
   2219  1.2    lneto 
   2220  1.2    lneto <p>
   2221  1.3    lneto The order of the assignments in a constructor is undefined.
   2222  1.3    lneto (This order would be relevant only when there are repeated keys.)
   2223  1.3    lneto 
   2224  1.3    lneto 
   2225  1.3    lneto <p>
   2226  1.2    lneto If the last field in the list has the form <code>exp</code>
   2227  1.2    lneto and the expression is a function call or a vararg expression,
   2228  1.2    lneto then all values returned by this expression enter the list consecutively
   2229  1.2    lneto (see <a href="#3.4.10">&sect;3.4.10</a>).
   2230  1.2    lneto 
   2231  1.2    lneto 
   2232  1.2    lneto <p>
   2233  1.2    lneto The field list can have an optional trailing separator,
   2234  1.2    lneto as a convenience for machine-generated code.
   2235  1.2    lneto 
   2236  1.2    lneto 
   2237  1.2    lneto 
   2238  1.2    lneto 
   2239  1.2    lneto 
   2240  1.2    lneto <h3>3.4.10 &ndash; <a name="3.4.10">Function Calls</a></h3><p>
   2241  1.2    lneto A function call in Lua has the following syntax:
   2242  1.2    lneto 
   2243  1.2    lneto <pre>
   2244  1.2    lneto 	functioncall ::= prefixexp args
   2245  1.2    lneto </pre><p>
   2246  1.2    lneto In a function call,
   2247  1.2    lneto first prefixexp and args are evaluated.
   2248  1.2    lneto If the value of prefixexp has type <em>function</em>,
   2249  1.2    lneto then this function is called
   2250  1.2    lneto with the given arguments.
   2251  1.2    lneto Otherwise, the prefixexp "call" metamethod is called,
   2252  1.2    lneto having as first parameter the value of prefixexp,
   2253  1.2    lneto followed by the original call arguments
   2254  1.2    lneto (see <a href="#2.4">&sect;2.4</a>).
   2255  1.2    lneto 
   2256  1.2    lneto 
   2257  1.2    lneto <p>
   2258  1.2    lneto The form
   2259  1.2    lneto 
   2260  1.2    lneto <pre>
   2261  1.2    lneto 	functioncall ::= prefixexp &lsquo;<b>:</b>&rsquo; Name args
   2262  1.2    lneto </pre><p>
   2263  1.2    lneto can be used to call "methods".
   2264  1.2    lneto A call <code>v:name(<em>args</em>)</code>
   2265  1.2    lneto is syntactic sugar for <code>v.name(v,<em>args</em>)</code>,
   2266  1.2    lneto except that <code>v</code> is evaluated only once.
   2267  1.2    lneto 
   2268  1.2    lneto 
   2269  1.2    lneto <p>
   2270  1.2    lneto Arguments have the following syntax:
   2271  1.2    lneto 
   2272  1.2    lneto <pre>
   2273  1.2    lneto 	args ::= &lsquo;<b>(</b>&rsquo; [explist] &lsquo;<b>)</b>&rsquo;
   2274  1.2    lneto 	args ::= tableconstructor
   2275  1.3    lneto 	args ::= LiteralString
   2276  1.2    lneto </pre><p>
   2277  1.2    lneto All argument expressions are evaluated before the call.
   2278  1.2    lneto A call of the form <code>f{<em>fields</em>}</code> is
   2279  1.2    lneto syntactic sugar for <code>f({<em>fields</em>})</code>;
   2280  1.2    lneto that is, the argument list is a single new table.
   2281  1.2    lneto A call of the form <code>f'<em>string</em>'</code>
   2282  1.2    lneto (or <code>f"<em>string</em>"</code> or <code>f[[<em>string</em>]]</code>)
   2283  1.2    lneto is syntactic sugar for <code>f('<em>string</em>')</code>;
   2284  1.2    lneto that is, the argument list is a single literal string.
   2285  1.2    lneto 
   2286  1.2    lneto 
   2287  1.2    lneto <p>
   2288  1.2    lneto A call of the form <code>return <em>functioncall</em></code> is called
   2289  1.2    lneto a <em>tail call</em>.
   2290  1.2    lneto Lua implements <em>proper tail calls</em>
   2291  1.2    lneto (or <em>proper tail recursion</em>):
   2292  1.2    lneto in a tail call,
   2293  1.2    lneto the called function reuses the stack entry of the calling function.
   2294  1.2    lneto Therefore, there is no limit on the number of nested tail calls that
   2295  1.2    lneto a program can execute.
   2296  1.2    lneto However, a tail call erases any debug information about the
   2297  1.2    lneto calling function.
   2298  1.2    lneto Note that a tail call only happens with a particular syntax,
   2299  1.2    lneto where the <b>return</b> has one single function call as argument;
   2300  1.2    lneto this syntax makes the calling function return exactly
   2301  1.2    lneto the returns of the called function.
   2302  1.2    lneto So, none of the following examples are tail calls:
   2303  1.2    lneto 
   2304  1.2    lneto <pre>
   2305  1.2    lneto      return (f(x))        -- results adjusted to 1
   2306  1.2    lneto      return 2 * f(x)
   2307  1.2    lneto      return x, f(x)       -- additional results
   2308  1.2    lneto      f(x); return         -- results discarded
   2309  1.2    lneto      return x or f(x)     -- results adjusted to 1
   2310  1.2    lneto </pre>
   2311  1.2    lneto 
   2312  1.2    lneto 
   2313  1.2    lneto 
   2314  1.2    lneto 
   2315  1.2    lneto <h3>3.4.11 &ndash; <a name="3.4.11">Function Definitions</a></h3>
   2316  1.2    lneto 
   2317  1.2    lneto <p>
   2318  1.2    lneto The syntax for function definition is
   2319  1.2    lneto 
   2320  1.2    lneto <pre>
   2321  1.2    lneto 	functiondef ::= <b>function</b> funcbody
   2322  1.2    lneto 	funcbody ::= &lsquo;<b>(</b>&rsquo; [parlist] &lsquo;<b>)</b>&rsquo; block <b>end</b>
   2323  1.2    lneto </pre>
   2324  1.2    lneto 
   2325  1.2    lneto <p>
   2326  1.2    lneto The following syntactic sugar simplifies function definitions:
   2327  1.2    lneto 
   2328  1.2    lneto <pre>
   2329  1.2    lneto 	stat ::= <b>function</b> funcname funcbody
   2330  1.2    lneto 	stat ::= <b>local</b> <b>function</b> Name funcbody
   2331  1.2    lneto 	funcname ::= Name {&lsquo;<b>.</b>&rsquo; Name} [&lsquo;<b>:</b>&rsquo; Name]
   2332  1.2    lneto </pre><p>
   2333  1.2    lneto The statement
   2334  1.2    lneto 
   2335  1.2    lneto <pre>
   2336  1.2    lneto      function f () <em>body</em> end
   2337  1.2    lneto </pre><p>
   2338  1.2    lneto translates to
   2339  1.2    lneto 
   2340  1.2    lneto <pre>
   2341  1.2    lneto      f = function () <em>body</em> end
   2342  1.2    lneto </pre><p>
   2343  1.2    lneto The statement
   2344  1.2    lneto 
   2345  1.2    lneto <pre>
   2346  1.2    lneto      function t.a.b.c.f () <em>body</em> end
   2347  1.2    lneto </pre><p>
   2348  1.2    lneto translates to
   2349  1.2    lneto 
   2350  1.2    lneto <pre>
   2351  1.2    lneto      t.a.b.c.f = function () <em>body</em> end
   2352  1.2    lneto </pre><p>
   2353  1.2    lneto The statement
   2354  1.2    lneto 
   2355  1.2    lneto <pre>
   2356  1.2    lneto      local function f () <em>body</em> end
   2357  1.2    lneto </pre><p>
   2358  1.2    lneto translates to
   2359  1.2    lneto 
   2360  1.2    lneto <pre>
   2361  1.2    lneto      local f; f = function () <em>body</em> end
   2362  1.2    lneto </pre><p>
   2363  1.2    lneto not to
   2364  1.2    lneto 
   2365  1.2    lneto <pre>
   2366  1.2    lneto      local f = function () <em>body</em> end
   2367  1.2    lneto </pre><p>
   2368  1.2    lneto (This only makes a difference when the body of the function
   2369  1.2    lneto contains references to <code>f</code>.)
   2370  1.2    lneto 
   2371  1.2    lneto 
   2372  1.2    lneto <p>
   2373  1.2    lneto A function definition is an executable expression,
   2374  1.2    lneto whose value has type <em>function</em>.
   2375  1.2    lneto When Lua precompiles a chunk,
   2376  1.2    lneto all its function bodies are precompiled too.
   2377  1.2    lneto Then, whenever Lua executes the function definition,
   2378  1.2    lneto the function is <em>instantiated</em> (or <em>closed</em>).
   2379  1.2    lneto This function instance (or <em>closure</em>)
   2380  1.2    lneto is the final value of the expression.
   2381  1.2    lneto 
   2382  1.2    lneto 
   2383  1.2    lneto <p>
   2384  1.2    lneto Parameters act as local variables that are
   2385  1.2    lneto initialized with the argument values:
   2386  1.2    lneto 
   2387  1.2    lneto <pre>
   2388  1.2    lneto 	parlist ::= namelist [&lsquo;<b>,</b>&rsquo; &lsquo;<b>...</b>&rsquo;] | &lsquo;<b>...</b>&rsquo;
   2389  1.2    lneto </pre><p>
   2390  1.2    lneto When a function is called,
   2391  1.2    lneto the list of arguments is adjusted to
   2392  1.2    lneto the length of the list of parameters,
   2393  1.2    lneto unless the function is a <em>vararg function</em>,
   2394  1.2    lneto which is indicated by three dots ('<code>...</code>')
   2395  1.2    lneto at the end of its parameter list.
   2396  1.2    lneto A vararg function does not adjust its argument list;
   2397  1.2    lneto instead, it collects all extra arguments and supplies them
   2398  1.2    lneto to the function through a <em>vararg expression</em>,
   2399  1.2    lneto which is also written as three dots.
   2400  1.2    lneto The value of this expression is a list of all actual extra arguments,
   2401  1.2    lneto similar to a function with multiple results.
   2402  1.2    lneto If a vararg expression is used inside another expression
   2403  1.2    lneto or in the middle of a list of expressions,
   2404  1.2    lneto then its return list is adjusted to one element.
   2405  1.2    lneto If the expression is used as the last element of a list of expressions,
   2406  1.2    lneto then no adjustment is made
   2407  1.2    lneto (unless that last expression is enclosed in parentheses).
   2408  1.2    lneto 
   2409  1.2    lneto 
   2410  1.2    lneto <p>
   2411  1.2    lneto As an example, consider the following definitions:
   2412  1.2    lneto 
   2413  1.2    lneto <pre>
   2414  1.2    lneto      function f(a, b) end
   2415  1.2    lneto      function g(a, b, ...) end
   2416  1.2    lneto      function r() return 1,2,3 end
   2417  1.2    lneto </pre><p>
   2418  1.2    lneto Then, we have the following mapping from arguments to parameters and
   2419  1.2    lneto to the vararg expression:
   2420  1.1  mbalmer 
   2421  1.1  mbalmer <pre>
   2422  1.2    lneto      CALL            PARAMETERS
   2423  1.2    lneto      
   2424  1.2    lneto      f(3)             a=3, b=nil
   2425  1.2    lneto      f(3, 4)          a=3, b=4
   2426  1.2    lneto      f(3, 4, 5)       a=3, b=4
   2427  1.2    lneto      f(r(), 10)       a=1, b=10
   2428  1.2    lneto      f(r())           a=1, b=2
   2429  1.2    lneto      
   2430  1.2    lneto      g(3)             a=3, b=nil, ... --&gt;  (nothing)
   2431  1.2    lneto      g(3, 4)          a=3, b=4,   ... --&gt;  (nothing)
   2432  1.2    lneto      g(3, 4, 5, 8)    a=3, b=4,   ... --&gt;  5  8
   2433  1.2    lneto      g(5, r())        a=5, b=1,   ... --&gt;  2  3
   2434  1.1  mbalmer </pre>
   2435  1.1  mbalmer 
   2436  1.1  mbalmer <p>
   2437  1.2    lneto Results are returned using the <b>return</b> statement (see <a href="#3.3.4">&sect;3.3.4</a>).
   2438  1.2    lneto If control reaches the end of a function
   2439  1.2    lneto without encountering a <b>return</b> statement,
   2440  1.2    lneto then the function returns with no results.
   2441  1.1  mbalmer 
   2442  1.1  mbalmer 
   2443  1.1  mbalmer <p>
   2444  1.1  mbalmer 
   2445  1.2    lneto There is a system-dependent limit on the number of values
   2446  1.2    lneto that a function may return.
   2447  1.2    lneto This limit is guaranteed to be larger than 1000.
   2448  1.1  mbalmer 
   2449  1.1  mbalmer 
   2450  1.1  mbalmer <p>
   2451  1.2    lneto The <em>colon</em> syntax
   2452  1.2    lneto is used for defining <em>methods</em>,
   2453  1.2    lneto that is, functions that have an implicit extra parameter <code>self</code>.
   2454  1.2    lneto Thus, the statement
   2455  1.1  mbalmer 
   2456  1.2    lneto <pre>
   2457  1.2    lneto      function t.a.b.c:f (<em>params</em>) <em>body</em> end
   2458  1.2    lneto </pre><p>
   2459  1.2    lneto is syntactic sugar for
   2460  1.1  mbalmer 
   2461  1.2    lneto <pre>
   2462  1.2    lneto      t.a.b.c.f = function (self, <em>params</em>) <em>body</em> end
   2463  1.2    lneto </pre>
   2464  1.1  mbalmer 
   2465  1.1  mbalmer 
   2466  1.1  mbalmer 
   2467  1.1  mbalmer 
   2468  1.1  mbalmer 
   2469  1.1  mbalmer 
   2470  1.2    lneto <h2>3.5 &ndash; <a name="3.5">Visibility Rules</a></h2>
   2471  1.1  mbalmer 
   2472  1.1  mbalmer <p>
   2473  1.1  mbalmer 
   2474  1.2    lneto Lua is a lexically scoped language.
   2475  1.2    lneto The scope of a local variable begins at the first statement after
   2476  1.2    lneto its declaration and lasts until the last non-void statement
   2477  1.2    lneto of the innermost block that includes the declaration.
   2478  1.2    lneto Consider the following example:
   2479  1.1  mbalmer 
   2480  1.2    lneto <pre>
   2481  1.2    lneto      x = 10                -- global variable
   2482  1.2    lneto      do                    -- new block
   2483  1.2    lneto        local x = x         -- new 'x', with value 10
   2484  1.2    lneto        print(x)            --&gt; 10
   2485  1.2    lneto        x = x+1
   2486  1.2    lneto        do                  -- another block
   2487  1.2    lneto          local x = x+1     -- another 'x'
   2488  1.2    lneto          print(x)          --&gt; 12
   2489  1.2    lneto        end
   2490  1.2    lneto        print(x)            --&gt; 11
   2491  1.2    lneto      end
   2492  1.2    lneto      print(x)              --&gt; 10  (the global one)
   2493  1.2    lneto </pre>
   2494  1.1  mbalmer 
   2495  1.1  mbalmer <p>
   2496  1.2    lneto Notice that, in a declaration like <code>local x = x</code>,
   2497  1.2    lneto the new <code>x</code> being declared is not in scope yet,
   2498  1.2    lneto and so the second <code>x</code> refers to the outside variable.
   2499  1.1  mbalmer 
   2500  1.1  mbalmer 
   2501  1.1  mbalmer <p>
   2502  1.2    lneto Because of the lexical scoping rules,
   2503  1.2    lneto local variables can be freely accessed by functions
   2504  1.2    lneto defined inside their scope.
   2505  1.2    lneto A local variable used by an inner function is called
   2506  1.2    lneto an <em>upvalue</em>, or <em>external local variable</em>,
   2507  1.2    lneto inside the inner function.
   2508  1.1  mbalmer 
   2509  1.1  mbalmer 
   2510  1.1  mbalmer <p>
   2511  1.2    lneto Notice that each execution of a <b>local</b> statement
   2512  1.2    lneto defines new local variables.
   2513  1.2    lneto Consider the following example:
   2514  1.1  mbalmer 
   2515  1.1  mbalmer <pre>
   2516  1.2    lneto      a = {}
   2517  1.2    lneto      local x = 20
   2518  1.2    lneto      for i=1,10 do
   2519  1.2    lneto        local y = 0
   2520  1.2    lneto        a[i] = function () y=y+1; return x+y end
   2521  1.1  mbalmer      end
   2522  1.1  mbalmer </pre><p>
   2523  1.2    lneto The loop creates ten closures
   2524  1.2    lneto (that is, ten instances of the anonymous function).
   2525  1.2    lneto Each of these closures uses a different <code>y</code> variable,
   2526  1.2    lneto while all of them share the same <code>x</code>.
   2527  1.1  mbalmer 
   2528  1.1  mbalmer 
   2529  1.1  mbalmer 
   2530  1.1  mbalmer 
   2531  1.1  mbalmer 
   2532  1.2    lneto <h1>4 &ndash; <a name="4">The Application Program Interface</a></h1>
   2533  1.1  mbalmer 
   2534  1.1  mbalmer <p>
   2535  1.1  mbalmer 
   2536  1.1  mbalmer This section describes the C&nbsp;API for Lua, that is,
   2537  1.1  mbalmer the set of C&nbsp;functions available to the host program to communicate
   2538  1.1  mbalmer with Lua.
   2539  1.1  mbalmer All API functions and related types and constants
   2540  1.1  mbalmer are declared in the header file <a name="pdf-lua.h"><code>lua.h</code></a>.
   2541  1.1  mbalmer 
   2542  1.1  mbalmer 
   2543  1.1  mbalmer <p>
   2544  1.1  mbalmer Even when we use the term "function",
   2545  1.1  mbalmer any facility in the API may be provided as a macro instead.
   2546  1.2    lneto Except where stated otherwise,
   2547  1.2    lneto all such macros use each of their arguments exactly once
   2548  1.1  mbalmer (except for the first argument, which is always a Lua state),
   2549  1.1  mbalmer and so do not generate any hidden side-effects.
   2550  1.1  mbalmer 
   2551  1.1  mbalmer 
   2552  1.1  mbalmer <p>
   2553  1.1  mbalmer As in most C&nbsp;libraries,
   2554  1.1  mbalmer the Lua API functions do not check their arguments for validity or consistency.
   2555  1.1  mbalmer However, you can change this behavior by compiling Lua
   2556  1.2    lneto with the macro <a name="pdf-LUA_USE_APICHECK"><code>LUA_USE_APICHECK</code></a> defined.
   2557  1.1  mbalmer 
   2558  1.1  mbalmer 
   2559  1.1  mbalmer 
   2560  1.2    lneto <h2>4.1 &ndash; <a name="4.1">The Stack</a></h2>
   2561  1.1  mbalmer 
   2562  1.1  mbalmer <p>
   2563  1.1  mbalmer Lua uses a <em>virtual stack</em> to pass values to and from C.
   2564  1.1  mbalmer Each element in this stack represents a Lua value
   2565  1.1  mbalmer (<b>nil</b>, number, string, etc.).
   2566  1.1  mbalmer 
   2567  1.1  mbalmer 
   2568  1.1  mbalmer <p>
   2569  1.1  mbalmer Whenever Lua calls C, the called function gets a new stack,
   2570  1.1  mbalmer which is independent of previous stacks and of stacks of
   2571  1.1  mbalmer C&nbsp;functions that are still active.
   2572  1.1  mbalmer This stack initially contains any arguments to the C&nbsp;function
   2573  1.1  mbalmer and it is where the C&nbsp;function pushes its results
   2574  1.1  mbalmer to be returned to the caller (see <a href="#lua_CFunction"><code>lua_CFunction</code></a>).
   2575  1.1  mbalmer 
   2576  1.1  mbalmer 
   2577  1.1  mbalmer <p>
   2578  1.1  mbalmer For convenience,
   2579  1.1  mbalmer most query operations in the API do not follow a strict stack discipline.
   2580  1.1  mbalmer Instead, they can refer to any element in the stack
   2581  1.1  mbalmer by using an <em>index</em>:
   2582  1.2    lneto A positive index represents an absolute stack position
   2583  1.1  mbalmer (starting at&nbsp;1);
   2584  1.2    lneto a negative index represents an offset relative to the top of the stack.
   2585  1.1  mbalmer More specifically, if the stack has <em>n</em> elements,
   2586  1.1  mbalmer then index&nbsp;1 represents the first element
   2587  1.1  mbalmer (that is, the element that was pushed onto the stack first)
   2588  1.1  mbalmer and
   2589  1.1  mbalmer index&nbsp;<em>n</em> represents the last element;
   2590  1.1  mbalmer index&nbsp;-1 also represents the last element
   2591  1.1  mbalmer (that is, the element at the&nbsp;top)
   2592  1.1  mbalmer and index <em>-n</em> represents the first element.
   2593  1.1  mbalmer 
   2594  1.1  mbalmer 
   2595  1.1  mbalmer 
   2596  1.1  mbalmer 
   2597  1.1  mbalmer 
   2598  1.2    lneto <h2>4.2 &ndash; <a name="4.2">Stack Size</a></h2>
   2599  1.1  mbalmer 
   2600  1.1  mbalmer <p>
   2601  1.2    lneto When you interact with the Lua API,
   2602  1.1  mbalmer you are responsible for ensuring consistency.
   2603  1.1  mbalmer In particular,
   2604  1.1  mbalmer <em>you are responsible for controlling stack overflow</em>.
   2605  1.1  mbalmer You can use the function <a href="#lua_checkstack"><code>lua_checkstack</code></a>
   2606  1.3    lneto to ensure that the stack has enough space for pushing new elements.
   2607  1.1  mbalmer 
   2608  1.1  mbalmer 
   2609  1.1  mbalmer <p>
   2610  1.1  mbalmer Whenever Lua calls C,
   2611  1.3    lneto it ensures that the stack has space for
   2612  1.3    lneto at least <a name="pdf-LUA_MINSTACK"><code>LUA_MINSTACK</code></a> extra slots.
   2613  1.1  mbalmer <code>LUA_MINSTACK</code> is defined as 20,
   2614  1.1  mbalmer so that usually you do not have to worry about stack space
   2615  1.1  mbalmer unless your code has loops pushing elements onto the stack.
   2616  1.1  mbalmer 
   2617  1.1  mbalmer 
   2618  1.1  mbalmer <p>
   2619  1.2    lneto When you call a Lua function
   2620  1.2    lneto without a fixed number of results (see <a href="#lua_call"><code>lua_call</code></a>),
   2621  1.3    lneto Lua ensures that the stack has enough space for all results,
   2622  1.2    lneto but it does not ensure any extra space.
   2623  1.2    lneto So, before pushing anything in the stack after such a call
   2624  1.2    lneto you should use <a href="#lua_checkstack"><code>lua_checkstack</code></a>.
   2625  1.2    lneto 
   2626  1.2    lneto 
   2627  1.2    lneto 
   2628  1.2    lneto 
   2629  1.1  mbalmer 
   2630  1.2    lneto <h2>4.3 &ndash; <a name="4.3">Valid and Acceptable Indices</a></h2>
   2631  1.1  mbalmer 
   2632  1.2    lneto <p>
   2633  1.2    lneto Any function in the API that receives stack indices
   2634  1.2    lneto works only with <em>valid indices</em> or <em>acceptable indices</em>.
   2635  1.1  mbalmer 
   2636  1.1  mbalmer 
   2637  1.2    lneto <p>
   2638  1.2    lneto A <em>valid index</em> is an index that refers to a
   2639  1.2    lneto real position within the stack, that is,
   2640  1.2    lneto its position lies between&nbsp;1 and the stack top
   2641  1.2    lneto (<code>1 &le; abs(index) &le; top</code>).
   2642  1.1  mbalmer 
   2643  1.2    lneto Usually, functions that can modify the value at an index
   2644  1.2    lneto require valid indices.
   2645  1.1  mbalmer 
   2646  1.1  mbalmer 
   2647  1.1  mbalmer <p>
   2648  1.1  mbalmer Unless otherwise noted,
   2649  1.2    lneto any function that accepts valid indices also accepts <em>pseudo-indices</em>,
   2650  1.1  mbalmer which represent some Lua values that are accessible to C&nbsp;code
   2651  1.1  mbalmer but which are not in the stack.
   2652  1.2    lneto Pseudo-indices are used to access the registry
   2653  1.2    lneto and the upvalues of a C&nbsp;function (see <a href="#4.4">&sect;4.4</a>).
   2654  1.2    lneto 
   2655  1.2    lneto 
   2656  1.2    lneto <p>
   2657  1.2    lneto Functions that do not need a specific stack position,
   2658  1.2    lneto but only a value in the stack (e.g., query functions),
   2659  1.2    lneto can be called with acceptable indices.
   2660  1.2    lneto An <em>acceptable index</em> can be any valid index,
   2661  1.2    lneto including the pseudo-indices,
   2662  1.2    lneto but it also can be any positive index after the stack top
   2663  1.2    lneto within the space allocated for the stack,
   2664  1.2    lneto that is, indices up to the stack size.
   2665  1.2    lneto (Note that 0 is never an acceptable index.)
   2666  1.2    lneto Except when noted otherwise,
   2667  1.2    lneto functions in the API work with acceptable indices.
   2668  1.1  mbalmer 
   2669  1.1  mbalmer 
   2670  1.1  mbalmer <p>
   2671  1.2    lneto Acceptable indices serve to avoid extra tests
   2672  1.2    lneto against the stack top when querying the stack.
   2673  1.2    lneto For instance, a C&nbsp;function can query its third argument
   2674  1.2    lneto without the need to first check whether there is a third argument,
   2675  1.2    lneto that is, without the need to check whether 3 is a valid index.
   2676  1.1  mbalmer 
   2677  1.1  mbalmer 
   2678  1.1  mbalmer <p>
   2679  1.2    lneto For functions that can be called with acceptable indices,
   2680  1.2    lneto any non-valid index is treated as if it
   2681  1.2    lneto contains a value of a virtual type <a name="pdf-LUA_TNONE"><code>LUA_TNONE</code></a>,
   2682  1.2    lneto which behaves like a nil value.
   2683  1.1  mbalmer 
   2684  1.1  mbalmer 
   2685  1.1  mbalmer 
   2686  1.1  mbalmer 
   2687  1.1  mbalmer 
   2688  1.2    lneto <h2>4.4 &ndash; <a name="4.4">C Closures</a></h2>
   2689  1.1  mbalmer 
   2690  1.1  mbalmer <p>
   2691  1.1  mbalmer When a C&nbsp;function is created,
   2692  1.1  mbalmer it is possible to associate some values with it,
   2693  1.2    lneto thus creating a <em>C&nbsp;closure</em>
   2694  1.2    lneto (see <a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a>);
   2695  1.1  mbalmer these values are called <em>upvalues</em> and are
   2696  1.2    lneto accessible to the function whenever it is called.
   2697  1.1  mbalmer 
   2698  1.1  mbalmer 
   2699  1.1  mbalmer <p>
   2700  1.1  mbalmer Whenever a C&nbsp;function is called,
   2701  1.1  mbalmer its upvalues are located at specific pseudo-indices.
   2702  1.1  mbalmer These pseudo-indices are produced by the macro
   2703  1.2    lneto <a href="#lua_upvalueindex"><code>lua_upvalueindex</code></a>.
   2704  1.1  mbalmer The first value associated with a function is at position
   2705  1.1  mbalmer <code>lua_upvalueindex(1)</code>, and so on.
   2706  1.1  mbalmer Any access to <code>lua_upvalueindex(<em>n</em>)</code>,
   2707  1.1  mbalmer where <em>n</em> is greater than the number of upvalues of the
   2708  1.1  mbalmer current function (but not greater than 256),
   2709  1.2    lneto produces an acceptable but invalid index.
   2710  1.1  mbalmer 
   2711  1.1  mbalmer 
   2712  1.1  mbalmer 
   2713  1.1  mbalmer 
   2714  1.1  mbalmer 
   2715  1.2    lneto <h2>4.5 &ndash; <a name="4.5">Registry</a></h2>
   2716  1.1  mbalmer 
   2717  1.1  mbalmer <p>
   2718  1.1  mbalmer Lua provides a <em>registry</em>,
   2719  1.2    lneto a predefined table that can be used by any C&nbsp;code to
   2720  1.2    lneto store whatever Lua values it needs to store.
   2721  1.2    lneto The registry table is always located at pseudo-index
   2722  1.2    lneto <a name="pdf-LUA_REGISTRYINDEX"><code>LUA_REGISTRYINDEX</code></a>,
   2723  1.2    lneto which is a valid index.
   2724  1.1  mbalmer Any C&nbsp;library can store data into this table,
   2725  1.2    lneto but it must take care to choose keys
   2726  1.2    lneto that are different from those used
   2727  1.1  mbalmer by other libraries, to avoid collisions.
   2728  1.2    lneto Typically, you should use as key a string containing your library name,
   2729  1.2    lneto or a light userdata with the address of a C&nbsp;object in your code,
   2730  1.2    lneto or any Lua object created by your code.
   2731  1.3    lneto As with variable names,
   2732  1.2    lneto string keys starting with an underscore followed by
   2733  1.2    lneto uppercase letters are reserved for Lua.
   2734  1.1  mbalmer 
   2735  1.1  mbalmer 
   2736  1.1  mbalmer <p>
   2737  1.3    lneto The integer keys in the registry are used
   2738  1.3    lneto by the reference mechanism (see <a href="#luaL_ref"><code>luaL_ref</code></a>)
   2739  1.2    lneto and by some predefined values.
   2740  1.2    lneto Therefore, integer keys must not be used for other purposes.
   2741  1.2    lneto 
   2742  1.1  mbalmer 
   2743  1.2    lneto <p>
   2744  1.2    lneto When you create a new Lua state,
   2745  1.2    lneto its registry comes with some predefined values.
   2746  1.2    lneto These predefined values are indexed with integer keys
   2747  1.2    lneto defined as constants in <code>lua.h</code>.
   2748  1.2    lneto The following constants are defined:
   2749  1.2    lneto 
   2750  1.2    lneto <ul>
   2751  1.2    lneto <li><b><a name="pdf-LUA_RIDX_MAINTHREAD"><code>LUA_RIDX_MAINTHREAD</code></a>: </b> At this index the registry has
   2752  1.2    lneto the main thread of the state.
   2753  1.2    lneto (The main thread is the one created together with the state.)
   2754  1.2    lneto </li>
   2755  1.1  mbalmer 
   2756  1.2    lneto <li><b><a name="pdf-LUA_RIDX_GLOBALS"><code>LUA_RIDX_GLOBALS</code></a>: </b> At this index the registry has
   2757  1.2    lneto the global environment.
   2758  1.2    lneto </li>
   2759  1.2    lneto </ul>
   2760  1.1  mbalmer 
   2761  1.1  mbalmer 
   2762  1.1  mbalmer 
   2763  1.2    lneto 
   2764  1.2    lneto <h2>4.6 &ndash; <a name="4.6">Error Handling in C</a></h2>
   2765  1.1  mbalmer 
   2766  1.1  mbalmer <p>
   2767  1.1  mbalmer Internally, Lua uses the C <code>longjmp</code> facility to handle errors.
   2768  1.3    lneto (Lua will use exceptions if you compile it as C++;
   2769  1.3    lneto search for <code>LUAI_THROW</code> in the source code for details.)
   2770  1.1  mbalmer When Lua faces any error
   2771  1.2    lneto (such as a memory allocation error, type errors, syntax errors,
   2772  1.1  mbalmer and runtime errors)
   2773  1.1  mbalmer it <em>raises</em> an error;
   2774  1.1  mbalmer that is, it does a long jump.
   2775  1.1  mbalmer A <em>protected environment</em> uses <code>setjmp</code>
   2776  1.2    lneto to set a recovery point;
   2777  1.2    lneto any error jumps to the most recent active recovery point.
   2778  1.2    lneto 
   2779  1.2    lneto 
   2780  1.2    lneto <p>
   2781  1.2    lneto If an error happens outside any protected environment,
   2782  1.2    lneto Lua calls a <em>panic function</em> (see <a href="#lua_atpanic"><code>lua_atpanic</code></a>)
   2783  1.2    lneto and then calls <code>abort</code>,
   2784  1.2    lneto thus exiting the host application.
   2785  1.2    lneto Your panic function can avoid this exit by
   2786  1.2    lneto never returning
   2787  1.2    lneto (e.g., doing a long jump to your own recovery point outside Lua).
   2788  1.2    lneto 
   2789  1.2    lneto 
   2790  1.2    lneto <p>
   2791  1.2    lneto The panic function runs as if it were a message handler (see <a href="#2.3">&sect;2.3</a>);
   2792  1.2    lneto in particular, the error message is at the top of the stack.
   2793  1.3    lneto However, there is no guarantee about stack space.
   2794  1.2    lneto To push anything on the stack,
   2795  1.2    lneto the panic function must first check the available space (see <a href="#4.2">&sect;4.2</a>).
   2796  1.1  mbalmer 
   2797  1.1  mbalmer 
   2798  1.1  mbalmer <p>
   2799  1.2    lneto Most functions in the API can raise an error,
   2800  1.1  mbalmer for instance due to a memory allocation error.
   2801  1.2    lneto The documentation for each function indicates whether
   2802  1.2    lneto it can raise errors.
   2803  1.2    lneto 
   2804  1.2    lneto 
   2805  1.2    lneto <p>
   2806  1.2    lneto Inside a C&nbsp;function you can raise an error by calling <a href="#lua_error"><code>lua_error</code></a>.
   2807  1.2    lneto 
   2808  1.2    lneto 
   2809  1.2    lneto 
   2810  1.2    lneto 
   2811  1.2    lneto 
   2812  1.2    lneto <h2>4.7 &ndash; <a name="4.7">Handling Yields in C</a></h2>
   2813  1.2    lneto 
   2814  1.2    lneto <p>
   2815  1.2    lneto Internally, Lua uses the C <code>longjmp</code> facility to yield a coroutine.
   2816  1.2    lneto Therefore, if a C function <code>foo</code> calls an API function
   2817  1.2    lneto and this API function yields
   2818  1.2    lneto (directly or indirectly by calling another function that yields),
   2819  1.2    lneto Lua cannot return to <code>foo</code> any more,
   2820  1.2    lneto because the <code>longjmp</code> removes its frame from the C stack.
   2821  1.2    lneto 
   2822  1.2    lneto 
   2823  1.2    lneto <p>
   2824  1.2    lneto To avoid this kind of problem,
   2825  1.2    lneto Lua raises an error whenever it tries to yield across an API call,
   2826  1.2    lneto except for three functions:
   2827  1.2    lneto <a href="#lua_yieldk"><code>lua_yieldk</code></a>, <a href="#lua_callk"><code>lua_callk</code></a>, and <a href="#lua_pcallk"><code>lua_pcallk</code></a>.
   2828  1.2    lneto All those functions receive a <em>continuation function</em>
   2829  1.3    lneto (as a parameter named <code>k</code>) to continue execution after a yield.
   2830  1.2    lneto 
   2831  1.2    lneto 
   2832  1.2    lneto <p>
   2833  1.2    lneto We need to set some terminology to explain continuations.
   2834  1.2    lneto We have a C function called from Lua which we will call
   2835  1.2    lneto the <em>original function</em>.
   2836  1.2    lneto This original function then calls one of those three functions in the C API,
   2837  1.2    lneto which we will call the <em>callee function</em>,
   2838  1.2    lneto that then yields the current thread.
   2839  1.2    lneto (This can happen when the callee function is <a href="#lua_yieldk"><code>lua_yieldk</code></a>,
   2840  1.2    lneto or when the callee function is either <a href="#lua_callk"><code>lua_callk</code></a> or <a href="#lua_pcallk"><code>lua_pcallk</code></a>
   2841  1.2    lneto and the function called by them yields.)
   2842  1.2    lneto 
   2843  1.2    lneto 
   2844  1.2    lneto <p>
   2845  1.2    lneto Suppose the running thread yields while executing the callee function.
   2846  1.2    lneto After the thread resumes,
   2847  1.2    lneto it eventually will finish running the callee function.
   2848  1.2    lneto However,
   2849  1.2    lneto the callee function cannot return to the original function,
   2850  1.2    lneto because its frame in the C stack was destroyed by the yield.
   2851  1.2    lneto Instead, Lua calls a <em>continuation function</em>,
   2852  1.2    lneto which was given as an argument to the callee function.
   2853  1.2    lneto As the name implies,
   2854  1.2    lneto the continuation function should continue the task
   2855  1.2    lneto of the original function.
   2856  1.2    lneto 
   2857  1.2    lneto 
   2858  1.2    lneto <p>
   2859  1.2    lneto As an illustration, consider the following function:
   2860  1.2    lneto 
   2861  1.2    lneto <pre>
   2862  1.2    lneto      int original_function (lua_State *L) {
   2863  1.2    lneto        ...     /* code 1 */
   2864  1.2    lneto        status = lua_pcall(L, n, m, h);  /* calls Lua */
   2865  1.2    lneto        ...     /* code 2 */
   2866  1.2    lneto      }
   2867  1.2    lneto </pre><p>
   2868  1.2    lneto Now we want to allow
   2869  1.3    lneto the Lua code being run by <a href="#lua_pcall"><code>lua_pcall</code></a> to yield.
   2870  1.2    lneto First, we can rewrite our function like here:
   2871  1.2    lneto 
   2872  1.2    lneto <pre>
   2873  1.3    lneto      int k (lua_State *L, int status, lua_KContext ctx) {
   2874  1.2    lneto        ...  /* code 2 */
   2875  1.2    lneto      }
   2876  1.2    lneto      
   2877  1.2    lneto      int original_function (lua_State *L) {
   2878  1.2    lneto        ...     /* code 1 */
   2879  1.2    lneto        return k(L, lua_pcall(L, n, m, h), ctx);
   2880  1.2    lneto      }
   2881  1.2    lneto </pre><p>
   2882  1.2    lneto In the above code,
   2883  1.2    lneto the new function <code>k</code> is a
   2884  1.2    lneto <em>continuation function</em> (with type <a href="#lua_KFunction"><code>lua_KFunction</code></a>),
   2885  1.2    lneto which should do all the work that the original function
   2886  1.2    lneto was doing after calling <a href="#lua_pcall"><code>lua_pcall</code></a>.
   2887  1.2    lneto Now, we must inform Lua that it must call <code>k</code> if the Lua code
   2888  1.3    lneto being executed by <a href="#lua_pcall"><code>lua_pcall</code></a> gets interrupted in some way
   2889  1.2    lneto (errors or yielding),
   2890  1.2    lneto so we rewrite the code as here,
   2891  1.2    lneto replacing <a href="#lua_pcall"><code>lua_pcall</code></a> by <a href="#lua_pcallk"><code>lua_pcallk</code></a>:
   2892  1.2    lneto 
   2893  1.2    lneto <pre>
   2894  1.2    lneto      int original_function (lua_State *L) {
   2895  1.2    lneto        ...     /* code 1 */
   2896  1.2    lneto        return k(L, lua_pcallk(L, n, m, h, ctx2, k), ctx1);
   2897  1.2    lneto      }
   2898  1.3    lneto </pre><p>
   2899  1.3    lneto Note the external, explicit call to the continuation:
   2900  1.3    lneto Lua will call the continuation only if needed, that is,
   2901  1.3    lneto in case of errors or resuming after a yield.
   2902  1.3    lneto If the called function returns normally without ever yielding,
   2903  1.3    lneto <a href="#lua_pcallk"><code>lua_pcallk</code></a> (and <a href="#lua_callk"><code>lua_callk</code></a>) will also return normally.
   2904  1.3    lneto (Of course, instead of calling the continuation in that case,
   2905  1.3    lneto you can do the equivalent work directly inside the original function.)
   2906  1.3    lneto 
   2907  1.2    lneto 
   2908  1.2    lneto <p>
   2909  1.2    lneto Besides the Lua state,
   2910  1.2    lneto the continuation function has two other parameters:
   2911  1.2    lneto the final status of the call plus the context value (<code>ctx</code>) that
   2912  1.2    lneto was passed originally to <a href="#lua_pcallk"><code>lua_pcallk</code></a>.
   2913  1.2    lneto (Lua does not use this context value;
   2914  1.2    lneto it only passes this value from the original function to the
   2915  1.2    lneto continuation function.)
   2916  1.2    lneto For <a href="#lua_pcallk"><code>lua_pcallk</code></a>,
   2917  1.2    lneto the status is the same value that would be returned by <a href="#lua_pcallk"><code>lua_pcallk</code></a>,
   2918  1.3    lneto except that it is <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a> when being executed after a yield
   2919  1.2    lneto (instead of <a href="#pdf-LUA_OK"><code>LUA_OK</code></a>).
   2920  1.2    lneto For <a href="#lua_yieldk"><code>lua_yieldk</code></a> and <a href="#lua_callk"><code>lua_callk</code></a>,
   2921  1.2    lneto the status is always <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a> when Lua calls the continuation.
   2922  1.2    lneto (For these two functions,
   2923  1.2    lneto Lua will not call the continuation in case of errors,
   2924  1.2    lneto because they do not handle errors.)
   2925  1.3    lneto Similarly, when using <a href="#lua_callk"><code>lua_callk</code></a>,
   2926  1.3    lneto you should call the continuation function
   2927  1.3    lneto with <a href="#pdf-LUA_OK"><code>LUA_OK</code></a> as the status.
   2928  1.3    lneto (For <a href="#lua_yieldk"><code>lua_yieldk</code></a>, there is not much point in calling
   2929  1.3    lneto directly the continuation function,
   2930  1.3    lneto because <a href="#lua_yieldk"><code>lua_yieldk</code></a> usually does not return.)
   2931  1.1  mbalmer 
   2932  1.1  mbalmer 
   2933  1.1  mbalmer <p>
   2934  1.2    lneto Lua treats the continuation function as if it were the original function.
   2935  1.2    lneto The continuation function receives the same Lua stack
   2936  1.2    lneto from the original function,
   2937  1.2    lneto in the same state it would be if the callee function had returned.
   2938  1.2    lneto (For instance,
   2939  1.2    lneto after a <a href="#lua_callk"><code>lua_callk</code></a> the function and its arguments are
   2940  1.2    lneto removed from the stack and replaced by the results from the call.)
   2941  1.2    lneto It also has the same upvalues.
   2942  1.2    lneto Whatever it returns is handled by Lua as if it were the return
   2943  1.2    lneto of the original function.
   2944  1.1  mbalmer 
   2945  1.1  mbalmer 
   2946  1.1  mbalmer 
   2947  1.1  mbalmer 
   2948  1.1  mbalmer 
   2949  1.2    lneto <h2>4.8 &ndash; <a name="4.8">Functions and Types</a></h2>
   2950  1.1  mbalmer 
   2951  1.1  mbalmer <p>
   2952  1.1  mbalmer Here we list all functions and types from the C&nbsp;API in
   2953  1.1  mbalmer alphabetical order.
   2954  1.1  mbalmer Each function has an indicator like this:
   2955  1.1  mbalmer <span class="apii">[-o, +p, <em>x</em>]</span>
   2956  1.1  mbalmer 
   2957  1.1  mbalmer 
   2958  1.1  mbalmer <p>
   2959  1.1  mbalmer The first field, <code>o</code>,
   2960  1.1  mbalmer is how many elements the function pops from the stack.
   2961  1.1  mbalmer The second field, <code>p</code>,
   2962  1.1  mbalmer is how many elements the function pushes onto the stack.
   2963  1.1  mbalmer (Any function always pushes its results after popping its arguments.)
   2964  1.1  mbalmer A field in the form <code>x|y</code> means the function can push (or pop)
   2965  1.1  mbalmer <code>x</code> or <code>y</code> elements,
   2966  1.1  mbalmer depending on the situation;
   2967  1.1  mbalmer an interrogation mark '<code>?</code>' means that
   2968  1.1  mbalmer we cannot know how many elements the function pops/pushes
   2969  1.1  mbalmer by looking only at its arguments
   2970  1.1  mbalmer (e.g., they may depend on what is on the stack).
   2971  1.1  mbalmer The third field, <code>x</code>,
   2972  1.2    lneto tells whether the function may raise errors:
   2973  1.2    lneto '<code>-</code>' means the function never raises any error;
   2974  1.2    lneto '<code>e</code>' means the function may raise errors;
   2975  1.2    lneto '<code>v</code>' means the function may raise an error on purpose.
   2976  1.2    lneto 
   2977  1.2    lneto 
   2978  1.2    lneto 
   2979  1.2    lneto <hr><h3><a name="lua_absindex"><code>lua_absindex</code></a></h3><p>
   2980  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   2981  1.2    lneto <pre>int lua_absindex (lua_State *L, int idx);</pre>
   2982  1.2    lneto 
   2983  1.2    lneto <p>
   2984  1.2    lneto Converts the acceptable index <code>idx</code> into an absolute index
   2985  1.2    lneto (that is, one that does not depend on the stack top).
   2986  1.2    lneto 
   2987  1.2    lneto 
   2988  1.1  mbalmer 
   2989  1.1  mbalmer 
   2990  1.1  mbalmer 
   2991  1.1  mbalmer <hr><h3><a name="lua_Alloc"><code>lua_Alloc</code></a></h3>
   2992  1.1  mbalmer <pre>typedef void * (*lua_Alloc) (void *ud,
   2993  1.1  mbalmer                              void *ptr,
   2994  1.1  mbalmer                              size_t osize,
   2995  1.1  mbalmer                              size_t nsize);</pre>
   2996  1.1  mbalmer 
   2997  1.1  mbalmer <p>
   2998  1.1  mbalmer The type of the memory-allocation function used by Lua states.
   2999  1.1  mbalmer The allocator function must provide a
   3000  1.1  mbalmer functionality similar to <code>realloc</code>,
   3001  1.1  mbalmer but not exactly the same.
   3002  1.1  mbalmer Its arguments are
   3003  1.1  mbalmer <code>ud</code>, an opaque pointer passed to <a href="#lua_newstate"><code>lua_newstate</code></a>;
   3004  1.1  mbalmer <code>ptr</code>, a pointer to the block being allocated/reallocated/freed;
   3005  1.2    lneto <code>osize</code>, the original size of the block or some code about what
   3006  1.2    lneto is being allocated;
   3007  1.3    lneto and <code>nsize</code>, the new size of the block.
   3008  1.2    lneto 
   3009  1.2    lneto 
   3010  1.2    lneto <p>
   3011  1.2    lneto When <code>ptr</code> is not <code>NULL</code>,
   3012  1.2    lneto <code>osize</code> is the size of the block pointed by <code>ptr</code>,
   3013  1.2    lneto that is, the size given when it was allocated or reallocated.
   3014  1.2    lneto 
   3015  1.2    lneto 
   3016  1.2    lneto <p>
   3017  1.2    lneto When <code>ptr</code> is <code>NULL</code>,
   3018  1.2    lneto <code>osize</code> encodes the kind of object that Lua is allocating.
   3019  1.2    lneto <code>osize</code> is any of
   3020  1.2    lneto <a href="#pdf-LUA_TSTRING"><code>LUA_TSTRING</code></a>, <a href="#pdf-LUA_TTABLE"><code>LUA_TTABLE</code></a>, <a href="#pdf-LUA_TFUNCTION"><code>LUA_TFUNCTION</code></a>,
   3021  1.2    lneto <a href="#pdf-LUA_TUSERDATA"><code>LUA_TUSERDATA</code></a>, or <a href="#pdf-LUA_TTHREAD"><code>LUA_TTHREAD</code></a> when (and only when)
   3022  1.2    lneto Lua is creating a new object of that type.
   3023  1.2    lneto When <code>osize</code> is some other value,
   3024  1.2    lneto Lua is allocating memory for something else.
   3025  1.2    lneto 
   3026  1.2    lneto 
   3027  1.2    lneto <p>
   3028  1.2    lneto Lua assumes the following behavior from the allocator function:
   3029  1.2    lneto 
   3030  1.2    lneto 
   3031  1.2    lneto <p>
   3032  1.2    lneto When <code>nsize</code> is zero,
   3033  1.2    lneto the allocator must behave like <code>free</code>
   3034  1.2    lneto and return <code>NULL</code>.
   3035  1.2    lneto 
   3036  1.2    lneto 
   3037  1.2    lneto <p>
   3038  1.2    lneto When <code>nsize</code> is not zero,
   3039  1.2    lneto the allocator must behave like <code>realloc</code>.
   3040  1.2    lneto The allocator returns <code>NULL</code>
   3041  1.2    lneto if and only if it cannot fulfill the request.
   3042  1.1  mbalmer Lua assumes that the allocator never fails when
   3043  1.1  mbalmer <code>osize &gt;= nsize</code>.
   3044  1.1  mbalmer 
   3045  1.1  mbalmer 
   3046  1.1  mbalmer <p>
   3047  1.1  mbalmer Here is a simple implementation for the allocator function.
   3048  1.1  mbalmer It is used in the auxiliary library by <a href="#luaL_newstate"><code>luaL_newstate</code></a>.
   3049  1.1  mbalmer 
   3050  1.1  mbalmer <pre>
   3051  1.1  mbalmer      static void *l_alloc (void *ud, void *ptr, size_t osize,
   3052  1.1  mbalmer                                                 size_t nsize) {
   3053  1.1  mbalmer        (void)ud;  (void)osize;  /* not used */
   3054  1.1  mbalmer        if (nsize == 0) {
   3055  1.1  mbalmer          free(ptr);
   3056  1.1  mbalmer          return NULL;
   3057  1.1  mbalmer        }
   3058  1.1  mbalmer        else
   3059  1.1  mbalmer          return realloc(ptr, nsize);
   3060  1.1  mbalmer      }
   3061  1.1  mbalmer </pre><p>
   3062  1.2    lneto Note that Standard&nbsp;C ensures
   3063  1.1  mbalmer that <code>free(NULL)</code> has no effect and that
   3064  1.3    lneto <code>realloc(NULL,size)</code> is equivalent to <code>malloc(size)</code>.
   3065  1.2    lneto This code assumes that <code>realloc</code> does not fail when shrinking a block.
   3066  1.2    lneto (Although Standard&nbsp;C does not ensure this behavior,
   3067  1.2    lneto it seems to be a safe assumption.)
   3068  1.1  mbalmer 
   3069  1.1  mbalmer 
   3070  1.1  mbalmer 
   3071  1.1  mbalmer 
   3072  1.1  mbalmer 
   3073  1.2    lneto <hr><h3><a name="lua_arith"><code>lua_arith</code></a></h3><p>
   3074  1.2    lneto <span class="apii">[-(2|1), +1, <em>e</em>]</span>
   3075  1.2    lneto <pre>void lua_arith (lua_State *L, int op);</pre>
   3076  1.1  mbalmer 
   3077  1.1  mbalmer <p>
   3078  1.2    lneto Performs an arithmetic or bitwise operation over the two values
   3079  1.2    lneto (or one, in the case of negations)
   3080  1.2    lneto at the top of the stack,
   3081  1.2    lneto with the value at the top being the second operand,
   3082  1.2    lneto pops these values, and pushes the result of the operation.
   3083  1.2    lneto The function follows the semantics of the corresponding Lua operator
   3084  1.2    lneto (that is, it may call metamethods).
   3085  1.1  mbalmer 
   3086  1.1  mbalmer 
   3087  1.1  mbalmer <p>
   3088  1.2    lneto The value of <code>op</code> must be one of the following constants:
   3089  1.2    lneto 
   3090  1.2    lneto <ul>
   3091  1.2    lneto 
   3092  1.2    lneto <li><b><a name="pdf-LUA_OPADD"><code>LUA_OPADD</code></a>: </b> performs addition (<code>+</code>)</li>
   3093  1.2    lneto <li><b><a name="pdf-LUA_OPSUB"><code>LUA_OPSUB</code></a>: </b> performs subtraction (<code>-</code>)</li>
   3094  1.2    lneto <li><b><a name="pdf-LUA_OPMUL"><code>LUA_OPMUL</code></a>: </b> performs multiplication (<code>*</code>)</li>
   3095  1.2    lneto <li><b><a name="pdf-LUA_OPDIV"><code>LUA_OPDIV</code></a>: </b> performs float division (<code>/</code>)</li>
   3096  1.3    lneto <li><b><a name="pdf-LUA_OPIDIV"><code>LUA_OPIDIV</code></a>: </b> performs floor division (<code>//</code>)</li>
   3097  1.2    lneto <li><b><a name="pdf-LUA_OPMOD"><code>LUA_OPMOD</code></a>: </b> performs modulo (<code>%</code>)</li>
   3098  1.2    lneto <li><b><a name="pdf-LUA_OPPOW"><code>LUA_OPPOW</code></a>: </b> performs exponentiation (<code>^</code>)</li>
   3099  1.2    lneto <li><b><a name="pdf-LUA_OPUNM"><code>LUA_OPUNM</code></a>: </b> performs mathematical negation (unary <code>-</code>)</li>
   3100  1.2    lneto <li><b><a name="pdf-LUA_OPBNOT"><code>LUA_OPBNOT</code></a>: </b> performs bitwise negation (<code>~</code>)</li>
   3101  1.2    lneto <li><b><a name="pdf-LUA_OPBAND"><code>LUA_OPBAND</code></a>: </b> performs bitwise and (<code>&amp;</code>)</li>
   3102  1.2    lneto <li><b><a name="pdf-LUA_OPBOR"><code>LUA_OPBOR</code></a>: </b> performs bitwise or (<code>|</code>)</li>
   3103  1.2    lneto <li><b><a name="pdf-LUA_OPBXOR"><code>LUA_OPBXOR</code></a>: </b> performs bitwise exclusive or (<code>~</code>)</li>
   3104  1.2    lneto <li><b><a name="pdf-LUA_OPSHL"><code>LUA_OPSHL</code></a>: </b> performs left shift (<code>&lt;&lt;</code>)</li>
   3105  1.2    lneto <li><b><a name="pdf-LUA_OPSHR"><code>LUA_OPSHR</code></a>: </b> performs right shift (<code>&gt;&gt;</code>)</li>
   3106  1.2    lneto 
   3107  1.2    lneto </ul>
   3108  1.2    lneto 
   3109  1.2    lneto 
   3110  1.2    lneto 
   3111  1.1  mbalmer 
   3112  1.2    lneto <hr><h3><a name="lua_atpanic"><code>lua_atpanic</code></a></h3><p>
   3113  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3114  1.2    lneto <pre>lua_CFunction lua_atpanic (lua_State *L, lua_CFunction panicf);</pre>
   3115  1.1  mbalmer 
   3116  1.1  mbalmer <p>
   3117  1.2    lneto Sets a new panic function and returns the old one (see <a href="#4.6">&sect;4.6</a>).
   3118  1.1  mbalmer 
   3119  1.1  mbalmer 
   3120  1.1  mbalmer 
   3121  1.1  mbalmer 
   3122  1.1  mbalmer 
   3123  1.1  mbalmer <hr><h3><a name="lua_call"><code>lua_call</code></a></h3><p>
   3124  1.2    lneto <span class="apii">[-(nargs+1), +nresults, <em>e</em>]</span>
   3125  1.1  mbalmer <pre>void lua_call (lua_State *L, int nargs, int nresults);</pre>
   3126  1.1  mbalmer 
   3127  1.1  mbalmer <p>
   3128  1.1  mbalmer Calls a function.
   3129  1.1  mbalmer 
   3130  1.1  mbalmer 
   3131  1.1  mbalmer <p>
   3132  1.1  mbalmer To call a function you must use the following protocol:
   3133  1.1  mbalmer first, the function to be called is pushed onto the stack;
   3134  1.1  mbalmer then, the arguments to the function are pushed
   3135  1.1  mbalmer in direct order;
   3136  1.1  mbalmer that is, the first argument is pushed first.
   3137  1.1  mbalmer Finally you call <a href="#lua_call"><code>lua_call</code></a>;
   3138  1.1  mbalmer <code>nargs</code> is the number of arguments that you pushed onto the stack.
   3139  1.1  mbalmer All arguments and the function value are popped from the stack
   3140  1.1  mbalmer when the function is called.
   3141  1.1  mbalmer The function results are pushed onto the stack when the function returns.
   3142  1.1  mbalmer The number of results is adjusted to <code>nresults</code>,
   3143  1.1  mbalmer unless <code>nresults</code> is <a name="pdf-LUA_MULTRET"><code>LUA_MULTRET</code></a>.
   3144  1.2    lneto In this case, all results from the function are pushed.
   3145  1.1  mbalmer Lua takes care that the returned values fit into the stack space.
   3146  1.1  mbalmer The function results are pushed onto the stack in direct order
   3147  1.1  mbalmer (the first result is pushed first),
   3148  1.1  mbalmer so that after the call the last result is on the top of the stack.
   3149  1.1  mbalmer 
   3150  1.1  mbalmer 
   3151  1.1  mbalmer <p>
   3152  1.1  mbalmer Any error inside the called function is propagated upwards
   3153  1.1  mbalmer (with a <code>longjmp</code>).
   3154  1.1  mbalmer 
   3155  1.1  mbalmer 
   3156  1.1  mbalmer <p>
   3157  1.1  mbalmer The following example shows how the host program can do the
   3158  1.1  mbalmer equivalent to this Lua code:
   3159  1.1  mbalmer 
   3160  1.1  mbalmer <pre>
   3161  1.1  mbalmer      a = f("how", t.x, 14)
   3162  1.1  mbalmer </pre><p>
   3163  1.1  mbalmer Here it is in&nbsp;C:
   3164  1.1  mbalmer 
   3165  1.1  mbalmer <pre>
   3166  1.2    lneto      lua_getglobal(L, "f");                  /* function to be called */
   3167  1.3    lneto      lua_pushliteral(L, "how");                       /* 1st argument */
   3168  1.2    lneto      lua_getglobal(L, "t");                    /* table to be indexed */
   3169  1.1  mbalmer      lua_getfield(L, -1, "x");        /* push result of t.x (2nd arg) */
   3170  1.1  mbalmer      lua_remove(L, -2);                  /* remove 't' from the stack */
   3171  1.1  mbalmer      lua_pushinteger(L, 14);                          /* 3rd argument */
   3172  1.1  mbalmer      lua_call(L, 3, 1);     /* call 'f' with 3 arguments and 1 result */
   3173  1.2    lneto      lua_setglobal(L, "a");                         /* set global 'a' */
   3174  1.1  mbalmer </pre><p>
   3175  1.3    lneto Note that the code above is <em>balanced</em>:
   3176  1.1  mbalmer at its end, the stack is back to its original configuration.
   3177  1.1  mbalmer This is considered good programming practice.
   3178  1.1  mbalmer 
   3179  1.1  mbalmer 
   3180  1.1  mbalmer 
   3181  1.1  mbalmer 
   3182  1.1  mbalmer 
   3183  1.2    lneto <hr><h3><a name="lua_callk"><code>lua_callk</code></a></h3><p>
   3184  1.2    lneto <span class="apii">[-(nargs + 1), +nresults, <em>e</em>]</span>
   3185  1.3    lneto <pre>void lua_callk (lua_State *L,
   3186  1.3    lneto                 int nargs,
   3187  1.3    lneto                 int nresults,
   3188  1.3    lneto                 lua_KContext ctx,
   3189  1.2    lneto                 lua_KFunction k);</pre>
   3190  1.2    lneto 
   3191  1.2    lneto <p>
   3192  1.2    lneto This function behaves exactly like <a href="#lua_call"><code>lua_call</code></a>,
   3193  1.2    lneto but allows the called function to yield (see <a href="#4.7">&sect;4.7</a>).
   3194  1.2    lneto 
   3195  1.2    lneto 
   3196  1.2    lneto 
   3197  1.2    lneto 
   3198  1.2    lneto 
   3199  1.1  mbalmer <hr><h3><a name="lua_CFunction"><code>lua_CFunction</code></a></h3>
   3200  1.1  mbalmer <pre>typedef int (*lua_CFunction) (lua_State *L);</pre>
   3201  1.1  mbalmer 
   3202  1.1  mbalmer <p>
   3203  1.1  mbalmer Type for C&nbsp;functions.
   3204  1.1  mbalmer 
   3205  1.1  mbalmer 
   3206  1.1  mbalmer <p>
   3207  1.1  mbalmer In order to communicate properly with Lua,
   3208  1.1  mbalmer a C&nbsp;function must use the following protocol,
   3209  1.1  mbalmer which defines the way parameters and results are passed:
   3210  1.1  mbalmer a C&nbsp;function receives its arguments from Lua in its stack
   3211  1.1  mbalmer in direct order (the first argument is pushed first).
   3212  1.1  mbalmer So, when the function starts,
   3213  1.1  mbalmer <code>lua_gettop(L)</code> returns the number of arguments received by the function.
   3214  1.1  mbalmer The first argument (if any) is at index 1
   3215  1.1  mbalmer and its last argument is at index <code>lua_gettop(L)</code>.
   3216  1.1  mbalmer To return values to Lua, a C&nbsp;function just pushes them onto the stack,
   3217  1.1  mbalmer in direct order (the first result is pushed first),
   3218  1.1  mbalmer and returns the number of results.
   3219  1.1  mbalmer Any other value in the stack below the results will be properly
   3220  1.1  mbalmer discarded by Lua.
   3221  1.1  mbalmer Like a Lua function, a C&nbsp;function called by Lua can also return
   3222  1.1  mbalmer many results.
   3223  1.1  mbalmer 
   3224  1.1  mbalmer 
   3225  1.1  mbalmer <p>
   3226  1.1  mbalmer As an example, the following function receives a variable number
   3227  1.3    lneto of numerical arguments and returns their average and their sum:
   3228  1.1  mbalmer 
   3229  1.1  mbalmer <pre>
   3230  1.1  mbalmer      static int foo (lua_State *L) {
   3231  1.1  mbalmer        int n = lua_gettop(L);    /* number of arguments */
   3232  1.3    lneto        lua_Number sum = 0.0;
   3233  1.1  mbalmer        int i;
   3234  1.1  mbalmer        for (i = 1; i &lt;= n; i++) {
   3235  1.1  mbalmer          if (!lua_isnumber(L, i)) {
   3236  1.3    lneto            lua_pushliteral(L, "incorrect argument");
   3237  1.1  mbalmer            lua_error(L);
   3238  1.1  mbalmer          }
   3239  1.1  mbalmer          sum += lua_tonumber(L, i);
   3240  1.1  mbalmer        }
   3241  1.1  mbalmer        lua_pushnumber(L, sum/n);        /* first result */
   3242  1.1  mbalmer        lua_pushnumber(L, sum);         /* second result */
   3243  1.1  mbalmer        return 2;                   /* number of results */
   3244  1.1  mbalmer      }
   3245  1.1  mbalmer </pre>
   3246  1.1  mbalmer 
   3247  1.1  mbalmer 
   3248  1.1  mbalmer 
   3249  1.1  mbalmer 
   3250  1.1  mbalmer <hr><h3><a name="lua_checkstack"><code>lua_checkstack</code></a></h3><p>
   3251  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3252  1.3    lneto <pre>int lua_checkstack (lua_State *L, int n);</pre>
   3253  1.1  mbalmer 
   3254  1.1  mbalmer <p>
   3255  1.3    lneto Ensures that the stack has space for at least <code>n</code> extra slots.
   3256  1.2    lneto It returns false if it cannot fulfill the request,
   3257  1.3    lneto either because it would cause the stack
   3258  1.3    lneto to be larger than a fixed maximum size
   3259  1.3    lneto (typically at least several thousand elements) or
   3260  1.3    lneto because it cannot allocate memory for the extra space.
   3261  1.1  mbalmer This function never shrinks the stack;
   3262  1.1  mbalmer if the stack is already larger than the new size,
   3263  1.1  mbalmer it is left unchanged.
   3264  1.1  mbalmer 
   3265  1.1  mbalmer 
   3266  1.1  mbalmer 
   3267  1.1  mbalmer 
   3268  1.1  mbalmer 
   3269  1.1  mbalmer <hr><h3><a name="lua_close"><code>lua_close</code></a></h3><p>
   3270  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3271  1.1  mbalmer <pre>void lua_close (lua_State *L);</pre>
   3272  1.1  mbalmer 
   3273  1.1  mbalmer <p>
   3274  1.1  mbalmer Destroys all objects in the given Lua state
   3275  1.1  mbalmer (calling the corresponding garbage-collection metamethods, if any)
   3276  1.1  mbalmer and frees all dynamic memory used by this state.
   3277  1.1  mbalmer On several platforms, you may not need to call this function,
   3278  1.1  mbalmer because all resources are naturally released when the host program ends.
   3279  1.2    lneto On the other hand, long-running programs that create multiple states,
   3280  1.2    lneto such as daemons or web servers,
   3281  1.3    lneto will probably need to close states as soon as they are not needed.
   3282  1.2    lneto 
   3283  1.1  mbalmer 
   3284  1.1  mbalmer 
   3285  1.1  mbalmer 
   3286  1.1  mbalmer 
   3287  1.2    lneto <hr><h3><a name="lua_compare"><code>lua_compare</code></a></h3><p>
   3288  1.2    lneto <span class="apii">[-0, +0, <em>e</em>]</span>
   3289  1.2    lneto <pre>int lua_compare (lua_State *L, int index1, int index2, int op);</pre>
   3290  1.2    lneto 
   3291  1.2    lneto <p>
   3292  1.2    lneto Compares two Lua values.
   3293  1.2    lneto Returns 1 if the value at index <code>index1</code> satisfies <code>op</code>
   3294  1.2    lneto when compared with the value at index <code>index2</code>,
   3295  1.2    lneto following the semantics of the corresponding Lua operator
   3296  1.2    lneto (that is, it may call metamethods).
   3297  1.2    lneto Otherwise returns&nbsp;0.
   3298  1.3    lneto Also returns&nbsp;0 if any of the indices is not valid.
   3299  1.2    lneto 
   3300  1.2    lneto 
   3301  1.2    lneto <p>
   3302  1.2    lneto The value of <code>op</code> must be one of the following constants:
   3303  1.2    lneto 
   3304  1.2    lneto <ul>
   3305  1.2    lneto 
   3306  1.2    lneto <li><b><a name="pdf-LUA_OPEQ"><code>LUA_OPEQ</code></a>: </b> compares for equality (<code>==</code>)</li>
   3307  1.2    lneto <li><b><a name="pdf-LUA_OPLT"><code>LUA_OPLT</code></a>: </b> compares for less than (<code>&lt;</code>)</li>
   3308  1.2    lneto <li><b><a name="pdf-LUA_OPLE"><code>LUA_OPLE</code></a>: </b> compares for less or equal (<code>&lt;=</code>)</li>
   3309  1.2    lneto 
   3310  1.2    lneto </ul>
   3311  1.2    lneto 
   3312  1.2    lneto 
   3313  1.2    lneto 
   3314  1.1  mbalmer 
   3315  1.1  mbalmer <hr><h3><a name="lua_concat"><code>lua_concat</code></a></h3><p>
   3316  1.1  mbalmer <span class="apii">[-n, +1, <em>e</em>]</span>
   3317  1.1  mbalmer <pre>void lua_concat (lua_State *L, int n);</pre>
   3318  1.1  mbalmer 
   3319  1.1  mbalmer <p>
   3320  1.1  mbalmer Concatenates the <code>n</code> values at the top of the stack,
   3321  1.1  mbalmer pops them, and leaves the result at the top.
   3322  1.1  mbalmer If <code>n</code>&nbsp;is&nbsp;1, the result is the single value on the stack
   3323  1.1  mbalmer (that is, the function does nothing);
   3324  1.1  mbalmer if <code>n</code> is 0, the result is the empty string.
   3325  1.1  mbalmer Concatenation is performed following the usual semantics of Lua
   3326  1.2    lneto (see <a href="#3.4.6">&sect;3.4.6</a>).
   3327  1.1  mbalmer 
   3328  1.1  mbalmer 
   3329  1.1  mbalmer 
   3330  1.1  mbalmer 
   3331  1.1  mbalmer 
   3332  1.2    lneto <hr><h3><a name="lua_copy"><code>lua_copy</code></a></h3><p>
   3333  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3334  1.2    lneto <pre>void lua_copy (lua_State *L, int fromidx, int toidx);</pre>
   3335  1.1  mbalmer 
   3336  1.1  mbalmer <p>
   3337  1.3    lneto Copies the element at index <code>fromidx</code>
   3338  1.3    lneto into the valid index <code>toidx</code>,
   3339  1.3    lneto replacing the value at that position.
   3340  1.3    lneto Values at other positions are not affected.
   3341  1.1  mbalmer 
   3342  1.1  mbalmer 
   3343  1.1  mbalmer 
   3344  1.1  mbalmer 
   3345  1.1  mbalmer 
   3346  1.1  mbalmer <hr><h3><a name="lua_createtable"><code>lua_createtable</code></a></h3><p>
   3347  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   3348  1.1  mbalmer <pre>void lua_createtable (lua_State *L, int narr, int nrec);</pre>
   3349  1.1  mbalmer 
   3350  1.1  mbalmer <p>
   3351  1.1  mbalmer Creates a new empty table and pushes it onto the stack.
   3352  1.2    lneto Parameter <code>narr</code> is a hint for how many elements the table
   3353  1.2    lneto will have as a sequence;
   3354  1.2    lneto parameter <code>nrec</code> is a hint for how many other elements
   3355  1.1  mbalmer the table will have.
   3356  1.2    lneto Lua may use these hints to preallocate memory for the new table.
   3357  1.2    lneto This pre-allocation is useful for performance when you know in advance
   3358  1.2    lneto how many elements the table will have.
   3359  1.1  mbalmer Otherwise you can use the function <a href="#lua_newtable"><code>lua_newtable</code></a>.
   3360  1.1  mbalmer 
   3361  1.1  mbalmer 
   3362  1.1  mbalmer 
   3363  1.1  mbalmer 
   3364  1.1  mbalmer 
   3365  1.1  mbalmer <hr><h3><a name="lua_dump"><code>lua_dump</code></a></h3><p>
   3366  1.2    lneto <span class="apii">[-0, +0, <em>e</em>]</span>
   3367  1.2    lneto <pre>int lua_dump (lua_State *L,
   3368  1.2    lneto                         lua_Writer writer,
   3369  1.2    lneto                         void *data,
   3370  1.2    lneto                         int strip);</pre>
   3371  1.1  mbalmer 
   3372  1.1  mbalmer <p>
   3373  1.1  mbalmer Dumps a function as a binary chunk.
   3374  1.1  mbalmer Receives a Lua function on the top of the stack
   3375  1.1  mbalmer and produces a binary chunk that,
   3376  1.1  mbalmer if loaded again,
   3377  1.1  mbalmer results in a function equivalent to the one dumped.
   3378  1.1  mbalmer As it produces parts of the chunk,
   3379  1.1  mbalmer <a href="#lua_dump"><code>lua_dump</code></a> calls function <code>writer</code> (see <a href="#lua_Writer"><code>lua_Writer</code></a>)
   3380  1.1  mbalmer with the given <code>data</code>
   3381  1.1  mbalmer to write them.
   3382  1.1  mbalmer 
   3383  1.1  mbalmer 
   3384  1.1  mbalmer <p>
   3385  1.2    lneto If <code>strip</code> is true,
   3386  1.2    lneto the binary representation is created without debug information
   3387  1.2    lneto about the function.
   3388  1.2    lneto 
   3389  1.2    lneto 
   3390  1.2    lneto <p>
   3391  1.1  mbalmer The value returned is the error code returned by the last
   3392  1.1  mbalmer call to the writer;
   3393  1.1  mbalmer 0&nbsp;means no errors.
   3394  1.1  mbalmer 
   3395  1.1  mbalmer 
   3396  1.1  mbalmer <p>
   3397  1.1  mbalmer This function does not pop the Lua function from the stack.
   3398  1.1  mbalmer 
   3399  1.1  mbalmer 
   3400  1.1  mbalmer 
   3401  1.1  mbalmer 
   3402  1.1  mbalmer 
   3403  1.1  mbalmer <hr><h3><a name="lua_error"><code>lua_error</code></a></h3><p>
   3404  1.1  mbalmer <span class="apii">[-1, +0, <em>v</em>]</span>
   3405  1.1  mbalmer <pre>int lua_error (lua_State *L);</pre>
   3406  1.1  mbalmer 
   3407  1.1  mbalmer <p>
   3408  1.3    lneto Generates a Lua error,
   3409  1.3    lneto using the value at the top of the stack as the error object.
   3410  1.1  mbalmer This function does a long jump,
   3411  1.2    lneto and therefore never returns
   3412  1.1  mbalmer (see <a href="#luaL_error"><code>luaL_error</code></a>).
   3413  1.1  mbalmer 
   3414  1.1  mbalmer 
   3415  1.1  mbalmer 
   3416  1.1  mbalmer 
   3417  1.1  mbalmer 
   3418  1.1  mbalmer <hr><h3><a name="lua_gc"><code>lua_gc</code></a></h3><p>
   3419  1.1  mbalmer <span class="apii">[-0, +0, <em>e</em>]</span>
   3420  1.1  mbalmer <pre>int lua_gc (lua_State *L, int what, int data);</pre>
   3421  1.1  mbalmer 
   3422  1.1  mbalmer <p>
   3423  1.1  mbalmer Controls the garbage collector.
   3424  1.1  mbalmer 
   3425  1.1  mbalmer 
   3426  1.1  mbalmer <p>
   3427  1.1  mbalmer This function performs several tasks,
   3428  1.1  mbalmer according to the value of the parameter <code>what</code>:
   3429  1.1  mbalmer 
   3430  1.1  mbalmer <ul>
   3431  1.1  mbalmer 
   3432  1.2    lneto <li><b><code>LUA_GCSTOP</code>: </b>
   3433  1.1  mbalmer stops the garbage collector.
   3434  1.1  mbalmer </li>
   3435  1.1  mbalmer 
   3436  1.2    lneto <li><b><code>LUA_GCRESTART</code>: </b>
   3437  1.1  mbalmer restarts the garbage collector.
   3438  1.1  mbalmer </li>
   3439  1.1  mbalmer 
   3440  1.2    lneto <li><b><code>LUA_GCCOLLECT</code>: </b>
   3441  1.1  mbalmer performs a full garbage-collection cycle.
   3442  1.1  mbalmer </li>
   3443  1.1  mbalmer 
   3444  1.2    lneto <li><b><code>LUA_GCCOUNT</code>: </b>
   3445  1.1  mbalmer returns the current amount of memory (in Kbytes) in use by Lua.
   3446  1.1  mbalmer </li>
   3447  1.1  mbalmer 
   3448  1.2    lneto <li><b><code>LUA_GCCOUNTB</code>: </b>
   3449  1.1  mbalmer returns the remainder of dividing the current amount of bytes of
   3450  1.1  mbalmer memory in use by Lua by 1024.
   3451  1.1  mbalmer </li>
   3452  1.1  mbalmer 
   3453  1.2    lneto <li><b><code>LUA_GCSTEP</code>: </b>
   3454  1.1  mbalmer performs an incremental step of garbage collection.
   3455  1.1  mbalmer </li>
   3456  1.1  mbalmer 
   3457  1.2    lneto <li><b><code>LUA_GCSETPAUSE</code>: </b>
   3458  1.1  mbalmer sets <code>data</code> as the new value
   3459  1.2    lneto for the <em>pause</em> of the collector (see <a href="#2.5">&sect;2.5</a>)
   3460  1.2    lneto and returns the previous value of the pause.
   3461  1.1  mbalmer </li>
   3462  1.1  mbalmer 
   3463  1.2    lneto <li><b><code>LUA_GCSETSTEPMUL</code>: </b>
   3464  1.1  mbalmer sets <code>data</code> as the new value for the <em>step multiplier</em> of
   3465  1.2    lneto the collector (see <a href="#2.5">&sect;2.5</a>)
   3466  1.2    lneto and returns the previous value of the step multiplier.
   3467  1.2    lneto </li>
   3468  1.2    lneto 
   3469  1.2    lneto <li><b><code>LUA_GCISRUNNING</code>: </b>
   3470  1.2    lneto returns a boolean that tells whether the collector is running
   3471  1.2    lneto (i.e., not stopped).
   3472  1.1  mbalmer </li>
   3473  1.1  mbalmer 
   3474  1.1  mbalmer </ul>
   3475  1.1  mbalmer 
   3476  1.2    lneto <p>
   3477  1.2    lneto For more details about these options,
   3478  1.2    lneto see <a href="#pdf-collectgarbage"><code>collectgarbage</code></a>.
   3479  1.2    lneto 
   3480  1.2    lneto 
   3481  1.1  mbalmer 
   3482  1.1  mbalmer 
   3483  1.1  mbalmer 
   3484  1.1  mbalmer <hr><h3><a name="lua_getallocf"><code>lua_getallocf</code></a></h3><p>
   3485  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3486  1.1  mbalmer <pre>lua_Alloc lua_getallocf (lua_State *L, void **ud);</pre>
   3487  1.1  mbalmer 
   3488  1.1  mbalmer <p>
   3489  1.1  mbalmer Returns the memory-allocation function of a given state.
   3490  1.1  mbalmer If <code>ud</code> is not <code>NULL</code>, Lua stores in <code>*ud</code> the
   3491  1.3    lneto opaque pointer given when the memory-allocator function was set.
   3492  1.1  mbalmer 
   3493  1.1  mbalmer 
   3494  1.1  mbalmer 
   3495  1.1  mbalmer 
   3496  1.1  mbalmer 
   3497  1.1  mbalmer <hr><h3><a name="lua_getfield"><code>lua_getfield</code></a></h3><p>
   3498  1.1  mbalmer <span class="apii">[-0, +1, <em>e</em>]</span>
   3499  1.2    lneto <pre>int lua_getfield (lua_State *L, int index, const char *k);</pre>
   3500  1.1  mbalmer 
   3501  1.1  mbalmer <p>
   3502  1.1  mbalmer Pushes onto the stack the value <code>t[k]</code>,
   3503  1.2    lneto where <code>t</code> is the value at the given index.
   3504  1.1  mbalmer As in Lua, this function may trigger a metamethod
   3505  1.2    lneto for the "index" event (see <a href="#2.4">&sect;2.4</a>).
   3506  1.2    lneto 
   3507  1.2    lneto 
   3508  1.2    lneto <p>
   3509  1.2    lneto Returns the type of the pushed value.
   3510  1.1  mbalmer 
   3511  1.1  mbalmer 
   3512  1.1  mbalmer 
   3513  1.1  mbalmer 
   3514  1.1  mbalmer 
   3515  1.3    lneto <hr><h3><a name="lua_getextraspace"><code>lua_getextraspace</code></a></h3><p>
   3516  1.3    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3517  1.3    lneto <pre>void *lua_getextraspace (lua_State *L);</pre>
   3518  1.3    lneto 
   3519  1.3    lneto <p>
   3520  1.3    lneto Returns a pointer to a raw memory area associated with the
   3521  1.3    lneto given Lua state.
   3522  1.3    lneto The application can use this area for any purpose;
   3523  1.3    lneto Lua does not use it for anything.
   3524  1.3    lneto 
   3525  1.3    lneto 
   3526  1.3    lneto <p>
   3527  1.3    lneto Each new thread has this area initialized with a copy
   3528  1.3    lneto of the area of the main thread.
   3529  1.3    lneto 
   3530  1.3    lneto 
   3531  1.3    lneto <p>
   3532  1.3    lneto By default, this area has the size of a pointer to void,
   3533  1.3    lneto but you can recompile Lua with a different size for this area.
   3534  1.3    lneto (See <code>LUA_EXTRASPACE</code> in <code>luaconf.h</code>.)
   3535  1.3    lneto 
   3536  1.3    lneto 
   3537  1.3    lneto 
   3538  1.3    lneto 
   3539  1.3    lneto 
   3540  1.1  mbalmer <hr><h3><a name="lua_getglobal"><code>lua_getglobal</code></a></h3><p>
   3541  1.1  mbalmer <span class="apii">[-0, +1, <em>e</em>]</span>
   3542  1.2    lneto <pre>int lua_getglobal (lua_State *L, const char *name);</pre>
   3543  1.1  mbalmer 
   3544  1.1  mbalmer <p>
   3545  1.1  mbalmer Pushes onto the stack the value of the global <code>name</code>.
   3546  1.2    lneto Returns the type of that value.
   3547  1.1  mbalmer 
   3548  1.1  mbalmer 
   3549  1.1  mbalmer 
   3550  1.1  mbalmer 
   3551  1.1  mbalmer 
   3552  1.3    lneto <hr><h3><a name="lua_geti"><code>lua_geti</code></a></h3><p>
   3553  1.3    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   3554  1.3    lneto <pre>int lua_geti (lua_State *L, int index, lua_Integer i);</pre>
   3555  1.3    lneto 
   3556  1.3    lneto <p>
   3557  1.3    lneto Pushes onto the stack the value <code>t[i]</code>,
   3558  1.3    lneto where <code>t</code> is the value at the given index.
   3559  1.3    lneto As in Lua, this function may trigger a metamethod
   3560  1.3    lneto for the "index" event (see <a href="#2.4">&sect;2.4</a>).
   3561  1.3    lneto 
   3562  1.3    lneto 
   3563  1.3    lneto <p>
   3564  1.3    lneto Returns the type of the pushed value.
   3565  1.3    lneto 
   3566  1.3    lneto 
   3567  1.3    lneto 
   3568  1.3    lneto 
   3569  1.3    lneto 
   3570  1.1  mbalmer <hr><h3><a name="lua_getmetatable"><code>lua_getmetatable</code></a></h3><p>
   3571  1.2    lneto <span class="apii">[-0, +(0|1), &ndash;]</span>
   3572  1.1  mbalmer <pre>int lua_getmetatable (lua_State *L, int index);</pre>
   3573  1.1  mbalmer 
   3574  1.1  mbalmer <p>
   3575  1.3    lneto If the value at the given index has a metatable,
   3576  1.3    lneto the function pushes that metatable onto the stack and returns&nbsp;1.
   3577  1.3    lneto Otherwise,
   3578  1.1  mbalmer the function returns&nbsp;0 and pushes nothing on the stack.
   3579  1.1  mbalmer 
   3580  1.1  mbalmer 
   3581  1.1  mbalmer 
   3582  1.1  mbalmer 
   3583  1.1  mbalmer 
   3584  1.1  mbalmer <hr><h3><a name="lua_gettable"><code>lua_gettable</code></a></h3><p>
   3585  1.1  mbalmer <span class="apii">[-1, +1, <em>e</em>]</span>
   3586  1.2    lneto <pre>int lua_gettable (lua_State *L, int index);</pre>
   3587  1.1  mbalmer 
   3588  1.1  mbalmer <p>
   3589  1.1  mbalmer Pushes onto the stack the value <code>t[k]</code>,
   3590  1.2    lneto where <code>t</code> is the value at the given index
   3591  1.1  mbalmer and <code>k</code> is the value at the top of the stack.
   3592  1.1  mbalmer 
   3593  1.1  mbalmer 
   3594  1.1  mbalmer <p>
   3595  1.3    lneto This function pops the key from the stack,
   3596  1.3    lneto pushing the resulting value in its place.
   3597  1.1  mbalmer As in Lua, this function may trigger a metamethod
   3598  1.2    lneto for the "index" event (see <a href="#2.4">&sect;2.4</a>).
   3599  1.2    lneto 
   3600  1.2    lneto 
   3601  1.2    lneto <p>
   3602  1.2    lneto Returns the type of the pushed value.
   3603  1.1  mbalmer 
   3604  1.1  mbalmer 
   3605  1.1  mbalmer 
   3606  1.1  mbalmer 
   3607  1.1  mbalmer 
   3608  1.1  mbalmer <hr><h3><a name="lua_gettop"><code>lua_gettop</code></a></h3><p>
   3609  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3610  1.1  mbalmer <pre>int lua_gettop (lua_State *L);</pre>
   3611  1.1  mbalmer 
   3612  1.1  mbalmer <p>
   3613  1.1  mbalmer Returns the index of the top element in the stack.
   3614  1.1  mbalmer Because indices start at&nbsp;1,
   3615  1.3    lneto this result is equal to the number of elements in the stack;
   3616  1.3    lneto in particular, 0&nbsp;means an empty stack.
   3617  1.1  mbalmer 
   3618  1.1  mbalmer 
   3619  1.1  mbalmer 
   3620  1.1  mbalmer 
   3621  1.1  mbalmer 
   3622  1.2    lneto <hr><h3><a name="lua_getuservalue"><code>lua_getuservalue</code></a></h3><p>
   3623  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   3624  1.2    lneto <pre>int lua_getuservalue (lua_State *L, int index);</pre>
   3625  1.2    lneto 
   3626  1.2    lneto <p>
   3627  1.2    lneto Pushes onto the stack the Lua value associated with the userdata
   3628  1.2    lneto at the given index.
   3629  1.2    lneto 
   3630  1.2    lneto 
   3631  1.2    lneto <p>
   3632  1.2    lneto Returns the type of the pushed value.
   3633  1.2    lneto 
   3634  1.2    lneto 
   3635  1.2    lneto 
   3636  1.2    lneto 
   3637  1.2    lneto 
   3638  1.1  mbalmer <hr><h3><a name="lua_insert"><code>lua_insert</code></a></h3><p>
   3639  1.2    lneto <span class="apii">[-1, +1, &ndash;]</span>
   3640  1.1  mbalmer <pre>void lua_insert (lua_State *L, int index);</pre>
   3641  1.1  mbalmer 
   3642  1.1  mbalmer <p>
   3643  1.1  mbalmer Moves the top element into the given valid index,
   3644  1.1  mbalmer shifting up the elements above this index to open space.
   3645  1.2    lneto This function cannot be called with a pseudo-index,
   3646  1.1  mbalmer because a pseudo-index is not an actual stack position.
   3647  1.1  mbalmer 
   3648  1.1  mbalmer 
   3649  1.1  mbalmer 
   3650  1.1  mbalmer 
   3651  1.1  mbalmer 
   3652  1.1  mbalmer <hr><h3><a name="lua_Integer"><code>lua_Integer</code></a></h3>
   3653  1.2    lneto <pre>typedef ... lua_Integer;</pre>
   3654  1.1  mbalmer 
   3655  1.1  mbalmer <p>
   3656  1.2    lneto The type of integers in Lua.
   3657  1.1  mbalmer 
   3658  1.1  mbalmer 
   3659  1.1  mbalmer <p>
   3660  1.3    lneto By default this type is <code>long long</code>,
   3661  1.2    lneto (usually a 64-bit two-complement integer),
   3662  1.3    lneto but that can be changed to <code>long</code> or <code>int</code>
   3663  1.2    lneto (usually a 32-bit two-complement integer).
   3664  1.3    lneto (See <code>LUA_INT</code> in <code>luaconf.h</code>.)
   3665  1.2    lneto 
   3666  1.2    lneto 
   3667  1.2    lneto <p>
   3668  1.2    lneto Lua also defines the constants
   3669  1.2    lneto <a name="pdf-LUA_MININTEGER"><code>LUA_MININTEGER</code></a> and <a name="pdf-LUA_MAXINTEGER"><code>LUA_MAXINTEGER</code></a>,
   3670  1.2    lneto with the minimum and the maximum values that fit in this type.
   3671  1.1  mbalmer 
   3672  1.1  mbalmer 
   3673  1.1  mbalmer 
   3674  1.1  mbalmer 
   3675  1.1  mbalmer 
   3676  1.1  mbalmer <hr><h3><a name="lua_isboolean"><code>lua_isboolean</code></a></h3><p>
   3677  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3678  1.1  mbalmer <pre>int lua_isboolean (lua_State *L, int index);</pre>
   3679  1.1  mbalmer 
   3680  1.1  mbalmer <p>
   3681  1.2    lneto Returns 1 if the value at the given index is a boolean,
   3682  1.1  mbalmer and 0&nbsp;otherwise.
   3683  1.1  mbalmer 
   3684  1.1  mbalmer 
   3685  1.1  mbalmer 
   3686  1.1  mbalmer 
   3687  1.1  mbalmer 
   3688  1.1  mbalmer <hr><h3><a name="lua_iscfunction"><code>lua_iscfunction</code></a></h3><p>
   3689  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3690  1.1  mbalmer <pre>int lua_iscfunction (lua_State *L, int index);</pre>
   3691  1.1  mbalmer 
   3692  1.1  mbalmer <p>
   3693  1.2    lneto Returns 1 if the value at the given index is a C&nbsp;function,
   3694  1.1  mbalmer and 0&nbsp;otherwise.
   3695  1.1  mbalmer 
   3696  1.1  mbalmer 
   3697  1.1  mbalmer 
   3698  1.1  mbalmer 
   3699  1.1  mbalmer 
   3700  1.1  mbalmer <hr><h3><a name="lua_isfunction"><code>lua_isfunction</code></a></h3><p>
   3701  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3702  1.1  mbalmer <pre>int lua_isfunction (lua_State *L, int index);</pre>
   3703  1.1  mbalmer 
   3704  1.1  mbalmer <p>
   3705  1.2    lneto Returns 1 if the value at the given index is a function
   3706  1.1  mbalmer (either C or Lua), and 0&nbsp;otherwise.
   3707  1.1  mbalmer 
   3708  1.1  mbalmer 
   3709  1.1  mbalmer 
   3710  1.1  mbalmer 
   3711  1.1  mbalmer 
   3712  1.2    lneto <hr><h3><a name="lua_isinteger"><code>lua_isinteger</code></a></h3><p>
   3713  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3714  1.2    lneto <pre>int lua_isinteger (lua_State *L, int index);</pre>
   3715  1.2    lneto 
   3716  1.2    lneto <p>
   3717  1.2    lneto Returns 1 if the value at the given index is an integer
   3718  1.2    lneto (that is, the value is a number and is represented as an integer),
   3719  1.2    lneto and 0&nbsp;otherwise.
   3720  1.2    lneto 
   3721  1.2    lneto 
   3722  1.2    lneto 
   3723  1.2    lneto 
   3724  1.2    lneto 
   3725  1.1  mbalmer <hr><h3><a name="lua_islightuserdata"><code>lua_islightuserdata</code></a></h3><p>
   3726  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3727  1.1  mbalmer <pre>int lua_islightuserdata (lua_State *L, int index);</pre>
   3728  1.1  mbalmer 
   3729  1.1  mbalmer <p>
   3730  1.2    lneto Returns 1 if the value at the given index is a light userdata,
   3731  1.1  mbalmer and 0&nbsp;otherwise.
   3732  1.1  mbalmer 
   3733  1.1  mbalmer 
   3734  1.1  mbalmer 
   3735  1.1  mbalmer 
   3736  1.1  mbalmer 
   3737  1.1  mbalmer <hr><h3><a name="lua_isnil"><code>lua_isnil</code></a></h3><p>
   3738  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3739  1.1  mbalmer <pre>int lua_isnil (lua_State *L, int index);</pre>
   3740  1.1  mbalmer 
   3741  1.1  mbalmer <p>
   3742  1.2    lneto Returns 1 if the value at the given index is <b>nil</b>,
   3743  1.1  mbalmer and 0&nbsp;otherwise.
   3744  1.1  mbalmer 
   3745  1.1  mbalmer 
   3746  1.1  mbalmer 
   3747  1.1  mbalmer 
   3748  1.1  mbalmer 
   3749  1.1  mbalmer <hr><h3><a name="lua_isnone"><code>lua_isnone</code></a></h3><p>
   3750  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3751  1.1  mbalmer <pre>int lua_isnone (lua_State *L, int index);</pre>
   3752  1.1  mbalmer 
   3753  1.1  mbalmer <p>
   3754  1.2    lneto Returns 1 if the given index is not valid,
   3755  1.1  mbalmer and 0&nbsp;otherwise.
   3756  1.1  mbalmer 
   3757  1.1  mbalmer 
   3758  1.1  mbalmer 
   3759  1.1  mbalmer 
   3760  1.1  mbalmer 
   3761  1.1  mbalmer <hr><h3><a name="lua_isnoneornil"><code>lua_isnoneornil</code></a></h3><p>
   3762  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3763  1.1  mbalmer <pre>int lua_isnoneornil (lua_State *L, int index);</pre>
   3764  1.1  mbalmer 
   3765  1.1  mbalmer <p>
   3766  1.2    lneto Returns 1 if the given index is not valid
   3767  1.1  mbalmer or if the value at this index is <b>nil</b>,
   3768  1.1  mbalmer and 0&nbsp;otherwise.
   3769  1.1  mbalmer 
   3770  1.1  mbalmer 
   3771  1.1  mbalmer 
   3772  1.1  mbalmer 
   3773  1.1  mbalmer 
   3774  1.1  mbalmer <hr><h3><a name="lua_isnumber"><code>lua_isnumber</code></a></h3><p>
   3775  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3776  1.1  mbalmer <pre>int lua_isnumber (lua_State *L, int index);</pre>
   3777  1.1  mbalmer 
   3778  1.1  mbalmer <p>
   3779  1.2    lneto Returns 1 if the value at the given index is a number
   3780  1.1  mbalmer or a string convertible to a number,
   3781  1.1  mbalmer and 0&nbsp;otherwise.
   3782  1.1  mbalmer 
   3783  1.1  mbalmer 
   3784  1.1  mbalmer 
   3785  1.1  mbalmer 
   3786  1.1  mbalmer 
   3787  1.1  mbalmer <hr><h3><a name="lua_isstring"><code>lua_isstring</code></a></h3><p>
   3788  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3789  1.1  mbalmer <pre>int lua_isstring (lua_State *L, int index);</pre>
   3790  1.1  mbalmer 
   3791  1.1  mbalmer <p>
   3792  1.2    lneto Returns 1 if the value at the given index is a string
   3793  1.1  mbalmer or a number (which is always convertible to a string),
   3794  1.1  mbalmer and 0&nbsp;otherwise.
   3795  1.1  mbalmer 
   3796  1.1  mbalmer 
   3797  1.1  mbalmer 
   3798  1.1  mbalmer 
   3799  1.1  mbalmer 
   3800  1.1  mbalmer <hr><h3><a name="lua_istable"><code>lua_istable</code></a></h3><p>
   3801  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3802  1.1  mbalmer <pre>int lua_istable (lua_State *L, int index);</pre>
   3803  1.1  mbalmer 
   3804  1.1  mbalmer <p>
   3805  1.2    lneto Returns 1 if the value at the given index is a table,
   3806  1.1  mbalmer and 0&nbsp;otherwise.
   3807  1.1  mbalmer 
   3808  1.1  mbalmer 
   3809  1.1  mbalmer 
   3810  1.1  mbalmer 
   3811  1.1  mbalmer 
   3812  1.1  mbalmer <hr><h3><a name="lua_isthread"><code>lua_isthread</code></a></h3><p>
   3813  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3814  1.1  mbalmer <pre>int lua_isthread (lua_State *L, int index);</pre>
   3815  1.1  mbalmer 
   3816  1.1  mbalmer <p>
   3817  1.2    lneto Returns 1 if the value at the given index is a thread,
   3818  1.1  mbalmer and 0&nbsp;otherwise.
   3819  1.1  mbalmer 
   3820  1.1  mbalmer 
   3821  1.1  mbalmer 
   3822  1.1  mbalmer 
   3823  1.1  mbalmer 
   3824  1.1  mbalmer <hr><h3><a name="lua_isuserdata"><code>lua_isuserdata</code></a></h3><p>
   3825  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3826  1.1  mbalmer <pre>int lua_isuserdata (lua_State *L, int index);</pre>
   3827  1.1  mbalmer 
   3828  1.1  mbalmer <p>
   3829  1.2    lneto Returns 1 if the value at the given index is a userdata
   3830  1.1  mbalmer (either full or light), and 0&nbsp;otherwise.
   3831  1.1  mbalmer 
   3832  1.1  mbalmer 
   3833  1.1  mbalmer 
   3834  1.1  mbalmer 
   3835  1.1  mbalmer 
   3836  1.2    lneto <hr><h3><a name="lua_isyieldable"><code>lua_isyieldable</code></a></h3><p>
   3837  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3838  1.2    lneto <pre>int lua_isyieldable (lua_State *L);</pre>
   3839  1.2    lneto 
   3840  1.2    lneto <p>
   3841  1.2    lneto Returns 1 if the given coroutine can yield,
   3842  1.2    lneto and 0&nbsp;otherwise.
   3843  1.2    lneto 
   3844  1.2    lneto 
   3845  1.2    lneto 
   3846  1.2    lneto 
   3847  1.2    lneto 
   3848  1.3    lneto <hr><h3><a name="lua_KContext"><code>lua_KContext</code></a></h3>
   3849  1.3    lneto <pre>typedef ... lua_KContext;</pre>
   3850  1.3    lneto 
   3851  1.3    lneto <p>
   3852  1.3    lneto The type for continuation-function contexts.
   3853  1.3    lneto It must be a numerical type.
   3854  1.3    lneto This type is defined as <code>intptr_t</code>
   3855  1.3    lneto when <code>intptr_t</code> is available,
   3856  1.3    lneto so that it can store pointers too.
   3857  1.3    lneto Otherwise, it is defined as <code>ptrdiff_t</code>.
   3858  1.3    lneto 
   3859  1.3    lneto 
   3860  1.3    lneto 
   3861  1.3    lneto 
   3862  1.3    lneto 
   3863  1.2    lneto <hr><h3><a name="lua_KFunction"><code>lua_KFunction</code></a></h3>
   3864  1.3    lneto <pre>typedef int (*lua_KFunction) (lua_State *L, int status, lua_KContext ctx);</pre>
   3865  1.2    lneto 
   3866  1.2    lneto <p>
   3867  1.2    lneto Type for continuation functions (see <a href="#4.7">&sect;4.7</a>).
   3868  1.2    lneto 
   3869  1.2    lneto 
   3870  1.2    lneto 
   3871  1.2    lneto 
   3872  1.2    lneto 
   3873  1.2    lneto <hr><h3><a name="lua_len"><code>lua_len</code></a></h3><p>
   3874  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   3875  1.2    lneto <pre>void lua_len (lua_State *L, int index);</pre>
   3876  1.1  mbalmer 
   3877  1.1  mbalmer <p>
   3878  1.3    lneto Returns the length of the value at the given index.
   3879  1.3    lneto It is equivalent to the '<code>#</code>' operator in Lua (see <a href="#3.4.7">&sect;3.4.7</a>) and
   3880  1.3    lneto may trigger a metamethod for the "length" event (see <a href="#2.4">&sect;2.4</a>).
   3881  1.2    lneto The result is pushed on the stack.
   3882  1.1  mbalmer 
   3883  1.1  mbalmer 
   3884  1.1  mbalmer 
   3885  1.1  mbalmer 
   3886  1.1  mbalmer 
   3887  1.1  mbalmer <hr><h3><a name="lua_load"><code>lua_load</code></a></h3><p>
   3888  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   3889  1.1  mbalmer <pre>int lua_load (lua_State *L,
   3890  1.1  mbalmer               lua_Reader reader,
   3891  1.1  mbalmer               void *data,
   3892  1.3    lneto               const char *chunkname,
   3893  1.2    lneto               const char *mode);</pre>
   3894  1.1  mbalmer 
   3895  1.1  mbalmer <p>
   3896  1.3    lneto Loads a Lua chunk without running it.
   3897  1.1  mbalmer If there are no errors,
   3898  1.2    lneto <code>lua_load</code> pushes the compiled chunk as a Lua
   3899  1.1  mbalmer function on top of the stack.
   3900  1.1  mbalmer Otherwise, it pushes an error message.
   3901  1.2    lneto 
   3902  1.2    lneto 
   3903  1.2    lneto <p>
   3904  1.2    lneto The return values of <code>lua_load</code> are:
   3905  1.1  mbalmer 
   3906  1.1  mbalmer <ul>
   3907  1.1  mbalmer 
   3908  1.2    lneto <li><b><a href="#pdf-LUA_OK"><code>LUA_OK</code></a>: </b> no errors;</li>
   3909  1.2    lneto 
   3910  1.2    lneto <li><b><a name="pdf-LUA_ERRSYNTAX"><code>LUA_ERRSYNTAX</code></a>: </b>
   3911  1.2    lneto syntax error during precompilation;</li>
   3912  1.1  mbalmer 
   3913  1.2    lneto <li><b><a href="#pdf-LUA_ERRMEM"><code>LUA_ERRMEM</code></a>: </b>
   3914  1.2    lneto memory allocation error;</li>
   3915  1.1  mbalmer 
   3916  1.2    lneto <li><b><a href="#pdf-LUA_ERRGCMM"><code>LUA_ERRGCMM</code></a>: </b>
   3917  1.2    lneto error while running a <code>__gc</code> metamethod.
   3918  1.2    lneto (This error has no relation with the chunk being loaded.
   3919  1.2    lneto It is generated by the garbage collector.)
   3920  1.2    lneto </li>
   3921  1.1  mbalmer 
   3922  1.1  mbalmer </ul>
   3923  1.1  mbalmer 
   3924  1.1  mbalmer <p>
   3925  1.2    lneto The <code>lua_load</code> function uses a user-supplied <code>reader</code> function
   3926  1.2    lneto to read the chunk (see <a href="#lua_Reader"><code>lua_Reader</code></a>).
   3927  1.2    lneto The <code>data</code> argument is an opaque value passed to the reader function.
   3928  1.2    lneto 
   3929  1.2    lneto 
   3930  1.2    lneto <p>
   3931  1.3    lneto The <code>chunkname</code> argument gives a name to the chunk,
   3932  1.2    lneto which is used for error messages and in debug information (see <a href="#4.9">&sect;4.9</a>).
   3933  1.1  mbalmer 
   3934  1.1  mbalmer 
   3935  1.1  mbalmer <p>
   3936  1.2    lneto <code>lua_load</code> automatically detects whether the chunk is text or binary
   3937  1.1  mbalmer and loads it accordingly (see program <code>luac</code>).
   3938  1.2    lneto The string <code>mode</code> works as in function <a href="#pdf-load"><code>load</code></a>,
   3939  1.2    lneto with the addition that
   3940  1.2    lneto a <code>NULL</code> value is equivalent to the string "<code>bt</code>".
   3941  1.1  mbalmer 
   3942  1.1  mbalmer 
   3943  1.1  mbalmer <p>
   3944  1.2    lneto <code>lua_load</code> uses the stack internally,
   3945  1.2    lneto so the reader function must always leave the stack
   3946  1.2    lneto unmodified when returning.
   3947  1.1  mbalmer 
   3948  1.1  mbalmer 
   3949  1.1  mbalmer <p>
   3950  1.3    lneto If the resulting function has upvalues,
   3951  1.3    lneto its first upvalue is set to the value of the global environment
   3952  1.2    lneto stored at index <code>LUA_RIDX_GLOBALS</code> in the registry (see <a href="#4.5">&sect;4.5</a>).
   3953  1.2    lneto When loading main chunks,
   3954  1.2    lneto this upvalue will be the <code>_ENV</code> variable (see <a href="#2.2">&sect;2.2</a>).
   3955  1.3    lneto Other upvalues are initialized with <b>nil</b>.
   3956  1.1  mbalmer 
   3957  1.1  mbalmer 
   3958  1.1  mbalmer 
   3959  1.1  mbalmer 
   3960  1.1  mbalmer 
   3961  1.1  mbalmer <hr><h3><a name="lua_newstate"><code>lua_newstate</code></a></h3><p>
   3962  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   3963  1.1  mbalmer <pre>lua_State *lua_newstate (lua_Alloc f, void *ud);</pre>
   3964  1.1  mbalmer 
   3965  1.1  mbalmer <p>
   3966  1.2    lneto Creates a new thread running in a new, independent state.
   3967  1.2    lneto Returns <code>NULL</code> if it cannot create the thread or the state
   3968  1.1  mbalmer (due to lack of memory).
   3969  1.1  mbalmer The argument <code>f</code> is the allocator function;
   3970  1.1  mbalmer Lua does all memory allocation for this state through this function.
   3971  1.1  mbalmer The second argument, <code>ud</code>, is an opaque pointer that Lua
   3972  1.2    lneto passes to the allocator in every call.
   3973  1.1  mbalmer 
   3974  1.1  mbalmer 
   3975  1.1  mbalmer 
   3976  1.1  mbalmer 
   3977  1.1  mbalmer 
   3978  1.1  mbalmer <hr><h3><a name="lua_newtable"><code>lua_newtable</code></a></h3><p>
   3979  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   3980  1.1  mbalmer <pre>void lua_newtable (lua_State *L);</pre>
   3981  1.1  mbalmer 
   3982  1.1  mbalmer <p>
   3983  1.1  mbalmer Creates a new empty table and pushes it onto the stack.
   3984  1.1  mbalmer It is equivalent to <code>lua_createtable(L, 0, 0)</code>.
   3985  1.1  mbalmer 
   3986  1.1  mbalmer 
   3987  1.1  mbalmer 
   3988  1.1  mbalmer 
   3989  1.1  mbalmer 
   3990  1.1  mbalmer <hr><h3><a name="lua_newthread"><code>lua_newthread</code></a></h3><p>
   3991  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   3992  1.1  mbalmer <pre>lua_State *lua_newthread (lua_State *L);</pre>
   3993  1.1  mbalmer 
   3994  1.1  mbalmer <p>
   3995  1.1  mbalmer Creates a new thread, pushes it on the stack,
   3996  1.1  mbalmer and returns a pointer to a <a href="#lua_State"><code>lua_State</code></a> that represents this new thread.
   3997  1.2    lneto The new thread returned by this function shares with the original thread
   3998  1.2    lneto its global environment,
   3999  1.1  mbalmer but has an independent execution stack.
   4000  1.1  mbalmer 
   4001  1.1  mbalmer 
   4002  1.1  mbalmer <p>
   4003  1.1  mbalmer There is no explicit function to close or to destroy a thread.
   4004  1.1  mbalmer Threads are subject to garbage collection,
   4005  1.1  mbalmer like any Lua object.
   4006  1.1  mbalmer 
   4007  1.1  mbalmer 
   4008  1.1  mbalmer 
   4009  1.1  mbalmer 
   4010  1.1  mbalmer 
   4011  1.1  mbalmer <hr><h3><a name="lua_newuserdata"><code>lua_newuserdata</code></a></h3><p>
   4012  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   4013  1.1  mbalmer <pre>void *lua_newuserdata (lua_State *L, size_t size);</pre>
   4014  1.1  mbalmer 
   4015  1.1  mbalmer <p>
   4016  1.1  mbalmer This function allocates a new block of memory with the given size,
   4017  1.1  mbalmer pushes onto the stack a new full userdata with the block address,
   4018  1.1  mbalmer and returns this address.
   4019  1.2    lneto The host program can freely use this memory.
   4020  1.1  mbalmer 
   4021  1.1  mbalmer 
   4022  1.1  mbalmer 
   4023  1.1  mbalmer 
   4024  1.1  mbalmer 
   4025  1.1  mbalmer <hr><h3><a name="lua_next"><code>lua_next</code></a></h3><p>
   4026  1.1  mbalmer <span class="apii">[-1, +(2|0), <em>e</em>]</span>
   4027  1.1  mbalmer <pre>int lua_next (lua_State *L, int index);</pre>
   4028  1.1  mbalmer 
   4029  1.1  mbalmer <p>
   4030  1.1  mbalmer Pops a key from the stack,
   4031  1.2    lneto and pushes a key&ndash;value pair from the table at the given index
   4032  1.1  mbalmer (the "next" pair after the given key).
   4033  1.1  mbalmer If there are no more elements in the table,
   4034  1.1  mbalmer then <a href="#lua_next"><code>lua_next</code></a> returns 0 (and pushes nothing).
   4035  1.1  mbalmer 
   4036  1.1  mbalmer 
   4037  1.1  mbalmer <p>
   4038  1.1  mbalmer A typical traversal looks like this:
   4039  1.1  mbalmer 
   4040  1.1  mbalmer <pre>
   4041  1.1  mbalmer      /* table is in the stack at index 't' */
   4042  1.1  mbalmer      lua_pushnil(L);  /* first key */
   4043  1.1  mbalmer      while (lua_next(L, t) != 0) {
   4044  1.1  mbalmer        /* uses 'key' (at index -2) and 'value' (at index -1) */
   4045  1.1  mbalmer        printf("%s - %s\n",
   4046  1.1  mbalmer               lua_typename(L, lua_type(L, -2)),
   4047  1.1  mbalmer               lua_typename(L, lua_type(L, -1)));
   4048  1.1  mbalmer        /* removes 'value'; keeps 'key' for next iteration */
   4049  1.1  mbalmer        lua_pop(L, 1);
   4050  1.1  mbalmer      }
   4051  1.1  mbalmer </pre>
   4052  1.1  mbalmer 
   4053  1.1  mbalmer <p>
   4054  1.1  mbalmer While traversing a table,
   4055  1.1  mbalmer do not call <a href="#lua_tolstring"><code>lua_tolstring</code></a> directly on a key,
   4056  1.1  mbalmer unless you know that the key is actually a string.
   4057  1.2    lneto Recall that <a href="#lua_tolstring"><code>lua_tolstring</code></a> may change
   4058  1.1  mbalmer the value at the given index;
   4059  1.1  mbalmer this confuses the next call to <a href="#lua_next"><code>lua_next</code></a>.
   4060  1.1  mbalmer 
   4061  1.1  mbalmer 
   4062  1.2    lneto <p>
   4063  1.2    lneto See function <a href="#pdf-next"><code>next</code></a> for the caveats of modifying
   4064  1.2    lneto the table during its traversal.
   4065  1.2    lneto 
   4066  1.2    lneto 
   4067  1.1  mbalmer 
   4068  1.1  mbalmer 
   4069  1.1  mbalmer 
   4070  1.1  mbalmer <hr><h3><a name="lua_Number"><code>lua_Number</code></a></h3>
   4071  1.1  mbalmer <pre>typedef double lua_Number;</pre>
   4072  1.1  mbalmer 
   4073  1.1  mbalmer <p>
   4074  1.2    lneto The type of floats in Lua.
   4075  1.1  mbalmer 
   4076  1.1  mbalmer 
   4077  1.1  mbalmer <p>
   4078  1.2    lneto By default this type is double,
   4079  1.3    lneto but that can be changed to a single float.
   4080  1.3    lneto (See <code>LUA_REAL</code> in <code>luaconf.h</code>.)
   4081  1.2    lneto 
   4082  1.2    lneto 
   4083  1.1  mbalmer 
   4084  1.1  mbalmer 
   4085  1.1  mbalmer 
   4086  1.3    lneto <hr><h3><a name="lua_numbertointeger"><code>lua_numbertointeger</code></a></h3>
   4087  1.3    lneto <pre>int lua_numbertointeger (lua_Number n, lua_Integer *p);</pre>
   4088  1.1  mbalmer 
   4089  1.2    lneto <p>
   4090  1.2    lneto Converts a Lua float to a Lua integer.
   4091  1.2    lneto This macro assumes that <code>n</code> has an integral value.
   4092  1.2    lneto If that value is within the range of Lua integers,
   4093  1.2    lneto it is converted to an integer and assigned to <code>*p</code>.
   4094  1.2    lneto The macro results in a boolean indicating whether the
   4095  1.2    lneto conversion was successful.
   4096  1.2    lneto (Note that this range test can be tricky to do
   4097  1.2    lneto correctly without this macro,
   4098  1.2    lneto due to roundings.)
   4099  1.1  mbalmer 
   4100  1.1  mbalmer 
   4101  1.1  mbalmer <p>
   4102  1.2    lneto This macro may evaluate its arguments more than once.
   4103  1.1  mbalmer 
   4104  1.1  mbalmer 
   4105  1.1  mbalmer 
   4106  1.1  mbalmer 
   4107  1.1  mbalmer 
   4108  1.1  mbalmer <hr><h3><a name="lua_pcall"><code>lua_pcall</code></a></h3><p>
   4109  1.2    lneto <span class="apii">[-(nargs + 1), +(nresults|1), &ndash;]</span>
   4110  1.2    lneto <pre>int lua_pcall (lua_State *L, int nargs, int nresults, int msgh);</pre>
   4111  1.1  mbalmer 
   4112  1.1  mbalmer <p>
   4113  1.1  mbalmer Calls a function in protected mode.
   4114  1.1  mbalmer 
   4115  1.1  mbalmer 
   4116  1.1  mbalmer <p>
   4117  1.1  mbalmer Both <code>nargs</code> and <code>nresults</code> have the same meaning as
   4118  1.1  mbalmer in <a href="#lua_call"><code>lua_call</code></a>.
   4119  1.1  mbalmer If there are no errors during the call,
   4120  1.1  mbalmer <a href="#lua_pcall"><code>lua_pcall</code></a> behaves exactly like <a href="#lua_call"><code>lua_call</code></a>.
   4121  1.1  mbalmer However, if there is any error,
   4122  1.1  mbalmer <a href="#lua_pcall"><code>lua_pcall</code></a> catches it,
   4123  1.1  mbalmer pushes a single value on the stack (the error message),
   4124  1.1  mbalmer and returns an error code.
   4125  1.1  mbalmer Like <a href="#lua_call"><code>lua_call</code></a>,
   4126  1.1  mbalmer <a href="#lua_pcall"><code>lua_pcall</code></a> always removes the function
   4127  1.1  mbalmer and its arguments from the stack.
   4128  1.1  mbalmer 
   4129  1.1  mbalmer 
   4130  1.1  mbalmer <p>
   4131  1.2    lneto If <code>msgh</code> is 0,
   4132  1.1  mbalmer then the error message returned on the stack
   4133  1.1  mbalmer is exactly the original error message.
   4134  1.2    lneto Otherwise, <code>msgh</code> is the stack index of a
   4135  1.2    lneto <em>message handler</em>.
   4136  1.1  mbalmer (In the current implementation, this index cannot be a pseudo-index.)
   4137  1.1  mbalmer In case of runtime errors,
   4138  1.1  mbalmer this function will be called with the error message
   4139  1.2    lneto and its return value will be the message
   4140  1.2    lneto returned on the stack by <a href="#lua_pcall"><code>lua_pcall</code></a>.
   4141  1.1  mbalmer 
   4142  1.1  mbalmer 
   4143  1.1  mbalmer <p>
   4144  1.2    lneto Typically, the message handler is used to add more debug
   4145  1.1  mbalmer information to the error message, such as a stack traceback.
   4146  1.1  mbalmer Such information cannot be gathered after the return of <a href="#lua_pcall"><code>lua_pcall</code></a>,
   4147  1.1  mbalmer since by then the stack has unwound.
   4148  1.1  mbalmer 
   4149  1.1  mbalmer 
   4150  1.1  mbalmer <p>
   4151  1.2    lneto The <a href="#lua_pcall"><code>lua_pcall</code></a> function returns one of the following constants
   4152  1.1  mbalmer (defined in <code>lua.h</code>):
   4153  1.1  mbalmer 
   4154  1.1  mbalmer <ul>
   4155  1.1  mbalmer 
   4156  1.2    lneto <li><b><a name="pdf-LUA_OK"><code>LUA_OK</code></a> (0): </b>
   4157  1.2    lneto success.</li>
   4158  1.2    lneto 
   4159  1.2    lneto <li><b><a name="pdf-LUA_ERRRUN"><code>LUA_ERRRUN</code></a>: </b>
   4160  1.1  mbalmer a runtime error.
   4161  1.1  mbalmer </li>
   4162  1.1  mbalmer 
   4163  1.2    lneto <li><b><a name="pdf-LUA_ERRMEM"><code>LUA_ERRMEM</code></a>: </b>
   4164  1.1  mbalmer memory allocation error.
   4165  1.2    lneto For such errors, Lua does not call the message handler.
   4166  1.2    lneto </li>
   4167  1.2    lneto 
   4168  1.2    lneto <li><b><a name="pdf-LUA_ERRERR"><code>LUA_ERRERR</code></a>: </b>
   4169  1.2    lneto error while running the message handler.
   4170  1.1  mbalmer </li>
   4171  1.1  mbalmer 
   4172  1.2    lneto <li><b><a name="pdf-LUA_ERRGCMM"><code>LUA_ERRGCMM</code></a>: </b>
   4173  1.2    lneto error while running a <code>__gc</code> metamethod.
   4174  1.2    lneto (This error typically has no relation with the function being called.)
   4175  1.1  mbalmer </li>
   4176  1.1  mbalmer 
   4177  1.1  mbalmer </ul>
   4178  1.1  mbalmer 
   4179  1.1  mbalmer 
   4180  1.1  mbalmer 
   4181  1.1  mbalmer 
   4182  1.2    lneto <hr><h3><a name="lua_pcallk"><code>lua_pcallk</code></a></h3><p>
   4183  1.2    lneto <span class="apii">[-(nargs + 1), +(nresults|1), &ndash;]</span>
   4184  1.2    lneto <pre>int lua_pcallk (lua_State *L,
   4185  1.2    lneto                 int nargs,
   4186  1.2    lneto                 int nresults,
   4187  1.3    lneto                 int msgh,
   4188  1.3    lneto                 lua_KContext ctx,
   4189  1.2    lneto                 lua_KFunction k);</pre>
   4190  1.2    lneto 
   4191  1.2    lneto <p>
   4192  1.2    lneto This function behaves exactly like <a href="#lua_pcall"><code>lua_pcall</code></a>,
   4193  1.2    lneto but allows the called function to yield (see <a href="#4.7">&sect;4.7</a>).
   4194  1.2    lneto 
   4195  1.2    lneto 
   4196  1.2    lneto 
   4197  1.2    lneto 
   4198  1.2    lneto 
   4199  1.1  mbalmer <hr><h3><a name="lua_pop"><code>lua_pop</code></a></h3><p>
   4200  1.2    lneto <span class="apii">[-n, +0, &ndash;]</span>
   4201  1.1  mbalmer <pre>void lua_pop (lua_State *L, int n);</pre>
   4202  1.1  mbalmer 
   4203  1.1  mbalmer <p>
   4204  1.1  mbalmer Pops <code>n</code> elements from the stack.
   4205  1.1  mbalmer 
   4206  1.1  mbalmer 
   4207  1.1  mbalmer 
   4208  1.1  mbalmer 
   4209  1.1  mbalmer 
   4210  1.1  mbalmer <hr><h3><a name="lua_pushboolean"><code>lua_pushboolean</code></a></h3><p>
   4211  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   4212  1.1  mbalmer <pre>void lua_pushboolean (lua_State *L, int b);</pre>
   4213  1.1  mbalmer 
   4214  1.1  mbalmer <p>
   4215  1.1  mbalmer Pushes a boolean value with value <code>b</code> onto the stack.
   4216  1.1  mbalmer 
   4217  1.1  mbalmer 
   4218  1.1  mbalmer 
   4219  1.1  mbalmer 
   4220  1.1  mbalmer 
   4221  1.1  mbalmer <hr><h3><a name="lua_pushcclosure"><code>lua_pushcclosure</code></a></h3><p>
   4222  1.2    lneto <span class="apii">[-n, +1, <em>e</em>]</span>
   4223  1.1  mbalmer <pre>void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n);</pre>
   4224  1.1  mbalmer 
   4225  1.1  mbalmer <p>
   4226  1.1  mbalmer Pushes a new C&nbsp;closure onto the stack.
   4227  1.1  mbalmer 
   4228  1.1  mbalmer 
   4229  1.1  mbalmer <p>
   4230  1.1  mbalmer When a C&nbsp;function is created,
   4231  1.1  mbalmer it is possible to associate some values with it,
   4232  1.2    lneto thus creating a C&nbsp;closure (see <a href="#4.4">&sect;4.4</a>);
   4233  1.1  mbalmer these values are then accessible to the function whenever it is called.
   4234  1.1  mbalmer To associate values with a C&nbsp;function,
   4235  1.2    lneto first these values must be pushed onto the stack
   4236  1.1  mbalmer (when there are multiple values, the first value is pushed first).
   4237  1.1  mbalmer Then <a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a>
   4238  1.1  mbalmer is called to create and push the C&nbsp;function onto the stack,
   4239  1.2    lneto with the argument <code>n</code> telling how many values will be
   4240  1.1  mbalmer associated with the function.
   4241  1.1  mbalmer <a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a> also pops these values from the stack.
   4242  1.1  mbalmer 
   4243  1.1  mbalmer 
   4244  1.1  mbalmer <p>
   4245  1.1  mbalmer The maximum value for <code>n</code> is 255.
   4246  1.1  mbalmer 
   4247  1.1  mbalmer 
   4248  1.2    lneto <p>
   4249  1.2    lneto When <code>n</code> is zero,
   4250  1.2    lneto this function creates a <em>light C function</em>,
   4251  1.2    lneto which is just a pointer to the C&nbsp;function.
   4252  1.2    lneto In that case, it never raises a memory error.
   4253  1.2    lneto 
   4254  1.2    lneto 
   4255  1.1  mbalmer 
   4256  1.1  mbalmer 
   4257  1.1  mbalmer 
   4258  1.1  mbalmer <hr><h3><a name="lua_pushcfunction"><code>lua_pushcfunction</code></a></h3><p>
   4259  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   4260  1.1  mbalmer <pre>void lua_pushcfunction (lua_State *L, lua_CFunction f);</pre>
   4261  1.1  mbalmer 
   4262  1.1  mbalmer <p>
   4263  1.1  mbalmer Pushes a C&nbsp;function onto the stack.
   4264  1.1  mbalmer This function receives a pointer to a C function
   4265  1.1  mbalmer and pushes onto the stack a Lua value of type <code>function</code> that,
   4266  1.1  mbalmer when called, invokes the corresponding C&nbsp;function.
   4267  1.1  mbalmer 
   4268  1.1  mbalmer 
   4269  1.1  mbalmer <p>
   4270  1.1  mbalmer Any function to be registered in Lua must
   4271  1.1  mbalmer follow the correct protocol to receive its parameters
   4272  1.1  mbalmer and return its results (see <a href="#lua_CFunction"><code>lua_CFunction</code></a>).
   4273  1.1  mbalmer 
   4274  1.1  mbalmer 
   4275  1.1  mbalmer <p>
   4276  1.1  mbalmer <code>lua_pushcfunction</code> is defined as a macro:
   4277  1.1  mbalmer 
   4278  1.1  mbalmer <pre>
   4279  1.1  mbalmer      #define lua_pushcfunction(L,f)  lua_pushcclosure(L,f,0)
   4280  1.2    lneto </pre><p>
   4281  1.2    lneto Note that <code>f</code> is used twice.
   4282  1.2    lneto 
   4283  1.1  mbalmer 
   4284  1.1  mbalmer 
   4285  1.1  mbalmer 
   4286  1.1  mbalmer 
   4287  1.1  mbalmer <hr><h3><a name="lua_pushfstring"><code>lua_pushfstring</code></a></h3><p>
   4288  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   4289  1.1  mbalmer <pre>const char *lua_pushfstring (lua_State *L, const char *fmt, ...);</pre>
   4290  1.1  mbalmer 
   4291  1.1  mbalmer <p>
   4292  1.1  mbalmer Pushes onto the stack a formatted string
   4293  1.1  mbalmer and returns a pointer to this string.
   4294  1.3    lneto It is similar to the ISO&nbsp;C function <code>sprintf</code>,
   4295  1.1  mbalmer but has some important differences:
   4296  1.1  mbalmer 
   4297  1.1  mbalmer <ul>
   4298  1.1  mbalmer 
   4299  1.1  mbalmer <li>
   4300  1.1  mbalmer You do not have to allocate space for the result:
   4301  1.1  mbalmer the result is a Lua string and Lua takes care of memory allocation
   4302  1.1  mbalmer (and deallocation, through garbage collection).
   4303  1.1  mbalmer </li>
   4304  1.1  mbalmer 
   4305  1.1  mbalmer <li>
   4306  1.1  mbalmer The conversion specifiers are quite restricted.
   4307  1.1  mbalmer There are no flags, widths, or precisions.
   4308  1.1  mbalmer The conversion specifiers can only be
   4309  1.2    lneto '<code>%%</code>' (inserts the character '<code>%</code>'),
   4310  1.1  mbalmer '<code>%s</code>' (inserts a zero-terminated string, with no size restrictions),
   4311  1.1  mbalmer '<code>%f</code>' (inserts a <a href="#lua_Number"><code>lua_Number</code></a>),
   4312  1.2    lneto '<code>%L</code>' (inserts a <a href="#lua_Integer"><code>lua_Integer</code></a>),
   4313  1.1  mbalmer '<code>%p</code>' (inserts a pointer as a hexadecimal numeral),
   4314  1.2    lneto '<code>%d</code>' (inserts an <code>int</code>),
   4315  1.2    lneto '<code>%c</code>' (inserts an <code>int</code> as a one-byte character), and
   4316  1.3    lneto '<code>%U</code>' (inserts a <code>long int</code> as a UTF-8 byte sequence).
   4317  1.1  mbalmer </li>
   4318  1.1  mbalmer 
   4319  1.1  mbalmer </ul>
   4320  1.1  mbalmer 
   4321  1.1  mbalmer 
   4322  1.1  mbalmer 
   4323  1.1  mbalmer 
   4324  1.2    lneto <hr><h3><a name="lua_pushglobaltable"><code>lua_pushglobaltable</code></a></h3><p>
   4325  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   4326  1.2    lneto <pre>void lua_pushglobaltable (lua_State *L);</pre>
   4327  1.2    lneto 
   4328  1.2    lneto <p>
   4329  1.2    lneto Pushes the global environment onto the stack.
   4330  1.2    lneto 
   4331  1.2    lneto 
   4332  1.2    lneto 
   4333  1.2    lneto 
   4334  1.2    lneto 
   4335  1.1  mbalmer <hr><h3><a name="lua_pushinteger"><code>lua_pushinteger</code></a></h3><p>
   4336  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   4337  1.1  mbalmer <pre>void lua_pushinteger (lua_State *L, lua_Integer n);</pre>
   4338  1.1  mbalmer 
   4339  1.1  mbalmer <p>
   4340  1.2    lneto Pushes an integer with value <code>n</code> onto the stack.
   4341  1.1  mbalmer 
   4342  1.1  mbalmer 
   4343  1.1  mbalmer 
   4344  1.1  mbalmer 
   4345  1.1  mbalmer 
   4346  1.1  mbalmer <hr><h3><a name="lua_pushlightuserdata"><code>lua_pushlightuserdata</code></a></h3><p>
   4347  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   4348  1.1  mbalmer <pre>void lua_pushlightuserdata (lua_State *L, void *p);</pre>
   4349  1.1  mbalmer 
   4350  1.1  mbalmer <p>
   4351  1.1  mbalmer Pushes a light userdata onto the stack.
   4352  1.1  mbalmer 
   4353  1.1  mbalmer 
   4354  1.1  mbalmer <p>
   4355  1.1  mbalmer Userdata represent C&nbsp;values in Lua.
   4356  1.2    lneto A <em>light userdata</em> represents a pointer, a <code>void*</code>.
   4357  1.1  mbalmer It is a value (like a number):
   4358  1.1  mbalmer you do not create it, it has no individual metatable,
   4359  1.1  mbalmer and it is not collected (as it was never created).
   4360  1.1  mbalmer A light userdata is equal to "any"
   4361  1.1  mbalmer light userdata with the same C&nbsp;address.
   4362  1.1  mbalmer 
   4363  1.1  mbalmer 
   4364  1.1  mbalmer 
   4365  1.1  mbalmer 
   4366  1.1  mbalmer 
   4367  1.1  mbalmer <hr><h3><a name="lua_pushliteral"><code>lua_pushliteral</code></a></h3><p>
   4368  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   4369  1.2    lneto <pre>const char *lua_pushliteral (lua_State *L, const char *s);</pre>
   4370  1.1  mbalmer 
   4371  1.1  mbalmer <p>
   4372  1.1  mbalmer This macro is equivalent to <a href="#lua_pushlstring"><code>lua_pushlstring</code></a>,
   4373  1.1  mbalmer but can be used only when <code>s</code> is a literal string.
   4374  1.2    lneto It automatically provides the string length.
   4375  1.1  mbalmer 
   4376  1.1  mbalmer 
   4377  1.1  mbalmer 
   4378  1.1  mbalmer 
   4379  1.1  mbalmer 
   4380  1.1  mbalmer <hr><h3><a name="lua_pushlstring"><code>lua_pushlstring</code></a></h3><p>
   4381  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   4382  1.2    lneto <pre>const char *lua_pushlstring (lua_State *L, const char *s, size_t len);</pre>
   4383  1.1  mbalmer 
   4384  1.1  mbalmer <p>
   4385  1.1  mbalmer Pushes the string pointed to by <code>s</code> with size <code>len</code>
   4386  1.1  mbalmer onto the stack.
   4387  1.1  mbalmer Lua makes (or reuses) an internal copy of the given string,
   4388  1.1  mbalmer so the memory at <code>s</code> can be freed or reused immediately after
   4389  1.1  mbalmer the function returns.
   4390  1.2    lneto The string can contain any binary data,
   4391  1.2    lneto including embedded zeros.
   4392  1.2    lneto 
   4393  1.2    lneto 
   4394  1.2    lneto <p>
   4395  1.2    lneto Returns a pointer to the internal copy of the string.
   4396  1.1  mbalmer 
   4397  1.1  mbalmer 
   4398  1.1  mbalmer 
   4399  1.1  mbalmer 
   4400  1.1  mbalmer 
   4401  1.1  mbalmer <hr><h3><a name="lua_pushnil"><code>lua_pushnil</code></a></h3><p>
   4402  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   4403  1.1  mbalmer <pre>void lua_pushnil (lua_State *L);</pre>
   4404  1.1  mbalmer 
   4405  1.1  mbalmer <p>
   4406  1.1  mbalmer Pushes a nil value onto the stack.
   4407  1.1  mbalmer 
   4408  1.1  mbalmer 
   4409  1.1  mbalmer 
   4410  1.1  mbalmer 
   4411  1.1  mbalmer 
   4412  1.1  mbalmer <hr><h3><a name="lua_pushnumber"><code>lua_pushnumber</code></a></h3><p>
   4413  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   4414  1.1  mbalmer <pre>void lua_pushnumber (lua_State *L, lua_Number n);</pre>
   4415  1.1  mbalmer 
   4416  1.1  mbalmer <p>
   4417  1.2    lneto Pushes a float with value <code>n</code> onto the stack.
   4418  1.1  mbalmer 
   4419  1.1  mbalmer 
   4420  1.1  mbalmer 
   4421  1.1  mbalmer 
   4422  1.1  mbalmer 
   4423  1.1  mbalmer <hr><h3><a name="lua_pushstring"><code>lua_pushstring</code></a></h3><p>
   4424  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   4425  1.2    lneto <pre>const char *lua_pushstring (lua_State *L, const char *s);</pre>
   4426  1.1  mbalmer 
   4427  1.1  mbalmer <p>
   4428  1.1  mbalmer Pushes the zero-terminated string pointed to by <code>s</code>
   4429  1.1  mbalmer onto the stack.
   4430  1.1  mbalmer Lua makes (or reuses) an internal copy of the given string,
   4431  1.1  mbalmer so the memory at <code>s</code> can be freed or reused immediately after
   4432  1.1  mbalmer the function returns.
   4433  1.2    lneto 
   4434  1.2    lneto 
   4435  1.2    lneto <p>
   4436  1.2    lneto Returns a pointer to the internal copy of the string.
   4437  1.2    lneto 
   4438  1.2    lneto 
   4439  1.2    lneto <p>
   4440  1.2    lneto If <code>s</code> is <code>NULL</code>, pushes <b>nil</b> and returns <code>NULL</code>.
   4441  1.1  mbalmer 
   4442  1.1  mbalmer 
   4443  1.1  mbalmer 
   4444  1.1  mbalmer 
   4445  1.1  mbalmer 
   4446  1.1  mbalmer <hr><h3><a name="lua_pushthread"><code>lua_pushthread</code></a></h3><p>
   4447  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   4448  1.1  mbalmer <pre>int lua_pushthread (lua_State *L);</pre>
   4449  1.1  mbalmer 
   4450  1.1  mbalmer <p>
   4451  1.1  mbalmer Pushes the thread represented by <code>L</code> onto the stack.
   4452  1.1  mbalmer Returns 1 if this thread is the main thread of its state.
   4453  1.1  mbalmer 
   4454  1.1  mbalmer 
   4455  1.1  mbalmer 
   4456  1.1  mbalmer 
   4457  1.1  mbalmer 
   4458  1.1  mbalmer <hr><h3><a name="lua_pushvalue"><code>lua_pushvalue</code></a></h3><p>
   4459  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   4460  1.1  mbalmer <pre>void lua_pushvalue (lua_State *L, int index);</pre>
   4461  1.1  mbalmer 
   4462  1.1  mbalmer <p>
   4463  1.2    lneto Pushes a copy of the element at the given index
   4464  1.1  mbalmer onto the stack.
   4465  1.1  mbalmer 
   4466  1.1  mbalmer 
   4467  1.1  mbalmer 
   4468  1.1  mbalmer 
   4469  1.1  mbalmer 
   4470  1.1  mbalmer <hr><h3><a name="lua_pushvfstring"><code>lua_pushvfstring</code></a></h3><p>
   4471  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   4472  1.1  mbalmer <pre>const char *lua_pushvfstring (lua_State *L,
   4473  1.1  mbalmer                               const char *fmt,
   4474  1.1  mbalmer                               va_list argp);</pre>
   4475  1.1  mbalmer 
   4476  1.1  mbalmer <p>
   4477  1.1  mbalmer Equivalent to <a href="#lua_pushfstring"><code>lua_pushfstring</code></a>, except that it receives a <code>va_list</code>
   4478  1.1  mbalmer instead of a variable number of arguments.
   4479  1.1  mbalmer 
   4480  1.1  mbalmer 
   4481  1.1  mbalmer 
   4482  1.1  mbalmer 
   4483  1.1  mbalmer 
   4484  1.1  mbalmer <hr><h3><a name="lua_rawequal"><code>lua_rawequal</code></a></h3><p>
   4485  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   4486  1.1  mbalmer <pre>int lua_rawequal (lua_State *L, int index1, int index2);</pre>
   4487  1.1  mbalmer 
   4488  1.1  mbalmer <p>
   4489  1.2    lneto Returns 1 if the two values in indices <code>index1</code> and
   4490  1.1  mbalmer <code>index2</code> are primitively equal
   4491  1.1  mbalmer (that is, without calling metamethods).
   4492  1.1  mbalmer Otherwise returns&nbsp;0.
   4493  1.3    lneto Also returns&nbsp;0 if any of the indices are not valid.
   4494  1.1  mbalmer 
   4495  1.1  mbalmer 
   4496  1.1  mbalmer 
   4497  1.1  mbalmer 
   4498  1.1  mbalmer 
   4499  1.1  mbalmer <hr><h3><a name="lua_rawget"><code>lua_rawget</code></a></h3><p>
   4500  1.2    lneto <span class="apii">[-1, +1, &ndash;]</span>
   4501  1.2    lneto <pre>int lua_rawget (lua_State *L, int index);</pre>
   4502  1.1  mbalmer 
   4503  1.1  mbalmer <p>
   4504  1.1  mbalmer Similar to <a href="#lua_gettable"><code>lua_gettable</code></a>, but does a raw access
   4505  1.1  mbalmer (i.e., without metamethods).
   4506  1.1  mbalmer 
   4507  1.1  mbalmer 
   4508  1.1  mbalmer 
   4509  1.1  mbalmer 
   4510  1.1  mbalmer 
   4511  1.2    lneto <hr><h3><a name="lua_rawgeti"><code>lua_rawgeti</code></a></h3><p>
   4512  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   4513  1.2    lneto <pre>int lua_rawgeti (lua_State *L, int index, lua_Integer n);</pre>
   4514  1.2    lneto 
   4515  1.2    lneto <p>
   4516  1.2    lneto Pushes onto the stack the value <code>t[n]</code>,
   4517  1.2    lneto where <code>t</code> is the table at the given index.
   4518  1.2    lneto The access is raw;
   4519  1.2    lneto that is, it does not invoke metamethods.
   4520  1.2    lneto 
   4521  1.2    lneto 
   4522  1.2    lneto <p>
   4523  1.2    lneto Returns the type of the pushed value.
   4524  1.2    lneto 
   4525  1.2    lneto 
   4526  1.2    lneto 
   4527  1.2    lneto 
   4528  1.2    lneto 
   4529  1.2    lneto <hr><h3><a name="lua_rawgetp"><code>lua_rawgetp</code></a></h3><p>
   4530  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   4531  1.2    lneto <pre>int lua_rawgetp (lua_State *L, int index, const void *p);</pre>
   4532  1.2    lneto 
   4533  1.2    lneto <p>
   4534  1.2    lneto Pushes onto the stack the value <code>t[k]</code>,
   4535  1.2    lneto where <code>t</code> is the table at the given index and
   4536  1.2    lneto <code>k</code> is the pointer <code>p</code> represented as a light userdata.
   4537  1.2    lneto The access is raw;
   4538  1.2    lneto that is, it does not invoke metamethods.
   4539  1.2    lneto 
   4540  1.2    lneto 
   4541  1.2    lneto <p>
   4542  1.2    lneto Returns the type of the pushed value.
   4543  1.2    lneto 
   4544  1.2    lneto 
   4545  1.2    lneto 
   4546  1.2    lneto 
   4547  1.2    lneto 
   4548  1.2    lneto <hr><h3><a name="lua_rawlen"><code>lua_rawlen</code></a></h3><p>
   4549  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   4550  1.2    lneto <pre>size_t lua_rawlen (lua_State *L, int index);</pre>
   4551  1.2    lneto 
   4552  1.2    lneto <p>
   4553  1.2    lneto Returns the raw "length" of the value at the given index:
   4554  1.2    lneto for strings, this is the string length;
   4555  1.2    lneto for tables, this is the result of the length operator ('<code>#</code>')
   4556  1.2    lneto with no metamethods;
   4557  1.2    lneto for userdata, this is the size of the block of memory allocated
   4558  1.2    lneto for the userdata;
   4559  1.2    lneto for other values, it is&nbsp;0.
   4560  1.1  mbalmer 
   4561  1.1  mbalmer 
   4562  1.1  mbalmer 
   4563  1.1  mbalmer 
   4564  1.1  mbalmer 
   4565  1.1  mbalmer <hr><h3><a name="lua_rawset"><code>lua_rawset</code></a></h3><p>
   4566  1.2    lneto <span class="apii">[-2, +0, <em>e</em>]</span>
   4567  1.1  mbalmer <pre>void lua_rawset (lua_State *L, int index);</pre>
   4568  1.1  mbalmer 
   4569  1.1  mbalmer <p>
   4570  1.1  mbalmer Similar to <a href="#lua_settable"><code>lua_settable</code></a>, but does a raw assignment
   4571  1.1  mbalmer (i.e., without metamethods).
   4572  1.1  mbalmer 
   4573  1.1  mbalmer 
   4574  1.1  mbalmer 
   4575  1.1  mbalmer 
   4576  1.1  mbalmer 
   4577  1.1  mbalmer <hr><h3><a name="lua_rawseti"><code>lua_rawseti</code></a></h3><p>
   4578  1.2    lneto <span class="apii">[-1, +0, <em>e</em>]</span>
   4579  1.3    lneto <pre>void lua_rawseti (lua_State *L, int index, lua_Integer i);</pre>
   4580  1.1  mbalmer 
   4581  1.1  mbalmer <p>
   4582  1.3    lneto Does the equivalent of <code>t[i] = v</code>,
   4583  1.2    lneto where <code>t</code> is the table at the given index
   4584  1.2    lneto and <code>v</code> is the value at the top of the stack.
   4585  1.2    lneto 
   4586  1.2    lneto 
   4587  1.2    lneto <p>
   4588  1.2    lneto This function pops the value from the stack.
   4589  1.2    lneto The assignment is raw;
   4590  1.2    lneto that is, it does not invoke metamethods.
   4591  1.2    lneto 
   4592  1.2    lneto 
   4593  1.2    lneto 
   4594  1.2    lneto 
   4595  1.2    lneto 
   4596  1.2    lneto <hr><h3><a name="lua_rawsetp"><code>lua_rawsetp</code></a></h3><p>
   4597  1.2    lneto <span class="apii">[-1, +0, <em>e</em>]</span>
   4598  1.2    lneto <pre>void lua_rawsetp (lua_State *L, int index, const void *p);</pre>
   4599  1.2    lneto 
   4600  1.2    lneto <p>
   4601  1.2    lneto Does the equivalent of <code>t[k] = v</code>,
   4602  1.2    lneto where <code>t</code> is the table at the given index,
   4603  1.2    lneto <code>k</code> is the pointer <code>p</code> represented as a light userdata,
   4604  1.1  mbalmer and <code>v</code> is the value at the top of the stack.
   4605  1.1  mbalmer 
   4606  1.1  mbalmer 
   4607  1.1  mbalmer <p>
   4608  1.1  mbalmer This function pops the value from the stack.
   4609  1.1  mbalmer The assignment is raw;
   4610  1.1  mbalmer that is, it does not invoke metamethods.
   4611  1.1  mbalmer 
   4612  1.1  mbalmer 
   4613  1.1  mbalmer 
   4614  1.1  mbalmer 
   4615  1.1  mbalmer 
   4616  1.1  mbalmer <hr><h3><a name="lua_Reader"><code>lua_Reader</code></a></h3>
   4617  1.1  mbalmer <pre>typedef const char * (*lua_Reader) (lua_State *L,
   4618  1.1  mbalmer                                     void *data,
   4619  1.1  mbalmer                                     size_t *size);</pre>
   4620  1.1  mbalmer 
   4621  1.1  mbalmer <p>
   4622  1.1  mbalmer The reader function used by <a href="#lua_load"><code>lua_load</code></a>.
   4623  1.1  mbalmer Every time it needs another piece of the chunk,
   4624  1.1  mbalmer <a href="#lua_load"><code>lua_load</code></a> calls the reader,
   4625  1.1  mbalmer passing along its <code>data</code> parameter.
   4626  1.1  mbalmer The reader must return a pointer to a block of memory
   4627  1.1  mbalmer with a new piece of the chunk
   4628  1.1  mbalmer and set <code>size</code> to the block size.
   4629  1.1  mbalmer The block must exist until the reader function is called again.
   4630  1.1  mbalmer To signal the end of the chunk,
   4631  1.1  mbalmer the reader must return <code>NULL</code> or set <code>size</code> to zero.
   4632  1.1  mbalmer The reader function may return pieces of any size greater than zero.
   4633  1.1  mbalmer 
   4634  1.1  mbalmer 
   4635  1.1  mbalmer 
   4636  1.1  mbalmer 
   4637  1.1  mbalmer 
   4638  1.1  mbalmer <hr><h3><a name="lua_register"><code>lua_register</code></a></h3><p>
   4639  1.1  mbalmer <span class="apii">[-0, +0, <em>e</em>]</span>
   4640  1.2    lneto <pre>void lua_register (lua_State *L, const char *name, lua_CFunction f);</pre>
   4641  1.1  mbalmer 
   4642  1.1  mbalmer <p>
   4643  1.1  mbalmer Sets the C function <code>f</code> as the new value of global <code>name</code>.
   4644  1.1  mbalmer It is defined as a macro:
   4645  1.1  mbalmer 
   4646  1.1  mbalmer <pre>
   4647  1.1  mbalmer      #define lua_register(L,n,f) \
   4648  1.1  mbalmer             (lua_pushcfunction(L, f), lua_setglobal(L, n))
   4649  1.1  mbalmer </pre>
   4650  1.1  mbalmer 
   4651  1.1  mbalmer 
   4652  1.1  mbalmer 
   4653  1.1  mbalmer 
   4654  1.1  mbalmer <hr><h3><a name="lua_remove"><code>lua_remove</code></a></h3><p>
   4655  1.2    lneto <span class="apii">[-1, +0, &ndash;]</span>
   4656  1.1  mbalmer <pre>void lua_remove (lua_State *L, int index);</pre>
   4657  1.1  mbalmer 
   4658  1.1  mbalmer <p>
   4659  1.1  mbalmer Removes the element at the given valid index,
   4660  1.1  mbalmer shifting down the elements above this index to fill the gap.
   4661  1.2    lneto This function cannot be called with a pseudo-index,
   4662  1.1  mbalmer because a pseudo-index is not an actual stack position.
   4663  1.1  mbalmer 
   4664  1.1  mbalmer 
   4665  1.1  mbalmer 
   4666  1.1  mbalmer 
   4667  1.1  mbalmer 
   4668  1.1  mbalmer <hr><h3><a name="lua_replace"><code>lua_replace</code></a></h3><p>
   4669  1.2    lneto <span class="apii">[-1, +0, &ndash;]</span>
   4670  1.1  mbalmer <pre>void lua_replace (lua_State *L, int index);</pre>
   4671  1.1  mbalmer 
   4672  1.1  mbalmer <p>
   4673  1.2    lneto Moves the top element into the given valid index
   4674  1.1  mbalmer without shifting any element
   4675  1.2    lneto (therefore replacing the value at the given index),
   4676  1.2    lneto and then pops the top element.
   4677  1.1  mbalmer 
   4678  1.1  mbalmer 
   4679  1.1  mbalmer 
   4680  1.1  mbalmer 
   4681  1.1  mbalmer 
   4682  1.1  mbalmer <hr><h3><a name="lua_resume"><code>lua_resume</code></a></h3><p>
   4683  1.2    lneto <span class="apii">[-?, +?, &ndash;]</span>
   4684  1.2    lneto <pre>int lua_resume (lua_State *L, lua_State *from, int nargs);</pre>
   4685  1.1  mbalmer 
   4686  1.1  mbalmer <p>
   4687  1.1  mbalmer Starts and resumes a coroutine in a given thread.
   4688  1.1  mbalmer 
   4689  1.1  mbalmer 
   4690  1.1  mbalmer <p>
   4691  1.2    lneto To start a coroutine,
   4692  1.2    lneto you push onto the thread stack the main function plus any arguments;
   4693  1.1  mbalmer then you call <a href="#lua_resume"><code>lua_resume</code></a>,
   4694  1.2    lneto with <code>nargs</code> being the number of arguments.
   4695  1.1  mbalmer This call returns when the coroutine suspends or finishes its execution.
   4696  1.1  mbalmer When it returns, the stack contains all values passed to <a href="#lua_yield"><code>lua_yield</code></a>,
   4697  1.1  mbalmer or all values returned by the body function.
   4698  1.1  mbalmer <a href="#lua_resume"><code>lua_resume</code></a> returns
   4699  1.1  mbalmer <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a> if the coroutine yields,
   4700  1.2    lneto <a href="#pdf-LUA_OK"><code>LUA_OK</code></a> if the coroutine finishes its execution
   4701  1.1  mbalmer without errors,
   4702  1.1  mbalmer or an error code in case of errors (see <a href="#lua_pcall"><code>lua_pcall</code></a>).
   4703  1.2    lneto 
   4704  1.2    lneto 
   4705  1.2    lneto <p>
   4706  1.1  mbalmer In case of errors,
   4707  1.1  mbalmer the stack is not unwound,
   4708  1.1  mbalmer so you can use the debug API over it.
   4709  1.1  mbalmer The error message is on the top of the stack.
   4710  1.2    lneto 
   4711  1.2    lneto 
   4712  1.2    lneto <p>
   4713  1.2    lneto To resume a coroutine,
   4714  1.2    lneto you remove any results from the last <a href="#lua_yield"><code>lua_yield</code></a>,
   4715  1.2    lneto put on its stack only the values to
   4716  1.1  mbalmer be passed as results from <code>yield</code>,
   4717  1.1  mbalmer and then call <a href="#lua_resume"><code>lua_resume</code></a>.
   4718  1.1  mbalmer 
   4719  1.1  mbalmer 
   4720  1.2    lneto <p>
   4721  1.2    lneto The parameter <code>from</code> represents the coroutine that is resuming <code>L</code>.
   4722  1.2    lneto If there is no such coroutine,
   4723  1.2    lneto this parameter can be <code>NULL</code>.
   4724  1.2    lneto 
   4725  1.2    lneto 
   4726  1.1  mbalmer 
   4727  1.1  mbalmer 
   4728  1.1  mbalmer 
   4729  1.2    lneto <hr><h3><a name="lua_rotate"><code>lua_rotate</code></a></h3><p>
   4730  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   4731  1.2    lneto <pre>void lua_rotate (lua_State *L, int idx, int n);</pre>
   4732  1.1  mbalmer 
   4733  1.1  mbalmer <p>
   4734  1.2    lneto Rotates the stack elements from <code>idx</code> to the top <code>n</code> positions
   4735  1.2    lneto in the direction of the top, for a positive <code>n</code>,
   4736  1.2    lneto or <code>-n</code> positions in the direction of the bottom,
   4737  1.2    lneto for a negative <code>n</code>.
   4738  1.2    lneto The absolute value of <code>n</code> must not be greater than the size
   4739  1.2    lneto of the slice being rotated.
   4740  1.1  mbalmer 
   4741  1.1  mbalmer 
   4742  1.1  mbalmer 
   4743  1.1  mbalmer 
   4744  1.1  mbalmer 
   4745  1.2    lneto <hr><h3><a name="lua_setallocf"><code>lua_setallocf</code></a></h3><p>
   4746  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   4747  1.2    lneto <pre>void lua_setallocf (lua_State *L, lua_Alloc f, void *ud);</pre>
   4748  1.1  mbalmer 
   4749  1.1  mbalmer <p>
   4750  1.2    lneto Changes the allocator function of a given state to <code>f</code>
   4751  1.2    lneto with user data <code>ud</code>.
   4752  1.1  mbalmer 
   4753  1.1  mbalmer 
   4754  1.1  mbalmer 
   4755  1.1  mbalmer 
   4756  1.1  mbalmer 
   4757  1.1  mbalmer <hr><h3><a name="lua_setfield"><code>lua_setfield</code></a></h3><p>
   4758  1.1  mbalmer <span class="apii">[-1, +0, <em>e</em>]</span>
   4759  1.1  mbalmer <pre>void lua_setfield (lua_State *L, int index, const char *k);</pre>
   4760  1.1  mbalmer 
   4761  1.1  mbalmer <p>
   4762  1.1  mbalmer Does the equivalent to <code>t[k] = v</code>,
   4763  1.2    lneto where <code>t</code> is the value at the given index
   4764  1.1  mbalmer and <code>v</code> is the value at the top of the stack.
   4765  1.1  mbalmer 
   4766  1.1  mbalmer 
   4767  1.1  mbalmer <p>
   4768  1.1  mbalmer This function pops the value from the stack.
   4769  1.1  mbalmer As in Lua, this function may trigger a metamethod
   4770  1.2    lneto for the "newindex" event (see <a href="#2.4">&sect;2.4</a>).
   4771  1.1  mbalmer 
   4772  1.1  mbalmer 
   4773  1.1  mbalmer 
   4774  1.1  mbalmer 
   4775  1.1  mbalmer 
   4776  1.1  mbalmer <hr><h3><a name="lua_setglobal"><code>lua_setglobal</code></a></h3><p>
   4777  1.1  mbalmer <span class="apii">[-1, +0, <em>e</em>]</span>
   4778  1.1  mbalmer <pre>void lua_setglobal (lua_State *L, const char *name);</pre>
   4779  1.1  mbalmer 
   4780  1.1  mbalmer <p>
   4781  1.1  mbalmer Pops a value from the stack and
   4782  1.1  mbalmer sets it as the new value of global <code>name</code>.
   4783  1.1  mbalmer 
   4784  1.1  mbalmer 
   4785  1.1  mbalmer 
   4786  1.1  mbalmer 
   4787  1.1  mbalmer 
   4788  1.3    lneto <hr><h3><a name="lua_seti"><code>lua_seti</code></a></h3><p>
   4789  1.3    lneto <span class="apii">[-1, +0, <em>e</em>]</span>
   4790  1.3    lneto <pre>void lua_seti (lua_State *L, int index, lua_Integer n);</pre>
   4791  1.3    lneto 
   4792  1.3    lneto <p>
   4793  1.3    lneto Does the equivalent to <code>t[n] = v</code>,
   4794  1.3    lneto where <code>t</code> is the value at the given index
   4795  1.3    lneto and <code>v</code> is the value at the top of the stack.
   4796  1.3    lneto 
   4797  1.3    lneto 
   4798  1.3    lneto <p>
   4799  1.3    lneto This function pops the value from the stack.
   4800  1.3    lneto As in Lua, this function may trigger a metamethod
   4801  1.3    lneto for the "newindex" event (see <a href="#2.4">&sect;2.4</a>).
   4802  1.3    lneto 
   4803  1.3    lneto 
   4804  1.3    lneto 
   4805  1.3    lneto 
   4806  1.3    lneto 
   4807  1.1  mbalmer <hr><h3><a name="lua_setmetatable"><code>lua_setmetatable</code></a></h3><p>
   4808  1.2    lneto <span class="apii">[-1, +0, &ndash;]</span>
   4809  1.2    lneto <pre>void lua_setmetatable (lua_State *L, int index);</pre>
   4810  1.1  mbalmer 
   4811  1.1  mbalmer <p>
   4812  1.1  mbalmer Pops a table from the stack and
   4813  1.2    lneto sets it as the new metatable for the value at the given index.
   4814  1.1  mbalmer 
   4815  1.1  mbalmer 
   4816  1.1  mbalmer 
   4817  1.1  mbalmer 
   4818  1.1  mbalmer 
   4819  1.1  mbalmer <hr><h3><a name="lua_settable"><code>lua_settable</code></a></h3><p>
   4820  1.1  mbalmer <span class="apii">[-2, +0, <em>e</em>]</span>
   4821  1.1  mbalmer <pre>void lua_settable (lua_State *L, int index);</pre>
   4822  1.1  mbalmer 
   4823  1.1  mbalmer <p>
   4824  1.1  mbalmer Does the equivalent to <code>t[k] = v</code>,
   4825  1.2    lneto where <code>t</code> is the value at the given index,
   4826  1.1  mbalmer <code>v</code> is the value at the top of the stack,
   4827  1.1  mbalmer and <code>k</code> is the value just below the top.
   4828  1.1  mbalmer 
   4829  1.1  mbalmer 
   4830  1.1  mbalmer <p>
   4831  1.1  mbalmer This function pops both the key and the value from the stack.
   4832  1.1  mbalmer As in Lua, this function may trigger a metamethod
   4833  1.2    lneto for the "newindex" event (see <a href="#2.4">&sect;2.4</a>).
   4834  1.1  mbalmer 
   4835  1.1  mbalmer 
   4836  1.1  mbalmer 
   4837  1.1  mbalmer 
   4838  1.1  mbalmer 
   4839  1.1  mbalmer <hr><h3><a name="lua_settop"><code>lua_settop</code></a></h3><p>
   4840  1.2    lneto <span class="apii">[-?, +?, &ndash;]</span>
   4841  1.1  mbalmer <pre>void lua_settop (lua_State *L, int index);</pre>
   4842  1.1  mbalmer 
   4843  1.1  mbalmer <p>
   4844  1.2    lneto Accepts any index, or&nbsp;0,
   4845  1.1  mbalmer and sets the stack top to this index.
   4846  1.1  mbalmer If the new top is larger than the old one,
   4847  1.1  mbalmer then the new elements are filled with <b>nil</b>.
   4848  1.1  mbalmer If <code>index</code> is&nbsp;0, then all stack elements are removed.
   4849  1.1  mbalmer 
   4850  1.1  mbalmer 
   4851  1.1  mbalmer 
   4852  1.1  mbalmer 
   4853  1.1  mbalmer 
   4854  1.2    lneto <hr><h3><a name="lua_setuservalue"><code>lua_setuservalue</code></a></h3><p>
   4855  1.2    lneto <span class="apii">[-1, +0, &ndash;]</span>
   4856  1.2    lneto <pre>void lua_setuservalue (lua_State *L, int index);</pre>
   4857  1.2    lneto 
   4858  1.2    lneto <p>
   4859  1.2    lneto Pops a value from the stack and sets it as
   4860  1.2    lneto the new value associated to the userdata at the given index.
   4861  1.2    lneto 
   4862  1.2    lneto 
   4863  1.2    lneto 
   4864  1.2    lneto 
   4865  1.2    lneto 
   4866  1.1  mbalmer <hr><h3><a name="lua_State"><code>lua_State</code></a></h3>
   4867  1.1  mbalmer <pre>typedef struct lua_State lua_State;</pre>
   4868  1.1  mbalmer 
   4869  1.1  mbalmer <p>
   4870  1.2    lneto An opaque structure that points to a thread and indirectly
   4871  1.2    lneto (through the thread) to the whole state of a Lua interpreter.
   4872  1.1  mbalmer The Lua library is fully reentrant:
   4873  1.1  mbalmer it has no global variables.
   4874  1.2    lneto All information about a state is accessible through this structure.
   4875  1.1  mbalmer 
   4876  1.1  mbalmer 
   4877  1.1  mbalmer <p>
   4878  1.2    lneto A pointer to this structure must be passed as the first argument to
   4879  1.1  mbalmer every function in the library, except to <a href="#lua_newstate"><code>lua_newstate</code></a>,
   4880  1.1  mbalmer which creates a Lua state from scratch.
   4881  1.1  mbalmer 
   4882  1.1  mbalmer 
   4883  1.1  mbalmer 
   4884  1.1  mbalmer 
   4885  1.1  mbalmer 
   4886  1.1  mbalmer <hr><h3><a name="lua_status"><code>lua_status</code></a></h3><p>
   4887  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   4888  1.1  mbalmer <pre>int lua_status (lua_State *L);</pre>
   4889  1.1  mbalmer 
   4890  1.1  mbalmer <p>
   4891  1.1  mbalmer Returns the status of the thread <code>L</code>.
   4892  1.1  mbalmer 
   4893  1.1  mbalmer 
   4894  1.1  mbalmer <p>
   4895  1.2    lneto The status can be 0 (<a href="#pdf-LUA_OK"><code>LUA_OK</code></a>) for a normal thread,
   4896  1.2    lneto an error code if the thread finished the execution
   4897  1.2    lneto of a <a href="#lua_resume"><code>lua_resume</code></a> with an error,
   4898  1.1  mbalmer or <a name="pdf-LUA_YIELD"><code>LUA_YIELD</code></a> if the thread is suspended.
   4899  1.1  mbalmer 
   4900  1.1  mbalmer 
   4901  1.2    lneto <p>
   4902  1.2    lneto You can only call functions in threads with status <a href="#pdf-LUA_OK"><code>LUA_OK</code></a>.
   4903  1.2    lneto You can resume threads with status <a href="#pdf-LUA_OK"><code>LUA_OK</code></a>
   4904  1.2    lneto (to start a new coroutine) or <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a>
   4905  1.2    lneto (to resume a coroutine).
   4906  1.2    lneto 
   4907  1.2    lneto 
   4908  1.2    lneto 
   4909  1.2    lneto 
   4910  1.2    lneto 
   4911  1.3    lneto <hr><h3><a name="lua_stringtonumber"><code>lua_stringtonumber</code></a></h3><p>
   4912  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   4913  1.3    lneto <pre>size_t lua_stringtonumber (lua_State *L, const char *s);</pre>
   4914  1.2    lneto 
   4915  1.2    lneto <p>
   4916  1.2    lneto Converts the zero-terminated string <code>s</code> to a number,
   4917  1.2    lneto pushes that number into the stack,
   4918  1.3    lneto and returns the total size of the string,
   4919  1.3    lneto that is, its length plus one.
   4920  1.2    lneto The conversion can result in an integer or a float,
   4921  1.2    lneto according to the lexical conventions of Lua (see <a href="#3.1">&sect;3.1</a>).
   4922  1.2    lneto The string may have leading and trailing spaces and a sign.
   4923  1.2    lneto If the string is not a valid numeral,
   4924  1.2    lneto returns 0 and pushes nothing.
   4925  1.3    lneto (Note that the result can be used as a boolean,
   4926  1.3    lneto true if the conversion succeeds.)
   4927  1.2    lneto 
   4928  1.2    lneto 
   4929  1.1  mbalmer 
   4930  1.1  mbalmer 
   4931  1.1  mbalmer 
   4932  1.1  mbalmer <hr><h3><a name="lua_toboolean"><code>lua_toboolean</code></a></h3><p>
   4933  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   4934  1.1  mbalmer <pre>int lua_toboolean (lua_State *L, int index);</pre>
   4935  1.1  mbalmer 
   4936  1.1  mbalmer <p>
   4937  1.2    lneto Converts the Lua value at the given index to a C&nbsp;boolean
   4938  1.1  mbalmer value (0&nbsp;or&nbsp;1).
   4939  1.1  mbalmer Like all tests in Lua,
   4940  1.2    lneto <a href="#lua_toboolean"><code>lua_toboolean</code></a> returns true for any Lua value
   4941  1.1  mbalmer different from <b>false</b> and <b>nil</b>;
   4942  1.2    lneto otherwise it returns false.
   4943  1.1  mbalmer (If you want to accept only actual boolean values,
   4944  1.1  mbalmer use <a href="#lua_isboolean"><code>lua_isboolean</code></a> to test the value's type.)
   4945  1.1  mbalmer 
   4946  1.1  mbalmer 
   4947  1.1  mbalmer 
   4948  1.1  mbalmer 
   4949  1.1  mbalmer 
   4950  1.1  mbalmer <hr><h3><a name="lua_tocfunction"><code>lua_tocfunction</code></a></h3><p>
   4951  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   4952  1.1  mbalmer <pre>lua_CFunction lua_tocfunction (lua_State *L, int index);</pre>
   4953  1.1  mbalmer 
   4954  1.1  mbalmer <p>
   4955  1.2    lneto Converts a value at the given index to a C&nbsp;function.
   4956  1.1  mbalmer That value must be a C&nbsp;function;
   4957  1.1  mbalmer otherwise, returns <code>NULL</code>.
   4958  1.1  mbalmer 
   4959  1.1  mbalmer 
   4960  1.1  mbalmer 
   4961  1.1  mbalmer 
   4962  1.1  mbalmer 
   4963  1.1  mbalmer <hr><h3><a name="lua_tointeger"><code>lua_tointeger</code></a></h3><p>
   4964  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   4965  1.1  mbalmer <pre>lua_Integer lua_tointeger (lua_State *L, int index);</pre>
   4966  1.1  mbalmer 
   4967  1.1  mbalmer <p>
   4968  1.2    lneto Equivalent to <a href="#lua_tointegerx"><code>lua_tointegerx</code></a> with <code>isnum</code> equal to <code>NULL</code>.
   4969  1.2    lneto 
   4970  1.2    lneto 
   4971  1.2    lneto 
   4972  1.2    lneto 
   4973  1.2    lneto 
   4974  1.2    lneto <hr><h3><a name="lua_tointegerx"><code>lua_tointegerx</code></a></h3><p>
   4975  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   4976  1.2    lneto <pre>lua_Integer lua_tointegerx (lua_State *L, int index, int *isnum);</pre>
   4977  1.2    lneto 
   4978  1.2    lneto <p>
   4979  1.2    lneto Converts the Lua value at the given index
   4980  1.1  mbalmer to the signed integral type <a href="#lua_Integer"><code>lua_Integer</code></a>.
   4981  1.2    lneto The Lua value must be an integer,
   4982  1.2    lneto or a number or string convertible to an integer (see <a href="#3.4.3">&sect;3.4.3</a>);
   4983  1.2    lneto otherwise, <code>lua_tointegerx</code> returns&nbsp;0.
   4984  1.1  mbalmer 
   4985  1.1  mbalmer 
   4986  1.1  mbalmer <p>
   4987  1.2    lneto If <code>isnum</code> is not <code>NULL</code>,
   4988  1.2    lneto its referent is assigned a boolean value that
   4989  1.2    lneto indicates whether the operation succeeded.
   4990  1.1  mbalmer 
   4991  1.1  mbalmer 
   4992  1.1  mbalmer 
   4993  1.1  mbalmer 
   4994  1.1  mbalmer 
   4995  1.1  mbalmer <hr><h3><a name="lua_tolstring"><code>lua_tolstring</code></a></h3><p>
   4996  1.2    lneto <span class="apii">[-0, +0, <em>e</em>]</span>
   4997  1.1  mbalmer <pre>const char *lua_tolstring (lua_State *L, int index, size_t *len);</pre>
   4998  1.1  mbalmer 
   4999  1.1  mbalmer <p>
   5000  1.2    lneto Converts the Lua value at the given index to a C&nbsp;string.
   5001  1.1  mbalmer If <code>len</code> is not <code>NULL</code>,
   5002  1.1  mbalmer it also sets <code>*len</code> with the string length.
   5003  1.1  mbalmer The Lua value must be a string or a number;
   5004  1.1  mbalmer otherwise, the function returns <code>NULL</code>.
   5005  1.1  mbalmer If the value is a number,
   5006  1.2    lneto then <code>lua_tolstring</code> also
   5007  1.1  mbalmer <em>changes the actual value in the stack to a string</em>.
   5008  1.1  mbalmer (This change confuses <a href="#lua_next"><code>lua_next</code></a>
   5009  1.2    lneto when <code>lua_tolstring</code> is applied to keys during a table traversal.)
   5010  1.1  mbalmer 
   5011  1.1  mbalmer 
   5012  1.1  mbalmer <p>
   5013  1.2    lneto <code>lua_tolstring</code> returns a fully aligned pointer
   5014  1.1  mbalmer to a string inside the Lua state.
   5015  1.1  mbalmer This string always has a zero ('<code>\0</code>')
   5016  1.1  mbalmer after its last character (as in&nbsp;C),
   5017  1.1  mbalmer but can contain other zeros in its body.
   5018  1.3    lneto 
   5019  1.3    lneto 
   5020  1.3    lneto <p>
   5021  1.1  mbalmer Because Lua has garbage collection,
   5022  1.2    lneto there is no guarantee that the pointer returned by <code>lua_tolstring</code>
   5023  1.3    lneto will be valid after the corresponding Lua value is removed from the stack.
   5024  1.1  mbalmer 
   5025  1.1  mbalmer 
   5026  1.1  mbalmer 
   5027  1.1  mbalmer 
   5028  1.1  mbalmer 
   5029  1.1  mbalmer <hr><h3><a name="lua_tonumber"><code>lua_tonumber</code></a></h3><p>
   5030  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5031  1.1  mbalmer <pre>lua_Number lua_tonumber (lua_State *L, int index);</pre>
   5032  1.1  mbalmer 
   5033  1.1  mbalmer <p>
   5034  1.2    lneto Equivalent to <a href="#lua_tonumberx"><code>lua_tonumberx</code></a> with <code>isnum</code> equal to <code>NULL</code>.
   5035  1.2    lneto 
   5036  1.2    lneto 
   5037  1.2    lneto 
   5038  1.2    lneto 
   5039  1.2    lneto 
   5040  1.2    lneto <hr><h3><a name="lua_tonumberx"><code>lua_tonumberx</code></a></h3><p>
   5041  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5042  1.2    lneto <pre>lua_Number lua_tonumberx (lua_State *L, int index, int *isnum);</pre>
   5043  1.2    lneto 
   5044  1.2    lneto <p>
   5045  1.2    lneto Converts the Lua value at the given index
   5046  1.1  mbalmer to the C&nbsp;type <a href="#lua_Number"><code>lua_Number</code></a> (see <a href="#lua_Number"><code>lua_Number</code></a>).
   5047  1.1  mbalmer The Lua value must be a number or a string convertible to a number
   5048  1.2    lneto (see <a href="#3.4.3">&sect;3.4.3</a>);
   5049  1.2    lneto otherwise, <a href="#lua_tonumberx"><code>lua_tonumberx</code></a> returns&nbsp;0.
   5050  1.2    lneto 
   5051  1.2    lneto 
   5052  1.2    lneto <p>
   5053  1.2    lneto If <code>isnum</code> is not <code>NULL</code>,
   5054  1.2    lneto its referent is assigned a boolean value that
   5055  1.2    lneto indicates whether the operation succeeded.
   5056  1.1  mbalmer 
   5057  1.1  mbalmer 
   5058  1.1  mbalmer 
   5059  1.1  mbalmer 
   5060  1.1  mbalmer 
   5061  1.1  mbalmer <hr><h3><a name="lua_topointer"><code>lua_topointer</code></a></h3><p>
   5062  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5063  1.1  mbalmer <pre>const void *lua_topointer (lua_State *L, int index);</pre>
   5064  1.1  mbalmer 
   5065  1.1  mbalmer <p>
   5066  1.2    lneto Converts the value at the given index to a generic
   5067  1.1  mbalmer C&nbsp;pointer (<code>void*</code>).
   5068  1.1  mbalmer The value can be a userdata, a table, a thread, or a function;
   5069  1.2    lneto otherwise, <code>lua_topointer</code> returns <code>NULL</code>.
   5070  1.1  mbalmer Different objects will give different pointers.
   5071  1.1  mbalmer There is no way to convert the pointer back to its original value.
   5072  1.1  mbalmer 
   5073  1.1  mbalmer 
   5074  1.1  mbalmer <p>
   5075  1.1  mbalmer Typically this function is used only for debug information.
   5076  1.1  mbalmer 
   5077  1.1  mbalmer 
   5078  1.1  mbalmer 
   5079  1.1  mbalmer 
   5080  1.1  mbalmer 
   5081  1.1  mbalmer <hr><h3><a name="lua_tostring"><code>lua_tostring</code></a></h3><p>
   5082  1.2    lneto <span class="apii">[-0, +0, <em>e</em>]</span>
   5083  1.1  mbalmer <pre>const char *lua_tostring (lua_State *L, int index);</pre>
   5084  1.1  mbalmer 
   5085  1.1  mbalmer <p>
   5086  1.1  mbalmer Equivalent to <a href="#lua_tolstring"><code>lua_tolstring</code></a> with <code>len</code> equal to <code>NULL</code>.
   5087  1.1  mbalmer 
   5088  1.1  mbalmer 
   5089  1.1  mbalmer 
   5090  1.1  mbalmer 
   5091  1.1  mbalmer 
   5092  1.1  mbalmer <hr><h3><a name="lua_tothread"><code>lua_tothread</code></a></h3><p>
   5093  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5094  1.1  mbalmer <pre>lua_State *lua_tothread (lua_State *L, int index);</pre>
   5095  1.1  mbalmer 
   5096  1.1  mbalmer <p>
   5097  1.2    lneto Converts the value at the given index to a Lua thread
   5098  1.1  mbalmer (represented as <code>lua_State*</code>).
   5099  1.1  mbalmer This value must be a thread;
   5100  1.1  mbalmer otherwise, the function returns <code>NULL</code>.
   5101  1.1  mbalmer 
   5102  1.1  mbalmer 
   5103  1.1  mbalmer 
   5104  1.1  mbalmer 
   5105  1.1  mbalmer 
   5106  1.1  mbalmer <hr><h3><a name="lua_touserdata"><code>lua_touserdata</code></a></h3><p>
   5107  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5108  1.1  mbalmer <pre>void *lua_touserdata (lua_State *L, int index);</pre>
   5109  1.1  mbalmer 
   5110  1.1  mbalmer <p>
   5111  1.2    lneto If the value at the given index is a full userdata,
   5112  1.1  mbalmer returns its block address.
   5113  1.1  mbalmer If the value is a light userdata,
   5114  1.1  mbalmer returns its pointer.
   5115  1.1  mbalmer Otherwise, returns <code>NULL</code>.
   5116  1.1  mbalmer 
   5117  1.1  mbalmer 
   5118  1.1  mbalmer 
   5119  1.1  mbalmer 
   5120  1.1  mbalmer 
   5121  1.1  mbalmer <hr><h3><a name="lua_type"><code>lua_type</code></a></h3><p>
   5122  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5123  1.1  mbalmer <pre>int lua_type (lua_State *L, int index);</pre>
   5124  1.1  mbalmer 
   5125  1.1  mbalmer <p>
   5126  1.2    lneto Returns the type of the value in the given valid index,
   5127  1.2    lneto or <code>LUA_TNONE</code> for a non-valid (but acceptable) index.
   5128  1.1  mbalmer The types returned by <a href="#lua_type"><code>lua_type</code></a> are coded by the following constants
   5129  1.1  mbalmer defined in <code>lua.h</code>:
   5130  1.2    lneto <a name="pdf-LUA_TNIL"><code>LUA_TNIL</code></a>,
   5131  1.2    lneto <a name="pdf-LUA_TNUMBER"><code>LUA_TNUMBER</code></a>,
   5132  1.2    lneto <a name="pdf-LUA_TBOOLEAN"><code>LUA_TBOOLEAN</code></a>,
   5133  1.2    lneto <a name="pdf-LUA_TSTRING"><code>LUA_TSTRING</code></a>,
   5134  1.2    lneto <a name="pdf-LUA_TTABLE"><code>LUA_TTABLE</code></a>,
   5135  1.2    lneto <a name="pdf-LUA_TFUNCTION"><code>LUA_TFUNCTION</code></a>,
   5136  1.2    lneto <a name="pdf-LUA_TUSERDATA"><code>LUA_TUSERDATA</code></a>,
   5137  1.2    lneto <a name="pdf-LUA_TTHREAD"><code>LUA_TTHREAD</code></a>,
   5138  1.1  mbalmer and
   5139  1.2    lneto <a name="pdf-LUA_TLIGHTUSERDATA"><code>LUA_TLIGHTUSERDATA</code></a>.
   5140  1.1  mbalmer 
   5141  1.1  mbalmer 
   5142  1.1  mbalmer 
   5143  1.1  mbalmer 
   5144  1.1  mbalmer 
   5145  1.1  mbalmer <hr><h3><a name="lua_typename"><code>lua_typename</code></a></h3><p>
   5146  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5147  1.2    lneto <pre>const char *lua_typename (lua_State *L, int tp);</pre>
   5148  1.1  mbalmer 
   5149  1.1  mbalmer <p>
   5150  1.1  mbalmer Returns the name of the type encoded by the value <code>tp</code>,
   5151  1.1  mbalmer which must be one the values returned by <a href="#lua_type"><code>lua_type</code></a>.
   5152  1.1  mbalmer 
   5153  1.1  mbalmer 
   5154  1.1  mbalmer 
   5155  1.1  mbalmer 
   5156  1.1  mbalmer 
   5157  1.2    lneto <hr><h3><a name="lua_Unsigned"><code>lua_Unsigned</code></a></h3>
   5158  1.2    lneto <pre>typedef ... lua_Unsigned;</pre>
   5159  1.2    lneto 
   5160  1.2    lneto <p>
   5161  1.2    lneto The unsigned version of <a href="#lua_Integer"><code>lua_Integer</code></a>.
   5162  1.2    lneto 
   5163  1.2    lneto 
   5164  1.2    lneto 
   5165  1.2    lneto 
   5166  1.2    lneto 
   5167  1.2    lneto <hr><h3><a name="lua_upvalueindex"><code>lua_upvalueindex</code></a></h3><p>
   5168  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5169  1.2    lneto <pre>int lua_upvalueindex (int i);</pre>
   5170  1.2    lneto 
   5171  1.2    lneto <p>
   5172  1.2    lneto Returns the pseudo-index that represents the <code>i</code>-th upvalue of
   5173  1.2    lneto the running function (see <a href="#4.4">&sect;4.4</a>).
   5174  1.2    lneto 
   5175  1.2    lneto 
   5176  1.2    lneto 
   5177  1.2    lneto 
   5178  1.2    lneto 
   5179  1.2    lneto <hr><h3><a name="lua_version"><code>lua_version</code></a></h3><p>
   5180  1.2    lneto <span class="apii">[-0, +0, <em>v</em>]</span>
   5181  1.2    lneto <pre>const lua_Number *lua_version (lua_State *L);</pre>
   5182  1.2    lneto 
   5183  1.2    lneto <p>
   5184  1.2    lneto Returns the address of the version number stored in the Lua core.
   5185  1.2    lneto When called with a valid <a href="#lua_State"><code>lua_State</code></a>,
   5186  1.2    lneto returns the address of the version used to create that state.
   5187  1.2    lneto When called with <code>NULL</code>,
   5188  1.2    lneto returns the address of the version running the call.
   5189  1.2    lneto 
   5190  1.2    lneto 
   5191  1.2    lneto 
   5192  1.2    lneto 
   5193  1.2    lneto 
   5194  1.1  mbalmer <hr><h3><a name="lua_Writer"><code>lua_Writer</code></a></h3>
   5195  1.1  mbalmer <pre>typedef int (*lua_Writer) (lua_State *L,
   5196  1.1  mbalmer                            const void* p,
   5197  1.1  mbalmer                            size_t sz,
   5198  1.1  mbalmer                            void* ud);</pre>
   5199  1.1  mbalmer 
   5200  1.1  mbalmer <p>
   5201  1.1  mbalmer The type of the writer function used by <a href="#lua_dump"><code>lua_dump</code></a>.
   5202  1.1  mbalmer Every time it produces another piece of chunk,
   5203  1.1  mbalmer <a href="#lua_dump"><code>lua_dump</code></a> calls the writer,
   5204  1.1  mbalmer passing along the buffer to be written (<code>p</code>),
   5205  1.1  mbalmer its size (<code>sz</code>),
   5206  1.1  mbalmer and the <code>data</code> parameter supplied to <a href="#lua_dump"><code>lua_dump</code></a>.
   5207  1.1  mbalmer 
   5208  1.1  mbalmer 
   5209  1.1  mbalmer <p>
   5210  1.1  mbalmer The writer returns an error code:
   5211  1.1  mbalmer 0&nbsp;means no errors;
   5212  1.1  mbalmer any other value means an error and stops <a href="#lua_dump"><code>lua_dump</code></a> from
   5213  1.1  mbalmer calling the writer again.
   5214  1.1  mbalmer 
   5215  1.1  mbalmer 
   5216  1.1  mbalmer 
   5217  1.1  mbalmer 
   5218  1.1  mbalmer 
   5219  1.1  mbalmer <hr><h3><a name="lua_xmove"><code>lua_xmove</code></a></h3><p>
   5220  1.2    lneto <span class="apii">[-?, +?, &ndash;]</span>
   5221  1.1  mbalmer <pre>void lua_xmove (lua_State *from, lua_State *to, int n);</pre>
   5222  1.1  mbalmer 
   5223  1.1  mbalmer <p>
   5224  1.2    lneto Exchange values between different threads of the same state.
   5225  1.1  mbalmer 
   5226  1.1  mbalmer 
   5227  1.1  mbalmer <p>
   5228  1.1  mbalmer This function pops <code>n</code> values from the stack <code>from</code>,
   5229  1.1  mbalmer and pushes them onto the stack <code>to</code>.
   5230  1.1  mbalmer 
   5231  1.1  mbalmer 
   5232  1.1  mbalmer 
   5233  1.1  mbalmer 
   5234  1.1  mbalmer 
   5235  1.1  mbalmer <hr><h3><a name="lua_yield"><code>lua_yield</code></a></h3><p>
   5236  1.3    lneto <span class="apii">[-?, +?, <em>e</em>]</span>
   5237  1.2    lneto <pre>int lua_yield (lua_State *L, int nresults);</pre>
   5238  1.2    lneto 
   5239  1.2    lneto <p>
   5240  1.2    lneto This function is equivalent to <a href="#lua_yieldk"><code>lua_yieldk</code></a>,
   5241  1.2    lneto but it has no continuation (see <a href="#4.7">&sect;4.7</a>).
   5242  1.2    lneto Therefore, when the thread resumes,
   5243  1.3    lneto it continues the function that called
   5244  1.2    lneto the function calling <code>lua_yield</code>.
   5245  1.2    lneto 
   5246  1.2    lneto 
   5247  1.2    lneto 
   5248  1.2    lneto 
   5249  1.2    lneto 
   5250  1.2    lneto <hr><h3><a name="lua_yieldk"><code>lua_yieldk</code></a></h3><p>
   5251  1.3    lneto <span class="apii">[-?, +?, <em>e</em>]</span>
   5252  1.3    lneto <pre>int lua_yieldk (lua_State *L,
   5253  1.3    lneto                 int nresults,
   5254  1.3    lneto                 lua_KContext ctx,
   5255  1.3    lneto                 lua_KFunction k);</pre>
   5256  1.1  mbalmer 
   5257  1.1  mbalmer <p>
   5258  1.3    lneto Yields a coroutine (thread).
   5259  1.1  mbalmer 
   5260  1.1  mbalmer 
   5261  1.1  mbalmer <p>
   5262  1.3    lneto When a C&nbsp;function calls <a href="#lua_yieldk"><code>lua_yieldk</code></a>,
   5263  1.1  mbalmer the running coroutine suspends its execution,
   5264  1.1  mbalmer and the call to <a href="#lua_resume"><code>lua_resume</code></a> that started this coroutine returns.
   5265  1.1  mbalmer The parameter <code>nresults</code> is the number of values from the stack
   5266  1.2    lneto that will be passed as results to <a href="#lua_resume"><code>lua_resume</code></a>.
   5267  1.2    lneto 
   5268  1.2    lneto 
   5269  1.2    lneto <p>
   5270  1.2    lneto When the coroutine is resumed again,
   5271  1.2    lneto Lua calls the given continuation function <code>k</code> to continue
   5272  1.2    lneto the execution of the C function that yielded (see <a href="#4.7">&sect;4.7</a>).
   5273  1.2    lneto This continuation function receives the same stack
   5274  1.2    lneto from the previous function,
   5275  1.2    lneto with the <code>n</code> results removed and
   5276  1.2    lneto replaced by the arguments passed to <a href="#lua_resume"><code>lua_resume</code></a>.
   5277  1.2    lneto Moreover,
   5278  1.2    lneto the continuation function receives the value <code>ctx</code>
   5279  1.2    lneto that was passed to <a href="#lua_yieldk"><code>lua_yieldk</code></a>.
   5280  1.1  mbalmer 
   5281  1.1  mbalmer 
   5282  1.3    lneto <p>
   5283  1.3    lneto Usually, this function does not return;
   5284  1.3    lneto when the coroutine eventually resumes,
   5285  1.3    lneto it continues executing the continuation function.
   5286  1.3    lneto However, there is one special case,
   5287  1.3    lneto which is when this function is called
   5288  1.3    lneto from inside a line hook (see <a href="#4.9">&sect;4.9</a>).
   5289  1.3    lneto In that case, <code>lua_yieldk</code> should be called with no continuation
   5290  1.3    lneto (probably in the form of <a href="#lua_yield"><code>lua_yield</code></a>),
   5291  1.3    lneto and the hook should return immediately after the call.
   5292  1.3    lneto Lua will yield and,
   5293  1.3    lneto when the coroutine resumes again,
   5294  1.3    lneto it will continue the normal execution
   5295  1.3    lneto of the (Lua) function that triggered the hook.
   5296  1.3    lneto 
   5297  1.3    lneto 
   5298  1.3    lneto <p>
   5299  1.3    lneto This function can raise an error if it is called from a thread
   5300  1.3    lneto with a pending C call with no continuation function,
   5301  1.3    lneto or it is called from a thread that is not running inside a resume
   5302  1.3    lneto (e.g., the main thread).
   5303  1.3    lneto 
   5304  1.3    lneto 
   5305  1.1  mbalmer 
   5306  1.1  mbalmer 
   5307  1.1  mbalmer 
   5308  1.1  mbalmer 
   5309  1.1  mbalmer 
   5310  1.2    lneto <h2>4.9 &ndash; <a name="4.9">The Debug Interface</a></h2>
   5311  1.1  mbalmer 
   5312  1.1  mbalmer <p>
   5313  1.1  mbalmer Lua has no built-in debugging facilities.
   5314  1.1  mbalmer Instead, it offers a special interface
   5315  1.1  mbalmer by means of functions and <em>hooks</em>.
   5316  1.1  mbalmer This interface allows the construction of different
   5317  1.1  mbalmer kinds of debuggers, profilers, and other tools
   5318  1.1  mbalmer that need "inside information" from the interpreter.
   5319  1.1  mbalmer 
   5320  1.1  mbalmer 
   5321  1.1  mbalmer 
   5322  1.1  mbalmer <hr><h3><a name="lua_Debug"><code>lua_Debug</code></a></h3>
   5323  1.1  mbalmer <pre>typedef struct lua_Debug {
   5324  1.1  mbalmer   int event;
   5325  1.1  mbalmer   const char *name;           /* (n) */
   5326  1.1  mbalmer   const char *namewhat;       /* (n) */
   5327  1.1  mbalmer   const char *what;           /* (S) */
   5328  1.1  mbalmer   const char *source;         /* (S) */
   5329  1.1  mbalmer   int currentline;            /* (l) */
   5330  1.1  mbalmer   int linedefined;            /* (S) */
   5331  1.1  mbalmer   int lastlinedefined;        /* (S) */
   5332  1.2    lneto   unsigned char nups;         /* (u) number of upvalues */
   5333  1.2    lneto   unsigned char nparams;      /* (u) number of parameters */
   5334  1.2    lneto   char isvararg;              /* (u) */
   5335  1.2    lneto   char istailcall;            /* (t) */
   5336  1.1  mbalmer   char short_src[LUA_IDSIZE]; /* (S) */
   5337  1.1  mbalmer   /* private part */
   5338  1.1  mbalmer   <em>other fields</em>
   5339  1.1  mbalmer } lua_Debug;</pre>
   5340  1.1  mbalmer 
   5341  1.1  mbalmer <p>
   5342  1.1  mbalmer A structure used to carry different pieces of
   5343  1.2    lneto information about a function or an activation record.
   5344  1.1  mbalmer <a href="#lua_getstack"><code>lua_getstack</code></a> fills only the private part
   5345  1.1  mbalmer of this structure, for later use.
   5346  1.1  mbalmer To fill the other fields of <a href="#lua_Debug"><code>lua_Debug</code></a> with useful information,
   5347  1.1  mbalmer call <a href="#lua_getinfo"><code>lua_getinfo</code></a>.
   5348  1.1  mbalmer 
   5349  1.1  mbalmer 
   5350  1.1  mbalmer <p>
   5351  1.1  mbalmer The fields of <a href="#lua_Debug"><code>lua_Debug</code></a> have the following meaning:
   5352  1.1  mbalmer 
   5353  1.1  mbalmer <ul>
   5354  1.1  mbalmer 
   5355  1.2    lneto <li><b><code>source</code>: </b>
   5356  1.3    lneto the name of the chunk that created the function.
   5357  1.2    lneto If <code>source</code> starts with a '<code>@</code>',
   5358  1.2    lneto it means that the function was defined in a file where
   5359  1.2    lneto the file name follows the '<code>@</code>'.
   5360  1.2    lneto If <code>source</code> starts with a '<code>=</code>',
   5361  1.2    lneto the remainder of its contents describe the source in a user-dependent manner.
   5362  1.2    lneto Otherwise,
   5363  1.2    lneto the function was defined in a string where
   5364  1.2    lneto <code>source</code> is that string.
   5365  1.1  mbalmer </li>
   5366  1.1  mbalmer 
   5367  1.2    lneto <li><b><code>short_src</code>: </b>
   5368  1.1  mbalmer a "printable" version of <code>source</code>, to be used in error messages.
   5369  1.1  mbalmer </li>
   5370  1.1  mbalmer 
   5371  1.2    lneto <li><b><code>linedefined</code>: </b>
   5372  1.1  mbalmer the line number where the definition of the function starts.
   5373  1.1  mbalmer </li>
   5374  1.1  mbalmer 
   5375  1.2    lneto <li><b><code>lastlinedefined</code>: </b>
   5376  1.1  mbalmer the line number where the definition of the function ends.
   5377  1.1  mbalmer </li>
   5378  1.1  mbalmer 
   5379  1.2    lneto <li><b><code>what</code>: </b>
   5380  1.1  mbalmer the string <code>"Lua"</code> if the function is a Lua function,
   5381  1.1  mbalmer <code>"C"</code> if it is a C&nbsp;function,
   5382  1.2    lneto <code>"main"</code> if it is the main part of a chunk.
   5383  1.1  mbalmer </li>
   5384  1.1  mbalmer 
   5385  1.2    lneto <li><b><code>currentline</code>: </b>
   5386  1.1  mbalmer the current line where the given function is executing.
   5387  1.1  mbalmer When no line information is available,
   5388  1.1  mbalmer <code>currentline</code> is set to -1.
   5389  1.1  mbalmer </li>
   5390  1.1  mbalmer 
   5391  1.2    lneto <li><b><code>name</code>: </b>
   5392  1.1  mbalmer a reasonable name for the given function.
   5393  1.1  mbalmer Because functions in Lua are first-class values,
   5394  1.1  mbalmer they do not have a fixed name:
   5395  1.1  mbalmer some functions can be the value of multiple global variables,
   5396  1.1  mbalmer while others can be stored only in a table field.
   5397  1.1  mbalmer The <code>lua_getinfo</code> function checks how the function was
   5398  1.1  mbalmer called to find a suitable name.
   5399  1.1  mbalmer If it cannot find a name,
   5400  1.1  mbalmer then <code>name</code> is set to <code>NULL</code>.
   5401  1.1  mbalmer </li>
   5402  1.1  mbalmer 
   5403  1.2    lneto <li><b><code>namewhat</code>: </b>
   5404  1.1  mbalmer explains the <code>name</code> field.
   5405  1.1  mbalmer The value of <code>namewhat</code> can be
   5406  1.1  mbalmer <code>"global"</code>, <code>"local"</code>, <code>"method"</code>,
   5407  1.1  mbalmer <code>"field"</code>, <code>"upvalue"</code>, or <code>""</code> (the empty string),
   5408  1.1  mbalmer according to how the function was called.
   5409  1.1  mbalmer (Lua uses the empty string when no other option seems to apply.)
   5410  1.1  mbalmer </li>
   5411  1.1  mbalmer 
   5412  1.2    lneto <li><b><code>istailcall</code>: </b>
   5413  1.2    lneto true if this function invocation was called by a tail call.
   5414  1.2    lneto In this case, the caller of this level is not in the stack.
   5415  1.2    lneto </li>
   5416  1.2    lneto 
   5417  1.2    lneto <li><b><code>nups</code>: </b>
   5418  1.1  mbalmer the number of upvalues of the function.
   5419  1.1  mbalmer </li>
   5420  1.1  mbalmer 
   5421  1.2    lneto <li><b><code>nparams</code>: </b>
   5422  1.2    lneto the number of fixed parameters of the function
   5423  1.2    lneto (always 0&nbsp;for C&nbsp;functions).
   5424  1.2    lneto </li>
   5425  1.2    lneto 
   5426  1.2    lneto <li><b><code>isvararg</code>: </b>
   5427  1.2    lneto true if the function is a vararg function
   5428  1.2    lneto (always true for C&nbsp;functions).
   5429  1.2    lneto </li>
   5430  1.2    lneto 
   5431  1.1  mbalmer </ul>
   5432  1.1  mbalmer 
   5433  1.1  mbalmer 
   5434  1.1  mbalmer 
   5435  1.1  mbalmer 
   5436  1.1  mbalmer <hr><h3><a name="lua_gethook"><code>lua_gethook</code></a></h3><p>
   5437  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5438  1.1  mbalmer <pre>lua_Hook lua_gethook (lua_State *L);</pre>
   5439  1.1  mbalmer 
   5440  1.1  mbalmer <p>
   5441  1.1  mbalmer Returns the current hook function.
   5442  1.1  mbalmer 
   5443  1.1  mbalmer 
   5444  1.1  mbalmer 
   5445  1.1  mbalmer 
   5446  1.1  mbalmer 
   5447  1.1  mbalmer <hr><h3><a name="lua_gethookcount"><code>lua_gethookcount</code></a></h3><p>
   5448  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5449  1.1  mbalmer <pre>int lua_gethookcount (lua_State *L);</pre>
   5450  1.1  mbalmer 
   5451  1.1  mbalmer <p>
   5452  1.1  mbalmer Returns the current hook count.
   5453  1.1  mbalmer 
   5454  1.1  mbalmer 
   5455  1.1  mbalmer 
   5456  1.1  mbalmer 
   5457  1.1  mbalmer 
   5458  1.1  mbalmer <hr><h3><a name="lua_gethookmask"><code>lua_gethookmask</code></a></h3><p>
   5459  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5460  1.1  mbalmer <pre>int lua_gethookmask (lua_State *L);</pre>
   5461  1.1  mbalmer 
   5462  1.1  mbalmer <p>
   5463  1.1  mbalmer Returns the current hook mask.
   5464  1.1  mbalmer 
   5465  1.1  mbalmer 
   5466  1.1  mbalmer 
   5467  1.1  mbalmer 
   5468  1.1  mbalmer 
   5469  1.1  mbalmer <hr><h3><a name="lua_getinfo"><code>lua_getinfo</code></a></h3><p>
   5470  1.2    lneto <span class="apii">[-(0|1), +(0|1|2), <em>e</em>]</span>
   5471  1.1  mbalmer <pre>int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar);</pre>
   5472  1.1  mbalmer 
   5473  1.1  mbalmer <p>
   5474  1.2    lneto Gets information about a specific function or function invocation.
   5475  1.1  mbalmer 
   5476  1.1  mbalmer 
   5477  1.1  mbalmer <p>
   5478  1.1  mbalmer To get information about a function invocation,
   5479  1.1  mbalmer the parameter <code>ar</code> must be a valid activation record that was
   5480  1.1  mbalmer filled by a previous call to <a href="#lua_getstack"><code>lua_getstack</code></a> or
   5481  1.1  mbalmer given as argument to a hook (see <a href="#lua_Hook"><code>lua_Hook</code></a>).
   5482  1.1  mbalmer 
   5483  1.1  mbalmer 
   5484  1.1  mbalmer <p>
   5485  1.1  mbalmer To get information about a function you push it onto the stack
   5486  1.1  mbalmer and start the <code>what</code> string with the character '<code>&gt;</code>'.
   5487  1.1  mbalmer (In that case,
   5488  1.2    lneto <code>lua_getinfo</code> pops the function from the top of the stack.)
   5489  1.1  mbalmer For instance, to know in which line a function <code>f</code> was defined,
   5490  1.1  mbalmer you can write the following code:
   5491  1.1  mbalmer 
   5492  1.1  mbalmer <pre>
   5493  1.1  mbalmer      lua_Debug ar;
   5494  1.2    lneto      lua_getglobal(L, "f");  /* get global 'f' */
   5495  1.1  mbalmer      lua_getinfo(L, "&gt;S", &amp;ar);
   5496  1.1  mbalmer      printf("%d\n", ar.linedefined);
   5497  1.1  mbalmer </pre>
   5498  1.1  mbalmer 
   5499  1.1  mbalmer <p>
   5500  1.1  mbalmer Each character in the string <code>what</code>
   5501  1.1  mbalmer selects some fields of the structure <code>ar</code> to be filled or
   5502  1.1  mbalmer a value to be pushed on the stack:
   5503  1.1  mbalmer 
   5504  1.1  mbalmer <ul>
   5505  1.1  mbalmer 
   5506  1.2    lneto <li><b>'<code>n</code>': </b> fills in the field <code>name</code> and <code>namewhat</code>;
   5507  1.1  mbalmer </li>
   5508  1.1  mbalmer 
   5509  1.2    lneto <li><b>'<code>S</code>': </b>
   5510  1.1  mbalmer fills in the fields <code>source</code>, <code>short_src</code>,
   5511  1.1  mbalmer <code>linedefined</code>, <code>lastlinedefined</code>, and <code>what</code>;
   5512  1.1  mbalmer </li>
   5513  1.1  mbalmer 
   5514  1.2    lneto <li><b>'<code>l</code>': </b> fills in the field <code>currentline</code>;
   5515  1.2    lneto </li>
   5516  1.2    lneto 
   5517  1.2    lneto <li><b>'<code>t</code>': </b> fills in the field <code>istailcall</code>;
   5518  1.1  mbalmer </li>
   5519  1.1  mbalmer 
   5520  1.2    lneto <li><b>'<code>u</code>': </b> fills in the fields
   5521  1.2    lneto <code>nups</code>, <code>nparams</code>, and <code>isvararg</code>;
   5522  1.1  mbalmer </li>
   5523  1.1  mbalmer 
   5524  1.2    lneto <li><b>'<code>f</code>': </b>
   5525  1.1  mbalmer pushes onto the stack the function that is
   5526  1.1  mbalmer running at the given level;
   5527  1.1  mbalmer </li>
   5528  1.1  mbalmer 
   5529  1.2    lneto <li><b>'<code>L</code>': </b>
   5530  1.1  mbalmer pushes onto the stack a table whose indices are the
   5531  1.1  mbalmer numbers of the lines that are valid on the function.
   5532  1.1  mbalmer (A <em>valid line</em> is a line with some associated code,
   5533  1.1  mbalmer that is, a line where you can put a break point.
   5534  1.1  mbalmer Non-valid lines include empty lines and comments.)
   5535  1.2    lneto 
   5536  1.2    lneto 
   5537  1.2    lneto <p>
   5538  1.2    lneto If this option is given together with option '<code>f</code>',
   5539  1.2    lneto its table is pushed after the function.
   5540  1.1  mbalmer </li>
   5541  1.1  mbalmer 
   5542  1.1  mbalmer </ul>
   5543  1.1  mbalmer 
   5544  1.1  mbalmer <p>
   5545  1.1  mbalmer This function returns 0 on error
   5546  1.1  mbalmer (for instance, an invalid option in <code>what</code>).
   5547  1.1  mbalmer 
   5548  1.1  mbalmer 
   5549  1.1  mbalmer 
   5550  1.1  mbalmer 
   5551  1.1  mbalmer 
   5552  1.1  mbalmer <hr><h3><a name="lua_getlocal"><code>lua_getlocal</code></a></h3><p>
   5553  1.2    lneto <span class="apii">[-0, +(0|1), &ndash;]</span>
   5554  1.3    lneto <pre>const char *lua_getlocal (lua_State *L, const lua_Debug *ar, int n);</pre>
   5555  1.1  mbalmer 
   5556  1.1  mbalmer <p>
   5557  1.2    lneto Gets information about a local variable of
   5558  1.2    lneto a given activation record or a given function.
   5559  1.2    lneto 
   5560  1.2    lneto 
   5561  1.2    lneto <p>
   5562  1.2    lneto In the first case,
   5563  1.2    lneto the parameter <code>ar</code> must be a valid activation record that was
   5564  1.1  mbalmer filled by a previous call to <a href="#lua_getstack"><code>lua_getstack</code></a> or
   5565  1.1  mbalmer given as argument to a hook (see <a href="#lua_Hook"><code>lua_Hook</code></a>).
   5566  1.2    lneto The index <code>n</code> selects which local variable to inspect;
   5567  1.2    lneto see <a href="#pdf-debug.getlocal"><code>debug.getlocal</code></a> for details about variable indices
   5568  1.2    lneto and names.
   5569  1.2    lneto 
   5570  1.2    lneto 
   5571  1.2    lneto <p>
   5572  1.1  mbalmer <a href="#lua_getlocal"><code>lua_getlocal</code></a> pushes the variable's value onto the stack
   5573  1.1  mbalmer and returns its name.
   5574  1.1  mbalmer 
   5575  1.1  mbalmer 
   5576  1.1  mbalmer <p>
   5577  1.2    lneto In the second case, <code>ar</code> must be <code>NULL</code> and the function
   5578  1.2    lneto to be inspected must be at the top of the stack.
   5579  1.2    lneto In this case, only parameters of Lua functions are visible
   5580  1.2    lneto (as there is no information about what variables are active)
   5581  1.2    lneto and no values are pushed onto the stack.
   5582  1.1  mbalmer 
   5583  1.1  mbalmer 
   5584  1.1  mbalmer <p>
   5585  1.1  mbalmer Returns <code>NULL</code> (and pushes nothing)
   5586  1.1  mbalmer when the index is greater than
   5587  1.1  mbalmer the number of active local variables.
   5588  1.1  mbalmer 
   5589  1.1  mbalmer 
   5590  1.1  mbalmer 
   5591  1.1  mbalmer 
   5592  1.1  mbalmer 
   5593  1.1  mbalmer <hr><h3><a name="lua_getstack"><code>lua_getstack</code></a></h3><p>
   5594  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5595  1.1  mbalmer <pre>int lua_getstack (lua_State *L, int level, lua_Debug *ar);</pre>
   5596  1.1  mbalmer 
   5597  1.1  mbalmer <p>
   5598  1.2    lneto Gets information about the interpreter runtime stack.
   5599  1.1  mbalmer 
   5600  1.1  mbalmer 
   5601  1.1  mbalmer <p>
   5602  1.1  mbalmer This function fills parts of a <a href="#lua_Debug"><code>lua_Debug</code></a> structure with
   5603  1.1  mbalmer an identification of the <em>activation record</em>
   5604  1.1  mbalmer of the function executing at a given level.
   5605  1.1  mbalmer Level&nbsp;0 is the current running function,
   5606  1.2    lneto whereas level <em>n+1</em> is the function that has called level <em>n</em>
   5607  1.2    lneto (except for tail calls, which do not count on the stack).
   5608  1.1  mbalmer When there are no errors, <a href="#lua_getstack"><code>lua_getstack</code></a> returns 1;
   5609  1.1  mbalmer when called with a level greater than the stack depth,
   5610  1.1  mbalmer it returns 0.
   5611  1.1  mbalmer 
   5612  1.1  mbalmer 
   5613  1.1  mbalmer 
   5614  1.1  mbalmer 
   5615  1.1  mbalmer 
   5616  1.1  mbalmer <hr><h3><a name="lua_getupvalue"><code>lua_getupvalue</code></a></h3><p>
   5617  1.2    lneto <span class="apii">[-0, +(0|1), &ndash;]</span>
   5618  1.1  mbalmer <pre>const char *lua_getupvalue (lua_State *L, int funcindex, int n);</pre>
   5619  1.1  mbalmer 
   5620  1.1  mbalmer <p>
   5621  1.1  mbalmer Gets information about a closure's upvalue.
   5622  1.1  mbalmer (For Lua functions,
   5623  1.1  mbalmer upvalues are the external local variables that the function uses,
   5624  1.1  mbalmer and that are consequently included in its closure.)
   5625  1.1  mbalmer <a href="#lua_getupvalue"><code>lua_getupvalue</code></a> gets the index <code>n</code> of an upvalue,
   5626  1.1  mbalmer pushes the upvalue's value onto the stack,
   5627  1.1  mbalmer and returns its name.
   5628  1.1  mbalmer <code>funcindex</code> points to the closure in the stack.
   5629  1.1  mbalmer (Upvalues have no particular order,
   5630  1.1  mbalmer as they are active through the whole function.
   5631  1.1  mbalmer So, they are numbered in an arbitrary order.)
   5632  1.1  mbalmer 
   5633  1.1  mbalmer 
   5634  1.1  mbalmer <p>
   5635  1.1  mbalmer Returns <code>NULL</code> (and pushes nothing)
   5636  1.1  mbalmer when the index is greater than the number of upvalues.
   5637  1.1  mbalmer For C&nbsp;functions, this function uses the empty string <code>""</code>
   5638  1.1  mbalmer as a name for all upvalues.
   5639  1.1  mbalmer 
   5640  1.1  mbalmer 
   5641  1.1  mbalmer 
   5642  1.1  mbalmer 
   5643  1.1  mbalmer 
   5644  1.1  mbalmer <hr><h3><a name="lua_Hook"><code>lua_Hook</code></a></h3>
   5645  1.1  mbalmer <pre>typedef void (*lua_Hook) (lua_State *L, lua_Debug *ar);</pre>
   5646  1.1  mbalmer 
   5647  1.1  mbalmer <p>
   5648  1.1  mbalmer Type for debugging hook functions.
   5649  1.1  mbalmer 
   5650  1.1  mbalmer 
   5651  1.1  mbalmer <p>
   5652  1.1  mbalmer Whenever a hook is called, its <code>ar</code> argument has its field
   5653  1.1  mbalmer <code>event</code> set to the specific event that triggered the hook.
   5654  1.1  mbalmer Lua identifies these events with the following constants:
   5655  1.1  mbalmer <a name="pdf-LUA_HOOKCALL"><code>LUA_HOOKCALL</code></a>, <a name="pdf-LUA_HOOKRET"><code>LUA_HOOKRET</code></a>,
   5656  1.2    lneto <a name="pdf-LUA_HOOKTAILCALL"><code>LUA_HOOKTAILCALL</code></a>, <a name="pdf-LUA_HOOKLINE"><code>LUA_HOOKLINE</code></a>,
   5657  1.1  mbalmer and <a name="pdf-LUA_HOOKCOUNT"><code>LUA_HOOKCOUNT</code></a>.
   5658  1.1  mbalmer Moreover, for line events, the field <code>currentline</code> is also set.
   5659  1.1  mbalmer To get the value of any other field in <code>ar</code>,
   5660  1.1  mbalmer the hook must call <a href="#lua_getinfo"><code>lua_getinfo</code></a>.
   5661  1.2    lneto 
   5662  1.2    lneto 
   5663  1.2    lneto <p>
   5664  1.2    lneto For call events, <code>event</code> can be <code>LUA_HOOKCALL</code>,
   5665  1.2    lneto the normal value, or <code>LUA_HOOKTAILCALL</code>, for a tail call;
   5666  1.2    lneto in this case, there will be no corresponding return event.
   5667  1.1  mbalmer 
   5668  1.1  mbalmer 
   5669  1.1  mbalmer <p>
   5670  1.1  mbalmer While Lua is running a hook, it disables other calls to hooks.
   5671  1.1  mbalmer Therefore, if a hook calls back Lua to execute a function or a chunk,
   5672  1.1  mbalmer this execution occurs without any calls to hooks.
   5673  1.1  mbalmer 
   5674  1.1  mbalmer 
   5675  1.2    lneto <p>
   5676  1.2    lneto Hook functions cannot have continuations,
   5677  1.2    lneto that is, they cannot call <a href="#lua_yieldk"><code>lua_yieldk</code></a>,
   5678  1.2    lneto <a href="#lua_pcallk"><code>lua_pcallk</code></a>, or <a href="#lua_callk"><code>lua_callk</code></a> with a non-null <code>k</code>.
   5679  1.2    lneto 
   5680  1.2    lneto 
   5681  1.2    lneto <p>
   5682  1.2    lneto Hook functions can yield under the following conditions:
   5683  1.2    lneto Only count and line events can yield
   5684  1.2    lneto and they cannot yield any value;
   5685  1.2    lneto to yield a hook function must finish its execution
   5686  1.2    lneto calling <a href="#lua_yield"><code>lua_yield</code></a> with <code>nresults</code> equal to zero.
   5687  1.2    lneto 
   5688  1.2    lneto 
   5689  1.1  mbalmer 
   5690  1.1  mbalmer 
   5691  1.1  mbalmer 
   5692  1.1  mbalmer <hr><h3><a name="lua_sethook"><code>lua_sethook</code></a></h3><p>
   5693  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5694  1.2    lneto <pre>void lua_sethook (lua_State *L, lua_Hook f, int mask, int count);</pre>
   5695  1.1  mbalmer 
   5696  1.1  mbalmer <p>
   5697  1.1  mbalmer Sets the debugging hook function.
   5698  1.1  mbalmer 
   5699  1.1  mbalmer 
   5700  1.1  mbalmer <p>
   5701  1.1  mbalmer Argument <code>f</code> is the hook function.
   5702  1.1  mbalmer <code>mask</code> specifies on which events the hook will be called:
   5703  1.1  mbalmer it is formed by a bitwise or of the constants
   5704  1.1  mbalmer <a name="pdf-LUA_MASKCALL"><code>LUA_MASKCALL</code></a>,
   5705  1.1  mbalmer <a name="pdf-LUA_MASKRET"><code>LUA_MASKRET</code></a>,
   5706  1.1  mbalmer <a name="pdf-LUA_MASKLINE"><code>LUA_MASKLINE</code></a>,
   5707  1.1  mbalmer and <a name="pdf-LUA_MASKCOUNT"><code>LUA_MASKCOUNT</code></a>.
   5708  1.1  mbalmer The <code>count</code> argument is only meaningful when the mask
   5709  1.1  mbalmer includes <code>LUA_MASKCOUNT</code>.
   5710  1.1  mbalmer For each event, the hook is called as explained below:
   5711  1.1  mbalmer 
   5712  1.1  mbalmer <ul>
   5713  1.1  mbalmer 
   5714  1.2    lneto <li><b>The call hook: </b> is called when the interpreter calls a function.
   5715  1.1  mbalmer The hook is called just after Lua enters the new function,
   5716  1.1  mbalmer before the function gets its arguments.
   5717  1.1  mbalmer </li>
   5718  1.1  mbalmer 
   5719  1.2    lneto <li><b>The return hook: </b> is called when the interpreter returns from a function.
   5720  1.1  mbalmer The hook is called just before Lua leaves the function.
   5721  1.2    lneto There is no standard way to access the values
   5722  1.2    lneto to be returned by the function.
   5723  1.1  mbalmer </li>
   5724  1.1  mbalmer 
   5725  1.2    lneto <li><b>The line hook: </b> is called when the interpreter is about to
   5726  1.1  mbalmer start the execution of a new line of code,
   5727  1.1  mbalmer or when it jumps back in the code (even to the same line).
   5728  1.1  mbalmer (This event only happens while Lua is executing a Lua function.)
   5729  1.1  mbalmer </li>
   5730  1.1  mbalmer 
   5731  1.2    lneto <li><b>The count hook: </b> is called after the interpreter executes every
   5732  1.1  mbalmer <code>count</code> instructions.
   5733  1.1  mbalmer (This event only happens while Lua is executing a Lua function.)
   5734  1.1  mbalmer </li>
   5735  1.1  mbalmer 
   5736  1.1  mbalmer </ul>
   5737  1.1  mbalmer 
   5738  1.1  mbalmer <p>
   5739  1.1  mbalmer A hook is disabled by setting <code>mask</code> to zero.
   5740  1.1  mbalmer 
   5741  1.1  mbalmer 
   5742  1.1  mbalmer 
   5743  1.1  mbalmer 
   5744  1.1  mbalmer 
   5745  1.1  mbalmer <hr><h3><a name="lua_setlocal"><code>lua_setlocal</code></a></h3><p>
   5746  1.2    lneto <span class="apii">[-(0|1), +0, &ndash;]</span>
   5747  1.3    lneto <pre>const char *lua_setlocal (lua_State *L, const lua_Debug *ar, int n);</pre>
   5748  1.1  mbalmer 
   5749  1.1  mbalmer <p>
   5750  1.1  mbalmer Sets the value of a local variable of a given activation record.
   5751  1.1  mbalmer Parameters <code>ar</code> and <code>n</code> are as in <a href="#lua_getlocal"><code>lua_getlocal</code></a>
   5752  1.1  mbalmer (see <a href="#lua_getlocal"><code>lua_getlocal</code></a>).
   5753  1.1  mbalmer <a href="#lua_setlocal"><code>lua_setlocal</code></a> assigns the value at the top of the stack
   5754  1.1  mbalmer to the variable and returns its name.
   5755  1.1  mbalmer It also pops the value from the stack.
   5756  1.1  mbalmer 
   5757  1.1  mbalmer 
   5758  1.1  mbalmer <p>
   5759  1.1  mbalmer Returns <code>NULL</code> (and pops nothing)
   5760  1.1  mbalmer when the index is greater than
   5761  1.1  mbalmer the number of active local variables.
   5762  1.1  mbalmer 
   5763  1.1  mbalmer 
   5764  1.1  mbalmer 
   5765  1.1  mbalmer 
   5766  1.1  mbalmer 
   5767  1.1  mbalmer <hr><h3><a name="lua_setupvalue"><code>lua_setupvalue</code></a></h3><p>
   5768  1.2    lneto <span class="apii">[-(0|1), +0, &ndash;]</span>
   5769  1.1  mbalmer <pre>const char *lua_setupvalue (lua_State *L, int funcindex, int n);</pre>
   5770  1.1  mbalmer 
   5771  1.1  mbalmer <p>
   5772  1.1  mbalmer Sets the value of a closure's upvalue.
   5773  1.1  mbalmer It assigns the value at the top of the stack
   5774  1.1  mbalmer to the upvalue and returns its name.
   5775  1.1  mbalmer It also pops the value from the stack.
   5776  1.1  mbalmer Parameters <code>funcindex</code> and <code>n</code> are as in the <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>
   5777  1.1  mbalmer (see <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>).
   5778  1.1  mbalmer 
   5779  1.1  mbalmer 
   5780  1.1  mbalmer <p>
   5781  1.1  mbalmer Returns <code>NULL</code> (and pops nothing)
   5782  1.1  mbalmer when the index is greater than the number of upvalues.
   5783  1.1  mbalmer 
   5784  1.1  mbalmer 
   5785  1.1  mbalmer 
   5786  1.1  mbalmer 
   5787  1.1  mbalmer 
   5788  1.2    lneto <hr><h3><a name="lua_upvalueid"><code>lua_upvalueid</code></a></h3><p>
   5789  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5790  1.2    lneto <pre>void *lua_upvalueid (lua_State *L, int funcindex, int n);</pre>
   5791  1.2    lneto 
   5792  1.2    lneto <p>
   5793  1.3    lneto Returns a unique identifier for the upvalue numbered <code>n</code>
   5794  1.2    lneto from the closure at index <code>funcindex</code>.
   5795  1.2    lneto Parameters <code>funcindex</code> and <code>n</code> are as in the <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>
   5796  1.2    lneto (see <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>)
   5797  1.2    lneto (but <code>n</code> cannot be greater than the number of upvalues).
   5798  1.2    lneto 
   5799  1.2    lneto 
   5800  1.2    lneto <p>
   5801  1.2    lneto These unique identifiers allow a program to check whether different
   5802  1.2    lneto closures share upvalues.
   5803  1.2    lneto Lua closures that share an upvalue
   5804  1.2    lneto (that is, that access a same external local variable)
   5805  1.2    lneto will return identical ids for those upvalue indices.
   5806  1.2    lneto 
   5807  1.2    lneto 
   5808  1.2    lneto 
   5809  1.2    lneto 
   5810  1.2    lneto 
   5811  1.2    lneto <hr><h3><a name="lua_upvaluejoin"><code>lua_upvaluejoin</code></a></h3><p>
   5812  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   5813  1.2    lneto <pre>void lua_upvaluejoin (lua_State *L, int funcindex1, int n1,
   5814  1.2    lneto                                     int funcindex2, int n2);</pre>
   5815  1.2    lneto 
   5816  1.2    lneto <p>
   5817  1.2    lneto Make the <code>n1</code>-th upvalue of the Lua closure at index <code>funcindex1</code>
   5818  1.2    lneto refer to the <code>n2</code>-th upvalue of the Lua closure at index <code>funcindex2</code>.
   5819  1.2    lneto 
   5820  1.2    lneto 
   5821  1.2    lneto 
   5822  1.2    lneto 
   5823  1.2    lneto 
   5824  1.1  mbalmer 
   5825  1.1  mbalmer 
   5826  1.2    lneto <h1>5 &ndash; <a name="5">The Auxiliary Library</a></h1>
   5827  1.1  mbalmer 
   5828  1.1  mbalmer <p>
   5829  1.1  mbalmer 
   5830  1.1  mbalmer The <em>auxiliary library</em> provides several convenient functions
   5831  1.1  mbalmer to interface C with Lua.
   5832  1.2    lneto While the basic API provides the primitive functions for all
   5833  1.1  mbalmer interactions between C and Lua,
   5834  1.1  mbalmer the auxiliary library provides higher-level functions for some
   5835  1.1  mbalmer common tasks.
   5836  1.1  mbalmer 
   5837  1.1  mbalmer 
   5838  1.1  mbalmer <p>
   5839  1.2    lneto All functions and types from the auxiliary library
   5840  1.1  mbalmer are defined in header file <code>lauxlib.h</code> and
   5841  1.1  mbalmer have a prefix <code>luaL_</code>.
   5842  1.1  mbalmer 
   5843  1.1  mbalmer 
   5844  1.1  mbalmer <p>
   5845  1.1  mbalmer All functions in the auxiliary library are built on
   5846  1.1  mbalmer top of the basic API,
   5847  1.2    lneto and so they provide nothing that cannot be done with that API.
   5848  1.2    lneto Nevertheless, the use of the auxiliary library ensures
   5849  1.2    lneto more consistency to your code.
   5850  1.2    lneto 
   5851  1.2    lneto 
   5852  1.2    lneto <p>
   5853  1.2    lneto Several functions in the auxiliary library use internally some
   5854  1.2    lneto extra stack slots.
   5855  1.2    lneto When a function in the auxiliary library uses less than five slots,
   5856  1.2    lneto it does not check the stack size;
   5857  1.2    lneto it simply assumes that there are enough slots.
   5858  1.1  mbalmer 
   5859  1.1  mbalmer 
   5860  1.1  mbalmer <p>
   5861  1.1  mbalmer Several functions in the auxiliary library are used to
   5862  1.1  mbalmer check C&nbsp;function arguments.
   5863  1.1  mbalmer Because the error message is formatted for arguments
   5864  1.1  mbalmer (e.g., "<code>bad argument #1</code>"),
   5865  1.1  mbalmer you should not use these functions for other stack values.
   5866  1.1  mbalmer 
   5867  1.1  mbalmer 
   5868  1.2    lneto <p>
   5869  1.2    lneto Functions called <code>luaL_check*</code>
   5870  1.2    lneto always raise an error if the check is not satisfied.
   5871  1.2    lneto 
   5872  1.2    lneto 
   5873  1.1  mbalmer 
   5874  1.2    lneto <h2>5.1 &ndash; <a name="5.1">Functions and Types</a></h2>
   5875  1.1  mbalmer 
   5876  1.1  mbalmer <p>
   5877  1.1  mbalmer Here we list all functions and types from the auxiliary library
   5878  1.1  mbalmer in alphabetical order.
   5879  1.1  mbalmer 
   5880  1.1  mbalmer 
   5881  1.1  mbalmer 
   5882  1.1  mbalmer <hr><h3><a name="luaL_addchar"><code>luaL_addchar</code></a></h3><p>
   5883  1.2    lneto <span class="apii">[-?, +?, <em>e</em>]</span>
   5884  1.1  mbalmer <pre>void luaL_addchar (luaL_Buffer *B, char c);</pre>
   5885  1.1  mbalmer 
   5886  1.1  mbalmer <p>
   5887  1.2    lneto Adds the byte <code>c</code> to the buffer <code>B</code>
   5888  1.1  mbalmer (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
   5889  1.1  mbalmer 
   5890  1.1  mbalmer 
   5891  1.1  mbalmer 
   5892  1.1  mbalmer 
   5893  1.1  mbalmer 
   5894  1.1  mbalmer <hr><h3><a name="luaL_addlstring"><code>luaL_addlstring</code></a></h3><p>
   5895  1.2    lneto <span class="apii">[-?, +?, <em>e</em>]</span>
   5896  1.1  mbalmer <pre>void luaL_addlstring (luaL_Buffer *B, const char *s, size_t l);</pre>
   5897  1.1  mbalmer 
   5898  1.1  mbalmer <p>
   5899  1.1  mbalmer Adds the string pointed to by <code>s</code> with length <code>l</code> to
   5900  1.1  mbalmer the buffer <code>B</code>
   5901  1.1  mbalmer (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
   5902  1.2    lneto The string can contain embedded zeros.
   5903  1.1  mbalmer 
   5904  1.1  mbalmer 
   5905  1.1  mbalmer 
   5906  1.1  mbalmer 
   5907  1.1  mbalmer 
   5908  1.1  mbalmer <hr><h3><a name="luaL_addsize"><code>luaL_addsize</code></a></h3><p>
   5909  1.2    lneto <span class="apii">[-?, +?, <em>e</em>]</span>
   5910  1.1  mbalmer <pre>void luaL_addsize (luaL_Buffer *B, size_t n);</pre>
   5911  1.1  mbalmer 
   5912  1.1  mbalmer <p>
   5913  1.1  mbalmer Adds to the buffer <code>B</code> (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>)
   5914  1.1  mbalmer a string of length <code>n</code> previously copied to the
   5915  1.1  mbalmer buffer area (see <a href="#luaL_prepbuffer"><code>luaL_prepbuffer</code></a>).
   5916  1.1  mbalmer 
   5917  1.1  mbalmer 
   5918  1.1  mbalmer 
   5919  1.1  mbalmer 
   5920  1.1  mbalmer 
   5921  1.1  mbalmer <hr><h3><a name="luaL_addstring"><code>luaL_addstring</code></a></h3><p>
   5922  1.2    lneto <span class="apii">[-?, +?, <em>e</em>]</span>
   5923  1.1  mbalmer <pre>void luaL_addstring (luaL_Buffer *B, const char *s);</pre>
   5924  1.1  mbalmer 
   5925  1.1  mbalmer <p>
   5926  1.1  mbalmer Adds the zero-terminated string pointed to by <code>s</code>
   5927  1.1  mbalmer to the buffer <code>B</code>
   5928  1.1  mbalmer (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
   5929  1.1  mbalmer 
   5930  1.1  mbalmer 
   5931  1.1  mbalmer 
   5932  1.1  mbalmer 
   5933  1.1  mbalmer 
   5934  1.1  mbalmer <hr><h3><a name="luaL_addvalue"><code>luaL_addvalue</code></a></h3><p>
   5935  1.2    lneto <span class="apii">[-1, +?, <em>e</em>]</span>
   5936  1.1  mbalmer <pre>void luaL_addvalue (luaL_Buffer *B);</pre>
   5937  1.1  mbalmer 
   5938  1.1  mbalmer <p>
   5939  1.1  mbalmer Adds the value at the top of the stack
   5940  1.1  mbalmer to the buffer <code>B</code>
   5941  1.1  mbalmer (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
   5942  1.1  mbalmer Pops the value.
   5943  1.1  mbalmer 
   5944  1.1  mbalmer 
   5945  1.1  mbalmer <p>
   5946  1.1  mbalmer This is the only function on string buffers that can (and must)
   5947  1.1  mbalmer be called with an extra element on the stack,
   5948  1.1  mbalmer which is the value to be added to the buffer.
   5949  1.1  mbalmer 
   5950  1.1  mbalmer 
   5951  1.1  mbalmer 
   5952  1.1  mbalmer 
   5953  1.1  mbalmer 
   5954  1.1  mbalmer <hr><h3><a name="luaL_argcheck"><code>luaL_argcheck</code></a></h3><p>
   5955  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   5956  1.1  mbalmer <pre>void luaL_argcheck (lua_State *L,
   5957  1.1  mbalmer                     int cond,
   5958  1.2    lneto                     int arg,
   5959  1.1  mbalmer                     const char *extramsg);</pre>
   5960  1.1  mbalmer 
   5961  1.1  mbalmer <p>
   5962  1.1  mbalmer Checks whether <code>cond</code> is true.
   5963  1.2    lneto If it is not, raises an error with a standard message (see <a href="#luaL_argerror"><code>luaL_argerror</code></a>).
   5964  1.1  mbalmer 
   5965  1.1  mbalmer 
   5966  1.1  mbalmer 
   5967  1.1  mbalmer 
   5968  1.1  mbalmer 
   5969  1.1  mbalmer <hr><h3><a name="luaL_argerror"><code>luaL_argerror</code></a></h3><p>
   5970  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   5971  1.2    lneto <pre>int luaL_argerror (lua_State *L, int arg, const char *extramsg);</pre>
   5972  1.1  mbalmer 
   5973  1.1  mbalmer <p>
   5974  1.2    lneto Raises an error reporting a problem with argument <code>arg</code>
   5975  1.2    lneto of the C function that called it,
   5976  1.2    lneto using a standard message
   5977  1.2    lneto that includes <code>extramsg</code> as a comment:
   5978  1.1  mbalmer 
   5979  1.1  mbalmer <pre>
   5980  1.2    lneto      bad argument #<em>arg</em> to '<em>funcname</em>' (<em>extramsg</em>)
   5981  1.2    lneto </pre><p>
   5982  1.2    lneto This function never returns.
   5983  1.1  mbalmer 
   5984  1.1  mbalmer 
   5985  1.1  mbalmer 
   5986  1.1  mbalmer 
   5987  1.1  mbalmer 
   5988  1.1  mbalmer <hr><h3><a name="luaL_Buffer"><code>luaL_Buffer</code></a></h3>
   5989  1.1  mbalmer <pre>typedef struct luaL_Buffer luaL_Buffer;</pre>
   5990  1.1  mbalmer 
   5991  1.1  mbalmer <p>
   5992  1.1  mbalmer Type for a <em>string buffer</em>.
   5993  1.1  mbalmer 
   5994  1.1  mbalmer 
   5995  1.1  mbalmer <p>
   5996  1.1  mbalmer A string buffer allows C&nbsp;code to build Lua strings piecemeal.
   5997  1.1  mbalmer Its pattern of use is as follows:
   5998  1.1  mbalmer 
   5999  1.1  mbalmer <ul>
   6000  1.1  mbalmer 
   6001  1.2    lneto <li>First declare a variable <code>b</code> of type <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>.</li>
   6002  1.1  mbalmer 
   6003  1.2    lneto <li>Then initialize it with a call <code>luaL_buffinit(L, &amp;b)</code>.</li>
   6004  1.1  mbalmer 
   6005  1.1  mbalmer <li>
   6006  1.2    lneto Then add string pieces to the buffer calling any of
   6007  1.1  mbalmer the <code>luaL_add*</code> functions.
   6008  1.1  mbalmer </li>
   6009  1.1  mbalmer 
   6010  1.1  mbalmer <li>
   6011  1.2    lneto Finish by calling <code>luaL_pushresult(&amp;b)</code>.
   6012  1.1  mbalmer This call leaves the final string on the top of the stack.
   6013  1.1  mbalmer </li>
   6014  1.1  mbalmer 
   6015  1.1  mbalmer </ul>
   6016  1.1  mbalmer 
   6017  1.1  mbalmer <p>
   6018  1.2    lneto If you know beforehand the total size of the resulting string,
   6019  1.2    lneto you can use the buffer like this:
   6020  1.2    lneto 
   6021  1.2    lneto <ul>
   6022  1.2    lneto 
   6023  1.2    lneto <li>First declare a variable <code>b</code> of type <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>.</li>
   6024  1.2    lneto 
   6025  1.2    lneto <li>Then initialize it and preallocate a space of
   6026  1.2    lneto size <code>sz</code> with a call <code>luaL_buffinitsize(L, &amp;b, sz)</code>.</li>
   6027  1.2    lneto 
   6028  1.2    lneto <li>Then copy the string into that space.</li>
   6029  1.2    lneto 
   6030  1.2    lneto <li>
   6031  1.2    lneto Finish by calling <code>luaL_pushresultsize(&amp;b, sz)</code>,
   6032  1.2    lneto where <code>sz</code> is the total size of the resulting string
   6033  1.2    lneto copied into that space.
   6034  1.2    lneto </li>
   6035  1.2    lneto 
   6036  1.2    lneto </ul>
   6037  1.2    lneto 
   6038  1.2    lneto <p>
   6039  1.1  mbalmer During its normal operation,
   6040  1.1  mbalmer a string buffer uses a variable number of stack slots.
   6041  1.1  mbalmer So, while using a buffer, you cannot assume that you know where
   6042  1.1  mbalmer the top of the stack is.
   6043  1.1  mbalmer You can use the stack between successive calls to buffer operations
   6044  1.1  mbalmer as long as that use is balanced;
   6045  1.1  mbalmer that is,
   6046  1.1  mbalmer when you call a buffer operation,
   6047  1.1  mbalmer the stack is at the same level
   6048  1.1  mbalmer it was immediately after the previous buffer operation.
   6049  1.1  mbalmer (The only exception to this rule is <a href="#luaL_addvalue"><code>luaL_addvalue</code></a>.)
   6050  1.1  mbalmer After calling <a href="#luaL_pushresult"><code>luaL_pushresult</code></a> the stack is back to its
   6051  1.1  mbalmer level when the buffer was initialized,
   6052  1.1  mbalmer plus the final string on its top.
   6053  1.1  mbalmer 
   6054  1.1  mbalmer 
   6055  1.1  mbalmer 
   6056  1.1  mbalmer 
   6057  1.1  mbalmer 
   6058  1.1  mbalmer <hr><h3><a name="luaL_buffinit"><code>luaL_buffinit</code></a></h3><p>
   6059  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   6060  1.1  mbalmer <pre>void luaL_buffinit (lua_State *L, luaL_Buffer *B);</pre>
   6061  1.1  mbalmer 
   6062  1.1  mbalmer <p>
   6063  1.1  mbalmer Initializes a buffer <code>B</code>.
   6064  1.1  mbalmer This function does not allocate any space;
   6065  1.1  mbalmer the buffer must be declared as a variable
   6066  1.1  mbalmer (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
   6067  1.1  mbalmer 
   6068  1.1  mbalmer 
   6069  1.1  mbalmer 
   6070  1.1  mbalmer 
   6071  1.1  mbalmer 
   6072  1.2    lneto <hr><h3><a name="luaL_buffinitsize"><code>luaL_buffinitsize</code></a></h3><p>
   6073  1.2    lneto <span class="apii">[-?, +?, <em>e</em>]</span>
   6074  1.2    lneto <pre>char *luaL_buffinitsize (lua_State *L, luaL_Buffer *B, size_t sz);</pre>
   6075  1.2    lneto 
   6076  1.2    lneto <p>
   6077  1.2    lneto Equivalent to the sequence
   6078  1.2    lneto <a href="#luaL_buffinit"><code>luaL_buffinit</code></a>, <a href="#luaL_prepbuffsize"><code>luaL_prepbuffsize</code></a>.
   6079  1.2    lneto 
   6080  1.2    lneto 
   6081  1.2    lneto 
   6082  1.2    lneto 
   6083  1.2    lneto 
   6084  1.1  mbalmer <hr><h3><a name="luaL_callmeta"><code>luaL_callmeta</code></a></h3><p>
   6085  1.1  mbalmer <span class="apii">[-0, +(0|1), <em>e</em>]</span>
   6086  1.1  mbalmer <pre>int luaL_callmeta (lua_State *L, int obj, const char *e);</pre>
   6087  1.1  mbalmer 
   6088  1.1  mbalmer <p>
   6089  1.1  mbalmer Calls a metamethod.
   6090  1.1  mbalmer 
   6091  1.1  mbalmer 
   6092  1.1  mbalmer <p>
   6093  1.1  mbalmer If the object at index <code>obj</code> has a metatable and this
   6094  1.1  mbalmer metatable has a field <code>e</code>,
   6095  1.2    lneto this function calls this field passing the object as its only argument.
   6096  1.2    lneto In this case this function returns true and pushes onto the
   6097  1.1  mbalmer stack the value returned by the call.
   6098  1.1  mbalmer If there is no metatable or no metamethod,
   6099  1.2    lneto this function returns false (without pushing any value on the stack).
   6100  1.1  mbalmer 
   6101  1.1  mbalmer 
   6102  1.1  mbalmer 
   6103  1.1  mbalmer 
   6104  1.1  mbalmer 
   6105  1.1  mbalmer <hr><h3><a name="luaL_checkany"><code>luaL_checkany</code></a></h3><p>
   6106  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6107  1.2    lneto <pre>void luaL_checkany (lua_State *L, int arg);</pre>
   6108  1.1  mbalmer 
   6109  1.1  mbalmer <p>
   6110  1.1  mbalmer Checks whether the function has an argument
   6111  1.2    lneto of any type (including <b>nil</b>) at position <code>arg</code>.
   6112  1.1  mbalmer 
   6113  1.1  mbalmer 
   6114  1.1  mbalmer 
   6115  1.1  mbalmer 
   6116  1.1  mbalmer 
   6117  1.1  mbalmer <hr><h3><a name="luaL_checkinteger"><code>luaL_checkinteger</code></a></h3><p>
   6118  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6119  1.2    lneto <pre>lua_Integer luaL_checkinteger (lua_State *L, int arg);</pre>
   6120  1.1  mbalmer 
   6121  1.1  mbalmer <p>
   6122  1.2    lneto Checks whether the function argument <code>arg</code> is an integer
   6123  1.2    lneto (or can be converted to an integer)
   6124  1.2    lneto and returns this integer cast to a <a href="#lua_Integer"><code>lua_Integer</code></a>.
   6125  1.1  mbalmer 
   6126  1.1  mbalmer 
   6127  1.1  mbalmer 
   6128  1.1  mbalmer 
   6129  1.1  mbalmer 
   6130  1.1  mbalmer <hr><h3><a name="luaL_checklstring"><code>luaL_checklstring</code></a></h3><p>
   6131  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6132  1.2    lneto <pre>const char *luaL_checklstring (lua_State *L, int arg, size_t *l);</pre>
   6133  1.1  mbalmer 
   6134  1.1  mbalmer <p>
   6135  1.2    lneto Checks whether the function argument <code>arg</code> is a string
   6136  1.1  mbalmer and returns this string;
   6137  1.1  mbalmer if <code>l</code> is not <code>NULL</code> fills <code>*l</code>
   6138  1.1  mbalmer with the string's length.
   6139  1.1  mbalmer 
   6140  1.1  mbalmer 
   6141  1.1  mbalmer <p>
   6142  1.1  mbalmer This function uses <a href="#lua_tolstring"><code>lua_tolstring</code></a> to get its result,
   6143  1.1  mbalmer so all conversions and caveats of that function apply here.
   6144  1.1  mbalmer 
   6145  1.1  mbalmer 
   6146  1.1  mbalmer 
   6147  1.1  mbalmer 
   6148  1.1  mbalmer 
   6149  1.1  mbalmer <hr><h3><a name="luaL_checknumber"><code>luaL_checknumber</code></a></h3><p>
   6150  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6151  1.2    lneto <pre>lua_Number luaL_checknumber (lua_State *L, int arg);</pre>
   6152  1.1  mbalmer 
   6153  1.1  mbalmer <p>
   6154  1.2    lneto Checks whether the function argument <code>arg</code> is a number
   6155  1.1  mbalmer and returns this number.
   6156  1.1  mbalmer 
   6157  1.1  mbalmer 
   6158  1.1  mbalmer 
   6159  1.1  mbalmer 
   6160  1.1  mbalmer 
   6161  1.1  mbalmer <hr><h3><a name="luaL_checkoption"><code>luaL_checkoption</code></a></h3><p>
   6162  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6163  1.1  mbalmer <pre>int luaL_checkoption (lua_State *L,
   6164  1.2    lneto                       int arg,
   6165  1.1  mbalmer                       const char *def,
   6166  1.1  mbalmer                       const char *const lst[]);</pre>
   6167  1.1  mbalmer 
   6168  1.1  mbalmer <p>
   6169  1.2    lneto Checks whether the function argument <code>arg</code> is a string and
   6170  1.1  mbalmer searches for this string in the array <code>lst</code>
   6171  1.1  mbalmer (which must be NULL-terminated).
   6172  1.1  mbalmer Returns the index in the array where the string was found.
   6173  1.1  mbalmer Raises an error if the argument is not a string or
   6174  1.1  mbalmer if the string cannot be found.
   6175  1.1  mbalmer 
   6176  1.1  mbalmer 
   6177  1.1  mbalmer <p>
   6178  1.1  mbalmer If <code>def</code> is not <code>NULL</code>,
   6179  1.1  mbalmer the function uses <code>def</code> as a default value when
   6180  1.2    lneto there is no argument <code>arg</code> or when this argument is <b>nil</b>.
   6181  1.1  mbalmer 
   6182  1.1  mbalmer 
   6183  1.1  mbalmer <p>
   6184  1.1  mbalmer This is a useful function for mapping strings to C&nbsp;enums.
   6185  1.1  mbalmer (The usual convention in Lua libraries is
   6186  1.1  mbalmer to use strings instead of numbers to select options.)
   6187  1.1  mbalmer 
   6188  1.1  mbalmer 
   6189  1.1  mbalmer 
   6190  1.1  mbalmer 
   6191  1.1  mbalmer 
   6192  1.1  mbalmer <hr><h3><a name="luaL_checkstack"><code>luaL_checkstack</code></a></h3><p>
   6193  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6194  1.1  mbalmer <pre>void luaL_checkstack (lua_State *L, int sz, const char *msg);</pre>
   6195  1.1  mbalmer 
   6196  1.1  mbalmer <p>
   6197  1.1  mbalmer Grows the stack size to <code>top + sz</code> elements,
   6198  1.1  mbalmer raising an error if the stack cannot grow to that size.
   6199  1.2    lneto <code>msg</code> is an additional text to go into the error message
   6200  1.2    lneto (or <code>NULL</code> for no additional text).
   6201  1.1  mbalmer 
   6202  1.1  mbalmer 
   6203  1.1  mbalmer 
   6204  1.1  mbalmer 
   6205  1.1  mbalmer 
   6206  1.1  mbalmer <hr><h3><a name="luaL_checkstring"><code>luaL_checkstring</code></a></h3><p>
   6207  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6208  1.2    lneto <pre>const char *luaL_checkstring (lua_State *L, int arg);</pre>
   6209  1.1  mbalmer 
   6210  1.1  mbalmer <p>
   6211  1.2    lneto Checks whether the function argument <code>arg</code> is a string
   6212  1.1  mbalmer and returns this string.
   6213  1.1  mbalmer 
   6214  1.1  mbalmer 
   6215  1.1  mbalmer <p>
   6216  1.1  mbalmer This function uses <a href="#lua_tolstring"><code>lua_tolstring</code></a> to get its result,
   6217  1.1  mbalmer so all conversions and caveats of that function apply here.
   6218  1.1  mbalmer 
   6219  1.1  mbalmer 
   6220  1.1  mbalmer 
   6221  1.1  mbalmer 
   6222  1.1  mbalmer 
   6223  1.1  mbalmer <hr><h3><a name="luaL_checktype"><code>luaL_checktype</code></a></h3><p>
   6224  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6225  1.2    lneto <pre>void luaL_checktype (lua_State *L, int arg, int t);</pre>
   6226  1.1  mbalmer 
   6227  1.1  mbalmer <p>
   6228  1.2    lneto Checks whether the function argument <code>arg</code> has type <code>t</code>.
   6229  1.1  mbalmer See <a href="#lua_type"><code>lua_type</code></a> for the encoding of types for <code>t</code>.
   6230  1.1  mbalmer 
   6231  1.1  mbalmer 
   6232  1.1  mbalmer 
   6233  1.1  mbalmer 
   6234  1.1  mbalmer 
   6235  1.1  mbalmer <hr><h3><a name="luaL_checkudata"><code>luaL_checkudata</code></a></h3><p>
   6236  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6237  1.2    lneto <pre>void *luaL_checkudata (lua_State *L, int arg, const char *tname);</pre>
   6238  1.2    lneto 
   6239  1.2    lneto <p>
   6240  1.2    lneto Checks whether the function argument <code>arg</code> is a userdata
   6241  1.2    lneto of the type <code>tname</code> (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>) and
   6242  1.2    lneto returns the userdata address (see <a href="#lua_touserdata"><code>lua_touserdata</code></a>).
   6243  1.2    lneto 
   6244  1.2    lneto 
   6245  1.2    lneto 
   6246  1.2    lneto 
   6247  1.2    lneto 
   6248  1.2    lneto <hr><h3><a name="luaL_checkversion"><code>luaL_checkversion</code></a></h3><p>
   6249  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   6250  1.2    lneto <pre>void luaL_checkversion (lua_State *L);</pre>
   6251  1.1  mbalmer 
   6252  1.1  mbalmer <p>
   6253  1.2    lneto Checks whether the core running the call,
   6254  1.2    lneto the core that created the Lua state,
   6255  1.2    lneto and the code making the call are all using the same version of Lua.
   6256  1.2    lneto Also checks whether the core running the call
   6257  1.2    lneto and the core that created the Lua state
   6258  1.2    lneto are using the same address space.
   6259  1.1  mbalmer 
   6260  1.1  mbalmer 
   6261  1.1  mbalmer 
   6262  1.1  mbalmer 
   6263  1.1  mbalmer 
   6264  1.1  mbalmer <hr><h3><a name="luaL_dofile"><code>luaL_dofile</code></a></h3><p>
   6265  1.2    lneto <span class="apii">[-0, +?, <em>e</em>]</span>
   6266  1.1  mbalmer <pre>int luaL_dofile (lua_State *L, const char *filename);</pre>
   6267  1.1  mbalmer 
   6268  1.1  mbalmer <p>
   6269  1.1  mbalmer Loads and runs the given file.
   6270  1.1  mbalmer It is defined as the following macro:
   6271  1.1  mbalmer 
   6272  1.1  mbalmer <pre>
   6273  1.1  mbalmer      (luaL_loadfile(L, filename) || lua_pcall(L, 0, LUA_MULTRET, 0))
   6274  1.1  mbalmer </pre><p>
   6275  1.2    lneto It returns false if there are no errors
   6276  1.2    lneto or true in case of errors.
   6277  1.1  mbalmer 
   6278  1.1  mbalmer 
   6279  1.1  mbalmer 
   6280  1.1  mbalmer 
   6281  1.1  mbalmer 
   6282  1.1  mbalmer <hr><h3><a name="luaL_dostring"><code>luaL_dostring</code></a></h3><p>
   6283  1.2    lneto <span class="apii">[-0, +?, &ndash;]</span>
   6284  1.1  mbalmer <pre>int luaL_dostring (lua_State *L, const char *str);</pre>
   6285  1.1  mbalmer 
   6286  1.1  mbalmer <p>
   6287  1.1  mbalmer Loads and runs the given string.
   6288  1.1  mbalmer It is defined as the following macro:
   6289  1.1  mbalmer 
   6290  1.1  mbalmer <pre>
   6291  1.1  mbalmer      (luaL_loadstring(L, str) || lua_pcall(L, 0, LUA_MULTRET, 0))
   6292  1.1  mbalmer </pre><p>
   6293  1.2    lneto It returns false if there are no errors
   6294  1.2    lneto or true in case of errors.
   6295  1.1  mbalmer 
   6296  1.1  mbalmer 
   6297  1.1  mbalmer 
   6298  1.1  mbalmer 
   6299  1.1  mbalmer 
   6300  1.1  mbalmer <hr><h3><a name="luaL_error"><code>luaL_error</code></a></h3><p>
   6301  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6302  1.1  mbalmer <pre>int luaL_error (lua_State *L, const char *fmt, ...);</pre>
   6303  1.1  mbalmer 
   6304  1.1  mbalmer <p>
   6305  1.1  mbalmer Raises an error.
   6306  1.2    lneto The error message format is given by <code>fmt</code>
   6307  1.2    lneto plus any extra arguments,
   6308  1.2    lneto following the same rules of <a href="#lua_pushfstring"><code>lua_pushfstring</code></a>.
   6309  1.2    lneto It also adds at the beginning of the message the file name and
   6310  1.2    lneto the line number where the error occurred,
   6311  1.2    lneto if this information is available.
   6312  1.2    lneto 
   6313  1.2    lneto 
   6314  1.2    lneto <p>
   6315  1.2    lneto This function never returns,
   6316  1.2    lneto but it is an idiom to use it in C&nbsp;functions
   6317  1.2    lneto as <code>return luaL_error(<em>args</em>)</code>.
   6318  1.2    lneto 
   6319  1.2    lneto 
   6320  1.2    lneto 
   6321  1.2    lneto 
   6322  1.2    lneto 
   6323  1.2    lneto <hr><h3><a name="luaL_execresult"><code>luaL_execresult</code></a></h3><p>
   6324  1.2    lneto <span class="apii">[-0, +3, <em>e</em>]</span>
   6325  1.2    lneto <pre>int luaL_execresult (lua_State *L, int stat);</pre>
   6326  1.2    lneto 
   6327  1.2    lneto <p>
   6328  1.2    lneto This function produces the return values for
   6329  1.2    lneto process-related functions in the standard library
   6330  1.2    lneto (<a href="#pdf-os.execute"><code>os.execute</code></a> and <a href="#pdf-io.close"><code>io.close</code></a>).
   6331  1.2    lneto 
   6332  1.2    lneto 
   6333  1.2    lneto 
   6334  1.2    lneto 
   6335  1.1  mbalmer 
   6336  1.2    lneto <hr><h3><a name="luaL_fileresult"><code>luaL_fileresult</code></a></h3><p>
   6337  1.2    lneto <span class="apii">[-0, +(1|3), <em>e</em>]</span>
   6338  1.2    lneto <pre>int luaL_fileresult (lua_State *L, int stat, const char *fname);</pre>
   6339  1.1  mbalmer 
   6340  1.1  mbalmer <p>
   6341  1.2    lneto This function produces the return values for
   6342  1.2    lneto file-related functions in the standard library
   6343  1.2    lneto (<a href="#pdf-io.open"><code>io.open</code></a>, <a href="#pdf-os.rename"><code>os.rename</code></a>, <a href="#pdf-file:seek"><code>file:seek</code></a>, etc.).
   6344  1.1  mbalmer 
   6345  1.1  mbalmer 
   6346  1.1  mbalmer 
   6347  1.1  mbalmer 
   6348  1.1  mbalmer 
   6349  1.1  mbalmer <hr><h3><a name="luaL_getmetafield"><code>luaL_getmetafield</code></a></h3><p>
   6350  1.2    lneto <span class="apii">[-0, +(0|1), <em>e</em>]</span>
   6351  1.1  mbalmer <pre>int luaL_getmetafield (lua_State *L, int obj, const char *e);</pre>
   6352  1.1  mbalmer 
   6353  1.1  mbalmer <p>
   6354  1.1  mbalmer Pushes onto the stack the field <code>e</code> from the metatable
   6355  1.3    lneto of the object at index <code>obj</code> and returns the type of pushed value.
   6356  1.1  mbalmer If the object does not have a metatable,
   6357  1.1  mbalmer or if the metatable does not have this field,
   6358  1.3    lneto pushes nothing and returns <code>LUA_TNIL</code>.
   6359  1.1  mbalmer 
   6360  1.1  mbalmer 
   6361  1.1  mbalmer 
   6362  1.1  mbalmer 
   6363  1.1  mbalmer 
   6364  1.1  mbalmer <hr><h3><a name="luaL_getmetatable"><code>luaL_getmetatable</code></a></h3><p>
   6365  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   6366  1.3    lneto <pre>int luaL_getmetatable (lua_State *L, const char *tname);</pre>
   6367  1.1  mbalmer 
   6368  1.1  mbalmer <p>
   6369  1.1  mbalmer Pushes onto the stack the metatable associated with name <code>tname</code>
   6370  1.1  mbalmer in the registry (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>).
   6371  1.3    lneto If there is no metatable associated with <code>tname</code>,
   6372  1.3    lneto returns false and pushes <b>nil</b>.
   6373  1.1  mbalmer 
   6374  1.1  mbalmer 
   6375  1.1  mbalmer 
   6376  1.1  mbalmer 
   6377  1.1  mbalmer 
   6378  1.2    lneto <hr><h3><a name="luaL_getsubtable"><code>luaL_getsubtable</code></a></h3><p>
   6379  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   6380  1.2    lneto <pre>int luaL_getsubtable (lua_State *L, int idx, const char *fname);</pre>
   6381  1.2    lneto 
   6382  1.2    lneto <p>
   6383  1.2    lneto Ensures that the value <code>t[fname]</code>,
   6384  1.2    lneto where <code>t</code> is the value at index <code>idx</code>,
   6385  1.2    lneto is a table,
   6386  1.2    lneto and pushes that table onto the stack.
   6387  1.2    lneto Returns true if it finds a previous table there
   6388  1.2    lneto and false if it creates a new table.
   6389  1.2    lneto 
   6390  1.2    lneto 
   6391  1.2    lneto 
   6392  1.2    lneto 
   6393  1.2    lneto 
   6394  1.1  mbalmer <hr><h3><a name="luaL_gsub"><code>luaL_gsub</code></a></h3><p>
   6395  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   6396  1.1  mbalmer <pre>const char *luaL_gsub (lua_State *L,
   6397  1.1  mbalmer                        const char *s,
   6398  1.1  mbalmer                        const char *p,
   6399  1.1  mbalmer                        const char *r);</pre>
   6400  1.1  mbalmer 
   6401  1.1  mbalmer <p>
   6402  1.1  mbalmer Creates a copy of string <code>s</code> by replacing
   6403  1.1  mbalmer any occurrence of the string <code>p</code>
   6404  1.1  mbalmer with the string <code>r</code>.
   6405  1.1  mbalmer Pushes the resulting string on the stack and returns it.
   6406  1.1  mbalmer 
   6407  1.1  mbalmer 
   6408  1.1  mbalmer 
   6409  1.1  mbalmer 
   6410  1.1  mbalmer 
   6411  1.2    lneto <hr><h3><a name="luaL_len"><code>luaL_len</code></a></h3><p>
   6412  1.2    lneto <span class="apii">[-0, +0, <em>e</em>]</span>
   6413  1.2    lneto <pre>lua_Integer luaL_len (lua_State *L, int index);</pre>
   6414  1.2    lneto 
   6415  1.2    lneto <p>
   6416  1.2    lneto Returns the "length" of the value at the given index
   6417  1.2    lneto as a number;
   6418  1.2    lneto it is equivalent to the '<code>#</code>' operator in Lua (see <a href="#3.4.7">&sect;3.4.7</a>).
   6419  1.2    lneto Raises an error if the result of the operation is not an integer.
   6420  1.2    lneto (This case only can happen through metamethods.)
   6421  1.2    lneto 
   6422  1.2    lneto 
   6423  1.2    lneto 
   6424  1.2    lneto 
   6425  1.2    lneto 
   6426  1.1  mbalmer <hr><h3><a name="luaL_loadbuffer"><code>luaL_loadbuffer</code></a></h3><p>
   6427  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   6428  1.1  mbalmer <pre>int luaL_loadbuffer (lua_State *L,
   6429  1.1  mbalmer                      const char *buff,
   6430  1.1  mbalmer                      size_t sz,
   6431  1.1  mbalmer                      const char *name);</pre>
   6432  1.1  mbalmer 
   6433  1.1  mbalmer <p>
   6434  1.2    lneto Equivalent to <a href="#luaL_loadbufferx"><code>luaL_loadbufferx</code></a> with <code>mode</code> equal to <code>NULL</code>.
   6435  1.2    lneto 
   6436  1.2    lneto 
   6437  1.2    lneto 
   6438  1.2    lneto 
   6439  1.2    lneto 
   6440  1.2    lneto <hr><h3><a name="luaL_loadbufferx"><code>luaL_loadbufferx</code></a></h3><p>
   6441  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   6442  1.2    lneto <pre>int luaL_loadbufferx (lua_State *L,
   6443  1.2    lneto                       const char *buff,
   6444  1.2    lneto                       size_t sz,
   6445  1.2    lneto                       const char *name,
   6446  1.2    lneto                       const char *mode);</pre>
   6447  1.2    lneto 
   6448  1.2    lneto <p>
   6449  1.1  mbalmer Loads a buffer as a Lua chunk.
   6450  1.1  mbalmer This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chunk in the
   6451  1.1  mbalmer buffer pointed to by <code>buff</code> with size <code>sz</code>.
   6452  1.1  mbalmer 
   6453  1.1  mbalmer 
   6454  1.1  mbalmer <p>
   6455  1.1  mbalmer This function returns the same results as <a href="#lua_load"><code>lua_load</code></a>.
   6456  1.1  mbalmer <code>name</code> is the chunk name,
   6457  1.1  mbalmer used for debug information and error messages.
   6458  1.2    lneto The string <code>mode</code> works as in function <a href="#lua_load"><code>lua_load</code></a>.
   6459  1.1  mbalmer 
   6460  1.1  mbalmer 
   6461  1.1  mbalmer 
   6462  1.1  mbalmer 
   6463  1.1  mbalmer 
   6464  1.1  mbalmer <hr><h3><a name="luaL_loadfile"><code>luaL_loadfile</code></a></h3><p>
   6465  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   6466  1.1  mbalmer <pre>int luaL_loadfile (lua_State *L, const char *filename);</pre>
   6467  1.1  mbalmer 
   6468  1.1  mbalmer <p>
   6469  1.2    lneto Equivalent to <a href="#luaL_loadfilex"><code>luaL_loadfilex</code></a> with <code>mode</code> equal to <code>NULL</code>.
   6470  1.2    lneto 
   6471  1.2    lneto 
   6472  1.2    lneto 
   6473  1.2    lneto 
   6474  1.2    lneto 
   6475  1.2    lneto <hr><h3><a name="luaL_loadfilex"><code>luaL_loadfilex</code></a></h3><p>
   6476  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   6477  1.2    lneto <pre>int luaL_loadfilex (lua_State *L, const char *filename,
   6478  1.2    lneto                                             const char *mode);</pre>
   6479  1.2    lneto 
   6480  1.2    lneto <p>
   6481  1.1  mbalmer Loads a file as a Lua chunk.
   6482  1.1  mbalmer This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chunk in the file
   6483  1.1  mbalmer named <code>filename</code>.
   6484  1.1  mbalmer If <code>filename</code> is <code>NULL</code>,
   6485  1.1  mbalmer then it loads from the standard input.
   6486  1.1  mbalmer The first line in the file is ignored if it starts with a <code>#</code>.
   6487  1.1  mbalmer 
   6488  1.1  mbalmer 
   6489  1.1  mbalmer <p>
   6490  1.2    lneto The string <code>mode</code> works as in function <a href="#lua_load"><code>lua_load</code></a>.
   6491  1.2    lneto 
   6492  1.2    lneto 
   6493  1.2    lneto <p>
   6494  1.1  mbalmer This function returns the same results as <a href="#lua_load"><code>lua_load</code></a>,
   6495  1.1  mbalmer but it has an extra error code <a name="pdf-LUA_ERRFILE"><code>LUA_ERRFILE</code></a>
   6496  1.2    lneto if it cannot open/read the file or the file has a wrong mode.
   6497  1.1  mbalmer 
   6498  1.1  mbalmer 
   6499  1.1  mbalmer <p>
   6500  1.1  mbalmer As <a href="#lua_load"><code>lua_load</code></a>, this function only loads the chunk;
   6501  1.1  mbalmer it does not run it.
   6502  1.1  mbalmer 
   6503  1.1  mbalmer 
   6504  1.1  mbalmer 
   6505  1.1  mbalmer 
   6506  1.1  mbalmer 
   6507  1.1  mbalmer <hr><h3><a name="luaL_loadstring"><code>luaL_loadstring</code></a></h3><p>
   6508  1.2    lneto <span class="apii">[-0, +1, &ndash;]</span>
   6509  1.1  mbalmer <pre>int luaL_loadstring (lua_State *L, const char *s);</pre>
   6510  1.1  mbalmer 
   6511  1.1  mbalmer <p>
   6512  1.1  mbalmer Loads a string as a Lua chunk.
   6513  1.1  mbalmer This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chunk in
   6514  1.1  mbalmer the zero-terminated string <code>s</code>.
   6515  1.1  mbalmer 
   6516  1.1  mbalmer 
   6517  1.1  mbalmer <p>
   6518  1.1  mbalmer This function returns the same results as <a href="#lua_load"><code>lua_load</code></a>.
   6519  1.1  mbalmer 
   6520  1.1  mbalmer 
   6521  1.1  mbalmer <p>
   6522  1.1  mbalmer Also as <a href="#lua_load"><code>lua_load</code></a>, this function only loads the chunk;
   6523  1.1  mbalmer it does not run it.
   6524  1.1  mbalmer 
   6525  1.1  mbalmer 
   6526  1.1  mbalmer 
   6527  1.1  mbalmer 
   6528  1.1  mbalmer 
   6529  1.2    lneto <hr><h3><a name="luaL_newlib"><code>luaL_newlib</code></a></h3><p>
   6530  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   6531  1.3    lneto <pre>void luaL_newlib (lua_State *L, const luaL_Reg l[]);</pre>
   6532  1.2    lneto 
   6533  1.2    lneto <p>
   6534  1.2    lneto Creates a new table and registers there
   6535  1.2    lneto the functions in list <code>l</code>.
   6536  1.3    lneto 
   6537  1.3    lneto 
   6538  1.3    lneto <p>
   6539  1.2    lneto It is implemented as the following macro:
   6540  1.2    lneto 
   6541  1.2    lneto <pre>
   6542  1.2    lneto      (luaL_newlibtable(L,l), luaL_setfuncs(L,l,0))
   6543  1.3    lneto </pre><p>
   6544  1.3    lneto The array <code>l</code> must be the actual array,
   6545  1.3    lneto not a pointer to it.
   6546  1.3    lneto 
   6547  1.2    lneto 
   6548  1.2    lneto 
   6549  1.2    lneto 
   6550  1.2    lneto 
   6551  1.2    lneto <hr><h3><a name="luaL_newlibtable"><code>luaL_newlibtable</code></a></h3><p>
   6552  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   6553  1.2    lneto <pre>void luaL_newlibtable (lua_State *L, const luaL_Reg l[]);</pre>
   6554  1.2    lneto 
   6555  1.2    lneto <p>
   6556  1.2    lneto Creates a new table with a size optimized
   6557  1.2    lneto to store all entries in the array <code>l</code>
   6558  1.2    lneto (but does not actually store them).
   6559  1.2    lneto It is intended to be used in conjunction with <a href="#luaL_setfuncs"><code>luaL_setfuncs</code></a>
   6560  1.2    lneto (see <a href="#luaL_newlib"><code>luaL_newlib</code></a>).
   6561  1.2    lneto 
   6562  1.2    lneto 
   6563  1.2    lneto <p>
   6564  1.2    lneto It is implemented as a macro.
   6565  1.2    lneto The array <code>l</code> must be the actual array,
   6566  1.2    lneto not a pointer to it.
   6567  1.2    lneto 
   6568  1.2    lneto 
   6569  1.2    lneto 
   6570  1.2    lneto 
   6571  1.2    lneto 
   6572  1.1  mbalmer <hr><h3><a name="luaL_newmetatable"><code>luaL_newmetatable</code></a></h3><p>
   6573  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   6574  1.1  mbalmer <pre>int luaL_newmetatable (lua_State *L, const char *tname);</pre>
   6575  1.1  mbalmer 
   6576  1.1  mbalmer <p>
   6577  1.1  mbalmer If the registry already has the key <code>tname</code>,
   6578  1.1  mbalmer returns 0.
   6579  1.1  mbalmer Otherwise,
   6580  1.1  mbalmer creates a new table to be used as a metatable for userdata,
   6581  1.2    lneto adds to this new table the pair <code>__name = tname</code>,
   6582  1.2    lneto adds to the registry the pair <code>[tname] = new table</code>,
   6583  1.1  mbalmer and returns 1.
   6584  1.3    lneto (The entry <code>__name</code> is used by some error-reporting functions.)
   6585  1.1  mbalmer 
   6586  1.1  mbalmer 
   6587  1.1  mbalmer <p>
   6588  1.1  mbalmer In both cases pushes onto the stack the final value associated
   6589  1.1  mbalmer with <code>tname</code> in the registry.
   6590  1.1  mbalmer 
   6591  1.1  mbalmer 
   6592  1.1  mbalmer 
   6593  1.1  mbalmer 
   6594  1.1  mbalmer 
   6595  1.1  mbalmer <hr><h3><a name="luaL_newstate"><code>luaL_newstate</code></a></h3><p>
   6596  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   6597  1.1  mbalmer <pre>lua_State *luaL_newstate (void);</pre>
   6598  1.1  mbalmer 
   6599  1.1  mbalmer <p>
   6600  1.1  mbalmer Creates a new Lua state.
   6601  1.1  mbalmer It calls <a href="#lua_newstate"><code>lua_newstate</code></a> with an
   6602  1.1  mbalmer allocator based on the standard&nbsp;C <code>realloc</code> function
   6603  1.2    lneto and then sets a panic function (see <a href="#4.6">&sect;4.6</a>) that prints
   6604  1.1  mbalmer an error message to the standard error output in case of fatal
   6605  1.1  mbalmer errors.
   6606  1.1  mbalmer 
   6607  1.1  mbalmer 
   6608  1.1  mbalmer <p>
   6609  1.1  mbalmer Returns the new state,
   6610  1.1  mbalmer or <code>NULL</code> if there is a memory allocation error.
   6611  1.1  mbalmer 
   6612  1.1  mbalmer 
   6613  1.1  mbalmer 
   6614  1.1  mbalmer 
   6615  1.1  mbalmer 
   6616  1.1  mbalmer <hr><h3><a name="luaL_openlibs"><code>luaL_openlibs</code></a></h3><p>
   6617  1.2    lneto <span class="apii">[-0, +0, <em>e</em>]</span>
   6618  1.1  mbalmer <pre>void luaL_openlibs (lua_State *L);</pre>
   6619  1.1  mbalmer 
   6620  1.1  mbalmer <p>
   6621  1.1  mbalmer Opens all standard Lua libraries into the given state.
   6622  1.1  mbalmer 
   6623  1.1  mbalmer 
   6624  1.1  mbalmer 
   6625  1.1  mbalmer 
   6626  1.1  mbalmer 
   6627  1.1  mbalmer <hr><h3><a name="luaL_optinteger"><code>luaL_optinteger</code></a></h3><p>
   6628  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6629  1.1  mbalmer <pre>lua_Integer luaL_optinteger (lua_State *L,
   6630  1.2    lneto                              int arg,
   6631  1.1  mbalmer                              lua_Integer d);</pre>
   6632  1.1  mbalmer 
   6633  1.1  mbalmer <p>
   6634  1.2    lneto If the function argument <code>arg</code> is an integer
   6635  1.2    lneto (or convertible to an integer),
   6636  1.2    lneto returns this integer.
   6637  1.1  mbalmer If this argument is absent or is <b>nil</b>,
   6638  1.1  mbalmer returns <code>d</code>.
   6639  1.1  mbalmer Otherwise, raises an error.
   6640  1.1  mbalmer 
   6641  1.1  mbalmer 
   6642  1.1  mbalmer 
   6643  1.1  mbalmer 
   6644  1.1  mbalmer 
   6645  1.1  mbalmer <hr><h3><a name="luaL_optlstring"><code>luaL_optlstring</code></a></h3><p>
   6646  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6647  1.1  mbalmer <pre>const char *luaL_optlstring (lua_State *L,
   6648  1.2    lneto                              int arg,
   6649  1.1  mbalmer                              const char *d,
   6650  1.1  mbalmer                              size_t *l);</pre>
   6651  1.1  mbalmer 
   6652  1.1  mbalmer <p>
   6653  1.2    lneto If the function argument <code>arg</code> is a string,
   6654  1.1  mbalmer returns this string.
   6655  1.1  mbalmer If this argument is absent or is <b>nil</b>,
   6656  1.1  mbalmer returns <code>d</code>.
   6657  1.1  mbalmer Otherwise, raises an error.
   6658  1.1  mbalmer 
   6659  1.1  mbalmer 
   6660  1.1  mbalmer <p>
   6661  1.1  mbalmer If <code>l</code> is not <code>NULL</code>,
   6662  1.2    lneto fills the position <code>*l</code> with the result's length.
   6663  1.1  mbalmer 
   6664  1.1  mbalmer 
   6665  1.1  mbalmer 
   6666  1.1  mbalmer 
   6667  1.1  mbalmer 
   6668  1.1  mbalmer <hr><h3><a name="luaL_optnumber"><code>luaL_optnumber</code></a></h3><p>
   6669  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6670  1.2    lneto <pre>lua_Number luaL_optnumber (lua_State *L, int arg, lua_Number d);</pre>
   6671  1.1  mbalmer 
   6672  1.1  mbalmer <p>
   6673  1.2    lneto If the function argument <code>arg</code> is a number,
   6674  1.1  mbalmer returns this number.
   6675  1.1  mbalmer If this argument is absent or is <b>nil</b>,
   6676  1.1  mbalmer returns <code>d</code>.
   6677  1.1  mbalmer Otherwise, raises an error.
   6678  1.1  mbalmer 
   6679  1.1  mbalmer 
   6680  1.1  mbalmer 
   6681  1.1  mbalmer 
   6682  1.1  mbalmer 
   6683  1.1  mbalmer <hr><h3><a name="luaL_optstring"><code>luaL_optstring</code></a></h3><p>
   6684  1.1  mbalmer <span class="apii">[-0, +0, <em>v</em>]</span>
   6685  1.1  mbalmer <pre>const char *luaL_optstring (lua_State *L,
   6686  1.2    lneto                             int arg,
   6687  1.1  mbalmer                             const char *d);</pre>
   6688  1.1  mbalmer 
   6689  1.1  mbalmer <p>
   6690  1.2    lneto If the function argument <code>arg</code> is a string,
   6691  1.1  mbalmer returns this string.
   6692  1.1  mbalmer If this argument is absent or is <b>nil</b>,
   6693  1.1  mbalmer returns <code>d</code>.
   6694  1.1  mbalmer Otherwise, raises an error.
   6695  1.1  mbalmer 
   6696  1.1  mbalmer 
   6697  1.1  mbalmer 
   6698  1.1  mbalmer 
   6699  1.1  mbalmer 
   6700  1.1  mbalmer <hr><h3><a name="luaL_prepbuffer"><code>luaL_prepbuffer</code></a></h3><p>
   6701  1.2    lneto <span class="apii">[-?, +?, <em>e</em>]</span>
   6702  1.1  mbalmer <pre>char *luaL_prepbuffer (luaL_Buffer *B);</pre>
   6703  1.1  mbalmer 
   6704  1.1  mbalmer <p>
   6705  1.2    lneto Equivalent to <a href="#luaL_prepbuffsize"><code>luaL_prepbuffsize</code></a>
   6706  1.2    lneto with the predefined size <a name="pdf-LUAL_BUFFERSIZE"><code>LUAL_BUFFERSIZE</code></a>.
   6707  1.2    lneto 
   6708  1.2    lneto 
   6709  1.2    lneto 
   6710  1.2    lneto 
   6711  1.2    lneto 
   6712  1.2    lneto <hr><h3><a name="luaL_prepbuffsize"><code>luaL_prepbuffsize</code></a></h3><p>
   6713  1.2    lneto <span class="apii">[-?, +?, <em>e</em>]</span>
   6714  1.2    lneto <pre>char *luaL_prepbuffsize (luaL_Buffer *B, size_t sz);</pre>
   6715  1.2    lneto 
   6716  1.2    lneto <p>
   6717  1.2    lneto Returns an address to a space of size <code>sz</code>
   6718  1.1  mbalmer where you can copy a string to be added to buffer <code>B</code>
   6719  1.1  mbalmer (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
   6720  1.1  mbalmer After copying the string into this space you must call
   6721  1.2    lneto <a href="#luaL_addsize"><code>luaL_addsize</code></a> with the size of the string to actually add
   6722  1.1  mbalmer it to the buffer.
   6723  1.1  mbalmer 
   6724  1.1  mbalmer 
   6725  1.1  mbalmer 
   6726  1.1  mbalmer 
   6727  1.1  mbalmer 
   6728  1.1  mbalmer <hr><h3><a name="luaL_pushresult"><code>luaL_pushresult</code></a></h3><p>
   6729  1.2    lneto <span class="apii">[-?, +1, <em>e</em>]</span>
   6730  1.1  mbalmer <pre>void luaL_pushresult (luaL_Buffer *B);</pre>
   6731  1.1  mbalmer 
   6732  1.1  mbalmer <p>
   6733  1.1  mbalmer Finishes the use of buffer <code>B</code> leaving the final string on
   6734  1.1  mbalmer the top of the stack.
   6735  1.1  mbalmer 
   6736  1.1  mbalmer 
   6737  1.1  mbalmer 
   6738  1.1  mbalmer 
   6739  1.1  mbalmer 
   6740  1.2    lneto <hr><h3><a name="luaL_pushresultsize"><code>luaL_pushresultsize</code></a></h3><p>
   6741  1.2    lneto <span class="apii">[-?, +1, <em>e</em>]</span>
   6742  1.2    lneto <pre>void luaL_pushresultsize (luaL_Buffer *B, size_t sz);</pre>
   6743  1.2    lneto 
   6744  1.2    lneto <p>
   6745  1.2    lneto Equivalent to the sequence <a href="#luaL_addsize"><code>luaL_addsize</code></a>, <a href="#luaL_pushresult"><code>luaL_pushresult</code></a>.
   6746  1.2    lneto 
   6747  1.2    lneto 
   6748  1.2    lneto 
   6749  1.2    lneto 
   6750  1.2    lneto 
   6751  1.1  mbalmer <hr><h3><a name="luaL_ref"><code>luaL_ref</code></a></h3><p>
   6752  1.2    lneto <span class="apii">[-1, +0, <em>e</em>]</span>
   6753  1.1  mbalmer <pre>int luaL_ref (lua_State *L, int t);</pre>
   6754  1.1  mbalmer 
   6755  1.1  mbalmer <p>
   6756  1.1  mbalmer Creates and returns a <em>reference</em>,
   6757  1.1  mbalmer in the table at index <code>t</code>,
   6758  1.1  mbalmer for the object at the top of the stack (and pops the object).
   6759  1.1  mbalmer 
   6760  1.1  mbalmer 
   6761  1.1  mbalmer <p>
   6762  1.1  mbalmer A reference is a unique integer key.
   6763  1.1  mbalmer As long as you do not manually add integer keys into table <code>t</code>,
   6764  1.1  mbalmer <a href="#luaL_ref"><code>luaL_ref</code></a> ensures the uniqueness of the key it returns.
   6765  1.1  mbalmer You can retrieve an object referred by reference <code>r</code>
   6766  1.1  mbalmer by calling <code>lua_rawgeti(L, t, r)</code>.
   6767  1.1  mbalmer Function <a href="#luaL_unref"><code>luaL_unref</code></a> frees a reference and its associated object.
   6768  1.1  mbalmer 
   6769  1.1  mbalmer 
   6770  1.1  mbalmer <p>
   6771  1.1  mbalmer If the object at the top of the stack is <b>nil</b>,
   6772  1.1  mbalmer <a href="#luaL_ref"><code>luaL_ref</code></a> returns the constant <a name="pdf-LUA_REFNIL"><code>LUA_REFNIL</code></a>.
   6773  1.1  mbalmer The constant <a name="pdf-LUA_NOREF"><code>LUA_NOREF</code></a> is guaranteed to be different
   6774  1.1  mbalmer from any reference returned by <a href="#luaL_ref"><code>luaL_ref</code></a>.
   6775  1.1  mbalmer 
   6776  1.1  mbalmer 
   6777  1.1  mbalmer 
   6778  1.1  mbalmer 
   6779  1.1  mbalmer 
   6780  1.1  mbalmer <hr><h3><a name="luaL_Reg"><code>luaL_Reg</code></a></h3>
   6781  1.1  mbalmer <pre>typedef struct luaL_Reg {
   6782  1.1  mbalmer   const char *name;
   6783  1.1  mbalmer   lua_CFunction func;
   6784  1.1  mbalmer } luaL_Reg;</pre>
   6785  1.1  mbalmer 
   6786  1.1  mbalmer <p>
   6787  1.1  mbalmer Type for arrays of functions to be registered by
   6788  1.2    lneto <a href="#luaL_setfuncs"><code>luaL_setfuncs</code></a>.
   6789  1.1  mbalmer <code>name</code> is the function name and <code>func</code> is a pointer to
   6790  1.1  mbalmer the function.
   6791  1.3    lneto Any array of <a href="#luaL_Reg"><code>luaL_Reg</code></a> must end with a sentinel entry
   6792  1.1  mbalmer in which both <code>name</code> and <code>func</code> are <code>NULL</code>.
   6793  1.1  mbalmer 
   6794  1.1  mbalmer 
   6795  1.1  mbalmer 
   6796  1.1  mbalmer 
   6797  1.1  mbalmer 
   6798  1.2    lneto <hr><h3><a name="luaL_requiref"><code>luaL_requiref</code></a></h3><p>
   6799  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   6800  1.2    lneto <pre>void luaL_requiref (lua_State *L, const char *modname,
   6801  1.2    lneto                     lua_CFunction openf, int glb);</pre>
   6802  1.2    lneto 
   6803  1.2    lneto <p>
   6804  1.3    lneto If <code>modname</code> is not already present in <a href="#pdf-package.loaded"><code>package.loaded</code></a>,
   6805  1.3    lneto calls function <code>openf</code> with string <code>modname</code> as an argument
   6806  1.2    lneto and sets the call result in <code>package.loaded[modname]</code>,
   6807  1.2    lneto as if that function has been called through <a href="#pdf-require"><code>require</code></a>.
   6808  1.2    lneto 
   6809  1.2    lneto 
   6810  1.2    lneto <p>
   6811  1.2    lneto If <code>glb</code> is true,
   6812  1.3    lneto also stores the module into global <code>modname</code>.
   6813  1.2    lneto 
   6814  1.2    lneto 
   6815  1.2    lneto <p>
   6816  1.3    lneto Leaves a copy of the module on the stack.
   6817  1.2    lneto 
   6818  1.2    lneto 
   6819  1.2    lneto 
   6820  1.2    lneto 
   6821  1.2    lneto 
   6822  1.2    lneto <hr><h3><a name="luaL_setfuncs"><code>luaL_setfuncs</code></a></h3><p>
   6823  1.2    lneto <span class="apii">[-nup, +0, <em>e</em>]</span>
   6824  1.2    lneto <pre>void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup);</pre>
   6825  1.2    lneto 
   6826  1.2    lneto <p>
   6827  1.2    lneto Registers all functions in the array <code>l</code>
   6828  1.2    lneto (see <a href="#luaL_Reg"><code>luaL_Reg</code></a>) into the table on the top of the stack
   6829  1.2    lneto (below optional upvalues, see next).
   6830  1.2    lneto 
   6831  1.1  mbalmer 
   6832  1.1  mbalmer <p>
   6833  1.2    lneto When <code>nup</code> is not zero,
   6834  1.2    lneto all functions are created sharing <code>nup</code> upvalues,
   6835  1.2    lneto which must be previously pushed on the stack
   6836  1.2    lneto on top of the library table.
   6837  1.2    lneto These values are popped from the stack after the registration.
   6838  1.1  mbalmer 
   6839  1.1  mbalmer 
   6840  1.2    lneto 
   6841  1.2    lneto 
   6842  1.2    lneto 
   6843  1.2    lneto <hr><h3><a name="luaL_setmetatable"><code>luaL_setmetatable</code></a></h3><p>
   6844  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   6845  1.2    lneto <pre>void luaL_setmetatable (lua_State *L, const char *tname);</pre>
   6846  1.2    lneto 
   6847  1.2    lneto <p>
   6848  1.2    lneto Sets the metatable of the object at the top of the stack
   6849  1.2    lneto as the metatable associated with name <code>tname</code>
   6850  1.2    lneto in the registry (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>).
   6851  1.2    lneto 
   6852  1.2    lneto 
   6853  1.2    lneto 
   6854  1.2    lneto 
   6855  1.2    lneto 
   6856  1.2    lneto <hr><h3><a name="luaL_Stream"><code>luaL_Stream</code></a></h3>
   6857  1.2    lneto <pre>typedef struct luaL_Stream {
   6858  1.2    lneto   FILE *f;
   6859  1.2    lneto   lua_CFunction closef;
   6860  1.2    lneto } luaL_Stream;</pre>
   6861  1.2    lneto 
   6862  1.1  mbalmer <p>
   6863  1.2    lneto The standard representation for file handles,
   6864  1.2    lneto which is used by the standard I/O library.
   6865  1.1  mbalmer 
   6866  1.1  mbalmer 
   6867  1.1  mbalmer <p>
   6868  1.2    lneto A file handle is implemented as a full userdata,
   6869  1.3    lneto with a metatable called <code>LUA_FILEHANDLE</code>
   6870  1.3    lneto (where <code>LUA_FILEHANDLE</code> is a macro with the actual metatable's name).
   6871  1.2    lneto The metatable is created by the I/O library
   6872  1.2    lneto (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>).
   6873  1.2    lneto 
   6874  1.2    lneto 
   6875  1.2    lneto <p>
   6876  1.2    lneto This userdata must start with the structure <code>luaL_Stream</code>;
   6877  1.2    lneto it can contain other data after this initial structure.
   6878  1.2    lneto Field <code>f</code> points to the corresponding C stream
   6879  1.2    lneto (or it can be <code>NULL</code> to indicate an incompletely created handle).
   6880  1.2    lneto Field <code>closef</code> points to a Lua function
   6881  1.2    lneto that will be called to close the stream
   6882  1.2    lneto when the handle is closed or collected;
   6883  1.2    lneto this function receives the file handle as its sole argument and
   6884  1.2    lneto must return either <b>true</b> (in case of success)
   6885  1.2    lneto or <b>nil</b> plus an error message (in case of error).
   6886  1.2    lneto Once Lua calls this field,
   6887  1.3    lneto the field value is changed to <code>NULL</code>
   6888  1.3    lneto to signal that the handle is closed.
   6889  1.2    lneto 
   6890  1.1  mbalmer 
   6891  1.1  mbalmer 
   6892  1.2    lneto 
   6893  1.2    lneto 
   6894  1.2    lneto <hr><h3><a name="luaL_testudata"><code>luaL_testudata</code></a></h3><p>
   6895  1.2    lneto <span class="apii">[-0, +0, <em>e</em>]</span>
   6896  1.2    lneto <pre>void *luaL_testudata (lua_State *L, int arg, const char *tname);</pre>
   6897  1.2    lneto 
   6898  1.1  mbalmer <p>
   6899  1.2    lneto This function works like <a href="#luaL_checkudata"><code>luaL_checkudata</code></a>,
   6900  1.2    lneto except that, when the test fails,
   6901  1.2    lneto it returns <code>NULL</code> instead of raising an error.
   6902  1.1  mbalmer 
   6903  1.1  mbalmer 
   6904  1.1  mbalmer 
   6905  1.1  mbalmer 
   6906  1.1  mbalmer 
   6907  1.2    lneto <hr><h3><a name="luaL_tolstring"><code>luaL_tolstring</code></a></h3><p>
   6908  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   6909  1.2    lneto <pre>const char *luaL_tolstring (lua_State *L, int idx, size_t *len);</pre>
   6910  1.2    lneto 
   6911  1.2    lneto <p>
   6912  1.2    lneto Converts any Lua value at the given index to a C&nbsp;string
   6913  1.2    lneto in a reasonable format.
   6914  1.2    lneto The resulting string is pushed onto the stack and also
   6915  1.2    lneto returned by the function.
   6916  1.2    lneto If <code>len</code> is not <code>NULL</code>,
   6917  1.2    lneto the function also sets <code>*len</code> with the string length.
   6918  1.2    lneto 
   6919  1.1  mbalmer 
   6920  1.1  mbalmer <p>
   6921  1.2    lneto If the value has a metatable with a <code>"__tostring"</code> field,
   6922  1.2    lneto then <code>luaL_tolstring</code> calls the corresponding metamethod
   6923  1.2    lneto with the value as argument,
   6924  1.2    lneto and uses the result of the call as its result.
   6925  1.1  mbalmer 
   6926  1.1  mbalmer 
   6927  1.1  mbalmer 
   6928  1.1  mbalmer 
   6929  1.1  mbalmer 
   6930  1.2    lneto <hr><h3><a name="luaL_traceback"><code>luaL_traceback</code></a></h3><p>
   6931  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   6932  1.2    lneto <pre>void luaL_traceback (lua_State *L, lua_State *L1, const char *msg,
   6933  1.2    lneto                      int level);</pre>
   6934  1.1  mbalmer 
   6935  1.1  mbalmer <p>
   6936  1.2    lneto Creates and pushes a traceback of the stack <code>L1</code>.
   6937  1.2    lneto If <code>msg</code> is not <code>NULL</code> it is appended
   6938  1.2    lneto at the beginning of the traceback.
   6939  1.2    lneto The <code>level</code> parameter tells at which level
   6940  1.2    lneto to start the traceback.
   6941  1.1  mbalmer 
   6942  1.2    lneto 
   6943  1.2    lneto 
   6944  1.2    lneto 
   6945  1.2    lneto 
   6946  1.2    lneto <hr><h3><a name="luaL_typename"><code>luaL_typename</code></a></h3><p>
   6947  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   6948  1.2    lneto <pre>const char *luaL_typename (lua_State *L, int index);</pre>
   6949  1.2    lneto 
   6950  1.2    lneto <p>
   6951  1.2    lneto Returns the name of the type of the value at the given index.
   6952  1.1  mbalmer 
   6953  1.1  mbalmer 
   6954  1.1  mbalmer 
   6955  1.1  mbalmer 
   6956  1.1  mbalmer 
   6957  1.1  mbalmer <hr><h3><a name="luaL_unref"><code>luaL_unref</code></a></h3><p>
   6958  1.2    lneto <span class="apii">[-0, +0, &ndash;]</span>
   6959  1.1  mbalmer <pre>void luaL_unref (lua_State *L, int t, int ref);</pre>
   6960  1.1  mbalmer 
   6961  1.1  mbalmer <p>
   6962  1.1  mbalmer Releases reference <code>ref</code> from the table at index <code>t</code>
   6963  1.1  mbalmer (see <a href="#luaL_ref"><code>luaL_ref</code></a>).
   6964  1.1  mbalmer The entry is removed from the table,
   6965  1.1  mbalmer so that the referred object can be collected.
   6966  1.1  mbalmer The reference <code>ref</code> is also freed to be used again.
   6967  1.1  mbalmer 
   6968  1.1  mbalmer 
   6969  1.1  mbalmer <p>
   6970  1.1  mbalmer If <code>ref</code> is <a href="#pdf-LUA_NOREF"><code>LUA_NOREF</code></a> or <a href="#pdf-LUA_REFNIL"><code>LUA_REFNIL</code></a>,
   6971  1.1  mbalmer <a href="#luaL_unref"><code>luaL_unref</code></a> does nothing.
   6972  1.1  mbalmer 
   6973  1.1  mbalmer 
   6974  1.1  mbalmer 
   6975  1.1  mbalmer 
   6976  1.1  mbalmer 
   6977  1.1  mbalmer <hr><h3><a name="luaL_where"><code>luaL_where</code></a></h3><p>
   6978  1.2    lneto <span class="apii">[-0, +1, <em>e</em>]</span>
   6979  1.1  mbalmer <pre>void luaL_where (lua_State *L, int lvl);</pre>
   6980  1.1  mbalmer 
   6981  1.1  mbalmer <p>
   6982  1.1  mbalmer Pushes onto the stack a string identifying the current position
   6983  1.1  mbalmer of the control at level <code>lvl</code> in the call stack.
   6984  1.1  mbalmer Typically this string has the following format:
   6985  1.1  mbalmer 
   6986  1.1  mbalmer <pre>
   6987  1.1  mbalmer      <em>chunkname</em>:<em>currentline</em>:
   6988  1.1  mbalmer </pre><p>
   6989  1.1  mbalmer Level&nbsp;0 is the running function,
   6990  1.1  mbalmer level&nbsp;1 is the function that called the running function,
   6991  1.1  mbalmer etc.
   6992  1.1  mbalmer 
   6993  1.1  mbalmer 
   6994  1.1  mbalmer <p>
   6995  1.1  mbalmer This function is used to build a prefix for error messages.
   6996  1.1  mbalmer 
   6997  1.1  mbalmer 
   6998  1.1  mbalmer 
   6999  1.1  mbalmer 
   7000  1.1  mbalmer 
   7001  1.1  mbalmer 
   7002  1.1  mbalmer 
   7003  1.2    lneto <h1>6 &ndash; <a name="6">Standard Libraries</a></h1>
   7004  1.1  mbalmer 
   7005  1.1  mbalmer <p>
   7006  1.1  mbalmer The standard Lua libraries provide useful functions
   7007  1.1  mbalmer that are implemented directly through the C&nbsp;API.
   7008  1.1  mbalmer Some of these functions provide essential services to the language
   7009  1.1  mbalmer (e.g., <a href="#pdf-type"><code>type</code></a> and <a href="#pdf-getmetatable"><code>getmetatable</code></a>);
   7010  1.1  mbalmer others provide access to "outside" services (e.g., I/O);
   7011  1.1  mbalmer and others could be implemented in Lua itself,
   7012  1.1  mbalmer but are quite useful or have critical performance requirements that
   7013  1.1  mbalmer deserve an implementation in C (e.g., <a href="#pdf-table.sort"><code>table.sort</code></a>).
   7014  1.1  mbalmer 
   7015  1.1  mbalmer 
   7016  1.1  mbalmer <p>
   7017  1.1  mbalmer All libraries are implemented through the official C&nbsp;API
   7018  1.1  mbalmer and are provided as separate C&nbsp;modules.
   7019  1.1  mbalmer Currently, Lua has the following standard libraries:
   7020  1.1  mbalmer 
   7021  1.1  mbalmer <ul>
   7022  1.1  mbalmer 
   7023  1.2    lneto <li>basic library (<a href="#6.1">&sect;6.1</a>);</li>
   7024  1.1  mbalmer 
   7025  1.2    lneto <li>coroutine library (<a href="#6.2">&sect;6.2</a>);</li>
   7026  1.1  mbalmer 
   7027  1.2    lneto <li>package library (<a href="#6.3">&sect;6.3</a>);</li>
   7028  1.1  mbalmer 
   7029  1.2    lneto <li>string manipulation (<a href="#6.4">&sect;6.4</a>);</li>
   7030  1.1  mbalmer 
   7031  1.2    lneto <li>basic UTF-8 support (<a href="#6.5">&sect;6.5</a>);</li>
   7032  1.1  mbalmer 
   7033  1.2    lneto <li>table manipulation (<a href="#6.6">&sect;6.6</a>);</li>
   7034  1.1  mbalmer 
   7035  1.2    lneto <li>mathematical functions (<a href="#6.7">&sect;6.7</a>) (sin, log, etc.);</li>
   7036  1.1  mbalmer 
   7037  1.2    lneto <li>input and output (<a href="#6.8">&sect;6.8</a>);</li>
   7038  1.2    lneto 
   7039  1.2    lneto <li>operating system facilities (<a href="#6.9">&sect;6.9</a>);</li>
   7040  1.2    lneto 
   7041  1.2    lneto <li>debug facilities (<a href="#6.10">&sect;6.10</a>).</li>
   7042  1.1  mbalmer 
   7043  1.1  mbalmer </ul><p>
   7044  1.2    lneto Except for the basic and the package libraries,
   7045  1.1  mbalmer each library provides all its functions as fields of a global table
   7046  1.1  mbalmer or as methods of its objects.
   7047  1.1  mbalmer 
   7048  1.1  mbalmer 
   7049  1.1  mbalmer <p>
   7050  1.1  mbalmer To have access to these libraries,
   7051  1.1  mbalmer the C&nbsp;host program should call the <a href="#luaL_openlibs"><code>luaL_openlibs</code></a> function,
   7052  1.1  mbalmer which opens all standard libraries.
   7053  1.1  mbalmer Alternatively,
   7054  1.2    lneto the host program can open them individually by using
   7055  1.2    lneto <a href="#luaL_requiref"><code>luaL_requiref</code></a> to call
   7056  1.1  mbalmer <a name="pdf-luaopen_base"><code>luaopen_base</code></a> (for the basic library),
   7057  1.1  mbalmer <a name="pdf-luaopen_package"><code>luaopen_package</code></a> (for the package library),
   7058  1.2    lneto <a name="pdf-luaopen_coroutine"><code>luaopen_coroutine</code></a> (for the coroutine library),
   7059  1.1  mbalmer <a name="pdf-luaopen_string"><code>luaopen_string</code></a> (for the string library),
   7060  1.3    lneto <a name="pdf-luaopen_utf8"><code>luaopen_utf8</code></a> (for the UTF8 library),
   7061  1.1  mbalmer <a name="pdf-luaopen_table"><code>luaopen_table</code></a> (for the table library),
   7062  1.1  mbalmer <a name="pdf-luaopen_math"><code>luaopen_math</code></a> (for the mathematical library),
   7063  1.1  mbalmer <a name="pdf-luaopen_io"><code>luaopen_io</code></a> (for the I/O library),
   7064  1.3    lneto <a name="pdf-luaopen_os"><code>luaopen_os</code></a> (for the operating system library),
   7065  1.1  mbalmer and <a name="pdf-luaopen_debug"><code>luaopen_debug</code></a> (for the debug library).
   7066  1.2    lneto These functions are declared in <a name="pdf-lualib.h"><code>lualib.h</code></a>.
   7067  1.1  mbalmer 
   7068  1.1  mbalmer 
   7069  1.1  mbalmer 
   7070  1.2    lneto <h2>6.1 &ndash; <a name="6.1">Basic Functions</a></h2>
   7071  1.1  mbalmer 
   7072  1.1  mbalmer <p>
   7073  1.2    lneto The basic library provides core functions to Lua.
   7074  1.1  mbalmer If you do not include this library in your application,
   7075  1.2    lneto you should check carefully whether you need to provide
   7076  1.1  mbalmer implementations for some of its facilities.
   7077  1.1  mbalmer 
   7078  1.1  mbalmer 
   7079  1.1  mbalmer <p>
   7080  1.1  mbalmer <hr><h3><a name="pdf-assert"><code>assert (v [, message])</code></a></h3>
   7081  1.2    lneto 
   7082  1.2    lneto 
   7083  1.2    lneto <p>
   7084  1.2    lneto Calls <a href="#pdf-error"><code>error</code></a> if
   7085  1.1  mbalmer the value of its argument <code>v</code> is false (i.e., <b>nil</b> or <b>false</b>);
   7086  1.1  mbalmer otherwise, returns all its arguments.
   7087  1.2    lneto In case of error,
   7088  1.2    lneto <code>message</code> is the error object;
   7089  1.2    lneto when absent, it defaults to "<code>assertion failed!</code>"
   7090  1.1  mbalmer 
   7091  1.1  mbalmer 
   7092  1.1  mbalmer 
   7093  1.1  mbalmer 
   7094  1.1  mbalmer <p>
   7095  1.2    lneto <hr><h3><a name="pdf-collectgarbage"><code>collectgarbage ([opt [, arg]])</code></a></h3>
   7096  1.1  mbalmer 
   7097  1.1  mbalmer 
   7098  1.1  mbalmer <p>
   7099  1.1  mbalmer This function is a generic interface to the garbage collector.
   7100  1.1  mbalmer It performs different functions according to its first argument, <code>opt</code>:
   7101  1.1  mbalmer 
   7102  1.1  mbalmer <ul>
   7103  1.1  mbalmer 
   7104  1.2    lneto <li><b>"<code>collect</code>": </b>
   7105  1.2    lneto performs a full garbage-collection cycle.
   7106  1.2    lneto This is the default option.
   7107  1.1  mbalmer </li>
   7108  1.1  mbalmer 
   7109  1.2    lneto <li><b>"<code>stop</code>": </b>
   7110  1.2    lneto stops automatic execution of the garbage collector.
   7111  1.2    lneto The collector will run only when explicitly invoked,
   7112  1.2    lneto until a call to restart it.
   7113  1.1  mbalmer </li>
   7114  1.1  mbalmer 
   7115  1.2    lneto <li><b>"<code>restart</code>": </b>
   7116  1.2    lneto restarts automatic execution of the garbage collector.
   7117  1.1  mbalmer </li>
   7118  1.1  mbalmer 
   7119  1.2    lneto <li><b>"<code>count</code>": </b>
   7120  1.2    lneto returns the total memory in use by Lua in Kbytes.
   7121  1.2    lneto The value has a fractional part,
   7122  1.2    lneto so that it multiplied by 1024
   7123  1.2    lneto gives the exact number of bytes in use by Lua
   7124  1.2    lneto (except for overflows).
   7125  1.1  mbalmer </li>
   7126  1.1  mbalmer 
   7127  1.2    lneto <li><b>"<code>step</code>": </b>
   7128  1.1  mbalmer performs a garbage-collection step.
   7129  1.2    lneto The step "size" is controlled by <code>arg</code>.
   7130  1.2    lneto With a zero value,
   7131  1.2    lneto the collector will perform one basic (indivisible) step.
   7132  1.2    lneto For non-zero values,
   7133  1.2    lneto the collector will perform as if that amount of memory
   7134  1.2    lneto (in KBytes) had been allocated by Lua.
   7135  1.1  mbalmer Returns <b>true</b> if the step finished a collection cycle.
   7136  1.1  mbalmer </li>
   7137  1.1  mbalmer 
   7138  1.2    lneto <li><b>"<code>setpause</code>": </b>
   7139  1.1  mbalmer sets <code>arg</code> as the new value for the <em>pause</em> of
   7140  1.2    lneto the collector (see <a href="#2.5">&sect;2.5</a>).
   7141  1.1  mbalmer Returns the previous value for <em>pause</em>.
   7142  1.1  mbalmer </li>
   7143  1.1  mbalmer 
   7144  1.2    lneto <li><b>"<code>setstepmul</code>": </b>
   7145  1.1  mbalmer sets <code>arg</code> as the new value for the <em>step multiplier</em> of
   7146  1.2    lneto the collector (see <a href="#2.5">&sect;2.5</a>).
   7147  1.1  mbalmer Returns the previous value for <em>step</em>.
   7148  1.1  mbalmer </li>
   7149  1.1  mbalmer 
   7150  1.2    lneto <li><b>"<code>isrunning</code>": </b>
   7151  1.2    lneto returns a boolean that tells whether the collector is running
   7152  1.2    lneto (i.e., not stopped).
   7153  1.2    lneto </li>
   7154  1.2    lneto 
   7155  1.1  mbalmer </ul>
   7156  1.1  mbalmer 
   7157  1.1  mbalmer 
   7158  1.1  mbalmer 
   7159  1.1  mbalmer <p>
   7160  1.2    lneto <hr><h3><a name="pdf-dofile"><code>dofile ([filename])</code></a></h3>
   7161  1.1  mbalmer Opens the named file and executes its contents as a Lua chunk.
   7162  1.1  mbalmer When called without arguments,
   7163  1.1  mbalmer <code>dofile</code> executes the contents of the standard input (<code>stdin</code>).
   7164  1.1  mbalmer Returns all values returned by the chunk.
   7165  1.1  mbalmer In case of errors, <code>dofile</code> propagates the error
   7166  1.1  mbalmer to its caller (that is, <code>dofile</code> does not run in protected mode).
   7167  1.1  mbalmer 
   7168  1.1  mbalmer 
   7169  1.1  mbalmer 
   7170  1.1  mbalmer 
   7171  1.1  mbalmer <p>
   7172  1.1  mbalmer <hr><h3><a name="pdf-error"><code>error (message [, level])</code></a></h3>
   7173  1.1  mbalmer Terminates the last protected function called
   7174  1.2    lneto and returns <code>message</code> as the error object.
   7175  1.1  mbalmer Function <code>error</code> never returns.
   7176  1.1  mbalmer 
   7177  1.1  mbalmer 
   7178  1.1  mbalmer <p>
   7179  1.1  mbalmer Usually, <code>error</code> adds some information about the error position
   7180  1.2    lneto at the beginning of the message, if the message is a string.
   7181  1.1  mbalmer The <code>level</code> argument specifies how to get the error position.
   7182  1.1  mbalmer With level&nbsp;1 (the default), the error position is where the
   7183  1.1  mbalmer <code>error</code> function was called.
   7184  1.1  mbalmer Level&nbsp;2 points the error to where the function
   7185  1.1  mbalmer that called <code>error</code> was called; and so on.
   7186  1.1  mbalmer Passing a level&nbsp;0 avoids the addition of error position information
   7187  1.1  mbalmer to the message.
   7188  1.1  mbalmer 
   7189  1.1  mbalmer 
   7190  1.1  mbalmer 
   7191  1.1  mbalmer 
   7192  1.1  mbalmer <p>
   7193  1.1  mbalmer <hr><h3><a name="pdf-_G"><code>_G</code></a></h3>
   7194  1.1  mbalmer A global variable (not a function) that
   7195  1.2    lneto holds the global environment (see <a href="#2.2">&sect;2.2</a>).
   7196  1.1  mbalmer Lua itself does not use this variable;
   7197  1.1  mbalmer changing its value does not affect any environment,
   7198  1.2    lneto nor vice versa.
   7199  1.1  mbalmer 
   7200  1.1  mbalmer 
   7201  1.1  mbalmer 
   7202  1.1  mbalmer 
   7203  1.1  mbalmer <p>
   7204  1.1  mbalmer <hr><h3><a name="pdf-getmetatable"><code>getmetatable (object)</code></a></h3>
   7205  1.1  mbalmer 
   7206  1.1  mbalmer 
   7207  1.1  mbalmer <p>
   7208  1.1  mbalmer If <code>object</code> does not have a metatable, returns <b>nil</b>.
   7209  1.1  mbalmer Otherwise,
   7210  1.1  mbalmer if the object's metatable has a <code>"__metatable"</code> field,
   7211  1.1  mbalmer returns the associated value.
   7212  1.1  mbalmer Otherwise, returns the metatable of the given object.
   7213  1.1  mbalmer 
   7214  1.1  mbalmer 
   7215  1.1  mbalmer 
   7216  1.1  mbalmer 
   7217  1.1  mbalmer <p>
   7218  1.1  mbalmer <hr><h3><a name="pdf-ipairs"><code>ipairs (t)</code></a></h3>
   7219  1.1  mbalmer 
   7220  1.1  mbalmer 
   7221  1.1  mbalmer <p>
   7222  1.3    lneto Returns three values (an iterator function, the table <code>t</code>, and 0)
   7223  1.1  mbalmer so that the construction
   7224  1.1  mbalmer 
   7225  1.1  mbalmer <pre>
   7226  1.1  mbalmer      for i,v in ipairs(t) do <em>body</em> end
   7227  1.1  mbalmer </pre><p>
   7228  1.3    lneto will iterate over the key&ndash;value pairs
   7229  1.3    lneto (<code>1,t[1]</code>), (<code>2,t[2]</code>), ...,
   7230  1.3    lneto up to the first nil value.
   7231  1.1  mbalmer 
   7232  1.1  mbalmer 
   7233  1.1  mbalmer 
   7234  1.1  mbalmer 
   7235  1.1  mbalmer <p>
   7236  1.3    lneto <hr><h3><a name="pdf-load"><code>load (chunk [, chunkname [, mode [, env]]])</code></a></h3>
   7237  1.1  mbalmer 
   7238  1.1  mbalmer 
   7239  1.1  mbalmer <p>
   7240  1.2    lneto Loads a chunk.
   7241  1.2    lneto 
   7242  1.2    lneto 
   7243  1.2    lneto <p>
   7244  1.3    lneto If <code>chunk</code> is a string, the chunk is this string.
   7245  1.3    lneto If <code>chunk</code> is a function,
   7246  1.2    lneto <code>load</code> calls it repeatedly to get the chunk pieces.
   7247  1.3    lneto Each call to <code>chunk</code> must return a string that concatenates
   7248  1.1  mbalmer with previous results.
   7249  1.1  mbalmer A return of an empty string, <b>nil</b>, or no value signals the end of the chunk.
   7250  1.1  mbalmer 
   7251  1.1  mbalmer 
   7252  1.1  mbalmer <p>
   7253  1.2    lneto If there are no syntactic errors,
   7254  1.1  mbalmer returns the compiled chunk as a function;
   7255  1.1  mbalmer otherwise, returns <b>nil</b> plus the error message.
   7256  1.1  mbalmer 
   7257  1.1  mbalmer 
   7258  1.1  mbalmer <p>
   7259  1.2    lneto If the resulting function has upvalues,
   7260  1.2    lneto the first upvalue is set to the value of <code>env</code>,
   7261  1.2    lneto if that parameter is given,
   7262  1.2    lneto or to the value of the global environment.
   7263  1.3    lneto Other upvalues are initialized with <b>nil</b>.
   7264  1.2    lneto (When you load a main chunk,
   7265  1.2    lneto the resulting function will always have exactly one upvalue,
   7266  1.2    lneto the <code>_ENV</code> variable (see <a href="#2.2">&sect;2.2</a>).
   7267  1.3    lneto However,
   7268  1.3    lneto when you load a binary chunk created from a function (see <a href="#pdf-string.dump"><code>string.dump</code></a>),
   7269  1.3    lneto the resulting function can have an arbitrary number of upvalues.)
   7270  1.3    lneto All upvalues are fresh, that is,
   7271  1.3    lneto they are not shared with any other function.
   7272  1.1  mbalmer 
   7273  1.1  mbalmer 
   7274  1.2    lneto <p>
   7275  1.3    lneto <code>chunkname</code> is used as the name of the chunk for error messages
   7276  1.2    lneto and debug information (see <a href="#4.9">&sect;4.9</a>).
   7277  1.2    lneto When absent,
   7278  1.3    lneto it defaults to <code>chunk</code>, if <code>chunk</code> is a string,
   7279  1.2    lneto or to "<code>=(load)</code>" otherwise.
   7280  1.1  mbalmer 
   7281  1.1  mbalmer 
   7282  1.1  mbalmer <p>
   7283  1.2    lneto The string <code>mode</code> controls whether the chunk can be text or binary
   7284  1.2    lneto (that is, a precompiled chunk).
   7285  1.2    lneto It may be the string "<code>b</code>" (only binary chunks),
   7286  1.2    lneto "<code>t</code>" (only text chunks),
   7287  1.2    lneto or "<code>bt</code>" (both binary and text).
   7288  1.2    lneto The default is "<code>bt</code>".
   7289  1.1  mbalmer 
   7290  1.1  mbalmer 
   7291  1.1  mbalmer <p>
   7292  1.2    lneto Lua does not check the consistency of binary chunks.
   7293  1.2    lneto Maliciously crafted binary chunks can crash
   7294  1.2    lneto the interpreter.
   7295  1.1  mbalmer 
   7296  1.1  mbalmer 
   7297  1.1  mbalmer 
   7298  1.1  mbalmer 
   7299  1.1  mbalmer <p>
   7300  1.2    lneto <hr><h3><a name="pdf-loadfile"><code>loadfile ([filename [, mode [, env]]])</code></a></h3>
   7301  1.1  mbalmer 
   7302  1.1  mbalmer 
   7303  1.1  mbalmer <p>
   7304  1.1  mbalmer Similar to <a href="#pdf-load"><code>load</code></a>,
   7305  1.2    lneto but gets the chunk from file <code>filename</code>
   7306  1.2    lneto or from the standard input,
   7307  1.2    lneto if no file name is given.
   7308  1.1  mbalmer 
   7309  1.1  mbalmer 
   7310  1.1  mbalmer 
   7311  1.1  mbalmer 
   7312  1.1  mbalmer <p>
   7313  1.1  mbalmer <hr><h3><a name="pdf-next"><code>next (table [, index])</code></a></h3>
   7314  1.1  mbalmer 
   7315  1.1  mbalmer 
   7316  1.1  mbalmer <p>
   7317  1.1  mbalmer Allows a program to traverse all fields of a table.
   7318  1.1  mbalmer Its first argument is a table and its second argument
   7319  1.1  mbalmer is an index in this table.
   7320  1.1  mbalmer <code>next</code> returns the next index of the table
   7321  1.1  mbalmer and its associated value.
   7322  1.1  mbalmer When called with <b>nil</b> as its second argument,
   7323  1.1  mbalmer <code>next</code> returns an initial index
   7324  1.1  mbalmer and its associated value.
   7325  1.1  mbalmer When called with the last index,
   7326  1.1  mbalmer or with <b>nil</b> in an empty table,
   7327  1.1  mbalmer <code>next</code> returns <b>nil</b>.
   7328  1.1  mbalmer If the second argument is absent, then it is interpreted as <b>nil</b>.
   7329  1.1  mbalmer In particular,
   7330  1.1  mbalmer you can use <code>next(t)</code> to check whether a table is empty.
   7331  1.1  mbalmer 
   7332  1.1  mbalmer 
   7333  1.1  mbalmer <p>
   7334  1.1  mbalmer The order in which the indices are enumerated is not specified,
   7335  1.1  mbalmer <em>even for numeric indices</em>.
   7336  1.1  mbalmer (To traverse a table in numeric order,
   7337  1.2    lneto use a numerical <b>for</b>.)
   7338  1.1  mbalmer 
   7339  1.1  mbalmer 
   7340  1.1  mbalmer <p>
   7341  1.2    lneto The behavior of <code>next</code> is undefined if,
   7342  1.1  mbalmer during the traversal,
   7343  1.1  mbalmer you assign any value to a non-existent field in the table.
   7344  1.1  mbalmer You may however modify existing fields.
   7345  1.1  mbalmer In particular, you may clear existing fields.
   7346  1.1  mbalmer 
   7347  1.1  mbalmer 
   7348  1.1  mbalmer 
   7349  1.1  mbalmer 
   7350  1.1  mbalmer <p>
   7351  1.1  mbalmer <hr><h3><a name="pdf-pairs"><code>pairs (t)</code></a></h3>
   7352  1.1  mbalmer 
   7353  1.1  mbalmer 
   7354  1.1  mbalmer <p>
   7355  1.2    lneto If <code>t</code> has a metamethod <code>__pairs</code>,
   7356  1.2    lneto calls it with <code>t</code> as argument and returns the first three
   7357  1.2    lneto results from the call.
   7358  1.2    lneto 
   7359  1.2    lneto 
   7360  1.2    lneto <p>
   7361  1.2    lneto Otherwise,
   7362  1.2    lneto returns three values: the <a href="#pdf-next"><code>next</code></a> function, the table <code>t</code>, and <b>nil</b>,
   7363  1.1  mbalmer so that the construction
   7364  1.1  mbalmer 
   7365  1.1  mbalmer <pre>
   7366  1.1  mbalmer      for k,v in pairs(t) do <em>body</em> end
   7367  1.1  mbalmer </pre><p>
   7368  1.1  mbalmer will iterate over all key&ndash;value pairs of table <code>t</code>.
   7369  1.1  mbalmer 
   7370  1.1  mbalmer 
   7371  1.1  mbalmer <p>
   7372  1.1  mbalmer See function <a href="#pdf-next"><code>next</code></a> for the caveats of modifying
   7373  1.1  mbalmer the table during its traversal.
   7374  1.1  mbalmer 
   7375  1.1  mbalmer 
   7376  1.1  mbalmer 
   7377  1.1  mbalmer 
   7378  1.1  mbalmer <p>
   7379  1.2    lneto <hr><h3><a name="pdf-pcall"><code>pcall (f [, arg1, &middot;&middot;&middot;])</code></a></h3>
   7380  1.1  mbalmer 
   7381  1.1  mbalmer 
   7382  1.1  mbalmer <p>
   7383  1.1  mbalmer Calls function <code>f</code> with
   7384  1.1  mbalmer the given arguments in <em>protected mode</em>.
   7385  1.1  mbalmer This means that any error inside&nbsp;<code>f</code> is not propagated;
   7386  1.1  mbalmer instead, <code>pcall</code> catches the error
   7387  1.1  mbalmer and returns a status code.
   7388  1.1  mbalmer Its first result is the status code (a boolean),
   7389  1.1  mbalmer which is true if the call succeeds without errors.
   7390  1.1  mbalmer In such case, <code>pcall</code> also returns all results from the call,
   7391  1.1  mbalmer after this first result.
   7392  1.1  mbalmer In case of any error, <code>pcall</code> returns <b>false</b> plus the error message.
   7393  1.1  mbalmer 
   7394  1.1  mbalmer 
   7395  1.1  mbalmer 
   7396  1.1  mbalmer 
   7397  1.1  mbalmer <p>
   7398  1.1  mbalmer <hr><h3><a name="pdf-print"><code>print (&middot;&middot;&middot;)</code></a></h3>
   7399  1.2    lneto Receives any number of arguments
   7400  1.1  mbalmer and prints their values to <code>stdout</code>,
   7401  1.2    lneto using the <a href="#pdf-tostring"><code>tostring</code></a> function to convert each argument to a string.
   7402  1.1  mbalmer <code>print</code> is not intended for formatted output,
   7403  1.1  mbalmer but only as a quick way to show a value,
   7404  1.2    lneto for instance for debugging.
   7405  1.2    lneto For complete control over the output,
   7406  1.2    lneto use <a href="#pdf-string.format"><code>string.format</code></a> and <a href="#pdf-io.write"><code>io.write</code></a>.
   7407  1.1  mbalmer 
   7408  1.1  mbalmer 
   7409  1.1  mbalmer 
   7410  1.1  mbalmer 
   7411  1.1  mbalmer <p>
   7412  1.1  mbalmer <hr><h3><a name="pdf-rawequal"><code>rawequal (v1, v2)</code></a></h3>
   7413  1.1  mbalmer Checks whether <code>v1</code> is equal to <code>v2</code>,
   7414  1.1  mbalmer without invoking any metamethod.
   7415  1.1  mbalmer Returns a boolean.
   7416  1.1  mbalmer 
   7417  1.1  mbalmer 
   7418  1.1  mbalmer 
   7419  1.1  mbalmer 
   7420  1.1  mbalmer <p>
   7421  1.1  mbalmer <hr><h3><a name="pdf-rawget"><code>rawget (table, index)</code></a></h3>
   7422  1.1  mbalmer Gets the real value of <code>table[index]</code>,
   7423  1.1  mbalmer without invoking any metamethod.
   7424  1.1  mbalmer <code>table</code> must be a table;
   7425  1.1  mbalmer <code>index</code> may be any value.
   7426  1.1  mbalmer 
   7427  1.1  mbalmer 
   7428  1.1  mbalmer 
   7429  1.1  mbalmer 
   7430  1.1  mbalmer <p>
   7431  1.2    lneto <hr><h3><a name="pdf-rawlen"><code>rawlen (v)</code></a></h3>
   7432  1.2    lneto Returns the length of the object <code>v</code>,
   7433  1.2    lneto which must be a table or a string,
   7434  1.2    lneto without invoking any metamethod.
   7435  1.2    lneto Returns an integer.
   7436  1.2    lneto 
   7437  1.2    lneto 
   7438  1.2    lneto 
   7439  1.2    lneto 
   7440  1.2    lneto <p>
   7441  1.1  mbalmer <hr><h3><a name="pdf-rawset"><code>rawset (table, index, value)</code></a></h3>
   7442  1.1  mbalmer Sets the real value of <code>table[index]</code> to <code>value</code>,
   7443  1.1  mbalmer without invoking any metamethod.
   7444  1.1  mbalmer <code>table</code> must be a table,
   7445  1.2    lneto <code>index</code> any value different from <b>nil</b> and NaN,
   7446  1.1  mbalmer and <code>value</code> any Lua value.
   7447  1.1  mbalmer 
   7448  1.1  mbalmer 
   7449  1.1  mbalmer <p>
   7450  1.1  mbalmer This function returns <code>table</code>.
   7451  1.1  mbalmer 
   7452  1.1  mbalmer 
   7453  1.1  mbalmer 
   7454  1.1  mbalmer 
   7455  1.1  mbalmer <p>
   7456  1.1  mbalmer <hr><h3><a name="pdf-select"><code>select (index, &middot;&middot;&middot;)</code></a></h3>
   7457  1.1  mbalmer 
   7458  1.1  mbalmer 
   7459  1.1  mbalmer <p>
   7460  1.1  mbalmer If <code>index</code> is a number,
   7461  1.2    lneto returns all arguments after argument number <code>index</code>;
   7462  1.2    lneto a negative number indexes from the end (-1 is the last argument).
   7463  1.1  mbalmer Otherwise, <code>index</code> must be the string <code>"#"</code>,
   7464  1.1  mbalmer and <code>select</code> returns the total number of extra arguments it received.
   7465  1.1  mbalmer 
   7466  1.1  mbalmer 
   7467  1.1  mbalmer 
   7468  1.1  mbalmer 
   7469  1.1  mbalmer <p>
   7470  1.1  mbalmer <hr><h3><a name="pdf-setmetatable"><code>setmetatable (table, metatable)</code></a></h3>
   7471  1.1  mbalmer 
   7472  1.1  mbalmer 
   7473  1.1  mbalmer <p>
   7474  1.1  mbalmer Sets the metatable for the given table.
   7475  1.1  mbalmer (You cannot change the metatable of other types from Lua, only from&nbsp;C.)
   7476  1.1  mbalmer If <code>metatable</code> is <b>nil</b>,
   7477  1.1  mbalmer removes the metatable of the given table.
   7478  1.1  mbalmer If the original metatable has a <code>"__metatable"</code> field,
   7479  1.1  mbalmer raises an error.
   7480  1.1  mbalmer 
   7481  1.1  mbalmer 
   7482  1.1  mbalmer <p>
   7483  1.1  mbalmer This function returns <code>table</code>.
   7484  1.1  mbalmer 
   7485  1.1  mbalmer 
   7486  1.1  mbalmer 
   7487  1.1  mbalmer 
   7488  1.1  mbalmer <p>
   7489  1.1  mbalmer <hr><h3><a name="pdf-tonumber"><code>tonumber (e [, base])</code></a></h3>
   7490  1.2    lneto 
   7491  1.2    lneto 
   7492  1.2    lneto <p>
   7493  1.2    lneto When called with no <code>base</code>,
   7494  1.2    lneto <code>tonumber</code> tries to convert its argument to a number.
   7495  1.2    lneto If the argument is already a number or
   7496  1.2    lneto a string convertible to a number,
   7497  1.2    lneto then <code>tonumber</code> returns this number;
   7498  1.1  mbalmer otherwise, it returns <b>nil</b>.
   7499  1.1  mbalmer 
   7500  1.1  mbalmer 
   7501  1.1  mbalmer <p>
   7502  1.2    lneto The conversion of strings can result in integers or floats,
   7503  1.2    lneto according to the lexical conventions of Lua (see <a href="#3.1">&sect;3.1</a>).
   7504  1.2    lneto (The string may have leading and trailing spaces and a sign.)
   7505  1.2    lneto 
   7506  1.2    lneto 
   7507  1.2    lneto <p>
   7508  1.2    lneto When called with <code>base</code>,
   7509  1.2    lneto then <code>e</code> must be a string to be interpreted as
   7510  1.2    lneto an integer numeral in that base.
   7511  1.1  mbalmer The base may be any integer between 2 and 36, inclusive.
   7512  1.1  mbalmer In bases above&nbsp;10, the letter '<code>A</code>' (in either upper or lower case)
   7513  1.1  mbalmer represents&nbsp;10, '<code>B</code>' represents&nbsp;11, and so forth,
   7514  1.1  mbalmer with '<code>Z</code>' representing 35.
   7515  1.2    lneto If the string <code>e</code> is not a valid numeral in the given base,
   7516  1.2    lneto the function returns <b>nil</b>.
   7517  1.1  mbalmer 
   7518  1.1  mbalmer 
   7519  1.1  mbalmer 
   7520  1.1  mbalmer 
   7521  1.1  mbalmer <p>
   7522  1.2    lneto <hr><h3><a name="pdf-tostring"><code>tostring (v)</code></a></h3>
   7523  1.2    lneto Receives a value of any type and
   7524  1.2    lneto converts it to a string in a human-readable format.
   7525  1.2    lneto Floats always produce strings with some
   7526  1.2    lneto floating-point indication (either a decimal dot or an exponent).
   7527  1.2    lneto (For complete control of how numbers are converted,
   7528  1.2    lneto use <a href="#pdf-string.format"><code>string.format</code></a>.)
   7529  1.1  mbalmer 
   7530  1.1  mbalmer 
   7531  1.1  mbalmer <p>
   7532  1.2    lneto If the metatable of <code>v</code> has a <code>"__tostring"</code> field,
   7533  1.1  mbalmer then <code>tostring</code> calls the corresponding value
   7534  1.2    lneto with <code>v</code> as argument,
   7535  1.1  mbalmer and uses the result of the call as its result.
   7536  1.1  mbalmer 
   7537  1.1  mbalmer 
   7538  1.1  mbalmer 
   7539  1.1  mbalmer 
   7540  1.1  mbalmer <p>
   7541  1.1  mbalmer <hr><h3><a name="pdf-type"><code>type (v)</code></a></h3>
   7542  1.1  mbalmer Returns the type of its only argument, coded as a string.
   7543  1.1  mbalmer The possible results of this function are
   7544  1.1  mbalmer "<code>nil</code>" (a string, not the value <b>nil</b>),
   7545  1.1  mbalmer "<code>number</code>",
   7546  1.1  mbalmer "<code>string</code>",
   7547  1.1  mbalmer "<code>boolean</code>",
   7548  1.1  mbalmer "<code>table</code>",
   7549  1.1  mbalmer "<code>function</code>",
   7550  1.1  mbalmer "<code>thread</code>",
   7551  1.1  mbalmer and "<code>userdata</code>".
   7552  1.1  mbalmer 
   7553  1.1  mbalmer 
   7554  1.1  mbalmer 
   7555  1.1  mbalmer 
   7556  1.1  mbalmer <p>
   7557  1.1  mbalmer <hr><h3><a name="pdf-_VERSION"><code>_VERSION</code></a></h3>
   7558  1.1  mbalmer A global variable (not a function) that
   7559  1.1  mbalmer holds a string containing the current interpreter version.
   7560  1.2    lneto The current value of this variable is "<code>Lua 5.3</code>".
   7561  1.1  mbalmer 
   7562  1.1  mbalmer 
   7563  1.1  mbalmer 
   7564  1.1  mbalmer 
   7565  1.1  mbalmer <p>
   7566  1.2    lneto <hr><h3><a name="pdf-xpcall"><code>xpcall (f, msgh [, arg1, &middot;&middot;&middot;])</code></a></h3>
   7567  1.1  mbalmer 
   7568  1.1  mbalmer 
   7569  1.1  mbalmer <p>
   7570  1.1  mbalmer This function is similar to <a href="#pdf-pcall"><code>pcall</code></a>,
   7571  1.2    lneto except that it sets a new message handler <code>msgh</code>.
   7572  1.1  mbalmer 
   7573  1.1  mbalmer 
   7574  1.1  mbalmer 
   7575  1.1  mbalmer 
   7576  1.1  mbalmer 
   7577  1.1  mbalmer 
   7578  1.1  mbalmer 
   7579  1.2    lneto <h2>6.2 &ndash; <a name="6.2">Coroutine Manipulation</a></h2>
   7580  1.1  mbalmer 
   7581  1.1  mbalmer <p>
   7582  1.1  mbalmer The operations related to coroutines comprise a sub-library of
   7583  1.1  mbalmer the basic library and come inside the table <a name="pdf-coroutine"><code>coroutine</code></a>.
   7584  1.2    lneto See <a href="#2.6">&sect;2.6</a> for a general description of coroutines.
   7585  1.1  mbalmer 
   7586  1.1  mbalmer 
   7587  1.1  mbalmer <p>
   7588  1.1  mbalmer <hr><h3><a name="pdf-coroutine.create"><code>coroutine.create (f)</code></a></h3>
   7589  1.1  mbalmer 
   7590  1.1  mbalmer 
   7591  1.1  mbalmer <p>
   7592  1.1  mbalmer Creates a new coroutine, with body <code>f</code>.
   7593  1.2    lneto <code>f</code> must be a Lua function.
   7594  1.2    lneto Returns this new coroutine,
   7595  1.2    lneto an object with type <code>"thread"</code>.
   7596  1.2    lneto 
   7597  1.2    lneto 
   7598  1.2    lneto 
   7599  1.2    lneto 
   7600  1.2    lneto <p>
   7601  1.2    lneto <hr><h3><a name="pdf-coroutine.isyieldable"><code>coroutine.isyieldable ()</code></a></h3>
   7602  1.2    lneto 
   7603  1.2    lneto 
   7604  1.2    lneto <p>
   7605  1.2    lneto Returns true when the running coroutine can yield.
   7606  1.2    lneto 
   7607  1.2    lneto 
   7608  1.2    lneto <p>
   7609  1.2    lneto A running coroutine is yieldable if it is not the main thread and
   7610  1.2    lneto it is not inside a non-yieldable C function.
   7611  1.1  mbalmer 
   7612  1.1  mbalmer 
   7613  1.1  mbalmer 
   7614  1.1  mbalmer 
   7615  1.1  mbalmer <p>
   7616  1.1  mbalmer <hr><h3><a name="pdf-coroutine.resume"><code>coroutine.resume (co [, val1, &middot;&middot;&middot;])</code></a></h3>
   7617  1.1  mbalmer 
   7618  1.1  mbalmer 
   7619  1.1  mbalmer <p>
   7620  1.1  mbalmer Starts or continues the execution of coroutine <code>co</code>.
   7621  1.1  mbalmer The first time you resume a coroutine,
   7622  1.1  mbalmer it starts running its body.
   7623  1.2    lneto The values <code>val1</code>, ... are passed
   7624  1.1  mbalmer as the arguments to the body function.
   7625  1.1  mbalmer If the coroutine has yielded,
   7626  1.1  mbalmer <code>resume</code> restarts it;
   7627  1.2    lneto the values <code>val1</code>, ... are passed
   7628  1.1  mbalmer as the results from the yield.
   7629  1.1  mbalmer 
   7630  1.1  mbalmer 
   7631  1.1  mbalmer <p>
   7632  1.1  mbalmer If the coroutine runs without any errors,
   7633  1.1  mbalmer <code>resume</code> returns <b>true</b> plus any values passed to <code>yield</code>
   7634  1.2    lneto (when the coroutine yields) or any values returned by the body function
   7635  1.2    lneto (when the coroutine terminates).
   7636  1.1  mbalmer If there is any error,
   7637  1.1  mbalmer <code>resume</code> returns <b>false</b> plus the error message.
   7638  1.1  mbalmer 
   7639  1.1  mbalmer 
   7640  1.1  mbalmer 
   7641  1.1  mbalmer 
   7642  1.1  mbalmer <p>
   7643  1.1  mbalmer <hr><h3><a name="pdf-coroutine.running"><code>coroutine.running ()</code></a></h3>
   7644  1.1  mbalmer 
   7645  1.1  mbalmer 
   7646  1.1  mbalmer <p>
   7647  1.2    lneto Returns the running coroutine plus a boolean,
   7648  1.2    lneto true when the running coroutine is the main one.
   7649  1.1  mbalmer 
   7650  1.1  mbalmer 
   7651  1.1  mbalmer 
   7652  1.1  mbalmer 
   7653  1.1  mbalmer <p>
   7654  1.1  mbalmer <hr><h3><a name="pdf-coroutine.status"><code>coroutine.status (co)</code></a></h3>
   7655  1.1  mbalmer 
   7656  1.1  mbalmer 
   7657  1.1  mbalmer <p>
   7658  1.1  mbalmer Returns the status of coroutine <code>co</code>, as a string:
   7659  1.1  mbalmer <code>"running"</code>,
   7660  1.1  mbalmer if the coroutine is running (that is, it called <code>status</code>);
   7661  1.1  mbalmer <code>"suspended"</code>, if the coroutine is suspended in a call to <code>yield</code>,
   7662  1.1  mbalmer or if it has not started running yet;
   7663  1.1  mbalmer <code>"normal"</code> if the coroutine is active but not running
   7664  1.1  mbalmer (that is, it has resumed another coroutine);
   7665  1.1  mbalmer and <code>"dead"</code> if the coroutine has finished its body function,
   7666  1.1  mbalmer or if it has stopped with an error.
   7667  1.1  mbalmer 
   7668  1.1  mbalmer 
   7669  1.1  mbalmer 
   7670  1.1  mbalmer 
   7671  1.1  mbalmer <p>
   7672  1.1  mbalmer <hr><h3><a name="pdf-coroutine.wrap"><code>coroutine.wrap (f)</code></a></h3>
   7673  1.1  mbalmer 
   7674  1.1  mbalmer 
   7675  1.1  mbalmer <p>
   7676  1.1  mbalmer Creates a new coroutine, with body <code>f</code>.
   7677  1.1  mbalmer <code>f</code> must be a Lua function.
   7678  1.1  mbalmer Returns a function that resumes the coroutine each time it is called.
   7679  1.1  mbalmer Any arguments passed to the function behave as the
   7680  1.1  mbalmer extra arguments to <code>resume</code>.
   7681  1.1  mbalmer Returns the same values returned by <code>resume</code>,
   7682  1.1  mbalmer except the first boolean.
   7683  1.1  mbalmer In case of error, propagates the error.
   7684  1.1  mbalmer 
   7685  1.1  mbalmer 
   7686  1.1  mbalmer 
   7687  1.1  mbalmer 
   7688  1.1  mbalmer <p>
   7689  1.1  mbalmer <hr><h3><a name="pdf-coroutine.yield"><code>coroutine.yield (&middot;&middot;&middot;)</code></a></h3>
   7690  1.1  mbalmer 
   7691  1.1  mbalmer 
   7692  1.1  mbalmer <p>
   7693  1.1  mbalmer Suspends the execution of the calling coroutine.
   7694  1.1  mbalmer Any arguments to <code>yield</code> are passed as extra results to <code>resume</code>.
   7695  1.1  mbalmer 
   7696  1.1  mbalmer 
   7697  1.1  mbalmer 
   7698  1.1  mbalmer 
   7699  1.1  mbalmer 
   7700  1.1  mbalmer 
   7701  1.1  mbalmer 
   7702  1.2    lneto <h2>6.3 &ndash; <a name="6.3">Modules</a></h2>
   7703  1.1  mbalmer 
   7704  1.1  mbalmer <p>
   7705  1.1  mbalmer The package library provides basic
   7706  1.2    lneto facilities for loading modules in Lua.
   7707  1.2    lneto It exports one function directly in the global environment:
   7708  1.2    lneto <a href="#pdf-require"><code>require</code></a>.
   7709  1.1  mbalmer Everything else is exported in a table <a name="pdf-package"><code>package</code></a>.
   7710  1.1  mbalmer 
   7711  1.1  mbalmer 
   7712  1.1  mbalmer <p>
   7713  1.1  mbalmer <hr><h3><a name="pdf-require"><code>require (modname)</code></a></h3>
   7714  1.1  mbalmer 
   7715  1.1  mbalmer 
   7716  1.1  mbalmer <p>
   7717  1.1  mbalmer Loads the given module.
   7718  1.1  mbalmer The function starts by looking into the <a href="#pdf-package.loaded"><code>package.loaded</code></a> table
   7719  1.1  mbalmer to determine whether <code>modname</code> is already loaded.
   7720  1.1  mbalmer If it is, then <code>require</code> returns the value stored
   7721  1.1  mbalmer at <code>package.loaded[modname]</code>.
   7722  1.1  mbalmer Otherwise, it tries to find a <em>loader</em> for the module.
   7723  1.1  mbalmer 
   7724  1.1  mbalmer 
   7725  1.1  mbalmer <p>
   7726  1.1  mbalmer To find a loader,
   7727  1.2    lneto <code>require</code> is guided by the <a href="#pdf-package.searchers"><code>package.searchers</code></a> sequence.
   7728  1.2    lneto By changing this sequence,
   7729  1.1  mbalmer we can change how <code>require</code> looks for a module.
   7730  1.1  mbalmer The following explanation is based on the default configuration
   7731  1.2    lneto for <a href="#pdf-package.searchers"><code>package.searchers</code></a>.
   7732  1.1  mbalmer 
   7733  1.1  mbalmer 
   7734  1.1  mbalmer <p>
   7735  1.1  mbalmer First <code>require</code> queries <code>package.preload[modname]</code>.
   7736  1.1  mbalmer If it has a value,
   7737  1.2    lneto this value (which must be a function) is the loader.
   7738  1.1  mbalmer Otherwise <code>require</code> searches for a Lua loader using the
   7739  1.1  mbalmer path stored in <a href="#pdf-package.path"><code>package.path</code></a>.
   7740  1.1  mbalmer If that also fails, it searches for a C&nbsp;loader using the
   7741  1.1  mbalmer path stored in <a href="#pdf-package.cpath"><code>package.cpath</code></a>.
   7742  1.1  mbalmer If that also fails,
   7743  1.2    lneto it tries an <em>all-in-one</em> loader (see <a href="#pdf-package.searchers"><code>package.searchers</code></a>).
   7744  1.1  mbalmer 
   7745  1.1  mbalmer 
   7746  1.1  mbalmer <p>
   7747  1.1  mbalmer Once a loader is found,
   7748  1.2    lneto <code>require</code> calls the loader with two arguments:
   7749  1.2    lneto <code>modname</code> and an extra value dependent on how it got the loader.
   7750  1.2    lneto (If the loader came from a file,
   7751  1.2    lneto this extra value is the file name.)
   7752  1.2    lneto If the loader returns any non-nil value,
   7753  1.1  mbalmer <code>require</code> assigns the returned value to <code>package.loaded[modname]</code>.
   7754  1.2    lneto If the loader does not return a non-nil value and
   7755  1.1  mbalmer has not assigned any value to <code>package.loaded[modname]</code>,
   7756  1.1  mbalmer then <code>require</code> assigns <b>true</b> to this entry.
   7757  1.1  mbalmer In any case, <code>require</code> returns the
   7758  1.1  mbalmer final value of <code>package.loaded[modname]</code>.
   7759  1.1  mbalmer 
   7760  1.1  mbalmer 
   7761  1.1  mbalmer <p>
   7762  1.1  mbalmer If there is any error loading or running the module,
   7763  1.1  mbalmer or if it cannot find any loader for the module,
   7764  1.2    lneto then <code>require</code> raises an error.
   7765  1.2    lneto 
   7766  1.2    lneto 
   7767  1.2    lneto 
   7768  1.2    lneto 
   7769  1.2    lneto <p>
   7770  1.2    lneto <hr><h3><a name="pdf-package.config"><code>package.config</code></a></h3>
   7771  1.2    lneto 
   7772  1.2    lneto 
   7773  1.2    lneto <p>
   7774  1.2    lneto A string describing some compile-time configurations for packages.
   7775  1.2    lneto This string is a sequence of lines:
   7776  1.2    lneto 
   7777  1.2    lneto <ul>
   7778  1.2    lneto 
   7779  1.2    lneto <li>The first line is the directory separator string.
   7780  1.2    lneto Default is '<code>\</code>' for Windows and '<code>/</code>' for all other systems.</li>
   7781  1.1  mbalmer 
   7782  1.2    lneto <li>The second line is the character that separates templates in a path.
   7783  1.2    lneto Default is '<code>;</code>'.</li>
   7784  1.2    lneto 
   7785  1.2    lneto <li>The third line is the string that marks the
   7786  1.2    lneto substitution points in a template.
   7787  1.2    lneto Default is '<code>?</code>'.</li>
   7788  1.2    lneto 
   7789  1.2    lneto <li>The fourth line is a string that, in a path in Windows,
   7790  1.2    lneto is replaced by the executable's directory.
   7791  1.2    lneto Default is '<code>!</code>'.</li>
   7792  1.2    lneto 
   7793  1.3    lneto <li>The fifth line is a mark to ignore all text after it
   7794  1.2    lneto when building the <code>luaopen_</code> function name.
   7795  1.2    lneto Default is '<code>-</code>'.</li>
   7796  1.2    lneto 
   7797  1.2    lneto </ul>
   7798  1.1  mbalmer 
   7799  1.1  mbalmer 
   7800  1.1  mbalmer 
   7801  1.1  mbalmer <p>
   7802  1.1  mbalmer <hr><h3><a name="pdf-package.cpath"><code>package.cpath</code></a></h3>
   7803  1.1  mbalmer 
   7804  1.1  mbalmer 
   7805  1.1  mbalmer <p>
   7806  1.1  mbalmer The path used by <a href="#pdf-require"><code>require</code></a> to search for a C&nbsp;loader.
   7807  1.1  mbalmer 
   7808  1.1  mbalmer 
   7809  1.1  mbalmer <p>
   7810  1.1  mbalmer Lua initializes the C&nbsp;path <a href="#pdf-package.cpath"><code>package.cpath</code></a> in the same way
   7811  1.1  mbalmer it initializes the Lua path <a href="#pdf-package.path"><code>package.path</code></a>,
   7812  1.2    lneto using the environment variable <a name="pdf-LUA_CPATH_5_3"><code>LUA_CPATH_5_3</code></a>
   7813  1.2    lneto or the environment variable <a name="pdf-LUA_CPATH"><code>LUA_CPATH</code></a>
   7814  1.1  mbalmer or a default path defined in <code>luaconf.h</code>.
   7815  1.1  mbalmer 
   7816  1.1  mbalmer 
   7817  1.1  mbalmer 
   7818  1.1  mbalmer 
   7819  1.1  mbalmer <p>
   7820  1.1  mbalmer <hr><h3><a name="pdf-package.loaded"><code>package.loaded</code></a></h3>
   7821  1.1  mbalmer 
   7822  1.1  mbalmer 
   7823  1.1  mbalmer <p>
   7824  1.1  mbalmer A table used by <a href="#pdf-require"><code>require</code></a> to control which
   7825  1.1  mbalmer modules are already loaded.
   7826  1.1  mbalmer When you require a module <code>modname</code> and
   7827  1.1  mbalmer <code>package.loaded[modname]</code> is not false,
   7828  1.1  mbalmer <a href="#pdf-require"><code>require</code></a> simply returns the value stored there.
   7829  1.1  mbalmer 
   7830  1.1  mbalmer 
   7831  1.2    lneto <p>
   7832  1.2    lneto This variable is only a reference to the real table;
   7833  1.2    lneto assignments to this variable do not change the
   7834  1.2    lneto table used by <a href="#pdf-require"><code>require</code></a>.
   7835  1.2    lneto 
   7836  1.2    lneto 
   7837  1.2    lneto 
   7838  1.2    lneto 
   7839  1.2    lneto <p>
   7840  1.2    lneto <hr><h3><a name="pdf-package.loadlib"><code>package.loadlib (libname, funcname)</code></a></h3>
   7841  1.2    lneto 
   7842  1.2    lneto 
   7843  1.2    lneto <p>
   7844  1.2    lneto Dynamically links the host program with the C&nbsp;library <code>libname</code>.
   7845  1.2    lneto 
   7846  1.2    lneto 
   7847  1.2    lneto <p>
   7848  1.2    lneto If <code>funcname</code> is "<code>*</code>",
   7849  1.2    lneto then it only links with the library,
   7850  1.2    lneto making the symbols exported by the library
   7851  1.2    lneto available to other dynamically linked libraries.
   7852  1.2    lneto Otherwise,
   7853  1.2    lneto it looks for a function <code>funcname</code> inside the library
   7854  1.2    lneto and returns this function as a C&nbsp;function.
   7855  1.2    lneto So, <code>funcname</code> must follow the <a href="#lua_CFunction"><code>lua_CFunction</code></a> prototype
   7856  1.2    lneto (see <a href="#lua_CFunction"><code>lua_CFunction</code></a>).
   7857  1.2    lneto 
   7858  1.2    lneto 
   7859  1.2    lneto <p>
   7860  1.2    lneto This is a low-level function.
   7861  1.2    lneto It completely bypasses the package and module system.
   7862  1.2    lneto Unlike <a href="#pdf-require"><code>require</code></a>,
   7863  1.2    lneto it does not perform any path searching and
   7864  1.2    lneto does not automatically adds extensions.
   7865  1.2    lneto <code>libname</code> must be the complete file name of the C&nbsp;library,
   7866  1.2    lneto including if necessary a path and an extension.
   7867  1.2    lneto <code>funcname</code> must be the exact name exported by the C&nbsp;library
   7868  1.2    lneto (which may depend on the C&nbsp;compiler and linker used).
   7869  1.2    lneto 
   7870  1.2    lneto 
   7871  1.2    lneto <p>
   7872  1.2    lneto This function is not supported by Standard&nbsp;C.
   7873  1.2    lneto As such, it is only available on some platforms
   7874  1.2    lneto (Windows, Linux, Mac OS X, Solaris, BSD,
   7875  1.2    lneto plus other Unix systems that support the <code>dlfcn</code> standard).
   7876  1.2    lneto 
   7877  1.2    lneto 
   7878  1.2    lneto 
   7879  1.2    lneto 
   7880  1.2    lneto <p>
   7881  1.2    lneto <hr><h3><a name="pdf-package.path"><code>package.path</code></a></h3>
   7882  1.2    lneto 
   7883  1.2    lneto 
   7884  1.2    lneto <p>
   7885  1.2    lneto The path used by <a href="#pdf-require"><code>require</code></a> to search for a Lua loader.
   7886  1.2    lneto 
   7887  1.2    lneto 
   7888  1.2    lneto <p>
   7889  1.2    lneto At start-up, Lua initializes this variable with
   7890  1.2    lneto the value of the environment variable <a name="pdf-LUA_PATH_5_3"><code>LUA_PATH_5_3</code></a> or
   7891  1.2    lneto the environment variable <a name="pdf-LUA_PATH"><code>LUA_PATH</code></a> or
   7892  1.2    lneto with a default path defined in <code>luaconf.h</code>,
   7893  1.2    lneto if those environment variables are not defined.
   7894  1.2    lneto Any "<code>;;</code>" in the value of the environment variable
   7895  1.2    lneto is replaced by the default path.
   7896  1.2    lneto 
   7897  1.2    lneto 
   7898  1.2    lneto 
   7899  1.2    lneto 
   7900  1.2    lneto <p>
   7901  1.2    lneto <hr><h3><a name="pdf-package.preload"><code>package.preload</code></a></h3>
   7902  1.2    lneto 
   7903  1.2    lneto 
   7904  1.2    lneto <p>
   7905  1.2    lneto A table to store loaders for specific modules
   7906  1.2    lneto (see <a href="#pdf-require"><code>require</code></a>).
   7907  1.2    lneto 
   7908  1.2    lneto 
   7909  1.2    lneto <p>
   7910  1.2    lneto This variable is only a reference to the real table;
   7911  1.2    lneto assignments to this variable do not change the
   7912  1.2    lneto table used by <a href="#pdf-require"><code>require</code></a>.
   7913  1.2    lneto 
   7914  1.2    lneto 
   7915  1.1  mbalmer 
   7916  1.1  mbalmer 
   7917  1.1  mbalmer <p>
   7918  1.2    lneto <hr><h3><a name="pdf-package.searchers"><code>package.searchers</code></a></h3>
   7919  1.1  mbalmer 
   7920  1.1  mbalmer 
   7921  1.1  mbalmer <p>
   7922  1.1  mbalmer A table used by <a href="#pdf-require"><code>require</code></a> to control how to load modules.
   7923  1.1  mbalmer 
   7924  1.1  mbalmer 
   7925  1.1  mbalmer <p>
   7926  1.1  mbalmer Each entry in this table is a <em>searcher function</em>.
   7927  1.1  mbalmer When looking for a module,
   7928  1.1  mbalmer <a href="#pdf-require"><code>require</code></a> calls each of these searchers in ascending order,
   7929  1.1  mbalmer with the module name (the argument given to <a href="#pdf-require"><code>require</code></a>) as its
   7930  1.1  mbalmer sole parameter.
   7931  1.1  mbalmer The function can return another function (the module <em>loader</em>)
   7932  1.2    lneto plus an extra value that will be passed to that loader,
   7933  1.1  mbalmer or a string explaining why it did not find that module
   7934  1.1  mbalmer (or <b>nil</b> if it has nothing to say).
   7935  1.2    lneto 
   7936  1.2    lneto 
   7937  1.2    lneto <p>
   7938  1.2    lneto Lua initializes this table with four searcher functions.
   7939  1.1  mbalmer 
   7940  1.1  mbalmer 
   7941  1.1  mbalmer <p>
   7942  1.1  mbalmer The first searcher simply looks for a loader in the
   7943  1.1  mbalmer <a href="#pdf-package.preload"><code>package.preload</code></a> table.
   7944  1.1  mbalmer 
   7945  1.1  mbalmer 
   7946  1.1  mbalmer <p>
   7947  1.1  mbalmer The second searcher looks for a loader as a Lua library,
   7948  1.1  mbalmer using the path stored at <a href="#pdf-package.path"><code>package.path</code></a>.
   7949  1.2    lneto The search is done as described in function <a href="#pdf-package.searchpath"><code>package.searchpath</code></a>.
   7950  1.1  mbalmer 
   7951  1.1  mbalmer 
   7952  1.1  mbalmer <p>
   7953  1.1  mbalmer The third searcher looks for a loader as a C&nbsp;library,
   7954  1.1  mbalmer using the path given by the variable <a href="#pdf-package.cpath"><code>package.cpath</code></a>.
   7955  1.2    lneto Again,
   7956  1.2    lneto the search is done as described in function <a href="#pdf-package.searchpath"><code>package.searchpath</code></a>.
   7957  1.1  mbalmer For instance,
   7958  1.1  mbalmer if the C&nbsp;path is the string
   7959  1.1  mbalmer 
   7960  1.1  mbalmer <pre>
   7961  1.1  mbalmer      "./?.so;./?.dll;/usr/local/?/init.so"
   7962  1.1  mbalmer </pre><p>
   7963  1.1  mbalmer the searcher for module <code>foo</code>
   7964  1.1  mbalmer will try to open the files <code>./foo.so</code>, <code>./foo.dll</code>,
   7965  1.1  mbalmer and <code>/usr/local/foo/init.so</code>, in that order.
   7966  1.1  mbalmer Once it finds a C&nbsp;library,
   7967  1.1  mbalmer this searcher first uses a dynamic link facility to link the
   7968  1.1  mbalmer application with the library.
   7969  1.1  mbalmer Then it tries to find a C&nbsp;function inside the library to
   7970  1.1  mbalmer be used as the loader.
   7971  1.1  mbalmer The name of this C&nbsp;function is the string "<code>luaopen_</code>"
   7972  1.1  mbalmer concatenated with a copy of the module name where each dot
   7973  1.1  mbalmer is replaced by an underscore.
   7974  1.1  mbalmer Moreover, if the module name has a hyphen,
   7975  1.3    lneto its suffix after (and including) the first hyphen is removed.
   7976  1.3    lneto For instance, if the module name is <code>a.b.c-v2.1</code>,
   7977  1.3    lneto the function name will be <code>luaopen_a_b_c</code>.
   7978  1.1  mbalmer 
   7979  1.1  mbalmer 
   7980  1.1  mbalmer <p>
   7981  1.1  mbalmer The fourth searcher tries an <em>all-in-one loader</em>.
   7982  1.1  mbalmer It searches the C&nbsp;path for a library for
   7983  1.1  mbalmer the root name of the given module.
   7984  1.1  mbalmer For instance, when requiring <code>a.b.c</code>,
   7985  1.1  mbalmer it will search for a C&nbsp;library for <code>a</code>.
   7986  1.1  mbalmer If found, it looks into it for an open function for
   7987  1.1  mbalmer the submodule;
   7988  1.1  mbalmer in our example, that would be <code>luaopen_a_b_c</code>.
   7989  1.1  mbalmer With this facility, a package can pack several C&nbsp;submodules
   7990  1.1  mbalmer into one single library,
   7991  1.1  mbalmer with each submodule keeping its original open function.
   7992  1.1  mbalmer 
   7993  1.1  mbalmer 
   7994  1.1  mbalmer <p>
   7995  1.2    lneto All searchers except the first one (preload) return as the extra value
   7996  1.2    lneto the file name where the module was found,
   7997  1.2    lneto as returned by <a href="#pdf-package.searchpath"><code>package.searchpath</code></a>.
   7998  1.2    lneto The first searcher returns no extra value.
   7999  1.1  mbalmer 
   8000  1.1  mbalmer 
   8001  1.1  mbalmer 
   8002  1.1  mbalmer 
   8003  1.1  mbalmer <p>
   8004  1.2    lneto <hr><h3><a name="pdf-package.searchpath"><code>package.searchpath (name, path [, sep [, rep]])</code></a></h3>
   8005  1.1  mbalmer 
   8006  1.1  mbalmer 
   8007  1.1  mbalmer <p>
   8008  1.2    lneto Searches for the given <code>name</code> in the given <code>path</code>.
   8009  1.1  mbalmer 
   8010  1.1  mbalmer 
   8011  1.1  mbalmer <p>
   8012  1.2    lneto A path is a string containing a sequence of
   8013  1.2    lneto <em>templates</em> separated by semicolons.
   8014  1.2    lneto For each template,
   8015  1.2    lneto the function replaces each interrogation mark (if any)
   8016  1.2    lneto in the template with a copy of <code>name</code>
   8017  1.2    lneto wherein all occurrences of <code>sep</code>
   8018  1.2    lneto (a dot, by default)
   8019  1.2    lneto were replaced by <code>rep</code>
   8020  1.2    lneto (the system's directory separator, by default),
   8021  1.2    lneto and then tries to open the resulting file name.
   8022  1.1  mbalmer 
   8023  1.1  mbalmer 
   8024  1.1  mbalmer <p>
   8025  1.2    lneto For instance, if the path is the string
   8026  1.1  mbalmer 
   8027  1.2    lneto <pre>
   8028  1.2    lneto      "./?.lua;./?.lc;/usr/local/?/init.lua"
   8029  1.2    lneto </pre><p>
   8030  1.2    lneto the search for the name <code>foo.a</code>
   8031  1.2    lneto will try to open the files
   8032  1.2    lneto <code>./foo/a.lua</code>, <code>./foo/a.lc</code>, and
   8033  1.2    lneto <code>/usr/local/foo/a/init.lua</code>, in that order.
   8034  1.1  mbalmer 
   8035  1.1  mbalmer 
   8036  1.1  mbalmer <p>
   8037  1.2    lneto Returns the resulting name of the first file that it can
   8038  1.2    lneto open in read mode (after closing the file),
   8039  1.2    lneto or <b>nil</b> plus an error message if none succeeds.
   8040  1.2    lneto (This error message lists all file names it tried to open.)
   8041  1.1  mbalmer 
   8042  1.1  mbalmer 
   8043  1.1  mbalmer 
   8044  1.1  mbalmer 
   8045  1.1  mbalmer 
   8046  1.1  mbalmer 
   8047  1.1  mbalmer 
   8048  1.2    lneto <h2>6.4 &ndash; <a name="6.4">String Manipulation</a></h2>
   8049  1.1  mbalmer 
   8050  1.1  mbalmer <p>
   8051  1.1  mbalmer This library provides generic functions for string manipulation,
   8052  1.1  mbalmer such as finding and extracting substrings, and pattern matching.
   8053  1.1  mbalmer When indexing a string in Lua, the first character is at position&nbsp;1
   8054  1.1  mbalmer (not at&nbsp;0, as in C).
   8055  1.1  mbalmer Indices are allowed to be negative and are interpreted as indexing backwards,
   8056  1.1  mbalmer from the end of the string.
   8057  1.1  mbalmer Thus, the last character is at position -1, and so on.
   8058  1.1  mbalmer 
   8059  1.1  mbalmer 
   8060  1.1  mbalmer <p>
   8061  1.1  mbalmer The string library provides all its functions inside the table
   8062  1.1  mbalmer <a name="pdf-string"><code>string</code></a>.
   8063  1.1  mbalmer It also sets a metatable for strings
   8064  1.1  mbalmer where the <code>__index</code> field points to the <code>string</code> table.
   8065  1.1  mbalmer Therefore, you can use the string functions in object-oriented style.
   8066  1.2    lneto For instance, <code>string.byte(s,i)</code>
   8067  1.1  mbalmer can be written as <code>s:byte(i)</code>.
   8068  1.1  mbalmer 
   8069  1.1  mbalmer 
   8070  1.1  mbalmer <p>
   8071  1.1  mbalmer The string library assumes one-byte character encodings.
   8072  1.1  mbalmer 
   8073  1.1  mbalmer 
   8074  1.1  mbalmer <p>
   8075  1.1  mbalmer <hr><h3><a name="pdf-string.byte"><code>string.byte (s [, i [, j]])</code></a></h3>
   8076  1.1  mbalmer Returns the internal numerical codes of the characters <code>s[i]</code>,
   8077  1.2    lneto <code>s[i+1]</code>, ..., <code>s[j]</code>.
   8078  1.1  mbalmer The default value for <code>i</code> is&nbsp;1;
   8079  1.1  mbalmer the default value for <code>j</code> is&nbsp;<code>i</code>.
   8080  1.2    lneto These indices are corrected
   8081  1.2    lneto following the same rules of function <a href="#pdf-string.sub"><code>string.sub</code></a>.
   8082  1.1  mbalmer 
   8083  1.1  mbalmer 
   8084  1.1  mbalmer <p>
   8085  1.2    lneto Numerical codes are not necessarily portable across platforms.
   8086  1.1  mbalmer 
   8087  1.1  mbalmer 
   8088  1.1  mbalmer 
   8089  1.1  mbalmer 
   8090  1.1  mbalmer <p>
   8091  1.1  mbalmer <hr><h3><a name="pdf-string.char"><code>string.char (&middot;&middot;&middot;)</code></a></h3>
   8092  1.1  mbalmer Receives zero or more integers.
   8093  1.1  mbalmer Returns a string with length equal to the number of arguments,
   8094  1.1  mbalmer in which each character has the internal numerical code equal
   8095  1.1  mbalmer to its corresponding argument.
   8096  1.1  mbalmer 
   8097  1.1  mbalmer 
   8098  1.1  mbalmer <p>
   8099  1.2    lneto Numerical codes are not necessarily portable across platforms.
   8100  1.2    lneto 
   8101  1.2    lneto 
   8102  1.2    lneto 
   8103  1.2    lneto 
   8104  1.2    lneto <p>
   8105  1.2    lneto <hr><h3><a name="pdf-string.dump"><code>string.dump (function [, strip])</code></a></h3>
   8106  1.1  mbalmer 
   8107  1.1  mbalmer 
   8108  1.2    lneto <p>
   8109  1.2    lneto Returns a string containing a binary representation
   8110  1.2    lneto (a <em>binary chunk</em>)
   8111  1.2    lneto of the given function,
   8112  1.2    lneto so that a later <a href="#pdf-load"><code>load</code></a> on this string returns
   8113  1.2    lneto a copy of the function (but with new upvalues).
   8114  1.2    lneto If <code>strip</code> is a true value,
   8115  1.2    lneto the binary representation is created without debug information
   8116  1.2    lneto about the function
   8117  1.2    lneto (local variable names, lines, etc.).
   8118  1.2    lneto 
   8119  1.2    lneto 
   8120  1.2    lneto <p>
   8121  1.3    lneto Functions with upvalues have only their number of upvalues saved.
   8122  1.3    lneto When (re)loaded,
   8123  1.3    lneto those upvalues receive fresh instances containing <b>nil</b>.
   8124  1.3    lneto (You can use the debug library to serialize
   8125  1.3    lneto and reload the upvalues of a function
   8126  1.3    lneto in a way adequate to your needs.)
   8127  1.1  mbalmer 
   8128  1.1  mbalmer 
   8129  1.1  mbalmer 
   8130  1.1  mbalmer 
   8131  1.1  mbalmer <p>
   8132  1.1  mbalmer <hr><h3><a name="pdf-string.find"><code>string.find (s, pattern [, init [, plain]])</code></a></h3>
   8133  1.2    lneto 
   8134  1.2    lneto 
   8135  1.2    lneto <p>
   8136  1.1  mbalmer Looks for the first match of
   8137  1.3    lneto <code>pattern</code> (see <a href="#6.4.1">&sect;6.4.1</a>) in the string <code>s</code>.
   8138  1.1  mbalmer If it finds a match, then <code>find</code> returns the indices of&nbsp;<code>s</code>
   8139  1.1  mbalmer where this occurrence starts and ends;
   8140  1.1  mbalmer otherwise, it returns <b>nil</b>.
   8141  1.1  mbalmer A third, optional numerical argument <code>init</code> specifies
   8142  1.1  mbalmer where to start the search;
   8143  1.1  mbalmer its default value is&nbsp;1 and can be negative.
   8144  1.1  mbalmer A value of <b>true</b> as a fourth, optional argument <code>plain</code>
   8145  1.1  mbalmer turns off the pattern matching facilities,
   8146  1.1  mbalmer so the function does a plain "find substring" operation,
   8147  1.2    lneto with no characters in <code>pattern</code> being considered magic.
   8148  1.1  mbalmer Note that if <code>plain</code> is given, then <code>init</code> must be given as well.
   8149  1.1  mbalmer 
   8150  1.1  mbalmer 
   8151  1.1  mbalmer <p>
   8152  1.1  mbalmer If the pattern has captures,
   8153  1.1  mbalmer then in a successful match
   8154  1.1  mbalmer the captured values are also returned,
   8155  1.1  mbalmer after the two indices.
   8156  1.1  mbalmer 
   8157  1.1  mbalmer 
   8158  1.1  mbalmer 
   8159  1.1  mbalmer 
   8160  1.1  mbalmer <p>
   8161  1.1  mbalmer <hr><h3><a name="pdf-string.format"><code>string.format (formatstring, &middot;&middot;&middot;)</code></a></h3>
   8162  1.2    lneto 
   8163  1.2    lneto 
   8164  1.2    lneto <p>
   8165  1.1  mbalmer Returns a formatted version of its variable number of arguments
   8166  1.1  mbalmer following the description given in its first argument (which must be a string).
   8167  1.3    lneto The format string follows the same rules as the ISO&nbsp;C function <code>sprintf</code>.
   8168  1.1  mbalmer The only differences are that the options/modifiers
   8169  1.2    lneto <code>*</code>, <code>h</code>, <code>L</code>, <code>l</code>, <code>n</code>,
   8170  1.2    lneto and <code>p</code> are not supported
   8171  1.1  mbalmer and that there is an extra option, <code>q</code>.
   8172  1.2    lneto The <code>q</code> option formats a string between double quotes,
   8173  1.2    lneto using escape sequences when necessary to ensure that
   8174  1.2    lneto it can safely be read back by the Lua interpreter.
   8175  1.1  mbalmer For instance, the call
   8176  1.1  mbalmer 
   8177  1.1  mbalmer <pre>
   8178  1.1  mbalmer      string.format('%q', 'a string with "quotes" and \n new line')
   8179  1.1  mbalmer </pre><p>
   8180  1.2    lneto may produce the string:
   8181  1.1  mbalmer 
   8182  1.1  mbalmer <pre>
   8183  1.1  mbalmer      "a string with \"quotes\" and \
   8184  1.1  mbalmer       new line"
   8185  1.1  mbalmer </pre>
   8186  1.1  mbalmer 
   8187  1.1  mbalmer <p>
   8188  1.2    lneto Options
   8189  1.2    lneto <code>A</code> and <code>a</code> (when available),
   8190  1.2    lneto <code>E</code>, <code>e</code>, <code>f</code>,
   8191  1.2    lneto <code>G</code>, and <code>g</code> all expect a number as argument.
   8192  1.2    lneto Options <code>c</code>, <code>d</code>,
   8193  1.2    lneto <code>i</code>, <code>o</code>, <code>u</code>, <code>X</code>, and <code>x</code>
   8194  1.2    lneto expect an integer.
   8195  1.2    lneto Option <code>q</code> expects a string;
   8196  1.2    lneto option <code>s</code> expects a string without embedded zeros.
   8197  1.2    lneto If the argument to option <code>s</code> is not a string,
   8198  1.2    lneto it is converted to one following the same rules of <a href="#pdf-tostring"><code>tostring</code></a>.
   8199  1.1  mbalmer 
   8200  1.1  mbalmer 
   8201  1.1  mbalmer 
   8202  1.1  mbalmer 
   8203  1.1  mbalmer <p>
   8204  1.1  mbalmer <hr><h3><a name="pdf-string.gmatch"><code>string.gmatch (s, pattern)</code></a></h3>
   8205  1.1  mbalmer Returns an iterator function that,
   8206  1.1  mbalmer each time it is called,
   8207  1.3    lneto returns the next captures from <code>pattern</code> (see <a href="#6.4.1">&sect;6.4.1</a>)
   8208  1.3    lneto over the string <code>s</code>.
   8209  1.1  mbalmer If <code>pattern</code> specifies no captures,
   8210  1.1  mbalmer then the whole match is produced in each call.
   8211  1.1  mbalmer 
   8212  1.1  mbalmer 
   8213  1.1  mbalmer <p>
   8214  1.1  mbalmer As an example, the following loop
   8215  1.2    lneto will iterate over all the words from string <code>s</code>,
   8216  1.2    lneto printing one per line:
   8217  1.1  mbalmer 
   8218  1.1  mbalmer <pre>
   8219  1.1  mbalmer      s = "hello world from Lua"
   8220  1.1  mbalmer      for w in string.gmatch(s, "%a+") do
   8221  1.1  mbalmer        print(w)
   8222  1.1  mbalmer      end
   8223  1.1  mbalmer </pre><p>
   8224  1.1  mbalmer The next example collects all pairs <code>key=value</code> from the
   8225  1.1  mbalmer given string into a table:
   8226  1.1  mbalmer 
   8227  1.1  mbalmer <pre>
   8228  1.1  mbalmer      t = {}
   8229  1.1  mbalmer      s = "from=world, to=Lua"
   8230  1.1  mbalmer      for k, v in string.gmatch(s, "(%w+)=(%w+)") do
   8231  1.1  mbalmer        t[k] = v
   8232  1.1  mbalmer      end
   8233  1.1  mbalmer </pre>
   8234  1.1  mbalmer 
   8235  1.1  mbalmer <p>
   8236  1.2    lneto For this function, a caret '<code>^</code>' at the start of a pattern does not
   8237  1.1  mbalmer work as an anchor, as this would prevent the iteration.
   8238  1.1  mbalmer 
   8239  1.1  mbalmer 
   8240  1.1  mbalmer 
   8241  1.1  mbalmer 
   8242  1.1  mbalmer <p>
   8243  1.1  mbalmer <hr><h3><a name="pdf-string.gsub"><code>string.gsub (s, pattern, repl [, n])</code></a></h3>
   8244  1.1  mbalmer Returns a copy of <code>s</code>
   8245  1.1  mbalmer in which all (or the first <code>n</code>, if given)
   8246  1.3    lneto occurrences of the <code>pattern</code> (see <a href="#6.4.1">&sect;6.4.1</a>) have been
   8247  1.1  mbalmer replaced by a replacement string specified by <code>repl</code>,
   8248  1.1  mbalmer which can be a string, a table, or a function.
   8249  1.1  mbalmer <code>gsub</code> also returns, as its second value,
   8250  1.1  mbalmer the total number of matches that occurred.
   8251  1.2    lneto The name <code>gsub</code> comes from <em>Global SUBstitution</em>.
   8252  1.1  mbalmer 
   8253  1.1  mbalmer 
   8254  1.1  mbalmer <p>
   8255  1.1  mbalmer If <code>repl</code> is a string, then its value is used for replacement.
   8256  1.1  mbalmer The character&nbsp;<code>%</code> works as an escape character:
   8257  1.2    lneto any sequence in <code>repl</code> of the form <code>%<em>d</em></code>,
   8258  1.2    lneto with <em>d</em> between 1 and 9,
   8259  1.2    lneto stands for the value of the <em>d</em>-th captured substring.
   8260  1.1  mbalmer The sequence <code>%0</code> stands for the whole match.
   8261  1.1  mbalmer The sequence <code>%%</code> stands for a single&nbsp;<code>%</code>.
   8262  1.1  mbalmer 
   8263  1.1  mbalmer 
   8264  1.1  mbalmer <p>
   8265  1.1  mbalmer If <code>repl</code> is a table, then the table is queried for every match,
   8266  1.2    lneto using the first capture as the key.
   8267  1.1  mbalmer 
   8268  1.1  mbalmer 
   8269  1.1  mbalmer <p>
   8270  1.1  mbalmer If <code>repl</code> is a function, then this function is called every time a
   8271  1.1  mbalmer match occurs, with all captured substrings passed as arguments,
   8272  1.2    lneto in order.
   8273  1.2    lneto 
   8274  1.2    lneto 
   8275  1.2    lneto <p>
   8276  1.2    lneto In any case,
   8277  1.1  mbalmer if the pattern specifies no captures,
   8278  1.2    lneto then it behaves as if the whole pattern was inside a capture.
   8279  1.1  mbalmer 
   8280  1.1  mbalmer 
   8281  1.1  mbalmer <p>
   8282  1.1  mbalmer If the value returned by the table query or by the function call
   8283  1.1  mbalmer is a string or a number,
   8284  1.1  mbalmer then it is used as the replacement string;
   8285  1.1  mbalmer otherwise, if it is <b>false</b> or <b>nil</b>,
   8286  1.1  mbalmer then there is no replacement
   8287  1.1  mbalmer (that is, the original match is kept in the string).
   8288  1.1  mbalmer 
   8289  1.1  mbalmer 
   8290  1.1  mbalmer <p>
   8291  1.1  mbalmer Here are some examples:
   8292  1.1  mbalmer 
   8293  1.1  mbalmer <pre>
   8294  1.1  mbalmer      x = string.gsub("hello world", "(%w+)", "%1 %1")
   8295  1.1  mbalmer      --&gt; x="hello hello world world"
   8296  1.1  mbalmer      
   8297  1.1  mbalmer      x = string.gsub("hello world", "%w+", "%0 %0", 1)
   8298  1.1  mbalmer      --&gt; x="hello hello world"
   8299  1.1  mbalmer      
   8300  1.1  mbalmer      x = string.gsub("hello world from Lua", "(%w+)%s*(%w+)", "%2 %1")
   8301  1.1  mbalmer      --&gt; x="world hello Lua from"
   8302  1.1  mbalmer      
   8303  1.1  mbalmer      x = string.gsub("home = $HOME, user = $USER", "%$(%w+)", os.getenv)
   8304  1.1  mbalmer      --&gt; x="home = /home/roberto, user = roberto"
   8305  1.1  mbalmer      
   8306  1.1  mbalmer      x = string.gsub("4+5 = $return 4+5$", "%$(.-)%$", function (s)
   8307  1.2    lneto            return load(s)()
   8308  1.1  mbalmer          end)
   8309  1.1  mbalmer      --&gt; x="4+5 = 9"
   8310  1.1  mbalmer      
   8311  1.2    lneto      local t = {name="lua", version="5.3"}
   8312  1.1  mbalmer      x = string.gsub("$name-$version.tar.gz", "%$(%w+)", t)
   8313  1.2    lneto      --&gt; x="lua-5.3.tar.gz"
   8314  1.1  mbalmer </pre>
   8315  1.1  mbalmer 
   8316  1.1  mbalmer 
   8317  1.1  mbalmer 
   8318  1.1  mbalmer <p>
   8319  1.1  mbalmer <hr><h3><a name="pdf-string.len"><code>string.len (s)</code></a></h3>
   8320  1.1  mbalmer Receives a string and returns its length.
   8321  1.1  mbalmer The empty string <code>""</code> has length 0.
   8322  1.1  mbalmer Embedded zeros are counted,
   8323  1.1  mbalmer so <code>"a\000bc\000"</code> has length 5.
   8324  1.1  mbalmer 
   8325  1.1  mbalmer 
   8326  1.1  mbalmer 
   8327  1.1  mbalmer 
   8328  1.1  mbalmer <p>
   8329  1.1  mbalmer <hr><h3><a name="pdf-string.lower"><code>string.lower (s)</code></a></h3>
   8330  1.1  mbalmer Receives a string and returns a copy of this string with all
   8331  1.1  mbalmer uppercase letters changed to lowercase.
   8332  1.1  mbalmer All other characters are left unchanged.
   8333  1.1  mbalmer The definition of what an uppercase letter is depends on the current locale.
   8334  1.1  mbalmer 
   8335  1.1  mbalmer 
   8336  1.1  mbalmer 
   8337  1.1  mbalmer 
   8338  1.1  mbalmer <p>
   8339  1.1  mbalmer <hr><h3><a name="pdf-string.match"><code>string.match (s, pattern [, init])</code></a></h3>
   8340  1.1  mbalmer Looks for the first <em>match</em> of
   8341  1.3    lneto <code>pattern</code> (see <a href="#6.4.1">&sect;6.4.1</a>) in the string <code>s</code>.
   8342  1.1  mbalmer If it finds one, then <code>match</code> returns
   8343  1.1  mbalmer the captures from the pattern;
   8344  1.1  mbalmer otherwise it returns <b>nil</b>.
   8345  1.1  mbalmer If <code>pattern</code> specifies no captures,
   8346  1.1  mbalmer then the whole match is returned.
   8347  1.1  mbalmer A third, optional numerical argument <code>init</code> specifies
   8348  1.1  mbalmer where to start the search;
   8349  1.1  mbalmer its default value is&nbsp;1 and can be negative.
   8350  1.1  mbalmer 
   8351  1.1  mbalmer 
   8352  1.1  mbalmer 
   8353  1.1  mbalmer 
   8354  1.1  mbalmer <p>
   8355  1.3    lneto <hr><h3><a name="pdf-string.pack"><code>string.pack (fmt, v1, v2, &middot;&middot;&middot;)</code></a></h3>
   8356  1.3    lneto 
   8357  1.3    lneto 
   8358  1.3    lneto <p>
   8359  1.3    lneto Returns a binary string containing the values <code>v1</code>, <code>v2</code>, etc.
   8360  1.3    lneto packed (that is, serialized in binary form)
   8361  1.3    lneto according to the format string <code>fmt</code> (see <a href="#6.4.2">&sect;6.4.2</a>). 
   8362  1.3    lneto 
   8363  1.3    lneto 
   8364  1.3    lneto 
   8365  1.3    lneto 
   8366  1.3    lneto <p>
   8367  1.3    lneto <hr><h3><a name="pdf-string.packsize"><code>string.packsize (fmt)</code></a></h3>
   8368  1.3    lneto 
   8369  1.3    lneto 
   8370  1.3    lneto <p>
   8371  1.3    lneto Returns the size of a string resulting from <a href="#pdf-string.pack"><code>string.pack</code></a>
   8372  1.3    lneto with the given format.
   8373  1.3    lneto The format string cannot have the variable-length options
   8374  1.3    lneto '<code>s</code>' or '<code>z</code>' (see <a href="#6.4.2">&sect;6.4.2</a>).
   8375  1.3    lneto 
   8376  1.3    lneto 
   8377  1.3    lneto 
   8378  1.3    lneto 
   8379  1.3    lneto <p>
   8380  1.2    lneto <hr><h3><a name="pdf-string.rep"><code>string.rep (s, n [, sep])</code></a></h3>
   8381  1.1  mbalmer Returns a string that is the concatenation of <code>n</code> copies of
   8382  1.2    lneto the string <code>s</code> separated by the string <code>sep</code>.
   8383  1.2    lneto The default value for <code>sep</code> is the empty string
   8384  1.2    lneto (that is, no separator).
   8385  1.3    lneto Returns the empty string if <code>n</code> is not positive.
   8386  1.1  mbalmer 
   8387  1.1  mbalmer 
   8388  1.1  mbalmer 
   8389  1.1  mbalmer 
   8390  1.1  mbalmer <p>
   8391  1.1  mbalmer <hr><h3><a name="pdf-string.reverse"><code>string.reverse (s)</code></a></h3>
   8392  1.1  mbalmer Returns a string that is the string <code>s</code> reversed.
   8393  1.1  mbalmer 
   8394  1.1  mbalmer 
   8395  1.1  mbalmer 
   8396  1.1  mbalmer 
   8397  1.1  mbalmer <p>
   8398  1.1  mbalmer <hr><h3><a name="pdf-string.sub"><code>string.sub (s, i [, j])</code></a></h3>
   8399  1.1  mbalmer Returns the substring of <code>s</code> that
   8400  1.1  mbalmer starts at <code>i</code>  and continues until <code>j</code>;
   8401  1.1  mbalmer <code>i</code> and <code>j</code> can be negative.
   8402  1.1  mbalmer If <code>j</code> is absent, then it is assumed to be equal to -1
   8403  1.1  mbalmer (which is the same as the string length).
   8404  1.1  mbalmer In particular,
   8405  1.1  mbalmer the call <code>string.sub(s,1,j)</code> returns a prefix of <code>s</code>
   8406  1.1  mbalmer with length <code>j</code>,
   8407  1.1  mbalmer and <code>string.sub(s, -i)</code> returns a suffix of <code>s</code>
   8408  1.1  mbalmer with length <code>i</code>.
   8409  1.1  mbalmer 
   8410  1.1  mbalmer 
   8411  1.2    lneto <p>
   8412  1.2    lneto If, after the translation of negative indices,
   8413  1.2    lneto <code>i</code> is less than 1,
   8414  1.2    lneto it is corrected to 1.
   8415  1.2    lneto If <code>j</code> is greater than the string length,
   8416  1.2    lneto it is corrected to that length.
   8417  1.2    lneto If, after these corrections,
   8418  1.2    lneto <code>i</code> is greater than <code>j</code>,
   8419  1.2    lneto the function returns the empty string.
   8420  1.2    lneto 
   8421  1.2    lneto 
   8422  1.2    lneto 
   8423  1.2    lneto 
   8424  1.2    lneto <p>
   8425  1.3    lneto <hr><h3><a name="pdf-string.unpack"><code>string.unpack (fmt, s [, pos])</code></a></h3>
   8426  1.2    lneto 
   8427  1.2    lneto 
   8428  1.2    lneto <p>
   8429  1.3    lneto Returns the values packed in string <code>s</code> (see <a href="#pdf-string.pack"><code>string.pack</code></a>)
   8430  1.3    lneto according to the format string <code>fmt</code> (see <a href="#6.4.2">&sect;6.4.2</a>).
   8431  1.3    lneto An optional <code>pos</code> marks where
   8432  1.3    lneto to start reading in <code>s</code> (default is 1).
   8433  1.3    lneto After the read values,
   8434  1.3    lneto this function also returns the index of the first unread byte in <code>s</code>.
   8435  1.2    lneto 
   8436  1.2    lneto 
   8437  1.1  mbalmer 
   8438  1.1  mbalmer 
   8439  1.1  mbalmer <p>
   8440  1.1  mbalmer <hr><h3><a name="pdf-string.upper"><code>string.upper (s)</code></a></h3>
   8441  1.1  mbalmer Receives a string and returns a copy of this string with all
   8442  1.1  mbalmer lowercase letters changed to uppercase.
   8443  1.1  mbalmer All other characters are left unchanged.
   8444  1.1  mbalmer The definition of what a lowercase letter is depends on the current locale.
   8445  1.1  mbalmer 
   8446  1.1  mbalmer 
   8447  1.1  mbalmer 
   8448  1.3    lneto 
   8449  1.3    lneto 
   8450  1.2    lneto <h3>6.4.1 &ndash; <a name="6.4.1">Patterns</a></h3>
   8451  1.1  mbalmer 
   8452  1.3    lneto <p>
   8453  1.3    lneto Patterns in Lua are described by regular strings,
   8454  1.3    lneto which are interpreted as patterns by the pattern-matching functions
   8455  1.3    lneto <a href="#pdf-string.find"><code>string.find</code></a>,
   8456  1.3    lneto <a href="#pdf-string.gmatch"><code>string.gmatch</code></a>,
   8457  1.3    lneto <a href="#pdf-string.gsub"><code>string.gsub</code></a>,
   8458  1.3    lneto and <a href="#pdf-string.match"><code>string.match</code></a>.
   8459  1.3    lneto This section describes the syntax and the meaning
   8460  1.3    lneto (that is, what they match) of these strings.
   8461  1.3    lneto 
   8462  1.3    lneto 
   8463  1.1  mbalmer 
   8464  1.1  mbalmer <h4>Character Class:</h4><p>
   8465  1.1  mbalmer A <em>character class</em> is used to represent a set of characters.
   8466  1.1  mbalmer The following combinations are allowed in describing a character class:
   8467  1.1  mbalmer 
   8468  1.1  mbalmer <ul>
   8469  1.1  mbalmer 
   8470  1.2    lneto <li><b><em>x</em>: </b>
   8471  1.1  mbalmer (where <em>x</em> is not one of the <em>magic characters</em>
   8472  1.1  mbalmer <code>^$()%.[]*+-?</code>)
   8473  1.1  mbalmer represents the character <em>x</em> itself.
   8474  1.1  mbalmer </li>
   8475  1.1  mbalmer 
   8476  1.2    lneto <li><b><code>.</code>: </b> (a dot) represents all characters.</li>
   8477  1.1  mbalmer 
   8478  1.2    lneto <li><b><code>%a</code>: </b> represents all letters.</li>
   8479  1.1  mbalmer 
   8480  1.2    lneto <li><b><code>%c</code>: </b> represents all control characters.</li>
   8481  1.1  mbalmer 
   8482  1.2    lneto <li><b><code>%d</code>: </b> represents all digits.</li>
   8483  1.1  mbalmer 
   8484  1.2    lneto <li><b><code>%g</code>: </b> represents all printable characters except space.</li>
   8485  1.1  mbalmer 
   8486  1.2    lneto <li><b><code>%l</code>: </b> represents all lowercase letters.</li>
   8487  1.1  mbalmer 
   8488  1.2    lneto <li><b><code>%p</code>: </b> represents all punctuation characters.</li>
   8489  1.1  mbalmer 
   8490  1.2    lneto <li><b><code>%s</code>: </b> represents all space characters.</li>
   8491  1.1  mbalmer 
   8492  1.2    lneto <li><b><code>%u</code>: </b> represents all uppercase letters.</li>
   8493  1.1  mbalmer 
   8494  1.2    lneto <li><b><code>%w</code>: </b> represents all alphanumeric characters.</li>
   8495  1.1  mbalmer 
   8496  1.2    lneto <li><b><code>%x</code>: </b> represents all hexadecimal digits.</li>
   8497  1.1  mbalmer 
   8498  1.2    lneto <li><b><code>%<em>x</em></code>: </b> (where <em>x</em> is any non-alphanumeric character)
   8499  1.1  mbalmer represents the character <em>x</em>.
   8500  1.1  mbalmer This is the standard way to escape the magic characters.
   8501  1.3    lneto Any non-alphanumeric character
   8502  1.3    lneto (including all punctuations, even the non-magical)
   8503  1.1  mbalmer can be preceded by a '<code>%</code>'
   8504  1.1  mbalmer when used to represent itself in a pattern.
   8505  1.1  mbalmer </li>
   8506  1.1  mbalmer 
   8507  1.2    lneto <li><b><code>[<em>set</em>]</code>: </b>
   8508  1.1  mbalmer represents the class which is the union of all
   8509  1.1  mbalmer characters in <em>set</em>.
   8510  1.1  mbalmer A range of characters can be specified by
   8511  1.2    lneto separating the end characters of the range,
   8512  1.2    lneto in ascending order, with a '<code>-</code>'.
   8513  1.1  mbalmer All classes <code>%</code><em>x</em> described above can also be used as
   8514  1.1  mbalmer components in <em>set</em>.
   8515  1.1  mbalmer All other characters in <em>set</em> represent themselves.
   8516  1.1  mbalmer For example, <code>[%w_]</code> (or <code>[_%w]</code>)
   8517  1.1  mbalmer represents all alphanumeric characters plus the underscore,
   8518  1.1  mbalmer <code>[0-7]</code> represents the octal digits,
   8519  1.1  mbalmer and <code>[0-7%l%-]</code> represents the octal digits plus
   8520  1.1  mbalmer the lowercase letters plus the '<code>-</code>' character.
   8521  1.1  mbalmer 
   8522  1.1  mbalmer 
   8523  1.1  mbalmer <p>
   8524  1.1  mbalmer The interaction between ranges and classes is not defined.
   8525  1.1  mbalmer Therefore, patterns like <code>[%a-z]</code> or <code>[a-%%]</code>
   8526  1.1  mbalmer have no meaning.
   8527  1.1  mbalmer </li>
   8528  1.1  mbalmer 
   8529  1.2    lneto <li><b><code>[^<em>set</em>]</code>: </b>
   8530  1.1  mbalmer represents the complement of <em>set</em>,
   8531  1.1  mbalmer where <em>set</em> is interpreted as above.
   8532  1.1  mbalmer </li>
   8533  1.1  mbalmer 
   8534  1.1  mbalmer </ul><p>
   8535  1.1  mbalmer For all classes represented by single letters (<code>%a</code>, <code>%c</code>, etc.),
   8536  1.1  mbalmer the corresponding uppercase letter represents the complement of the class.
   8537  1.1  mbalmer For instance, <code>%S</code> represents all non-space characters.
   8538  1.1  mbalmer 
   8539  1.1  mbalmer 
   8540  1.1  mbalmer <p>
   8541  1.1  mbalmer The definitions of letter, space, and other character groups
   8542  1.1  mbalmer depend on the current locale.
   8543  1.1  mbalmer In particular, the class <code>[a-z]</code> may not be equivalent to <code>%l</code>.
   8544  1.1  mbalmer 
   8545  1.1  mbalmer 
   8546  1.1  mbalmer 
   8547  1.1  mbalmer 
   8548  1.1  mbalmer 
   8549  1.1  mbalmer <h4>Pattern Item:</h4><p>
   8550  1.1  mbalmer A <em>pattern item</em> can be
   8551  1.1  mbalmer 
   8552  1.1  mbalmer <ul>
   8553  1.1  mbalmer 
   8554  1.1  mbalmer <li>
   8555  1.1  mbalmer a single character class,
   8556  1.1  mbalmer which matches any single character in the class;
   8557  1.1  mbalmer </li>
   8558  1.1  mbalmer 
   8559  1.1  mbalmer <li>
   8560  1.1  mbalmer a single character class followed by '<code>*</code>',
   8561  1.3    lneto which matches zero or more repetitions of characters in the class.
   8562  1.1  mbalmer These repetition items will always match the longest possible sequence;
   8563  1.1  mbalmer </li>
   8564  1.1  mbalmer 
   8565  1.1  mbalmer <li>
   8566  1.1  mbalmer a single character class followed by '<code>+</code>',
   8567  1.3    lneto which matches one or more repetitions of characters in the class.
   8568  1.1  mbalmer These repetition items will always match the longest possible sequence;
   8569  1.1  mbalmer </li>
   8570  1.1  mbalmer 
   8571  1.1  mbalmer <li>
   8572  1.1  mbalmer a single character class followed by '<code>-</code>',
   8573  1.3    lneto which also matches zero or more repetitions of characters in the class.
   8574  1.1  mbalmer Unlike '<code>*</code>',
   8575  1.2    lneto these repetition items will always match the shortest possible sequence;
   8576  1.1  mbalmer </li>
   8577  1.1  mbalmer 
   8578  1.1  mbalmer <li>
   8579  1.1  mbalmer a single character class followed by '<code>?</code>',
   8580  1.3    lneto which matches zero or one occurrence of a character in the class.
   8581  1.3    lneto It always matches one occurrence if possible;
   8582  1.1  mbalmer </li>
   8583  1.1  mbalmer 
   8584  1.1  mbalmer <li>
   8585  1.1  mbalmer <code>%<em>n</em></code>, for <em>n</em> between 1 and 9;
   8586  1.1  mbalmer such item matches a substring equal to the <em>n</em>-th captured string
   8587  1.1  mbalmer (see below);
   8588  1.1  mbalmer </li>
   8589  1.1  mbalmer 
   8590  1.1  mbalmer <li>
   8591  1.1  mbalmer <code>%b<em>xy</em></code>, where <em>x</em> and <em>y</em> are two distinct characters;
   8592  1.1  mbalmer such item matches strings that start with&nbsp;<em>x</em>, end with&nbsp;<em>y</em>,
   8593  1.1  mbalmer and where the <em>x</em> and <em>y</em> are <em>balanced</em>.
   8594  1.1  mbalmer This means that, if one reads the string from left to right,
   8595  1.1  mbalmer counting <em>+1</em> for an <em>x</em> and <em>-1</em> for a <em>y</em>,
   8596  1.1  mbalmer the ending <em>y</em> is the first <em>y</em> where the count reaches 0.
   8597  1.1  mbalmer For instance, the item <code>%b()</code> matches expressions with
   8598  1.1  mbalmer balanced parentheses.
   8599  1.1  mbalmer </li>
   8600  1.1  mbalmer 
   8601  1.2    lneto <li>
   8602  1.2    lneto <code>%f[<em>set</em>]</code>, a <em>frontier pattern</em>;
   8603  1.2    lneto such item matches an empty string at any position such that
   8604  1.2    lneto the next character belongs to <em>set</em>
   8605  1.2    lneto and the previous character does not belong to <em>set</em>.
   8606  1.2    lneto The set <em>set</em> is interpreted as previously described.
   8607  1.2    lneto The beginning and the end of the subject are handled as if
   8608  1.2    lneto they were the character '<code>\0</code>'.
   8609  1.2    lneto </li>
   8610  1.2    lneto 
   8611  1.1  mbalmer </ul>
   8612  1.1  mbalmer 
   8613  1.1  mbalmer 
   8614  1.1  mbalmer 
   8615  1.1  mbalmer 
   8616  1.1  mbalmer <h4>Pattern:</h4><p>
   8617  1.1  mbalmer A <em>pattern</em> is a sequence of pattern items.
   8618  1.2    lneto A caret '<code>^</code>' at the beginning of a pattern anchors the match at the
   8619  1.1  mbalmer beginning of the subject string.
   8620  1.1  mbalmer A '<code>$</code>' at the end of a pattern anchors the match at the
   8621  1.1  mbalmer end of the subject string.
   8622  1.1  mbalmer At other positions,
   8623  1.1  mbalmer '<code>^</code>' and '<code>$</code>' have no special meaning and represent themselves.
   8624  1.1  mbalmer 
   8625  1.1  mbalmer 
   8626  1.1  mbalmer 
   8627  1.1  mbalmer 
   8628  1.1  mbalmer 
   8629  1.1  mbalmer <h4>Captures:</h4><p>
   8630  1.1  mbalmer A pattern can contain sub-patterns enclosed in parentheses;
   8631  1.1  mbalmer they describe <em>captures</em>.
   8632  1.1  mbalmer When a match succeeds, the substrings of the subject string
   8633  1.1  mbalmer that match captures are stored (<em>captured</em>) for future use.
   8634  1.1  mbalmer Captures are numbered according to their left parentheses.
   8635  1.1  mbalmer For instance, in the pattern <code>"(a*(.)%w(%s*))"</code>,
   8636  1.1  mbalmer the part of the string matching <code>"a*(.)%w(%s*)"</code> is
   8637  1.1  mbalmer stored as the first capture (and therefore has number&nbsp;1);
   8638  1.1  mbalmer the character matching "<code>.</code>" is captured with number&nbsp;2,
   8639  1.1  mbalmer and the part matching "<code>%s*</code>" has number&nbsp;3.
   8640  1.1  mbalmer 
   8641  1.1  mbalmer 
   8642  1.1  mbalmer <p>
   8643  1.1  mbalmer As a special case, the empty capture <code>()</code> captures
   8644  1.1  mbalmer the current string position (a number).
   8645  1.1  mbalmer For instance, if we apply the pattern <code>"()aa()"</code> on the
   8646  1.1  mbalmer string <code>"flaaap"</code>, there will be two captures: 3&nbsp;and&nbsp;5.
   8647  1.1  mbalmer 
   8648  1.1  mbalmer 
   8649  1.2    lneto 
   8650  1.2    lneto 
   8651  1.2    lneto 
   8652  1.2    lneto 
   8653  1.2    lneto 
   8654  1.3    lneto <h3>6.4.2 &ndash; <a name="6.4.2">Format Strings for Pack and Unpack</a></h3>
   8655  1.3    lneto 
   8656  1.3    lneto <p>
   8657  1.3    lneto The first argument to <a href="#pdf-string.pack"><code>string.pack</code></a>,
   8658  1.3    lneto <a href="#pdf-string.packsize"><code>string.packsize</code></a>, and <a href="#pdf-string.unpack"><code>string.unpack</code></a>
   8659  1.3    lneto is a format string,
   8660  1.3    lneto which describes the layout of the structure being created or read.
   8661  1.3    lneto 
   8662  1.3    lneto 
   8663  1.3    lneto <p>
   8664  1.3    lneto A format string is a sequence of conversion options.
   8665  1.3    lneto The conversion options are as follows:
   8666  1.3    lneto 
   8667  1.3    lneto <ul>
   8668  1.3    lneto <li><b><code>&lt;</code>: </b>sets little endian</li>
   8669  1.3    lneto <li><b><code>&gt;</code>: </b>sets big endian</li>
   8670  1.3    lneto <li><b><code>=</code>: </b>sets native endian</li>
   8671  1.3    lneto <li><b><code>![<em>n</em>]</code>: </b>sets maximum alignment to <code>n</code>
   8672  1.3    lneto (default is native alignment)</li>
   8673  1.3    lneto <li><b><code>b</code>: </b>a signed byte (<code>char</code>)</li>
   8674  1.3    lneto <li><b><code>B</code>: </b>an unsigned byte (<code>char</code>)</li>
   8675  1.3    lneto <li><b><code>h</code>: </b>a signed <code>short</code> (native size)</li>
   8676  1.3    lneto <li><b><code>H</code>: </b>an unsigned <code>short</code> (native size)</li>
   8677  1.3    lneto <li><b><code>l</code>: </b>a signed <code>long</code> (native size)</li>
   8678  1.3    lneto <li><b><code>L</code>: </b>an unsigned <code>long</code> (native size)</li>
   8679  1.3    lneto <li><b><code>j</code>: </b>a <code>lua_Integer</code></li>
   8680  1.3    lneto <li><b><code>J</code>: </b>a <code>lua_Unsigned</code></li>
   8681  1.3    lneto <li><b><code>T</code>: </b>a <code>size_t</code> (native size)</li>
   8682  1.3    lneto <li><b><code>i[<em>n</em>]</code>: </b>a signed <code>int</code> with <code>n</code> bytes
   8683  1.3    lneto (default is native size)</li>
   8684  1.3    lneto <li><b><code>I[<em>n</em>]</code>: </b>an unsigned <code>int</code> with <code>n</code> bytes
   8685  1.3    lneto (default is native size)</li>
   8686  1.3    lneto <li><b><code>f</code>: </b>a <code>float</code> (native size)</li>
   8687  1.3    lneto <li><b><code>d</code>: </b>a <code>double</code> (native size)</li>
   8688  1.3    lneto <li><b><code>n</code>: </b>a <code>lua_Number</code></li>
   8689  1.3    lneto <li><b><code>c<em>n</em></code>: </b>a fixed-sized string with <code>n</code> bytes</li>
   8690  1.3    lneto <li><b><code>z</code>: </b>a zero-terminated string</li>
   8691  1.3    lneto <li><b><code>s[<em>n</em>]</code>: </b>a string preceded by its length
   8692  1.3    lneto coded as an unsigned integer with <code>n</code> bytes
   8693  1.3    lneto (default is a <code>size_t</code>)</li>
   8694  1.3    lneto <li><b><code>x</code>: </b>one byte of padding</li>
   8695  1.3    lneto <li><b><code>X<em>op</em></code>: </b>an empty item that aligns
   8696  1.3    lneto according to option <code>op</code>
   8697  1.3    lneto (which is otherwise ignored)</li>
   8698  1.3    lneto <li><b>'<code> </code>': </b>(empty space) ignored</li>
   8699  1.3    lneto </ul><p>
   8700  1.3    lneto (A "<code>[<em>n</em>]</code>" means an optional integral numeral.)
   8701  1.3    lneto Except for padding, spaces, and configurations
   8702  1.3    lneto (options "<code>xX &lt;=&gt;!</code>"),
   8703  1.3    lneto each option corresponds to an argument (in <a href="#pdf-string.pack"><code>string.pack</code></a>)
   8704  1.3    lneto or a result (in <a href="#pdf-string.unpack"><code>string.unpack</code></a>).
   8705  1.3    lneto 
   8706  1.3    lneto 
   8707  1.3    lneto <p>
   8708  1.3    lneto For options "<code>!<em>n</em></code>", "<code>s<em>n</em></code>", "<code>i<em>n</em></code>", and "<code>I<em>n</em></code>",
   8709  1.3    lneto <code>n</code> can be any integer between 1 and 16.
   8710  1.3    lneto All integral options check overflows;
   8711  1.3    lneto <a href="#pdf-string.pack"><code>string.pack</code></a> checks whether the given value fits in the given size;
   8712  1.3    lneto <a href="#pdf-string.unpack"><code>string.unpack</code></a> checks whether the read value fits in a Lua integer.
   8713  1.3    lneto 
   8714  1.3    lneto 
   8715  1.3    lneto <p>
   8716  1.3    lneto Any format string starts as if prefixed by "<code>!1=</code>",
   8717  1.3    lneto that is,
   8718  1.3    lneto with maximum alignment of 1 (no alignment)
   8719  1.3    lneto and native endianness.
   8720  1.3    lneto 
   8721  1.3    lneto 
   8722  1.3    lneto <p>
   8723  1.3    lneto Alignment works as follows:
   8724  1.3    lneto For each option,
   8725  1.3    lneto the format gets extra padding until the data starts
   8726  1.3    lneto at an offset that is a multiple of the minimum between the
   8727  1.3    lneto option size and the maximum alignment;
   8728  1.3    lneto this minimum must be a power of 2.
   8729  1.3    lneto Options "<code>c</code>" and "<code>z</code>" are not aligned;
   8730  1.3    lneto option "<code>s</code>" follows the alignment of its starting integer.
   8731  1.3    lneto 
   8732  1.3    lneto 
   8733  1.3    lneto <p>
   8734  1.3    lneto All padding is filled with zeros by <a href="#pdf-string.pack"><code>string.pack</code></a>
   8735  1.3    lneto (and ignored by <a href="#pdf-string.unpack"><code>string.unpack</code></a>).
   8736  1.3    lneto 
   8737  1.3    lneto 
   8738  1.3    lneto 
   8739  1.2    lneto 
   8740  1.2    lneto 
   8741  1.2    lneto 
   8742  1.2    lneto 
   8743  1.2    lneto <h2>6.5 &ndash; <a name="6.5">UTF-8 Support</a></h2>
   8744  1.2    lneto 
   8745  1.2    lneto <p>
   8746  1.2    lneto This library provides basic support for UTF-8 encoding.
   8747  1.2    lneto It provides all its functions inside the table <a name="pdf-utf8"><code>utf8</code></a>.
   8748  1.2    lneto This library does not provide any support for Unicode other
   8749  1.2    lneto than the handling of the encoding.
   8750  1.2    lneto Any operation that needs the meaning of a character,
   8751  1.2    lneto such as character classification, is outside its scope.
   8752  1.2    lneto 
   8753  1.2    lneto 
   8754  1.2    lneto <p>
   8755  1.2    lneto Unless stated otherwise,
   8756  1.2    lneto all functions that expect a byte position as a parameter
   8757  1.2    lneto assume that the given position is either the start of a byte sequence
   8758  1.2    lneto or one plus the length of the subject string.
   8759  1.2    lneto As in the string library,
   8760  1.2    lneto negative indices count from the end of the string.
   8761  1.2    lneto 
   8762  1.2    lneto 
   8763  1.2    lneto <p>
   8764  1.2    lneto <hr><h3><a name="pdf-utf8.char"><code>utf8.char (&middot;&middot;&middot;)</code></a></h3>
   8765  1.2    lneto Receives zero or more integers,
   8766  1.2    lneto converts each one to its corresponding UTF-8 byte sequence
   8767  1.2    lneto and returns a string with the concatenation of all these sequences.
   8768  1.2    lneto 
   8769  1.2    lneto 
   8770  1.2    lneto 
   8771  1.2    lneto 
   8772  1.2    lneto <p>
   8773  1.3    lneto <hr><h3><a name="pdf-utf8.charpattern"><code>utf8.charpattern</code></a></h3>
   8774  1.2    lneto The pattern (a string, not a function) "<code>[\0-\x7F\xC2-\xF4][\x80-\xBF]*</code>"
   8775  1.2    lneto (see <a href="#6.4.1">&sect;6.4.1</a>),
   8776  1.2    lneto which matches exactly one UTF-8 byte sequence,
   8777  1.2    lneto assuming that the subject is a valid UTF-8 string.
   8778  1.2    lneto 
   8779  1.2    lneto 
   8780  1.2    lneto 
   8781  1.2    lneto 
   8782  1.2    lneto <p>
   8783  1.2    lneto <hr><h3><a name="pdf-utf8.codes"><code>utf8.codes (s)</code></a></h3>
   8784  1.2    lneto 
   8785  1.2    lneto 
   8786  1.2    lneto <p>
   8787  1.2    lneto Returns values so that the construction
   8788  1.2    lneto 
   8789  1.2    lneto <pre>
   8790  1.2    lneto      for p, c in utf8.codes(s) do <em>body</em> end
   8791  1.2    lneto </pre><p>
   8792  1.2    lneto will iterate over all characters in string <code>s</code>,
   8793  1.2    lneto with <code>p</code> being the position (in bytes) and <code>c</code> the code point
   8794  1.2    lneto of each character.
   8795  1.2    lneto It raises an error if it meets any invalid byte sequence.
   8796  1.2    lneto 
   8797  1.2    lneto 
   8798  1.2    lneto 
   8799  1.2    lneto 
   8800  1.2    lneto <p>
   8801  1.2    lneto <hr><h3><a name="pdf-utf8.codepoint"><code>utf8.codepoint (s [, i [, j]])</code></a></h3>
   8802  1.2    lneto Returns the codepoints (as integers) from all characters in <code>s</code>
   8803  1.2    lneto that start between byte position <code>i</code> and <code>j</code> (both included).
   8804  1.2    lneto The default for <code>i</code> is 1 and for <code>j</code> is <code>i</code>.
   8805  1.2    lneto It raises an error if it meets any invalid byte sequence.
   8806  1.2    lneto 
   8807  1.2    lneto 
   8808  1.2    lneto 
   8809  1.2    lneto 
   8810  1.2    lneto <p>
   8811  1.2    lneto <hr><h3><a name="pdf-utf8.len"><code>utf8.len (s [, i [, j]])</code></a></h3>
   8812  1.2    lneto Returns the number of UTF-8 characters in string <code>s</code>
   8813  1.3    lneto that start between positions <code>i</code> and <code>j</code> (both inclusive).
   8814  1.2    lneto The default for <code>i</code> is 1 and for <code>j</code> is -1.
   8815  1.2    lneto If it finds any invalid byte sequence,
   8816  1.3    lneto returns a false value plus the position of the first invalid byte. 
   8817  1.2    lneto 
   8818  1.2    lneto 
   8819  1.2    lneto 
   8820  1.2    lneto 
   8821  1.2    lneto <p>
   8822  1.2    lneto <hr><h3><a name="pdf-utf8.offset"><code>utf8.offset (s, n [, i])</code></a></h3>
   8823  1.2    lneto Returns the position (in bytes) where the encoding of the
   8824  1.2    lneto <code>n</code>-th character of <code>s</code>
   8825  1.2    lneto (counting from position <code>i</code>) starts.
   8826  1.2    lneto A negative <code>n</code> gets characters before position <code>i</code>.
   8827  1.2    lneto The default for <code>i</code> is 1 when <code>n</code> is non-negative
   8828  1.2    lneto and <code>#s + 1</code> otherwise,
   8829  1.2    lneto so that <code>utf8.offset(s, -n)</code> gets the offset of the
   8830  1.2    lneto <code>n</code>-th character from the end of the string.
   8831  1.3    lneto If the specified character is neither in the subject
   8832  1.3    lneto nor right after its end,
   8833  1.2    lneto the function returns <b>nil</b>.
   8834  1.2    lneto 
   8835  1.2    lneto 
   8836  1.2    lneto <p>
   8837  1.2    lneto As a special case,
   8838  1.2    lneto when <code>n</code> is 0 the function returns the start of the encoding
   8839  1.2    lneto of the character that contains the <code>i</code>-th byte of <code>s</code>.
   8840  1.2    lneto 
   8841  1.2    lneto 
   8842  1.1  mbalmer <p>
   8843  1.2    lneto This function assumes that <code>s</code> is a valid UTF-8 string.
   8844  1.1  mbalmer 
   8845  1.1  mbalmer 
   8846  1.1  mbalmer 
   8847  1.1  mbalmer 
   8848  1.1  mbalmer 
   8849  1.1  mbalmer 
   8850  1.1  mbalmer 
   8851  1.2    lneto <h2>6.6 &ndash; <a name="6.6">Table Manipulation</a></h2>
   8852  1.2    lneto 
   8853  1.2    lneto <p>
   8854  1.2    lneto This library provides generic functions for table manipulation.
   8855  1.2    lneto It provides all its functions inside the table <a name="pdf-table"><code>table</code></a>.
   8856  1.1  mbalmer 
   8857  1.1  mbalmer 
   8858  1.2    lneto <p>
   8859  1.2    lneto Remember that, whenever an operation needs the length of a table,
   8860  1.2    lneto the table must be a proper sequence
   8861  1.2    lneto or have a <code>__len</code> metamethod (see <a href="#3.4.7">&sect;3.4.7</a>).
   8862  1.2    lneto All functions ignore non-numeric keys
   8863  1.3    lneto in the tables given as arguments.
   8864  1.1  mbalmer 
   8865  1.1  mbalmer 
   8866  1.1  mbalmer <p>
   8867  1.2    lneto <hr><h3><a name="pdf-table.concat"><code>table.concat (list [, sep [, i [, j]]])</code></a></h3>
   8868  1.1  mbalmer 
   8869  1.1  mbalmer 
   8870  1.1  mbalmer <p>
   8871  1.2    lneto Given a list where all elements are strings or numbers,
   8872  1.2    lneto returns the string <code>list[i]..sep..list[i+1] &middot;&middot;&middot; sep..list[j]</code>.
   8873  1.1  mbalmer The default value for <code>sep</code> is the empty string,
   8874  1.1  mbalmer the default for <code>i</code> is 1,
   8875  1.2    lneto and the default for <code>j</code> is <code>#list</code>.
   8876  1.1  mbalmer If <code>i</code> is greater than <code>j</code>, returns the empty string.
   8877  1.1  mbalmer 
   8878  1.1  mbalmer 
   8879  1.1  mbalmer 
   8880  1.1  mbalmer 
   8881  1.1  mbalmer <p>
   8882  1.2    lneto <hr><h3><a name="pdf-table.insert"><code>table.insert (list, [pos,] value)</code></a></h3>
   8883  1.1  mbalmer 
   8884  1.1  mbalmer 
   8885  1.1  mbalmer <p>
   8886  1.2    lneto Inserts element <code>value</code> at position <code>pos</code> in <code>list</code>,
   8887  1.2    lneto shifting up the elements
   8888  1.2    lneto <code>list[pos], list[pos+1], &middot;&middot;&middot;, list[#list]</code>.
   8889  1.2    lneto The default value for <code>pos</code> is <code>#list+1</code>,
   8890  1.1  mbalmer so that a call <code>table.insert(t,x)</code> inserts <code>x</code> at the end
   8891  1.2    lneto of list <code>t</code>.
   8892  1.1  mbalmer 
   8893  1.1  mbalmer 
   8894  1.1  mbalmer 
   8895  1.1  mbalmer 
   8896  1.1  mbalmer <p>
   8897  1.3    lneto <hr><h3><a name="pdf-table.move"><code>table.move (a1, f, e, t [,a2])</code></a></h3>
   8898  1.3    lneto 
   8899  1.3    lneto 
   8900  1.3    lneto <p>
   8901  1.3    lneto Moves elements from table <code>a1</code> to table <code>a2</code>.
   8902  1.3    lneto This function performs the equivalent to the following
   8903  1.3    lneto multiple assignment:
   8904  1.3    lneto <code>a2[t],&middot;&middot;&middot; = a1[f],&middot;&middot;&middot;,a1[e]</code>.
   8905  1.3    lneto The default for <code>a2</code> is <code>a1</code>.
   8906  1.3    lneto The destination range can overlap with the source range.
   8907  1.3    lneto Index <code>f</code> must be positive.
   8908  1.3    lneto 
   8909  1.3    lneto 
   8910  1.3    lneto 
   8911  1.3    lneto 
   8912  1.3    lneto <p>
   8913  1.2    lneto <hr><h3><a name="pdf-table.pack"><code>table.pack (&middot;&middot;&middot;)</code></a></h3>
   8914  1.1  mbalmer 
   8915  1.1  mbalmer 
   8916  1.1  mbalmer <p>
   8917  1.2    lneto Returns a new table with all parameters stored into keys 1, 2, etc.
   8918  1.2    lneto and with a field "<code>n</code>" with the total number of parameters.
   8919  1.2    lneto Note that the resulting table may not be a sequence.
   8920  1.1  mbalmer 
   8921  1.1  mbalmer 
   8922  1.1  mbalmer 
   8923  1.1  mbalmer 
   8924  1.1  mbalmer <p>
   8925  1.2    lneto <hr><h3><a name="pdf-table.remove"><code>table.remove (list [, pos])</code></a></h3>
   8926  1.1  mbalmer 
   8927  1.1  mbalmer 
   8928  1.1  mbalmer <p>
   8929  1.2    lneto Removes from <code>list</code> the element at position <code>pos</code>,
   8930  1.2    lneto returning the value of the removed element.
   8931  1.2    lneto When <code>pos</code> is an integer between 1 and <code>#list</code>,
   8932  1.2    lneto it shifts down the elements
   8933  1.2    lneto <code>list[pos+1], list[pos+2], &middot;&middot;&middot;, list[#list]</code>
   8934  1.2    lneto and erases element <code>list[#list]</code>;
   8935  1.2    lneto The index <code>pos</code> can also be 0 when <code>#list</code> is 0,
   8936  1.2    lneto or <code>#list + 1</code>;
   8937  1.2    lneto in those cases, the function erases the element <code>list[pos]</code>.
   8938  1.2    lneto 
   8939  1.2    lneto 
   8940  1.2    lneto <p>
   8941  1.2    lneto The default value for <code>pos</code> is <code>#list</code>,
   8942  1.2    lneto so that a call <code>table.remove(l)</code> removes the last element
   8943  1.2    lneto of list <code>l</code>.
   8944  1.2    lneto 
   8945  1.1  mbalmer 
   8946  1.1  mbalmer 
   8947  1.1  mbalmer 
   8948  1.2    lneto <p>
   8949  1.2    lneto <hr><h3><a name="pdf-table.sort"><code>table.sort (list [, comp])</code></a></h3>
   8950  1.2    lneto 
   8951  1.1  mbalmer 
   8952  1.1  mbalmer <p>
   8953  1.2    lneto Sorts list elements in a given order, <em>in-place</em>,
   8954  1.2    lneto from <code>list[1]</code> to <code>list[#list]</code>.
   8955  1.1  mbalmer If <code>comp</code> is given,
   8956  1.2    lneto then it must be a function that receives two list elements
   8957  1.2    lneto and returns true when the first element must come
   8958  1.2    lneto before the second in the final order
   8959  1.2    lneto (so that <code>not comp(list[i+1],list[i])</code> will be true after the sort).
   8960  1.1  mbalmer If <code>comp</code> is not given,
   8961  1.1  mbalmer then the standard Lua operator <code>&lt;</code> is used instead.
   8962  1.1  mbalmer 
   8963  1.1  mbalmer 
   8964  1.1  mbalmer <p>
   8965  1.1  mbalmer The sort algorithm is not stable;
   8966  1.1  mbalmer that is, elements considered equal by the given order
   8967  1.1  mbalmer may have their relative positions changed by the sort.
   8968  1.1  mbalmer 
   8969  1.1  mbalmer 
   8970  1.1  mbalmer 
   8971  1.1  mbalmer 
   8972  1.2    lneto <p>
   8973  1.2    lneto <hr><h3><a name="pdf-table.unpack"><code>table.unpack (list [, i [, j]])</code></a></h3>
   8974  1.2    lneto 
   8975  1.2    lneto 
   8976  1.2    lneto <p>
   8977  1.2    lneto Returns the elements from the given list.
   8978  1.2    lneto This function is equivalent to
   8979  1.2    lneto 
   8980  1.2    lneto <pre>
   8981  1.2    lneto      return list[i], list[i+1], &middot;&middot;&middot;, list[j]
   8982  1.2    lneto </pre><p>
   8983  1.2    lneto By default, <code>i</code> is&nbsp;1 and <code>j</code> is <code>#list</code>.
   8984  1.2    lneto 
   8985  1.2    lneto 
   8986  1.2    lneto 
   8987  1.1  mbalmer 
   8988  1.1  mbalmer 
   8989  1.1  mbalmer 
   8990  1.2    lneto 
   8991  1.2    lneto <h2>6.7 &ndash; <a name="6.7">Mathematical Functions</a></h2>
   8992  1.1  mbalmer 
   8993  1.1  mbalmer <p>
   8994  1.2    lneto This library provides basic mathematical functions.
   8995  1.2    lneto It provides all its functions and constants inside the table <a name="pdf-math"><code>math</code></a>.
   8996  1.2    lneto Functions with the annotation "<code>integer/float</code>" give
   8997  1.2    lneto integer results for integer arguments
   8998  1.2    lneto and float results for float (or mixed) arguments.
   8999  1.2    lneto Rounding functions
   9000  1.2    lneto (<a href="#pdf-math.ceil"><code>math.ceil</code></a>, <a href="#pdf-math.floor"><code>math.floor</code></a>, and <a href="#pdf-math.modf"><code>math.modf</code></a>)
   9001  1.2    lneto return an integer when the result fits in the range of an integer,
   9002  1.3    lneto or a float otherwise.
   9003  1.1  mbalmer 
   9004  1.1  mbalmer 
   9005  1.1  mbalmer <p>
   9006  1.1  mbalmer <hr><h3><a name="pdf-math.abs"><code>math.abs (x)</code></a></h3>
   9007  1.1  mbalmer 
   9008  1.1  mbalmer 
   9009  1.1  mbalmer <p>
   9010  1.2    lneto Returns the absolute value of <code>x</code>. (integer/float)
   9011  1.1  mbalmer 
   9012  1.1  mbalmer 
   9013  1.1  mbalmer 
   9014  1.1  mbalmer 
   9015  1.1  mbalmer <p>
   9016  1.1  mbalmer <hr><h3><a name="pdf-math.acos"><code>math.acos (x)</code></a></h3>
   9017  1.1  mbalmer 
   9018  1.1  mbalmer 
   9019  1.1  mbalmer <p>
   9020  1.1  mbalmer Returns the arc cosine of <code>x</code> (in radians).
   9021  1.1  mbalmer 
   9022  1.1  mbalmer 
   9023  1.1  mbalmer 
   9024  1.1  mbalmer 
   9025  1.1  mbalmer <p>
   9026  1.1  mbalmer <hr><h3><a name="pdf-math.asin"><code>math.asin (x)</code></a></h3>
   9027  1.1  mbalmer 
   9028  1.1  mbalmer 
   9029  1.1  mbalmer <p>
   9030  1.1  mbalmer Returns the arc sine of <code>x</code> (in radians).
   9031  1.1  mbalmer 
   9032  1.1  mbalmer 
   9033  1.1  mbalmer 
   9034  1.1  mbalmer 
   9035  1.1  mbalmer <p>
   9036  1.2    lneto <hr><h3><a name="pdf-math.atan"><code>math.atan (y [, x])</code></a></h3>
   9037  1.1  mbalmer 
   9038  1.1  mbalmer 
   9039  1.1  mbalmer <p>
   9040  1.1  mbalmer 
   9041  1.1  mbalmer Returns the arc tangent of <code>y/x</code> (in radians),
   9042  1.1  mbalmer but uses the signs of both parameters to find the
   9043  1.1  mbalmer quadrant of the result.
   9044  1.1  mbalmer (It also handles correctly the case of <code>x</code> being zero.)
   9045  1.1  mbalmer 
   9046  1.1  mbalmer 
   9047  1.2    lneto <p>
   9048  1.2    lneto The default value for <code>x</code> is 1,
   9049  1.2    lneto so that the call <code>math.atan(y)</code>
   9050  1.2    lneto returns the arc tangent of <code>y</code>.
   9051  1.2    lneto 
   9052  1.2    lneto 
   9053  1.1  mbalmer 
   9054  1.1  mbalmer 
   9055  1.1  mbalmer <p>
   9056  1.1  mbalmer <hr><h3><a name="pdf-math.ceil"><code>math.ceil (x)</code></a></h3>
   9057  1.1  mbalmer 
   9058  1.1  mbalmer 
   9059  1.1  mbalmer <p>
   9060  1.3    lneto Returns the smallest integral value larger than or equal to <code>x</code>.
   9061  1.1  mbalmer 
   9062  1.1  mbalmer 
   9063  1.1  mbalmer 
   9064  1.1  mbalmer 
   9065  1.1  mbalmer <p>
   9066  1.1  mbalmer <hr><h3><a name="pdf-math.cos"><code>math.cos (x)</code></a></h3>
   9067  1.1  mbalmer 
   9068  1.1  mbalmer 
   9069  1.1  mbalmer <p>
   9070  1.1  mbalmer Returns the cosine of <code>x</code> (assumed to be in radians).
   9071  1.1  mbalmer 
   9072  1.1  mbalmer 
   9073  1.1  mbalmer 
   9074  1.1  mbalmer 
   9075  1.1  mbalmer <p>
   9076  1.1  mbalmer <hr><h3><a name="pdf-math.deg"><code>math.deg (x)</code></a></h3>
   9077  1.1  mbalmer 
   9078  1.1  mbalmer 
   9079  1.1  mbalmer <p>
   9080  1.2    lneto Converts the angle <code>x</code> from radians to degrees.
   9081  1.1  mbalmer 
   9082  1.1  mbalmer 
   9083  1.1  mbalmer 
   9084  1.1  mbalmer 
   9085  1.1  mbalmer <p>
   9086  1.3    lneto <hr><h3><a name="pdf-math.exp"><code>math.exp (x)</code></a></h3>
   9087  1.3    lneto 
   9088  1.3    lneto 
   9089  1.3    lneto <p>
   9090  1.3    lneto Returns the value <em>e<sup>x</sup></em>
   9091  1.3    lneto (where <code>e</code> is the base of natural logarithms).
   9092  1.3    lneto 
   9093  1.3    lneto 
   9094  1.3    lneto 
   9095  1.3    lneto 
   9096  1.3    lneto <p>
   9097  1.1  mbalmer <hr><h3><a name="pdf-math.floor"><code>math.floor (x)</code></a></h3>
   9098  1.1  mbalmer 
   9099  1.1  mbalmer 
   9100  1.1  mbalmer <p>
   9101  1.2    lneto Returns the largest integral value smaller than or equal to <code>x</code>.
   9102  1.1  mbalmer 
   9103  1.1  mbalmer 
   9104  1.1  mbalmer 
   9105  1.1  mbalmer 
   9106  1.1  mbalmer <p>
   9107  1.1  mbalmer <hr><h3><a name="pdf-math.fmod"><code>math.fmod (x, y)</code></a></h3>
   9108  1.1  mbalmer 
   9109  1.1  mbalmer 
   9110  1.1  mbalmer <p>
   9111  1.1  mbalmer Returns the remainder of the division of <code>x</code> by <code>y</code>
   9112  1.2    lneto that rounds the quotient towards zero. (integer/float)
   9113  1.1  mbalmer 
   9114  1.1  mbalmer 
   9115  1.1  mbalmer 
   9116  1.1  mbalmer 
   9117  1.1  mbalmer <p>
   9118  1.2    lneto <hr><h3><a name="pdf-math.huge"><code>math.huge</code></a></h3>
   9119  1.1  mbalmer 
   9120  1.1  mbalmer 
   9121  1.1  mbalmer <p>
   9122  1.2    lneto The float value <code>HUGE_VAL</code>,
   9123  1.2    lneto a value larger than any other numerical value.
   9124  1.1  mbalmer 
   9125  1.1  mbalmer 
   9126  1.1  mbalmer 
   9127  1.1  mbalmer 
   9128  1.1  mbalmer <p>
   9129  1.2    lneto <hr><h3><a name="pdf-math.log"><code>math.log (x [, base])</code></a></h3>
   9130  1.1  mbalmer 
   9131  1.1  mbalmer 
   9132  1.1  mbalmer <p>
   9133  1.2    lneto Returns the logarithm of <code>x</code> in the given base.
   9134  1.2    lneto The default for <code>base</code> is <em>e</em>
   9135  1.2    lneto (so that the function returns the natural logarithm of <code>x</code>).
   9136  1.1  mbalmer 
   9137  1.1  mbalmer 
   9138  1.1  mbalmer 
   9139  1.1  mbalmer 
   9140  1.1  mbalmer <p>
   9141  1.2    lneto <hr><h3><a name="pdf-math.max"><code>math.max (x, &middot;&middot;&middot;)</code></a></h3>
   9142  1.1  mbalmer 
   9143  1.1  mbalmer 
   9144  1.1  mbalmer <p>
   9145  1.2    lneto Returns the argument with the maximum value,
   9146  1.2    lneto according to the Lua operator <code>&lt;</code>. (integer/float)
   9147  1.1  mbalmer 
   9148  1.1  mbalmer 
   9149  1.1  mbalmer 
   9150  1.1  mbalmer 
   9151  1.1  mbalmer <p>
   9152  1.2    lneto <hr><h3><a name="pdf-math.maxinteger"><code>math.maxinteger</code></a></h3>
   9153  1.2    lneto An integer with the maximum value for an integer.
   9154  1.1  mbalmer 
   9155  1.1  mbalmer 
   9156  1.1  mbalmer 
   9157  1.1  mbalmer 
   9158  1.1  mbalmer <p>
   9159  1.2    lneto <hr><h3><a name="pdf-math.min"><code>math.min (x, &middot;&middot;&middot;)</code></a></h3>
   9160  1.1  mbalmer 
   9161  1.1  mbalmer 
   9162  1.1  mbalmer <p>
   9163  1.2    lneto Returns the argument with the minimum value,
   9164  1.2    lneto according to the Lua operator <code>&lt;</code>. (integer/float)
   9165  1.1  mbalmer 
   9166  1.1  mbalmer 
   9167  1.1  mbalmer 
   9168  1.1  mbalmer 
   9169  1.1  mbalmer <p>
   9170  1.2    lneto <hr><h3><a name="pdf-math.mininteger"><code>math.mininteger</code></a></h3>
   9171  1.2    lneto An integer with the minimum value for an integer.
   9172  1.1  mbalmer 
   9173  1.1  mbalmer 
   9174  1.1  mbalmer 
   9175  1.1  mbalmer 
   9176  1.1  mbalmer <p>
   9177  1.1  mbalmer <hr><h3><a name="pdf-math.modf"><code>math.modf (x)</code></a></h3>
   9178  1.1  mbalmer 
   9179  1.1  mbalmer 
   9180  1.1  mbalmer <p>
   9181  1.2    lneto Returns the integral part of <code>x</code> and the fractional part of <code>x</code>.
   9182  1.2    lneto Its second result is always a float.
   9183  1.1  mbalmer 
   9184  1.1  mbalmer 
   9185  1.1  mbalmer 
   9186  1.1  mbalmer 
   9187  1.1  mbalmer <p>
   9188  1.1  mbalmer <hr><h3><a name="pdf-math.pi"><code>math.pi</code></a></h3>
   9189  1.1  mbalmer 
   9190  1.1  mbalmer 
   9191  1.1  mbalmer <p>
   9192  1.2    lneto The value of <em>&pi;</em>.
   9193  1.1  mbalmer 
   9194  1.1  mbalmer 
   9195  1.1  mbalmer 
   9196  1.1  mbalmer 
   9197  1.1  mbalmer <p>
   9198  1.1  mbalmer <hr><h3><a name="pdf-math.rad"><code>math.rad (x)</code></a></h3>
   9199  1.1  mbalmer 
   9200  1.1  mbalmer 
   9201  1.1  mbalmer <p>
   9202  1.2    lneto Converts the angle <code>x</code> from degrees to radians.
   9203  1.1  mbalmer 
   9204  1.1  mbalmer 
   9205  1.1  mbalmer 
   9206  1.1  mbalmer 
   9207  1.1  mbalmer <p>
   9208  1.1  mbalmer <hr><h3><a name="pdf-math.random"><code>math.random ([m [, n]])</code></a></h3>
   9209  1.1  mbalmer 
   9210  1.1  mbalmer 
   9211  1.1  mbalmer <p>
   9212  1.2    lneto When called without arguments,
   9213  1.2    lneto returns a pseudo-random float with uniform distribution
   9214  1.2    lneto in the range  <em>[0,1)</em>.  
   9215  1.2    lneto When called with two integers <code>m</code> and <code>n</code>,
   9216  1.2    lneto <code>math.random</code> returns a pseudo-random integer
   9217  1.2    lneto with uniform distribution in the range <em>[m, n]</em>.
   9218  1.3    lneto (The value <em>m-n</em> cannot be negative and must fit in a Lua integer.)
   9219  1.2    lneto The call <code>math.random(n)</code> is equivalent to <code>math.random(1,n)</code>.
   9220  1.1  mbalmer 
   9221  1.1  mbalmer 
   9222  1.1  mbalmer <p>
   9223  1.2    lneto This function is an interface to the underling
   9224  1.2    lneto pseudo-random generator function provided by C.
   9225  1.2    lneto No guarantees can be given for its statistical properties.
   9226  1.1  mbalmer 
   9227  1.1  mbalmer 
   9228  1.1  mbalmer 
   9229  1.1  mbalmer 
   9230  1.1  mbalmer <p>
   9231  1.1  mbalmer <hr><h3><a name="pdf-math.randomseed"><code>math.randomseed (x)</code></a></h3>
   9232  1.1  mbalmer 
   9233  1.1  mbalmer 
   9234  1.1  mbalmer <p>
   9235  1.1  mbalmer Sets <code>x</code> as the "seed"
   9236  1.1  mbalmer for the pseudo-random generator:
   9237  1.1  mbalmer equal seeds produce equal sequences of numbers.
   9238  1.1  mbalmer 
   9239  1.1  mbalmer 
   9240  1.1  mbalmer 
   9241  1.1  mbalmer 
   9242  1.1  mbalmer <p>
   9243  1.1  mbalmer <hr><h3><a name="pdf-math.sin"><code>math.sin (x)</code></a></h3>
   9244  1.1  mbalmer 
   9245  1.1  mbalmer 
   9246  1.1  mbalmer <p>
   9247  1.1  mbalmer Returns the sine of <code>x</code> (assumed to be in radians).
   9248  1.1  mbalmer 
   9249  1.1  mbalmer 
   9250  1.1  mbalmer 
   9251  1.1  mbalmer 
   9252  1.1  mbalmer <p>
   9253  1.1  mbalmer <hr><h3><a name="pdf-math.sqrt"><code>math.sqrt (x)</code></a></h3>
   9254  1.1  mbalmer 
   9255  1.1  mbalmer 
   9256  1.1  mbalmer <p>
   9257  1.1  mbalmer Returns the square root of <code>x</code>.
   9258  1.1  mbalmer (You can also use the expression <code>x^0.5</code> to compute this value.)
   9259  1.1  mbalmer 
   9260  1.1  mbalmer 
   9261  1.1  mbalmer 
   9262  1.1  mbalmer 
   9263  1.1  mbalmer <p>
   9264  1.1  mbalmer <hr><h3><a name="pdf-math.tan"><code>math.tan (x)</code></a></h3>
   9265  1.1  mbalmer 
   9266  1.1  mbalmer 
   9267  1.1  mbalmer <p>
   9268  1.1  mbalmer Returns the tangent of <code>x</code> (assumed to be in radians).
   9269  1.1  mbalmer 
   9270  1.1  mbalmer 
   9271  1.1  mbalmer 
   9272  1.1  mbalmer 
   9273  1.1  mbalmer <p>
   9274  1.3    lneto <hr><h3><a name="pdf-math.tointeger"><code>math.tointeger (x)</code></a></h3>
   9275  1.3    lneto 
   9276  1.3    lneto 
   9277  1.3    lneto <p>
   9278  1.3    lneto If the value <code>x</code> is convertible to an integer,
   9279  1.3    lneto returns that integer.
   9280  1.3    lneto Otherwise, returns <b>nil</b>.
   9281  1.3    lneto 
   9282  1.3    lneto 
   9283  1.3    lneto 
   9284  1.3    lneto 
   9285  1.3    lneto <p>
   9286  1.2    lneto <hr><h3><a name="pdf-math.type"><code>math.type (x)</code></a></h3>
   9287  1.1  mbalmer 
   9288  1.1  mbalmer 
   9289  1.1  mbalmer <p>
   9290  1.2    lneto Returns "<code>integer</code>" if <code>x</code> is an integer,
   9291  1.2    lneto "<code>float</code>" if it is a float,
   9292  1.2    lneto or <b>nil</b> if <code>x</code> is not a number.
   9293  1.1  mbalmer 
   9294  1.1  mbalmer 
   9295  1.1  mbalmer 
   9296  1.1  mbalmer 
   9297  1.3    lneto <p>
   9298  1.3    lneto <hr><h3><a name="pdf-math.ult"><code>math.ult (m, n)</code></a></h3>
   9299  1.3    lneto 
   9300  1.3    lneto 
   9301  1.3    lneto <p>
   9302  1.3    lneto Returns a boolean,
   9303  1.3    lneto true if integer <code>m</code> is below integer <code>n</code> when
   9304  1.3    lneto they are compared as unsigned integers.
   9305  1.3    lneto 
   9306  1.3    lneto 
   9307  1.3    lneto 
   9308  1.3    lneto 
   9309  1.1  mbalmer 
   9310  1.1  mbalmer 
   9311  1.1  mbalmer 
   9312  1.2    lneto <h2>6.8 &ndash; <a name="6.8">Input and Output Facilities</a></h2>
   9313  1.1  mbalmer 
   9314  1.1  mbalmer <p>
   9315  1.1  mbalmer The I/O library provides two different styles for file manipulation.
   9316  1.2    lneto The first one uses implicit file handles;
   9317  1.1  mbalmer that is, there are operations to set a default input file and a
   9318  1.1  mbalmer default output file,
   9319  1.1  mbalmer and all input/output operations are over these default files.
   9320  1.2    lneto The second style uses explicit file handles.
   9321  1.1  mbalmer 
   9322  1.1  mbalmer 
   9323  1.1  mbalmer <p>
   9324  1.2    lneto When using implicit file handles,
   9325  1.1  mbalmer all operations are supplied by table <a name="pdf-io"><code>io</code></a>.
   9326  1.2    lneto When using explicit file handles,
   9327  1.2    lneto the operation <a href="#pdf-io.open"><code>io.open</code></a> returns a file handle
   9328  1.2    lneto and then all operations are supplied as methods of the file handle.
   9329  1.1  mbalmer 
   9330  1.1  mbalmer 
   9331  1.1  mbalmer <p>
   9332  1.1  mbalmer The table <code>io</code> also provides
   9333  1.2    lneto three predefined file handles with their usual meanings from C:
   9334  1.1  mbalmer <a name="pdf-io.stdin"><code>io.stdin</code></a>, <a name="pdf-io.stdout"><code>io.stdout</code></a>, and <a name="pdf-io.stderr"><code>io.stderr</code></a>.
   9335  1.1  mbalmer The I/O library never closes these files.
   9336  1.1  mbalmer 
   9337  1.1  mbalmer 
   9338  1.1  mbalmer <p>
   9339  1.1  mbalmer Unless otherwise stated,
   9340  1.1  mbalmer all I/O functions return <b>nil</b> on failure
   9341  1.1  mbalmer (plus an error message as a second result and
   9342  1.1  mbalmer a system-dependent error code as a third result)
   9343  1.1  mbalmer and some value different from <b>nil</b> on success.
   9344  1.2    lneto On non-POSIX systems,
   9345  1.2    lneto the computation of the error message and error code
   9346  1.2    lneto in case of errors
   9347  1.2    lneto may be not thread safe,
   9348  1.2    lneto because they rely on the global C variable <code>errno</code>.
   9349  1.1  mbalmer 
   9350  1.1  mbalmer 
   9351  1.1  mbalmer <p>
   9352  1.1  mbalmer <hr><h3><a name="pdf-io.close"><code>io.close ([file])</code></a></h3>
   9353  1.1  mbalmer 
   9354  1.1  mbalmer 
   9355  1.1  mbalmer <p>
   9356  1.1  mbalmer Equivalent to <code>file:close()</code>.
   9357  1.1  mbalmer Without a <code>file</code>, closes the default output file.
   9358  1.1  mbalmer 
   9359  1.1  mbalmer 
   9360  1.1  mbalmer 
   9361  1.1  mbalmer 
   9362  1.1  mbalmer <p>
   9363  1.1  mbalmer <hr><h3><a name="pdf-io.flush"><code>io.flush ()</code></a></h3>
   9364  1.1  mbalmer 
   9365  1.1  mbalmer 
   9366  1.1  mbalmer <p>
   9367  1.2    lneto Equivalent to <code>io.output():flush()</code>.
   9368  1.1  mbalmer 
   9369  1.1  mbalmer 
   9370  1.1  mbalmer 
   9371  1.1  mbalmer 
   9372  1.1  mbalmer <p>
   9373  1.1  mbalmer <hr><h3><a name="pdf-io.input"><code>io.input ([file])</code></a></h3>
   9374  1.1  mbalmer 
   9375  1.1  mbalmer 
   9376  1.1  mbalmer <p>
   9377  1.1  mbalmer When called with a file name, it opens the named file (in text mode),
   9378  1.1  mbalmer and sets its handle as the default input file.
   9379  1.1  mbalmer When called with a file handle,
   9380  1.1  mbalmer it simply sets this file handle as the default input file.
   9381  1.1  mbalmer When called without parameters,
   9382  1.1  mbalmer it returns the current default input file.
   9383  1.1  mbalmer 
   9384  1.1  mbalmer 
   9385  1.1  mbalmer <p>
   9386  1.1  mbalmer In case of errors this function raises the error,
   9387  1.1  mbalmer instead of returning an error code.
   9388  1.1  mbalmer 
   9389  1.1  mbalmer 
   9390  1.1  mbalmer 
   9391  1.1  mbalmer 
   9392  1.1  mbalmer <p>
   9393  1.2    lneto <hr><h3><a name="pdf-io.lines"><code>io.lines ([filename &middot;&middot;&middot;])</code></a></h3>
   9394  1.1  mbalmer 
   9395  1.1  mbalmer 
   9396  1.1  mbalmer <p>
   9397  1.1  mbalmer Opens the given file name in read mode
   9398  1.2    lneto and returns an iterator function that
   9399  1.2    lneto works like <code>file:lines(&middot;&middot;&middot;)</code> over the opened file.
   9400  1.1  mbalmer When the iterator function detects the end of file,
   9401  1.2    lneto it returns no values (to finish the loop) and automatically closes the file.
   9402  1.1  mbalmer 
   9403  1.1  mbalmer 
   9404  1.1  mbalmer <p>
   9405  1.1  mbalmer The call <code>io.lines()</code> (with no file name) is equivalent
   9406  1.2    lneto to <code>io.input():lines("*l")</code>;
   9407  1.1  mbalmer that is, it iterates over the lines of the default input file.
   9408  1.1  mbalmer In this case it does not close the file when the loop ends.
   9409  1.1  mbalmer 
   9410  1.1  mbalmer 
   9411  1.2    lneto <p>
   9412  1.2    lneto In case of errors this function raises the error,
   9413  1.2    lneto instead of returning an error code.
   9414  1.2    lneto 
   9415  1.2    lneto 
   9416  1.1  mbalmer 
   9417  1.1  mbalmer 
   9418  1.1  mbalmer <p>
   9419  1.1  mbalmer <hr><h3><a name="pdf-io.open"><code>io.open (filename [, mode])</code></a></h3>
   9420  1.1  mbalmer 
   9421  1.1  mbalmer 
   9422  1.1  mbalmer <p>
   9423  1.1  mbalmer This function opens a file,
   9424  1.1  mbalmer in the mode specified in the string <code>mode</code>.
   9425  1.1  mbalmer It returns a new file handle,
   9426  1.1  mbalmer or, in case of errors, <b>nil</b> plus an error message.
   9427  1.1  mbalmer 
   9428  1.1  mbalmer 
   9429  1.1  mbalmer <p>
   9430  1.1  mbalmer The <code>mode</code> string can be any of the following:
   9431  1.1  mbalmer 
   9432  1.1  mbalmer <ul>
   9433  1.2    lneto <li><b>"<code>r</code>": </b> read mode (the default);</li>
   9434  1.2    lneto <li><b>"<code>w</code>": </b> write mode;</li>
   9435  1.2    lneto <li><b>"<code>a</code>": </b> append mode;</li>
   9436  1.2    lneto <li><b>"<code>r+</code>": </b> update mode, all previous data is preserved;</li>
   9437  1.2    lneto <li><b>"<code>w+</code>": </b> update mode, all previous data is erased;</li>
   9438  1.2    lneto <li><b>"<code>a+</code>": </b> append update mode, previous data is preserved,
   9439  1.1  mbalmer   writing is only allowed at the end of file.</li>
   9440  1.1  mbalmer </ul><p>
   9441  1.1  mbalmer The <code>mode</code> string can also have a '<code>b</code>' at the end,
   9442  1.1  mbalmer which is needed in some systems to open the file in binary mode.
   9443  1.1  mbalmer 
   9444  1.1  mbalmer 
   9445  1.1  mbalmer 
   9446  1.1  mbalmer 
   9447  1.1  mbalmer <p>
   9448  1.1  mbalmer <hr><h3><a name="pdf-io.output"><code>io.output ([file])</code></a></h3>
   9449  1.1  mbalmer 
   9450  1.1  mbalmer 
   9451  1.1  mbalmer <p>
   9452  1.1  mbalmer Similar to <a href="#pdf-io.input"><code>io.input</code></a>, but operates over the default output file.
   9453  1.1  mbalmer 
   9454  1.1  mbalmer 
   9455  1.1  mbalmer 
   9456  1.1  mbalmer 
   9457  1.1  mbalmer <p>
   9458  1.1  mbalmer <hr><h3><a name="pdf-io.popen"><code>io.popen (prog [, mode])</code></a></h3>
   9459  1.1  mbalmer 
   9460  1.1  mbalmer 
   9461  1.1  mbalmer <p>
   9462  1.2    lneto This function is system dependent and is not available
   9463  1.2    lneto on all platforms.
   9464  1.2    lneto 
   9465  1.2    lneto 
   9466  1.2    lneto <p>
   9467  1.1  mbalmer Starts program <code>prog</code> in a separated process and returns
   9468  1.1  mbalmer a file handle that you can use to read data from this program
   9469  1.1  mbalmer (if <code>mode</code> is <code>"r"</code>, the default)
   9470  1.1  mbalmer or to write data to this program
   9471  1.1  mbalmer (if <code>mode</code> is <code>"w"</code>).
   9472  1.1  mbalmer 
   9473  1.1  mbalmer 
   9474  1.1  mbalmer 
   9475  1.1  mbalmer 
   9476  1.1  mbalmer <p>
   9477  1.1  mbalmer <hr><h3><a name="pdf-io.read"><code>io.read (&middot;&middot;&middot;)</code></a></h3>
   9478  1.1  mbalmer 
   9479  1.1  mbalmer 
   9480  1.1  mbalmer <p>
   9481  1.2    lneto Equivalent to <code>io.input():read(&middot;&middot;&middot;)</code>.
   9482  1.1  mbalmer 
   9483  1.1  mbalmer 
   9484  1.1  mbalmer 
   9485  1.1  mbalmer 
   9486  1.1  mbalmer <p>
   9487  1.1  mbalmer <hr><h3><a name="pdf-io.tmpfile"><code>io.tmpfile ()</code></a></h3>
   9488  1.1  mbalmer 
   9489  1.1  mbalmer 
   9490  1.1  mbalmer <p>
   9491  1.1  mbalmer Returns a handle for a temporary file.
   9492  1.1  mbalmer This file is opened in update mode
   9493  1.1  mbalmer and it is automatically removed when the program ends.
   9494  1.1  mbalmer 
   9495  1.1  mbalmer 
   9496  1.1  mbalmer 
   9497  1.1  mbalmer 
   9498  1.1  mbalmer <p>
   9499  1.1  mbalmer <hr><h3><a name="pdf-io.type"><code>io.type (obj)</code></a></h3>
   9500  1.1  mbalmer 
   9501  1.1  mbalmer 
   9502  1.1  mbalmer <p>
   9503  1.1  mbalmer Checks whether <code>obj</code> is a valid file handle.
   9504  1.1  mbalmer Returns the string <code>"file"</code> if <code>obj</code> is an open file handle,
   9505  1.1  mbalmer <code>"closed file"</code> if <code>obj</code> is a closed file handle,
   9506  1.1  mbalmer or <b>nil</b> if <code>obj</code> is not a file handle.
   9507  1.1  mbalmer 
   9508  1.1  mbalmer 
   9509  1.1  mbalmer 
   9510  1.1  mbalmer 
   9511  1.1  mbalmer <p>
   9512  1.1  mbalmer <hr><h3><a name="pdf-io.write"><code>io.write (&middot;&middot;&middot;)</code></a></h3>
   9513  1.1  mbalmer 
   9514  1.1  mbalmer 
   9515  1.1  mbalmer <p>
   9516  1.2    lneto Equivalent to <code>io.output():write(&middot;&middot;&middot;)</code>.
   9517  1.1  mbalmer 
   9518  1.1  mbalmer 
   9519  1.1  mbalmer 
   9520  1.1  mbalmer 
   9521  1.1  mbalmer <p>
   9522  1.1  mbalmer <hr><h3><a name="pdf-file:close"><code>file:close ()</code></a></h3>
   9523  1.1  mbalmer 
   9524  1.1  mbalmer 
   9525  1.1  mbalmer <p>
   9526  1.1  mbalmer Closes <code>file</code>.
   9527  1.1  mbalmer Note that files are automatically closed when
   9528  1.1  mbalmer their handles are garbage collected,
   9529  1.1  mbalmer but that takes an unpredictable amount of time to happen.
   9530  1.1  mbalmer 
   9531  1.1  mbalmer 
   9532  1.2    lneto <p>
   9533  1.2    lneto When closing a file handle created with <a href="#pdf-io.popen"><code>io.popen</code></a>,
   9534  1.2    lneto <a href="#pdf-file:close"><code>file:close</code></a> returns the same values
   9535  1.2    lneto returned by <a href="#pdf-os.execute"><code>os.execute</code></a>.
   9536  1.2    lneto 
   9537  1.2    lneto 
   9538  1.1  mbalmer 
   9539  1.1  mbalmer 
   9540  1.1  mbalmer <p>
   9541  1.1  mbalmer <hr><h3><a name="pdf-file:flush"><code>file:flush ()</code></a></h3>
   9542  1.1  mbalmer 
   9543  1.1  mbalmer 
   9544  1.1  mbalmer <p>
   9545  1.1  mbalmer Saves any written data to <code>file</code>.
   9546  1.1  mbalmer 
   9547  1.1  mbalmer 
   9548  1.1  mbalmer 
   9549  1.1  mbalmer 
   9550  1.1  mbalmer <p>
   9551  1.2    lneto <hr><h3><a name="pdf-file:lines"><code>file:lines (&middot;&middot;&middot;)</code></a></h3>
   9552  1.1  mbalmer 
   9553  1.1  mbalmer 
   9554  1.1  mbalmer <p>
   9555  1.1  mbalmer Returns an iterator function that,
   9556  1.1  mbalmer each time it is called,
   9557  1.2    lneto reads the file according to the given formats.
   9558  1.2    lneto When no format is given,
   9559  1.2    lneto uses "<code>l</code>" as a default.
   9560  1.2    lneto As an example, the construction
   9561  1.1  mbalmer 
   9562  1.1  mbalmer <pre>
   9563  1.2    lneto      for c in file:lines(1) do <em>body</em> end
   9564  1.2    lneto </pre><p>
   9565  1.2    lneto will iterate over all characters of the file,
   9566  1.2    lneto starting at the current position.
   9567  1.2    lneto Unlike <a href="#pdf-io.lines"><code>io.lines</code></a>, this function does not close the file
   9568  1.2    lneto when the loop ends.
   9569  1.2    lneto 
   9570  1.2    lneto 
   9571  1.2    lneto <p>
   9572  1.2    lneto In case of errors this function raises the error,
   9573  1.2    lneto instead of returning an error code.
   9574  1.1  mbalmer 
   9575  1.1  mbalmer 
   9576  1.1  mbalmer 
   9577  1.1  mbalmer 
   9578  1.1  mbalmer <p>
   9579  1.1  mbalmer <hr><h3><a name="pdf-file:read"><code>file:read (&middot;&middot;&middot;)</code></a></h3>
   9580  1.1  mbalmer 
   9581  1.1  mbalmer 
   9582  1.1  mbalmer <p>
   9583  1.1  mbalmer Reads the file <code>file</code>,
   9584  1.1  mbalmer according to the given formats, which specify what to read.
   9585  1.1  mbalmer For each format,
   9586  1.2    lneto the function returns a string or a number with the characters read,
   9587  1.1  mbalmer or <b>nil</b> if it cannot read data with the specified format.
   9588  1.3    lneto (In this latter case,
   9589  1.3    lneto the function does not read subsequent formats.)
   9590  1.1  mbalmer When called without formats,
   9591  1.2    lneto it uses a default format that reads the next line
   9592  1.1  mbalmer (see below).
   9593  1.1  mbalmer 
   9594  1.1  mbalmer 
   9595  1.1  mbalmer <p>
   9596  1.1  mbalmer The available formats are
   9597  1.1  mbalmer 
   9598  1.1  mbalmer <ul>
   9599  1.1  mbalmer 
   9600  1.2    lneto <li><b>"<code>n</code>": </b>
   9601  1.2    lneto reads a numeral and returns it as a float or an integer,
   9602  1.2    lneto following the lexical conventions of Lua.
   9603  1.2    lneto (The numeral may have leading spaces and a sign.)
   9604  1.2    lneto This format always reads the longest input sequence that
   9605  1.2    lneto is a valid prefix for a number;
   9606  1.2    lneto if that prefix does not form a valid number
   9607  1.2    lneto (e.g., an empty string, "<code>0x</code>", or "<code>3.4e-</code>"),
   9608  1.2    lneto it is discarded and the function returns <b>nil</b>.
   9609  1.2    lneto </li>
   9610  1.2    lneto 
   9611  1.2    lneto <li><b>"<code>i</code>": </b>
   9612  1.2    lneto reads an integral number and returns it as an integer.
   9613  1.1  mbalmer </li>
   9614  1.1  mbalmer 
   9615  1.2    lneto <li><b>"<code>a</code>": </b>
   9616  1.1  mbalmer reads the whole file, starting at the current position.
   9617  1.1  mbalmer On end of file, it returns the empty string.
   9618  1.1  mbalmer </li>
   9619  1.1  mbalmer 
   9620  1.2    lneto <li><b>"<code>l</code>": </b>
   9621  1.2    lneto reads the next line skipping the end of line,
   9622  1.1  mbalmer returning <b>nil</b> on end of file.
   9623  1.1  mbalmer This is the default format.
   9624  1.1  mbalmer </li>
   9625  1.1  mbalmer 
   9626  1.2    lneto <li><b>"<code>L</code>": </b>
   9627  1.2    lneto reads the next line keeping the end-of-line character (if present),
   9628  1.2    lneto returning <b>nil</b> on end of file.
   9629  1.2    lneto </li>
   9630  1.2    lneto 
   9631  1.2    lneto <li><b><em>number</em>: </b>
   9632  1.2    lneto reads a string with up to this number of bytes,
   9633  1.1  mbalmer returning <b>nil</b> on end of file.
   9634  1.2    lneto If <code>number</code> is zero,
   9635  1.1  mbalmer it reads nothing and returns an empty string,
   9636  1.1  mbalmer or <b>nil</b> on end of file.
   9637  1.1  mbalmer </li>
   9638  1.1  mbalmer 
   9639  1.2    lneto </ul><p>
   9640  1.2    lneto The formats "<code>l</code>" and "<code>L</code>" should be used only for text files.
   9641  1.2    lneto 
   9642  1.1  mbalmer 
   9643  1.1  mbalmer 
   9644  1.1  mbalmer 
   9645  1.1  mbalmer <p>
   9646  1.2    lneto <hr><h3><a name="pdf-file:seek"><code>file:seek ([whence [, offset]])</code></a></h3>
   9647  1.1  mbalmer 
   9648  1.1  mbalmer 
   9649  1.1  mbalmer <p>
   9650  1.1  mbalmer Sets and gets the file position,
   9651  1.1  mbalmer measured from the beginning of the file,
   9652  1.1  mbalmer to the position given by <code>offset</code> plus a base
   9653  1.1  mbalmer specified by the string <code>whence</code>, as follows:
   9654  1.1  mbalmer 
   9655  1.1  mbalmer <ul>
   9656  1.2    lneto <li><b>"<code>set</code>": </b> base is position 0 (beginning of the file);</li>
   9657  1.2    lneto <li><b>"<code>cur</code>": </b> base is current position;</li>
   9658  1.2    lneto <li><b>"<code>end</code>": </b> base is end of file;</li>
   9659  1.1  mbalmer </ul><p>
   9660  1.2    lneto In case of success, <code>seek</code> returns the final file position,
   9661  1.1  mbalmer measured in bytes from the beginning of the file.
   9662  1.2    lneto If <code>seek</code> fails, it returns <b>nil</b>,
   9663  1.1  mbalmer plus a string describing the error.
   9664  1.1  mbalmer 
   9665  1.1  mbalmer 
   9666  1.1  mbalmer <p>
   9667  1.1  mbalmer The default value for <code>whence</code> is <code>"cur"</code>,
   9668  1.1  mbalmer and for <code>offset</code> is 0.
   9669  1.1  mbalmer Therefore, the call <code>file:seek()</code> returns the current
   9670  1.1  mbalmer file position, without changing it;
   9671  1.1  mbalmer the call <code>file:seek("set")</code> sets the position to the
   9672  1.1  mbalmer beginning of the file (and returns 0);
   9673  1.1  mbalmer and the call <code>file:seek("end")</code> sets the position to the
   9674  1.1  mbalmer end of the file, and returns its size.
   9675  1.1  mbalmer 
   9676  1.1  mbalmer 
   9677  1.1  mbalmer 
   9678  1.1  mbalmer 
   9679  1.1  mbalmer <p>
   9680  1.1  mbalmer <hr><h3><a name="pdf-file:setvbuf"><code>file:setvbuf (mode [, size])</code></a></h3>
   9681  1.1  mbalmer 
   9682  1.1  mbalmer 
   9683  1.1  mbalmer <p>
   9684  1.1  mbalmer Sets the buffering mode for an output file.
   9685  1.1  mbalmer There are three available modes:
   9686  1.1  mbalmer 
   9687  1.1  mbalmer <ul>
   9688  1.1  mbalmer 
   9689  1.2    lneto <li><b>"<code>no</code>": </b>
   9690  1.1  mbalmer no buffering; the result of any output operation appears immediately.
   9691  1.1  mbalmer </li>
   9692  1.1  mbalmer 
   9693  1.2    lneto <li><b>"<code>full</code>": </b>
   9694  1.1  mbalmer full buffering; output operation is performed only
   9695  1.2    lneto when the buffer is full or when
   9696  1.2    lneto you explicitly <code>flush</code> the file (see <a href="#pdf-io.flush"><code>io.flush</code></a>).
   9697  1.1  mbalmer </li>
   9698  1.1  mbalmer 
   9699  1.2    lneto <li><b>"<code>line</code>": </b>
   9700  1.1  mbalmer line buffering; output is buffered until a newline is output
   9701  1.1  mbalmer or there is any input from some special files
   9702  1.1  mbalmer (such as a terminal device).
   9703  1.1  mbalmer </li>
   9704  1.1  mbalmer 
   9705  1.1  mbalmer </ul><p>
   9706  1.1  mbalmer For the last two cases, <code>size</code>
   9707  1.1  mbalmer specifies the size of the buffer, in bytes.
   9708  1.1  mbalmer The default is an appropriate size.
   9709  1.1  mbalmer 
   9710  1.1  mbalmer 
   9711  1.1  mbalmer 
   9712  1.1  mbalmer 
   9713  1.1  mbalmer <p>
   9714  1.1  mbalmer <hr><h3><a name="pdf-file:write"><code>file:write (&middot;&middot;&middot;)</code></a></h3>
   9715  1.1  mbalmer 
   9716  1.1  mbalmer 
   9717  1.1  mbalmer <p>
   9718  1.2    lneto Writes the value of each of its arguments to <code>file</code>.
   9719  1.1  mbalmer The arguments must be strings or numbers.
   9720  1.2    lneto 
   9721  1.2    lneto 
   9722  1.2    lneto <p>
   9723  1.2    lneto In case of success, this function returns <code>file</code>.
   9724  1.2    lneto Otherwise it returns <b>nil</b> plus a string describing the error.
   9725  1.1  mbalmer 
   9726  1.1  mbalmer 
   9727  1.1  mbalmer 
   9728  1.1  mbalmer 
   9729  1.1  mbalmer 
   9730  1.1  mbalmer 
   9731  1.1  mbalmer 
   9732  1.2    lneto <h2>6.9 &ndash; <a name="6.9">Operating System Facilities</a></h2>
   9733  1.1  mbalmer 
   9734  1.1  mbalmer <p>
   9735  1.1  mbalmer This library is implemented through table <a name="pdf-os"><code>os</code></a>.
   9736  1.1  mbalmer 
   9737  1.1  mbalmer 
   9738  1.1  mbalmer <p>
   9739  1.1  mbalmer <hr><h3><a name="pdf-os.clock"><code>os.clock ()</code></a></h3>
   9740  1.1  mbalmer 
   9741  1.1  mbalmer 
   9742  1.1  mbalmer <p>
   9743  1.1  mbalmer Returns an approximation of the amount in seconds of CPU time
   9744  1.1  mbalmer used by the program.
   9745  1.1  mbalmer 
   9746  1.1  mbalmer 
   9747  1.1  mbalmer 
   9748  1.1  mbalmer 
   9749  1.1  mbalmer <p>
   9750  1.1  mbalmer <hr><h3><a name="pdf-os.date"><code>os.date ([format [, time]])</code></a></h3>
   9751  1.1  mbalmer 
   9752  1.1  mbalmer 
   9753  1.1  mbalmer <p>
   9754  1.1  mbalmer Returns a string or a table containing date and time,
   9755  1.1  mbalmer formatted according to the given string <code>format</code>.
   9756  1.1  mbalmer 
   9757  1.1  mbalmer 
   9758  1.1  mbalmer <p>
   9759  1.1  mbalmer If the <code>time</code> argument is present,
   9760  1.1  mbalmer this is the time to be formatted
   9761  1.1  mbalmer (see the <a href="#pdf-os.time"><code>os.time</code></a> function for a description of this value).
   9762  1.1  mbalmer Otherwise, <code>date</code> formats the current time.
   9763  1.1  mbalmer 
   9764  1.1  mbalmer 
   9765  1.1  mbalmer <p>
   9766  1.1  mbalmer If <code>format</code> starts with '<code>!</code>',
   9767  1.1  mbalmer then the date is formatted in Coordinated Universal Time.
   9768  1.1  mbalmer After this optional character,
   9769  1.1  mbalmer if <code>format</code> is the string "<code>*t</code>",
   9770  1.1  mbalmer then <code>date</code> returns a table with the following fields:
   9771  1.2    lneto <code>year</code> (four digits), <code>month</code> (1&ndash;12), <code>day</code> (1&ndash;31),
   9772  1.2    lneto <code>hour</code> (0&ndash;23), <code>min</code> (0&ndash;59), <code>sec</code> (0&ndash;61),
   9773  1.1  mbalmer <code>wday</code> (weekday, Sunday is&nbsp;1),
   9774  1.1  mbalmer <code>yday</code> (day of the year),
   9775  1.1  mbalmer and <code>isdst</code> (daylight saving flag, a boolean).
   9776  1.2    lneto This last field may be absent
   9777  1.2    lneto if the information is not available.
   9778  1.1  mbalmer 
   9779  1.1  mbalmer 
   9780  1.1  mbalmer <p>
   9781  1.1  mbalmer If <code>format</code> is not "<code>*t</code>",
   9782  1.1  mbalmer then <code>date</code> returns the date as a string,
   9783  1.3    lneto formatted according to the same rules as the ISO&nbsp;C function <code>strftime</code>.
   9784  1.1  mbalmer 
   9785  1.1  mbalmer 
   9786  1.1  mbalmer <p>
   9787  1.1  mbalmer When called without arguments,
   9788  1.1  mbalmer <code>date</code> returns a reasonable date and time representation that depends on
   9789  1.1  mbalmer the host system and on the current locale
   9790  1.1  mbalmer (that is, <code>os.date()</code> is equivalent to <code>os.date("%c")</code>).
   9791  1.1  mbalmer 
   9792  1.1  mbalmer 
   9793  1.2    lneto <p>
   9794  1.2    lneto On non-POSIX systems,
   9795  1.2    lneto this function may be not thread safe
   9796  1.2    lneto because of its reliance on C&nbsp;function <code>gmtime</code> and C&nbsp;function <code>localtime</code>.
   9797  1.2    lneto 
   9798  1.2    lneto 
   9799  1.1  mbalmer 
   9800  1.1  mbalmer 
   9801  1.1  mbalmer <p>
   9802  1.1  mbalmer <hr><h3><a name="pdf-os.difftime"><code>os.difftime (t2, t1)</code></a></h3>
   9803  1.1  mbalmer 
   9804  1.1  mbalmer 
   9805  1.1  mbalmer <p>
   9806  1.3    lneto Returns the difference, in seconds,
   9807  1.3    lneto from time <code>t1</code> to time <code>t2</code>
   9808  1.3    lneto (where the times are values returned by <a href="#pdf-os.time"><code>os.time</code></a>).
   9809  1.1  mbalmer In POSIX, Windows, and some other systems,
   9810  1.1  mbalmer this value is exactly <code>t2</code><em>-</em><code>t1</code>.
   9811  1.1  mbalmer 
   9812  1.1  mbalmer 
   9813  1.1  mbalmer 
   9814  1.1  mbalmer 
   9815  1.1  mbalmer <p>
   9816  1.1  mbalmer <hr><h3><a name="pdf-os.execute"><code>os.execute ([command])</code></a></h3>
   9817  1.1  mbalmer 
   9818  1.1  mbalmer 
   9819  1.1  mbalmer <p>
   9820  1.3    lneto This function is equivalent to the ISO&nbsp;C function <code>system</code>.
   9821  1.1  mbalmer It passes <code>command</code> to be executed by an operating system shell.
   9822  1.2    lneto Its first result is <b>true</b>
   9823  1.2    lneto if the command terminated successfully,
   9824  1.2    lneto or <b>nil</b> otherwise.
   9825  1.2    lneto After this first result
   9826  1.2    lneto the function returns a string plus a number,
   9827  1.2    lneto as follows:
   9828  1.2    lneto 
   9829  1.2    lneto <ul>
   9830  1.2    lneto 
   9831  1.2    lneto <li><b>"<code>exit</code>": </b>
   9832  1.2    lneto the command terminated normally;
   9833  1.2    lneto the following number is the exit status of the command.
   9834  1.2    lneto </li>
   9835  1.2    lneto 
   9836  1.2    lneto <li><b>"<code>signal</code>": </b>
   9837  1.2    lneto the command was terminated by a signal;
   9838  1.2    lneto the following number is the signal that terminated the command.
   9839  1.2    lneto </li>
   9840  1.2    lneto 
   9841  1.2    lneto </ul>
   9842  1.2    lneto 
   9843  1.2    lneto <p>
   9844  1.2    lneto When called without a <code>command</code>,
   9845  1.2    lneto <code>os.execute</code> returns a boolean that is true if a shell is available.
   9846  1.2    lneto 
   9847  1.1  mbalmer 
   9848  1.1  mbalmer 
   9849  1.1  mbalmer 
   9850  1.2    lneto <p>
   9851  1.2    lneto <hr><h3><a name="pdf-os.exit"><code>os.exit ([code [, close]])</code></a></h3>
   9852  1.2    lneto 
   9853  1.1  mbalmer 
   9854  1.1  mbalmer <p>
   9855  1.3    lneto Calls the ISO&nbsp;C function <code>exit</code> to terminate the host program.
   9856  1.2    lneto If <code>code</code> is <b>true</b>,
   9857  1.2    lneto the returned status is <code>EXIT_SUCCESS</code>;
   9858  1.2    lneto if <code>code</code> is <b>false</b>,
   9859  1.2    lneto the returned status is <code>EXIT_FAILURE</code>;
   9860  1.2    lneto if <code>code</code> is a number,
   9861  1.2    lneto the returned status is this number.
   9862  1.2    lneto The default value for <code>code</code> is <b>true</b>.
   9863  1.1  mbalmer 
   9864  1.1  mbalmer 
   9865  1.1  mbalmer <p>
   9866  1.2    lneto If the optional second argument <code>close</code> is true,
   9867  1.2    lneto closes the Lua state before exiting.
   9868  1.1  mbalmer 
   9869  1.1  mbalmer 
   9870  1.1  mbalmer 
   9871  1.1  mbalmer 
   9872  1.1  mbalmer <p>
   9873  1.1  mbalmer <hr><h3><a name="pdf-os.getenv"><code>os.getenv (varname)</code></a></h3>
   9874  1.1  mbalmer 
   9875  1.1  mbalmer 
   9876  1.1  mbalmer <p>
   9877  1.1  mbalmer Returns the value of the process environment variable <code>varname</code>,
   9878  1.1  mbalmer or <b>nil</b> if the variable is not defined.
   9879  1.1  mbalmer 
   9880  1.1  mbalmer 
   9881  1.1  mbalmer 
   9882  1.1  mbalmer 
   9883  1.1  mbalmer <p>
   9884  1.1  mbalmer <hr><h3><a name="pdf-os.remove"><code>os.remove (filename)</code></a></h3>
   9885  1.1  mbalmer 
   9886  1.1  mbalmer 
   9887  1.1  mbalmer <p>
   9888  1.2    lneto Deletes the file (or empty directory, on POSIX systems)
   9889  1.2    lneto with the given name.
   9890  1.1  mbalmer If this function fails, it returns <b>nil</b>,
   9891  1.2    lneto plus a string describing the error and the error code.
   9892  1.1  mbalmer 
   9893  1.1  mbalmer 
   9894  1.1  mbalmer 
   9895  1.1  mbalmer 
   9896  1.1  mbalmer <p>
   9897  1.1  mbalmer <hr><h3><a name="pdf-os.rename"><code>os.rename (oldname, newname)</code></a></h3>
   9898  1.1  mbalmer 
   9899  1.1  mbalmer 
   9900  1.1  mbalmer <p>
   9901  1.1  mbalmer Renames file or directory named <code>oldname</code> to <code>newname</code>.
   9902  1.1  mbalmer If this function fails, it returns <b>nil</b>,
   9903  1.2    lneto plus a string describing the error and the error code.
   9904  1.1  mbalmer 
   9905  1.1  mbalmer 
   9906  1.1  mbalmer 
   9907  1.1  mbalmer 
   9908  1.1  mbalmer <p>
   9909  1.1  mbalmer <hr><h3><a name="pdf-os.setlocale"><code>os.setlocale (locale [, category])</code></a></h3>
   9910  1.1  mbalmer 
   9911  1.1  mbalmer 
   9912  1.1  mbalmer <p>
   9913  1.1  mbalmer Sets the current locale of the program.
   9914  1.2    lneto <code>locale</code> is a system-dependent string specifying a locale;
   9915  1.1  mbalmer <code>category</code> is an optional string describing which category to change:
   9916  1.1  mbalmer <code>"all"</code>, <code>"collate"</code>, <code>"ctype"</code>,
   9917  1.1  mbalmer <code>"monetary"</code>, <code>"numeric"</code>, or <code>"time"</code>;
   9918  1.1  mbalmer the default category is <code>"all"</code>.
   9919  1.1  mbalmer The function returns the name of the new locale,
   9920  1.1  mbalmer or <b>nil</b> if the request cannot be honored.
   9921  1.1  mbalmer 
   9922  1.1  mbalmer 
   9923  1.1  mbalmer <p>
   9924  1.1  mbalmer If <code>locale</code> is the empty string,
   9925  1.1  mbalmer the current locale is set to an implementation-defined native locale.
   9926  1.1  mbalmer If <code>locale</code> is the string "<code>C</code>",
   9927  1.1  mbalmer the current locale is set to the standard C locale.
   9928  1.1  mbalmer 
   9929  1.1  mbalmer 
   9930  1.1  mbalmer <p>
   9931  1.1  mbalmer When called with <b>nil</b> as the first argument,
   9932  1.1  mbalmer this function only returns the name of the current locale
   9933  1.1  mbalmer for the given category.
   9934  1.1  mbalmer 
   9935  1.1  mbalmer 
   9936  1.2    lneto <p>
   9937  1.2    lneto This function may be not thread safe
   9938  1.2    lneto because of its reliance on C&nbsp;function <code>setlocale</code>.
   9939  1.2    lneto 
   9940  1.2    lneto 
   9941  1.1  mbalmer 
   9942  1.1  mbalmer 
   9943  1.1  mbalmer <p>
   9944  1.1  mbalmer <hr><h3><a name="pdf-os.time"><code>os.time ([table])</code></a></h3>
   9945  1.1  mbalmer 
   9946  1.1  mbalmer 
   9947  1.1  mbalmer <p>
   9948  1.1  mbalmer Returns the current time when called without arguments,
   9949  1.1  mbalmer or a time representing the date and time specified by the given table.
   9950  1.1  mbalmer This table must have fields <code>year</code>, <code>month</code>, and <code>day</code>,
   9951  1.2    lneto and may have fields
   9952  1.2    lneto <code>hour</code> (default is 12),
   9953  1.2    lneto <code>min</code> (default is 0),
   9954  1.2    lneto <code>sec</code> (default is 0),
   9955  1.2    lneto and <code>isdst</code> (default is <b>nil</b>).
   9956  1.2    lneto For a description of these fields, see the <a href="#pdf-os.date"><code>os.date</code></a> function.
   9957  1.1  mbalmer 
   9958  1.1  mbalmer 
   9959  1.1  mbalmer <p>
   9960  1.1  mbalmer The returned value is a number, whose meaning depends on your system.
   9961  1.2    lneto In POSIX, Windows, and some other systems,
   9962  1.2    lneto this number counts the number
   9963  1.1  mbalmer of seconds since some given start time (the "epoch").
   9964  1.1  mbalmer In other systems, the meaning is not specified,
   9965  1.1  mbalmer and the number returned by <code>time</code> can be used only as an argument to
   9966  1.2    lneto <a href="#pdf-os.date"><code>os.date</code></a> and <a href="#pdf-os.difftime"><code>os.difftime</code></a>.
   9967  1.1  mbalmer 
   9968  1.1  mbalmer 
   9969  1.1  mbalmer 
   9970  1.1  mbalmer 
   9971  1.1  mbalmer <p>
   9972  1.1  mbalmer <hr><h3><a name="pdf-os.tmpname"><code>os.tmpname ()</code></a></h3>
   9973  1.1  mbalmer 
   9974  1.1  mbalmer 
   9975  1.1  mbalmer <p>
   9976  1.1  mbalmer Returns a string with a file name that can
   9977  1.1  mbalmer be used for a temporary file.
   9978  1.1  mbalmer The file must be explicitly opened before its use
   9979  1.1  mbalmer and explicitly removed when no longer needed.
   9980  1.1  mbalmer 
   9981  1.1  mbalmer 
   9982  1.1  mbalmer <p>
   9983  1.2    lneto On POSIX systems,
   9984  1.1  mbalmer this function also creates a file with that name,
   9985  1.1  mbalmer to avoid security risks.
   9986  1.1  mbalmer (Someone else might create the file with wrong permissions
   9987  1.1  mbalmer in the time between getting the name and creating the file.)
   9988  1.1  mbalmer You still have to open the file to use it
   9989  1.1  mbalmer and to remove it (even if you do not use it).
   9990  1.1  mbalmer 
   9991  1.1  mbalmer 
   9992  1.1  mbalmer <p>
   9993  1.1  mbalmer When possible,
   9994  1.1  mbalmer you may prefer to use <a href="#pdf-io.tmpfile"><code>io.tmpfile</code></a>,
   9995  1.1  mbalmer which automatically removes the file when the program ends.
   9996  1.1  mbalmer 
   9997  1.1  mbalmer 
   9998  1.1  mbalmer 
   9999  1.1  mbalmer 
   10000  1.1  mbalmer 
   10001  1.1  mbalmer 
   10002  1.1  mbalmer 
   10003  1.2    lneto <h2>6.10 &ndash; <a name="6.10">The Debug Library</a></h2>
   10004  1.1  mbalmer 
   10005  1.1  mbalmer <p>
   10006  1.1  mbalmer This library provides
   10007  1.2    lneto the functionality of the debug interface (<a href="#4.9">&sect;4.9</a>) to Lua programs.
   10008  1.1  mbalmer You should exert care when using this library.
   10009  1.2    lneto Several of its functions
   10010  1.2    lneto violate basic assumptions about Lua code
   10011  1.1  mbalmer (e.g., that variables local to a function
   10012  1.2    lneto cannot be accessed from outside;
   10013  1.2    lneto that userdata metatables cannot be changed by Lua code;
   10014  1.2    lneto that Lua programs do not crash)
   10015  1.1  mbalmer and therefore can compromise otherwise secure code.
   10016  1.2    lneto Moreover, some functions in this library may be slow.
   10017  1.1  mbalmer 
   10018  1.1  mbalmer 
   10019  1.1  mbalmer <p>
   10020  1.1  mbalmer All functions in this library are provided
   10021  1.1  mbalmer inside the <a name="pdf-debug"><code>debug</code></a> table.
   10022  1.1  mbalmer All functions that operate over a thread
   10023  1.1  mbalmer have an optional first argument which is the
   10024  1.1  mbalmer thread to operate over.
   10025  1.1  mbalmer The default is always the current thread.
   10026  1.1  mbalmer 
   10027  1.1  mbalmer 
   10028  1.1  mbalmer <p>
   10029  1.1  mbalmer <hr><h3><a name="pdf-debug.debug"><code>debug.debug ()</code></a></h3>
   10030  1.1  mbalmer 
   10031  1.1  mbalmer 
   10032  1.1  mbalmer <p>
   10033  1.1  mbalmer Enters an interactive mode with the user,
   10034  1.1  mbalmer running each string that the user enters.
   10035  1.1  mbalmer Using simple commands and other debug facilities,
   10036  1.1  mbalmer the user can inspect global and local variables,
   10037  1.1  mbalmer change their values, evaluate expressions, and so on.
   10038  1.1  mbalmer A line containing only the word <code>cont</code> finishes this function,
   10039  1.1  mbalmer so that the caller continues its execution.
   10040  1.1  mbalmer 
   10041  1.1  mbalmer 
   10042  1.1  mbalmer <p>
   10043  1.1  mbalmer Note that commands for <code>debug.debug</code> are not lexically nested
   10044  1.2    lneto within any function and so have no direct access to local variables.
   10045  1.1  mbalmer 
   10046  1.1  mbalmer 
   10047  1.1  mbalmer 
   10048  1.1  mbalmer 
   10049  1.1  mbalmer <p>
   10050  1.1  mbalmer <hr><h3><a name="pdf-debug.gethook"><code>debug.gethook ([thread])</code></a></h3>
   10051  1.1  mbalmer 
   10052  1.1  mbalmer 
   10053  1.1  mbalmer <p>
   10054  1.1  mbalmer Returns the current hook settings of the thread, as three values:
   10055  1.1  mbalmer the current hook function, the current hook mask,
   10056  1.1  mbalmer and the current hook count
   10057  1.1  mbalmer (as set by the <a href="#pdf-debug.sethook"><code>debug.sethook</code></a> function).
   10058  1.1  mbalmer 
   10059  1.1  mbalmer 
   10060  1.1  mbalmer 
   10061  1.1  mbalmer 
   10062  1.1  mbalmer <p>
   10063  1.2    lneto <hr><h3><a name="pdf-debug.getinfo"><code>debug.getinfo ([thread,] f [, what])</code></a></h3>
   10064  1.1  mbalmer 
   10065  1.1  mbalmer 
   10066  1.1  mbalmer <p>
   10067  1.1  mbalmer Returns a table with information about a function.
   10068  1.2    lneto You can give the function directly
   10069  1.2    lneto or you can give a number as the value of <code>f</code>,
   10070  1.2    lneto which means the function running at level <code>f</code> of the call stack
   10071  1.1  mbalmer of the given thread:
   10072  1.1  mbalmer level&nbsp;0 is the current function (<code>getinfo</code> itself);
   10073  1.2    lneto level&nbsp;1 is the function that called <code>getinfo</code>
   10074  1.2    lneto (except for tail calls, which do not count on the stack);
   10075  1.1  mbalmer and so on.
   10076  1.2    lneto If <code>f</code> is a number larger than the number of active functions,
   10077  1.1  mbalmer then <code>getinfo</code> returns <b>nil</b>.
   10078  1.1  mbalmer 
   10079  1.1  mbalmer 
   10080  1.1  mbalmer <p>
   10081  1.1  mbalmer The returned table can contain all the fields returned by <a href="#lua_getinfo"><code>lua_getinfo</code></a>,
   10082  1.1  mbalmer with the string <code>what</code> describing which fields to fill in.
   10083  1.1  mbalmer The default for <code>what</code> is to get all information available,
   10084  1.1  mbalmer except the table of valid lines.
   10085  1.1  mbalmer If present,
   10086  1.1  mbalmer the option '<code>f</code>'
   10087  1.1  mbalmer adds a field named <code>func</code> with the function itself.
   10088  1.1  mbalmer If present,
   10089  1.1  mbalmer the option '<code>L</code>'
   10090  1.1  mbalmer adds a field named <code>activelines</code> with the table of
   10091  1.1  mbalmer valid lines.
   10092  1.1  mbalmer 
   10093  1.1  mbalmer 
   10094  1.1  mbalmer <p>
   10095  1.1  mbalmer For instance, the expression <code>debug.getinfo(1,"n").name</code> returns
   10096  1.1  mbalmer a table with a name for the current function,
   10097  1.1  mbalmer if a reasonable name can be found,
   10098  1.1  mbalmer and the expression <code>debug.getinfo(print)</code>
   10099  1.1  mbalmer returns a table with all available information
   10100  1.1  mbalmer about the <a href="#pdf-print"><code>print</code></a> function.
   10101  1.1  mbalmer 
   10102  1.1  mbalmer 
   10103  1.1  mbalmer 
   10104  1.1  mbalmer 
   10105  1.1  mbalmer <p>
   10106  1.2    lneto <hr><h3><a name="pdf-debug.getlocal"><code>debug.getlocal ([thread,] f, local)</code></a></h3>
   10107  1.1  mbalmer 
   10108  1.1  mbalmer 
   10109  1.1  mbalmer <p>
   10110  1.1  mbalmer This function returns the name and the value of the local variable
   10111  1.2    lneto with index <code>local</code> of the function at level <code>f</code> of the stack.
   10112  1.2    lneto This function accesses not only explicit local variables,
   10113  1.2    lneto but also parameters, temporaries, etc.
   10114  1.2    lneto 
   10115  1.2    lneto 
   10116  1.2    lneto <p>
   10117  1.2    lneto The first parameter or local variable has index&nbsp;1, and so on,
   10118  1.3    lneto following the order that they are declared in the code,
   10119  1.3    lneto counting only the variables that are active
   10120  1.3    lneto in the current scope of the function.
   10121  1.2    lneto Negative indices refer to vararg parameters;
   10122  1.2    lneto -1 is the first vararg parameter.
   10123  1.2    lneto The function returns <b>nil</b> if there is no variable with the given index,
   10124  1.2    lneto and raises an error when called with a level out of range.
   10125  1.1  mbalmer (You can call <a href="#pdf-debug.getinfo"><code>debug.getinfo</code></a> to check whether the level is valid.)
   10126  1.1  mbalmer 
   10127  1.1  mbalmer 
   10128  1.1  mbalmer <p>
   10129  1.2    lneto Variable names starting with '<code>(</code>' (open parenthesis) 
   10130  1.2    lneto represent variables with no known names
   10131  1.3    lneto (internal variables such as loop control variables,
   10132  1.2    lneto and variables from chunks saved without debug information).
   10133  1.2    lneto 
   10134  1.2    lneto 
   10135  1.2    lneto <p>
   10136  1.2    lneto The parameter <code>f</code> may also be a function.
   10137  1.2    lneto In that case, <code>getlocal</code> returns only the name of function parameters.
   10138  1.1  mbalmer 
   10139  1.1  mbalmer 
   10140  1.1  mbalmer 
   10141  1.1  mbalmer 
   10142  1.1  mbalmer <p>
   10143  1.2    lneto <hr><h3><a name="pdf-debug.getmetatable"><code>debug.getmetatable (value)</code></a></h3>
   10144  1.1  mbalmer 
   10145  1.1  mbalmer 
   10146  1.1  mbalmer <p>
   10147  1.2    lneto Returns the metatable of the given <code>value</code>
   10148  1.1  mbalmer or <b>nil</b> if it does not have a metatable.
   10149  1.1  mbalmer 
   10150  1.1  mbalmer 
   10151  1.1  mbalmer 
   10152  1.1  mbalmer 
   10153  1.1  mbalmer <p>
   10154  1.1  mbalmer <hr><h3><a name="pdf-debug.getregistry"><code>debug.getregistry ()</code></a></h3>
   10155  1.1  mbalmer 
   10156  1.1  mbalmer 
   10157  1.1  mbalmer <p>
   10158  1.2    lneto Returns the registry table (see <a href="#4.5">&sect;4.5</a>).
   10159  1.1  mbalmer 
   10160  1.1  mbalmer 
   10161  1.1  mbalmer 
   10162  1.1  mbalmer 
   10163  1.1  mbalmer <p>
   10164  1.2    lneto <hr><h3><a name="pdf-debug.getupvalue"><code>debug.getupvalue (f, up)</code></a></h3>
   10165  1.1  mbalmer 
   10166  1.1  mbalmer 
   10167  1.1  mbalmer <p>
   10168  1.1  mbalmer This function returns the name and the value of the upvalue
   10169  1.2    lneto with index <code>up</code> of the function <code>f</code>.
   10170  1.1  mbalmer The function returns <b>nil</b> if there is no upvalue with the given index.
   10171  1.1  mbalmer 
   10172  1.1  mbalmer 
   10173  1.2    lneto <p>
   10174  1.2    lneto Variable names starting with '<code>(</code>' (open parenthesis) 
   10175  1.2    lneto represent variables with no known names
   10176  1.2    lneto (variables from chunks saved without debug information).
   10177  1.2    lneto 
   10178  1.2    lneto 
   10179  1.1  mbalmer 
   10180  1.1  mbalmer 
   10181  1.1  mbalmer <p>
   10182  1.2    lneto <hr><h3><a name="pdf-debug.getuservalue"><code>debug.getuservalue (u)</code></a></h3>
   10183  1.1  mbalmer 
   10184  1.1  mbalmer 
   10185  1.1  mbalmer <p>
   10186  1.2    lneto Returns the Lua value associated to <code>u</code>.
   10187  1.2    lneto If <code>u</code> is not a userdata,
   10188  1.2    lneto returns <b>nil</b>.
   10189  1.1  mbalmer 
   10190  1.1  mbalmer 
   10191  1.1  mbalmer 
   10192  1.1  mbalmer 
   10193  1.1  mbalmer <p>
   10194  1.1  mbalmer <hr><h3><a name="pdf-debug.sethook"><code>debug.sethook ([thread,] hook, mask [, count])</code></a></h3>
   10195  1.1  mbalmer 
   10196  1.1  mbalmer 
   10197  1.1  mbalmer <p>
   10198  1.1  mbalmer Sets the given function as a hook.
   10199  1.1  mbalmer The string <code>mask</code> and the number <code>count</code> describe
   10200  1.1  mbalmer when the hook will be called.
   10201  1.2    lneto The string mask may have any combination of the following characters,
   10202  1.1  mbalmer with the given meaning:
   10203  1.1  mbalmer 
   10204  1.1  mbalmer <ul>
   10205  1.2    lneto <li><b>'<code>c</code>': </b> the hook is called every time Lua calls a function;</li>
   10206  1.2    lneto <li><b>'<code>r</code>': </b> the hook is called every time Lua returns from a function;</li>
   10207  1.2    lneto <li><b>'<code>l</code>': </b> the hook is called every time Lua enters a new line of code.</li>
   10208  1.1  mbalmer </ul><p>
   10209  1.2    lneto Moreover,
   10210  1.2    lneto with a <code>count</code> different from zero,
   10211  1.2    lneto the hook is called also after every <code>count</code> instructions.
   10212  1.1  mbalmer 
   10213  1.1  mbalmer 
   10214  1.1  mbalmer <p>
   10215  1.1  mbalmer When called without arguments,
   10216  1.1  mbalmer <a href="#pdf-debug.sethook"><code>debug.sethook</code></a> turns off the hook.
   10217  1.1  mbalmer 
   10218  1.1  mbalmer 
   10219  1.1  mbalmer <p>
   10220  1.1  mbalmer When the hook is called, its first parameter is a string
   10221  1.1  mbalmer describing the event that has triggered its call:
   10222  1.2    lneto <code>"call"</code> (or <code>"tail call"</code>),
   10223  1.2    lneto <code>"return"</code>,
   10224  1.1  mbalmer <code>"line"</code>, and <code>"count"</code>.
   10225  1.1  mbalmer For line events,
   10226  1.1  mbalmer the hook also gets the new line number as its second parameter.
   10227  1.1  mbalmer Inside a hook,
   10228  1.1  mbalmer you can call <code>getinfo</code> with level&nbsp;2 to get more information about
   10229  1.1  mbalmer the running function
   10230  1.1  mbalmer (level&nbsp;0 is the <code>getinfo</code> function,
   10231  1.2    lneto and level&nbsp;1 is the hook function).
   10232  1.1  mbalmer 
   10233  1.1  mbalmer 
   10234  1.1  mbalmer 
   10235  1.1  mbalmer 
   10236  1.1  mbalmer <p>
   10237  1.1  mbalmer <hr><h3><a name="pdf-debug.setlocal"><code>debug.setlocal ([thread,] level, local, value)</code></a></h3>
   10238  1.1  mbalmer 
   10239  1.1  mbalmer 
   10240  1.1  mbalmer <p>
   10241  1.1  mbalmer This function assigns the value <code>value</code> to the local variable
   10242  1.1  mbalmer with index <code>local</code> of the function at level <code>level</code> of the stack.
   10243  1.1  mbalmer The function returns <b>nil</b> if there is no local
   10244  1.1  mbalmer variable with the given index,
   10245  1.1  mbalmer and raises an error when called with a <code>level</code> out of range.
   10246  1.1  mbalmer (You can call <code>getinfo</code> to check whether the level is valid.)
   10247  1.1  mbalmer Otherwise, it returns the name of the local variable.
   10248  1.1  mbalmer 
   10249  1.1  mbalmer 
   10250  1.2    lneto <p>
   10251  1.2    lneto See <a href="#pdf-debug.getlocal"><code>debug.getlocal</code></a> for more information about
   10252  1.2    lneto variable indices and names.
   10253  1.2    lneto 
   10254  1.2    lneto 
   10255  1.1  mbalmer 
   10256  1.1  mbalmer 
   10257  1.1  mbalmer <p>
   10258  1.2    lneto <hr><h3><a name="pdf-debug.setmetatable"><code>debug.setmetatable (value, table)</code></a></h3>
   10259  1.1  mbalmer 
   10260  1.1  mbalmer 
   10261  1.1  mbalmer <p>
   10262  1.2    lneto Sets the metatable for the given <code>value</code> to the given <code>table</code>
   10263  1.1  mbalmer (which can be <b>nil</b>).
   10264  1.2    lneto Returns <code>value</code>.
   10265  1.1  mbalmer 
   10266  1.1  mbalmer 
   10267  1.1  mbalmer 
   10268  1.1  mbalmer 
   10269  1.1  mbalmer <p>
   10270  1.2    lneto <hr><h3><a name="pdf-debug.setupvalue"><code>debug.setupvalue (f, up, value)</code></a></h3>
   10271  1.1  mbalmer 
   10272  1.1  mbalmer 
   10273  1.1  mbalmer <p>
   10274  1.1  mbalmer This function assigns the value <code>value</code> to the upvalue
   10275  1.2    lneto with index <code>up</code> of the function <code>f</code>.
   10276  1.1  mbalmer The function returns <b>nil</b> if there is no upvalue
   10277  1.1  mbalmer with the given index.
   10278  1.1  mbalmer Otherwise, it returns the name of the upvalue.
   10279  1.1  mbalmer 
   10280  1.1  mbalmer 
   10281  1.1  mbalmer 
   10282  1.1  mbalmer 
   10283  1.1  mbalmer <p>
   10284  1.2    lneto <hr><h3><a name="pdf-debug.setuservalue"><code>debug.setuservalue (udata, value)</code></a></h3>
   10285  1.2    lneto 
   10286  1.2    lneto 
   10287  1.2    lneto <p>
   10288  1.2    lneto Sets the given <code>value</code> as
   10289  1.2    lneto the Lua value associated to the given <code>udata</code>.
   10290  1.2    lneto <code>udata</code> must be a full userdata.
   10291  1.2    lneto 
   10292  1.2    lneto 
   10293  1.2    lneto <p>
   10294  1.2    lneto Returns <code>udata</code>.
   10295  1.2    lneto 
   10296  1.2    lneto 
   10297  1.2    lneto 
   10298  1.2    lneto 
   10299  1.2    lneto <p>
   10300  1.2    lneto <hr><h3><a name="pdf-debug.traceback"><code>debug.traceback ([thread,] [message [, level]])</code></a></h3>
   10301  1.1  mbalmer 
   10302  1.1  mbalmer 
   10303  1.1  mbalmer <p>
   10304  1.2    lneto If <code>message</code> is present but is neither a string nor <b>nil</b>,
   10305  1.2    lneto this function returns <code>message</code> without further processing.
   10306  1.2    lneto Otherwise,
   10307  1.2    lneto it returns a string with a traceback of the call stack.
   10308  1.3    lneto The optional <code>message</code> string is appended
   10309  1.1  mbalmer at the beginning of the traceback.
   10310  1.1  mbalmer An optional <code>level</code> number tells at which level
   10311  1.1  mbalmer to start the traceback
   10312  1.1  mbalmer (default is 1, the function calling <code>traceback</code>).
   10313  1.1  mbalmer 
   10314  1.1  mbalmer 
   10315  1.1  mbalmer 
   10316  1.1  mbalmer 
   10317  1.2    lneto <p>
   10318  1.2    lneto <hr><h3><a name="pdf-debug.upvalueid"><code>debug.upvalueid (f, n)</code></a></h3>
   10319  1.2    lneto 
   10320  1.2    lneto 
   10321  1.2    lneto <p>
   10322  1.3    lneto Returns a unique identifier (as a light userdata)
   10323  1.2    lneto for the upvalue numbered <code>n</code>
   10324  1.2    lneto from the given function.
   10325  1.2    lneto 
   10326  1.2    lneto 
   10327  1.2    lneto <p>
   10328  1.2    lneto These unique identifiers allow a program to check whether different
   10329  1.2    lneto closures share upvalues.
   10330  1.2    lneto Lua closures that share an upvalue
   10331  1.2    lneto (that is, that access a same external local variable)
   10332  1.2    lneto will return identical ids for those upvalue indices.
   10333  1.2    lneto 
   10334  1.2    lneto 
   10335  1.2    lneto 
   10336  1.2    lneto 
   10337  1.2    lneto <p>
   10338  1.2    lneto <hr><h3><a name="pdf-debug.upvaluejoin"><code>debug.upvaluejoin (f1, n1, f2, n2)</code></a></h3>
   10339  1.2    lneto 
   10340  1.2    lneto 
   10341  1.2    lneto <p>
   10342  1.2    lneto Make the <code>n1</code>-th upvalue of the Lua closure <code>f1</code>
   10343  1.2    lneto refer to the <code>n2</code>-th upvalue of the Lua closure <code>f2</code>.
   10344  1.2    lneto 
   10345  1.2    lneto 
   10346  1.2    lneto 
   10347  1.2    lneto 
   10348  1.1  mbalmer 
   10349  1.1  mbalmer 
   10350  1.1  mbalmer 
   10351  1.2    lneto <h1>7 &ndash; <a name="7">Lua Standalone</a></h1>
   10352  1.1  mbalmer 
   10353  1.1  mbalmer <p>
   10354  1.1  mbalmer Although Lua has been designed as an extension language,
   10355  1.1  mbalmer to be embedded in a host C&nbsp;program,
   10356  1.2    lneto it is also frequently used as a standalone language.
   10357  1.2    lneto An interpreter for Lua as a standalone language,
   10358  1.1  mbalmer called simply <code>lua</code>,
   10359  1.1  mbalmer is provided with the standard distribution.
   10360  1.2    lneto The standalone interpreter includes
   10361  1.1  mbalmer all standard libraries, including the debug library.
   10362  1.1  mbalmer Its usage is:
   10363  1.1  mbalmer 
   10364  1.1  mbalmer <pre>
   10365  1.1  mbalmer      lua [options] [script [args]]
   10366  1.1  mbalmer </pre><p>
   10367  1.1  mbalmer The options are:
   10368  1.1  mbalmer 
   10369  1.1  mbalmer <ul>
   10370  1.2    lneto <li><b><code>-e <em>stat</em></code>: </b> executes string <em>stat</em>;</li>
   10371  1.2    lneto <li><b><code>-l <em>mod</em></code>: </b> "requires" <em>mod</em>;</li>
   10372  1.2    lneto <li><b><code>-i</code>: </b> enters interactive mode after running <em>script</em>;</li>
   10373  1.2    lneto <li><b><code>-v</code>: </b> prints version information;</li>
   10374  1.2    lneto <li><b><code>-E</code>: </b> ignores environment variables;</li>
   10375  1.2    lneto <li><b><code>--</code>: </b> stops handling options;</li>
   10376  1.2    lneto <li><b><code>-</code>: </b> executes <code>stdin</code> as a file and stops handling options.</li>
   10377  1.1  mbalmer </ul><p>
   10378  1.3    lneto After handling its options, <code>lua</code> runs the given <em>script</em>.
   10379  1.1  mbalmer When called without arguments,
   10380  1.1  mbalmer <code>lua</code> behaves as <code>lua -v -i</code>
   10381  1.1  mbalmer when the standard input (<code>stdin</code>) is a terminal,
   10382  1.1  mbalmer and as <code>lua -</code> otherwise.
   10383  1.1  mbalmer 
   10384  1.1  mbalmer 
   10385  1.1  mbalmer <p>
   10386  1.2    lneto When called without option <code>-E</code>, 
   10387  1.2    lneto the interpreter checks for an environment variable <a name="pdf-LUA_INIT_5_3"><code>LUA_INIT_5_3</code></a>
   10388  1.3    lneto (or <a name="pdf-LUA_INIT"><code>LUA_INIT</code></a> if the versioned name is not defined)
   10389  1.2    lneto before running any argument.
   10390  1.2    lneto If the variable content has the format <code>@<em>filename</em></code>,
   10391  1.1  mbalmer then <code>lua</code> executes the file.
   10392  1.1  mbalmer Otherwise, <code>lua</code> executes the string itself.
   10393  1.1  mbalmer 
   10394  1.1  mbalmer 
   10395  1.1  mbalmer <p>
   10396  1.2    lneto When called with option <code>-E</code>,
   10397  1.2    lneto besides ignoring <code>LUA_INIT</code>,
   10398  1.2    lneto Lua also ignores
   10399  1.2    lneto the values of <code>LUA_PATH</code> and <code>LUA_CPATH</code>,
   10400  1.2    lneto setting the values of
   10401  1.2    lneto <a href="#pdf-package.path"><code>package.path</code></a> and <a href="#pdf-package.cpath"><code>package.cpath</code></a>
   10402  1.2    lneto with the default paths defined in <code>luaconf.h</code>.
   10403  1.2    lneto 
   10404  1.2    lneto 
   10405  1.2    lneto <p>
   10406  1.2    lneto All options are handled in order, except <code>-i</code> and <code>-E</code>.
   10407  1.1  mbalmer For instance, an invocation like
   10408  1.1  mbalmer 
   10409  1.1  mbalmer <pre>
   10410  1.1  mbalmer      $ lua -e'a=1' -e 'print(a)' script.lua
   10411  1.1  mbalmer </pre><p>
   10412  1.2    lneto will first set <code>a</code> to 1, then print the value of <code>a</code>,
   10413  1.1  mbalmer and finally run the file <code>script.lua</code> with no arguments.
   10414  1.1  mbalmer (Here <code>$</code> is the shell prompt. Your prompt may be different.)
   10415  1.1  mbalmer 
   10416  1.1  mbalmer 
   10417  1.1  mbalmer <p>
   10418  1.2    lneto Before running any code,
   10419  1.2    lneto <code>lua</code> collects all command-line arguments
   10420  1.1  mbalmer in a global table called <code>arg</code>.
   10421  1.2    lneto The script name goes to index 0,
   10422  1.1  mbalmer the first argument after the script name goes to index 1,
   10423  1.1  mbalmer and so on.
   10424  1.1  mbalmer Any arguments before the script name
   10425  1.2    lneto (that is, the interpreter name plus its options)
   10426  1.1  mbalmer go to negative indices.
   10427  1.1  mbalmer For instance, in the call
   10428  1.1  mbalmer 
   10429  1.1  mbalmer <pre>
   10430  1.1  mbalmer      $ lua -la b.lua t1 t2
   10431  1.1  mbalmer </pre><p>
   10432  1.2    lneto the table is like this:
   10433  1.1  mbalmer 
   10434  1.1  mbalmer <pre>
   10435  1.1  mbalmer      arg = { [-2] = "lua", [-1] = "-la",
   10436  1.1  mbalmer              [0] = "b.lua",
   10437  1.1  mbalmer              [1] = "t1", [2] = "t2" }
   10438  1.1  mbalmer </pre><p>
   10439  1.2    lneto If there is no script in the call,
   10440  1.2    lneto the interpreter name goes to index 0,
   10441  1.2    lneto followed by the other arguments.
   10442  1.2    lneto For instance, the call
   10443  1.2    lneto 
   10444  1.2    lneto <pre>
   10445  1.2    lneto      $ lua -e "print(arg[1])"
   10446  1.2    lneto </pre><p>
   10447  1.2    lneto will print "<code>-e</code>".
   10448  1.3    lneto If there is a script,
   10449  1.3    lneto the script is called with parameters
   10450  1.3    lneto <code>arg[1]</code>, &middot;&middot;&middot;, <code>arg[#arg]</code>.
   10451  1.3    lneto (Like all chunks in Lua,
   10452  1.3    lneto the script is compiled as a vararg function.)
   10453  1.1  mbalmer 
   10454  1.1  mbalmer 
   10455  1.1  mbalmer <p>
   10456  1.1  mbalmer In interactive mode,
   10457  1.2    lneto Lua repeatedly prompts and waits for a line.
   10458  1.2    lneto After reading a line,
   10459  1.2    lneto Lua first try to interpret the line as an expression.
   10460  1.2    lneto If it succeeds, it prints its value.
   10461  1.2    lneto Otherwise, it interprets the line as a statement.
   10462  1.2    lneto If you write an incomplete statement,
   10463  1.1  mbalmer the interpreter waits for its completion
   10464  1.1  mbalmer by issuing a different prompt.
   10465  1.1  mbalmer 
   10466  1.1  mbalmer 
   10467  1.1  mbalmer <p>
   10468  1.2    lneto In case of unprotected errors in the script,
   10469  1.2    lneto the interpreter reports the error to the standard error stream.
   10470  1.3    lneto If the error object is not a string but 
   10471  1.3    lneto has a metamethod <code>__tostring</code>,
   10472  1.2    lneto the interpreter calls this metamethod to produce the final message.
   10473  1.3    lneto Otherwise, the interpreter converts the error object to a string
   10474  1.3    lneto and adds a stack traceback to it.
   10475  1.2    lneto 
   10476  1.2    lneto 
   10477  1.2    lneto <p>
   10478  1.2    lneto When finishing normally,
   10479  1.2    lneto the interpreter closes its main Lua state
   10480  1.2    lneto (see <a href="#lua_close"><code>lua_close</code></a>).
   10481  1.2    lneto The script can avoid this step by
   10482  1.2    lneto calling <a href="#pdf-os.exit"><code>os.exit</code></a> to terminate.
   10483  1.1  mbalmer 
   10484  1.1  mbalmer 
   10485  1.1  mbalmer <p>
   10486  1.1  mbalmer To allow the use of Lua as a
   10487  1.1  mbalmer script interpreter in Unix systems,
   10488  1.2    lneto the standalone interpreter skips
   10489  1.1  mbalmer the first line of a chunk if it starts with <code>#</code>.
   10490  1.1  mbalmer Therefore, Lua scripts can be made into executable programs
   10491  1.1  mbalmer by using <code>chmod +x</code> and the&nbsp;<code>#!</code> form,
   10492  1.1  mbalmer as in
   10493  1.1  mbalmer 
   10494  1.1  mbalmer <pre>
   10495  1.1  mbalmer      #!/usr/local/bin/lua
   10496  1.1  mbalmer </pre><p>
   10497  1.1  mbalmer (Of course,
   10498  1.1  mbalmer the location of the Lua interpreter may be different in your machine.
   10499  1.1  mbalmer If <code>lua</code> is in your <code>PATH</code>,
   10500  1.2    lneto then
   10501  1.1  mbalmer 
   10502  1.1  mbalmer <pre>
   10503  1.1  mbalmer      #!/usr/bin/env lua
   10504  1.1  mbalmer </pre><p>
   10505  1.2    lneto is a more portable solution.)
   10506  1.1  mbalmer 
   10507  1.1  mbalmer 
   10508  1.1  mbalmer 
   10509  1.2    lneto <h1>8 &ndash; <a name="8">Incompatibilities with the Previous Version</a></h1>
   10510  1.1  mbalmer 
   10511  1.1  mbalmer <p>
   10512  1.1  mbalmer Here we list the incompatibilities that you may find when moving a program
   10513  1.2    lneto from Lua&nbsp;5.2 to Lua&nbsp;5.3.
   10514  1.2    lneto You can avoid some incompatibilities by compiling Lua with
   10515  1.1  mbalmer appropriate options (see file <code>luaconf.h</code>).
   10516  1.1  mbalmer However,
   10517  1.2    lneto all these compatibility options will be removed in the future.
   10518  1.1  mbalmer 
   10519  1.1  mbalmer 
   10520  1.2    lneto <p>
   10521  1.2    lneto Lua versions can always change the C API in ways that
   10522  1.2    lneto do not imply source-code changes in a program,
   10523  1.2    lneto such as the numeric values for constants
   10524  1.2    lneto or the implementation of functions as macros.
   10525  1.2    lneto Therefore,
   10526  1.3    lneto you should not assume that binaries are compatible between
   10527  1.2    lneto different Lua versions.
   10528  1.2    lneto Always recompile clients of the Lua API when
   10529  1.2    lneto using a new version.
   10530  1.1  mbalmer 
   10531  1.1  mbalmer 
   10532  1.2    lneto <p>
   10533  1.2    lneto Similarly, Lua versions can always change the internal representation
   10534  1.2    lneto of precompiled chunks;
   10535  1.3    lneto precompiled chunks are not compatible between different Lua versions.
   10536  1.1  mbalmer 
   10537  1.1  mbalmer 
   10538  1.2    lneto <p>
   10539  1.2    lneto The standard paths in the official distribution may
   10540  1.2    lneto change between versions.
   10541  1.1  mbalmer 
   10542  1.1  mbalmer 
   10543  1.1  mbalmer 
   10544  1.2    lneto <h2>8.1 &ndash; <a name="8.1">Changes in the Language</a></h2>
   10545  1.1  mbalmer <ul>
   10546  1.1  mbalmer 
   10547  1.1  mbalmer <li>
   10548  1.2    lneto The main difference between Lua&nbsp;5.2 and Lua&nbsp;5.3 is the
   10549  1.2    lneto introduction of an integer subtype for numbers.
   10550  1.2    lneto Although this change should not affect "normal" computations,
   10551  1.2    lneto some computations
   10552  1.2    lneto (mainly those that involve some kind of overflow)
   10553  1.2    lneto can give different results.
   10554  1.2    lneto 
   10555  1.1  mbalmer 
   10556  1.2    lneto <p>
   10557  1.2    lneto You can fix these differences by forcing a number to be a float
   10558  1.2    lneto (in Lua&nbsp;5.2 all numbers were float),
   10559  1.2    lneto in particular writing constants with an ending <code>.0</code>
   10560  1.2    lneto or using <code>x = x + 0.0</code> to convert a variable.
   10561  1.2    lneto (This recommendation is only for a quick fix
   10562  1.2    lneto for an occasional incompatibility;
   10563  1.2    lneto it is not a general guideline for good programming.
   10564  1.2    lneto For good programming,
   10565  1.2    lneto use floats where you need floats
   10566  1.2    lneto and integers where you need integers.)
   10567  1.1  mbalmer </li>
   10568  1.1  mbalmer 
   10569  1.1  mbalmer <li>
   10570  1.2    lneto The conversion of a float to a string now adds a <code>.0</code> suffix
   10571  1.2    lneto to the result if it looks like an integer.
   10572  1.2    lneto (For instance, the float 2.0 will be printed as <code>2.0</code>,
   10573  1.2    lneto not as <code>2</code>.)
   10574  1.2    lneto You should always use an explicit format
   10575  1.2    lneto when you need a specific format for numbers.
   10576  1.1  mbalmer 
   10577  1.1  mbalmer 
   10578  1.2    lneto <p>
   10579  1.2    lneto (Formally this is not an incompatibility,
   10580  1.2    lneto because Lua does not specify how numbers are formatted as strings,
   10581  1.2    lneto but some programs assumed a specific format.)
   10582  1.1  mbalmer </li>
   10583  1.1  mbalmer 
   10584  1.1  mbalmer <li>
   10585  1.2    lneto The generational mode for the garbage collector was removed.
   10586  1.2    lneto (It was an experimental feature in Lua&nbsp;5.2.)
   10587  1.1  mbalmer </li>
   10588  1.1  mbalmer 
   10589  1.1  mbalmer </ul>
   10590  1.1  mbalmer 
   10591  1.1  mbalmer 
   10592  1.1  mbalmer 
   10593  1.1  mbalmer 
   10594  1.2    lneto <h2>8.2 &ndash; <a name="8.2">Changes in the Libraries</a></h2>
   10595  1.1  mbalmer <ul>
   10596  1.1  mbalmer 
   10597  1.1  mbalmer <li>
   10598  1.2    lneto The <code>bit32</code> library has been deprecated.
   10599  1.2    lneto It is easy to require a compatible external library or,
   10600  1.2    lneto better yet, to replace its functions with appropriate bitwise operations.
   10601  1.2    lneto (Keep in mind that <code>bit32</code> operates on 32-bit integers,
   10602  1.3    lneto while the bitwise operators in standard Lua operate on 64-bit integers.)
   10603  1.3    lneto </li>
   10604  1.3    lneto 
   10605  1.3    lneto <li>
   10606  1.3    lneto The Table library now respects metamethods
   10607  1.3    lneto for setting and getting elements.
   10608  1.3    lneto </li>
   10609  1.3    lneto 
   10610  1.3    lneto <li>
   10611  1.3    lneto The <a href="#pdf-ipairs"><code>ipairs</code></a> iterator now respects metamethods and
   10612  1.3    lneto its <code>__ipairs</code> metamethod has been deprecated.
   10613  1.1  mbalmer </li>
   10614  1.1  mbalmer 
   10615  1.1  mbalmer <li>
   10616  1.2    lneto Option names in <a href="#pdf-io.read"><code>io.read</code></a> do not have a starting '<code>*</code>' anymore.
   10617  1.2    lneto For compatibility, Lua will continue to ignore this character.
   10618  1.1  mbalmer </li>
   10619  1.1  mbalmer 
   10620  1.1  mbalmer <li>
   10621  1.2    lneto The following functions were deprecated in the mathematical library:
   10622  1.2    lneto <code>atan2</code>, <code>cosh</code>, <code>sinh</code>, <code>tanh</code>, <code>pow</code>,
   10623  1.2    lneto <code>frexp</code>, and <code>ldexp</code>.
   10624  1.2    lneto You can replace <code>math.pow(x,y)</code> with <code>x^y</code>;
   10625  1.2    lneto you can replace <code>math.atan2</code> with <code>math.atan</code>,
   10626  1.3    lneto which now accepts one or two parameters;
   10627  1.2    lneto you can replace <code>math.ldexp(x,exp)</code> with <code>x * 2.0^exp</code>.
   10628  1.2    lneto For the other operations,
   10629  1.3    lneto you can either use an external library or
   10630  1.3    lneto implement them in Lua.
   10631  1.3    lneto </li>
   10632  1.3    lneto 
   10633  1.3    lneto <li>
   10634  1.3    lneto The searcher for C loaders used by <a href="#pdf-require"><code>require</code></a>
   10635  1.3    lneto changed the way it handles versioned names.
   10636  1.3    lneto Now, the version should come after the module name
   10637  1.3    lneto (as is usual in most other tools).
   10638  1.3    lneto For compatibility, that searcher still tries the old format
   10639  1.3    lneto if it cannot find an open function according to the new style.
   10640  1.3    lneto (Lua&nbsp;5.2 already worked that way,
   10641  1.3    lneto but it did not document the change.)
   10642  1.1  mbalmer </li>
   10643  1.1  mbalmer 
   10644  1.2    lneto </ul>
   10645  1.2    lneto 
   10646  1.2    lneto 
   10647  1.2    lneto 
   10648  1.2    lneto 
   10649  1.2    lneto <h2>8.3 &ndash; <a name="8.3">Changes in the API</a></h2>
   10650  1.2    lneto 
   10651  1.2    lneto 
   10652  1.2    lneto <ul>
   10653  1.2    lneto 
   10654  1.1  mbalmer <li>
   10655  1.2    lneto Continuation functions now receive as parameters what they needed
   10656  1.2    lneto to get through <code>lua_getctx</code>,
   10657  1.2    lneto so <code>lua_getctx</code> has been removed.
   10658  1.2    lneto Adapt your code accordingly.
   10659  1.1  mbalmer </li>
   10660  1.1  mbalmer 
   10661  1.1  mbalmer <li>
   10662  1.2    lneto Function <a href="#lua_dump"><code>lua_dump</code></a> has an extra parameter, <code>strip</code>.
   10663  1.2    lneto Use 0 as the value of this parameter to get the old behavior.
   10664  1.1  mbalmer </li>
   10665  1.1  mbalmer 
   10666  1.3    lneto <li>
   10667  1.3    lneto Functions to inject/project unsigned integers
   10668  1.3    lneto (<code>lua_pushunsigned</code>, <code>lua_tounsigned</code>, <code>lua_tounsignedx</code>,
   10669  1.3    lneto <code>luaL_checkunsigned</code>, <code>luaL_optunsigned</code>)
   10670  1.3    lneto were deprecated.
   10671  1.3    lneto Use their signed equivalents with a type cast.
   10672  1.3    lneto </li>
   10673  1.3    lneto 
   10674  1.3    lneto <li>
   10675  1.3    lneto Macros to project non-default integer types
   10676  1.3    lneto (<code>luaL_checkint</code>, <code>luaL_optint</code>, <code>luaL_checklong</code>, <code>luaL_optlong</code>)
   10677  1.3    lneto were deprecated.
   10678  1.3    lneto Use their equivalent over <a href="#lua_Integer"><code>lua_Integer</code></a> with a type cast
   10679  1.3    lneto (or, when possible, use <a href="#lua_Integer"><code>lua_Integer</code></a> in your code).
   10680  1.3    lneto </li>
   10681  1.3    lneto 
   10682  1.1  mbalmer </ul>
   10683  1.1  mbalmer 
   10684  1.1  mbalmer 
   10685  1.1  mbalmer 
   10686  1.1  mbalmer 
   10687  1.2    lneto <h1>9 &ndash; <a name="9">The Complete Syntax of Lua</a></h1>
   10688  1.1  mbalmer 
   10689  1.1  mbalmer <p>
   10690  1.1  mbalmer Here is the complete syntax of Lua in extended BNF.
   10691  1.3    lneto As usual in extended BNF,
   10692  1.3    lneto {A} means 0 or more As,
   10693  1.3    lneto and [A] means an optional A.
   10694  1.3    lneto (For operator precedences, see <a href="#3.4.8">&sect;3.4.8</a>;
   10695  1.3    lneto for a description of the terminals
   10696  1.3    lneto Name, Numeral,
   10697  1.3    lneto and LiteralString, see <a href="#3.1">&sect;3.1</a>.)
   10698  1.1  mbalmer 
   10699  1.1  mbalmer 
   10700  1.1  mbalmer 
   10701  1.1  mbalmer 
   10702  1.1  mbalmer <pre>
   10703  1.1  mbalmer 
   10704  1.2    lneto 	chunk ::= block
   10705  1.1  mbalmer 
   10706  1.2    lneto 	block ::= {stat} [retstat]
   10707  1.1  mbalmer 
   10708  1.2    lneto 	stat ::=  &lsquo;<b>;</b>&rsquo; | 
   10709  1.2    lneto 		 varlist &lsquo;<b>=</b>&rsquo; explist | 
   10710  1.1  mbalmer 		 functioncall | 
   10711  1.2    lneto 		 label | 
   10712  1.2    lneto 		 <b>break</b> | 
   10713  1.2    lneto 		 <b>goto</b> Name | 
   10714  1.1  mbalmer 		 <b>do</b> block <b>end</b> | 
   10715  1.1  mbalmer 		 <b>while</b> exp <b>do</b> block <b>end</b> | 
   10716  1.1  mbalmer 		 <b>repeat</b> block <b>until</b> exp | 
   10717  1.1  mbalmer 		 <b>if</b> exp <b>then</b> block {<b>elseif</b> exp <b>then</b> block} [<b>else</b> block] <b>end</b> | 
   10718  1.2    lneto 		 <b>for</b> Name &lsquo;<b>=</b>&rsquo; exp &lsquo;<b>,</b>&rsquo; exp [&lsquo;<b>,</b>&rsquo; exp] <b>do</b> block <b>end</b> | 
   10719  1.1  mbalmer 		 <b>for</b> namelist <b>in</b> explist <b>do</b> block <b>end</b> | 
   10720  1.1  mbalmer 		 <b>function</b> funcname funcbody | 
   10721  1.1  mbalmer 		 <b>local</b> <b>function</b> Name funcbody | 
   10722  1.2    lneto 		 <b>local</b> namelist [&lsquo;<b>=</b>&rsquo; explist] 
   10723  1.1  mbalmer 
   10724  1.2    lneto 	retstat ::= <b>return</b> [explist] [&lsquo;<b>;</b>&rsquo;]
   10725  1.1  mbalmer 
   10726  1.2    lneto 	label ::= &lsquo;<b>::</b>&rsquo; Name &lsquo;<b>::</b>&rsquo;
   10727  1.1  mbalmer 
   10728  1.2    lneto 	funcname ::= Name {&lsquo;<b>.</b>&rsquo; Name} [&lsquo;<b>:</b>&rsquo; Name]
   10729  1.1  mbalmer 
   10730  1.2    lneto 	varlist ::= var {&lsquo;<b>,</b>&rsquo; var}
   10731  1.1  mbalmer 
   10732  1.2    lneto 	var ::=  Name | prefixexp &lsquo;<b>[</b>&rsquo; exp &lsquo;<b>]</b>&rsquo; | prefixexp &lsquo;<b>.</b>&rsquo; Name 
   10733  1.1  mbalmer 
   10734  1.2    lneto 	namelist ::= Name {&lsquo;<b>,</b>&rsquo; Name}
   10735  1.1  mbalmer 
   10736  1.2    lneto 	explist ::= exp {&lsquo;<b>,</b>&rsquo; exp}
   10737  1.2    lneto 
   10738  1.3    lneto 	exp ::=  <b>nil</b> | <b>false</b> | <b>true</b> | Numeral | LiteralString | &lsquo;<b>...</b>&rsquo; | functiondef | 
   10739  1.1  mbalmer 		 prefixexp | tableconstructor | exp binop exp | unop exp 
   10740  1.1  mbalmer 
   10741  1.2    lneto 	prefixexp ::= var | functioncall | &lsquo;<b>(</b>&rsquo; exp &lsquo;<b>)</b>&rsquo;
   10742  1.1  mbalmer 
   10743  1.2    lneto 	functioncall ::=  prefixexp args | prefixexp &lsquo;<b>:</b>&rsquo; Name args 
   10744  1.1  mbalmer 
   10745  1.3    lneto 	args ::=  &lsquo;<b>(</b>&rsquo; [explist] &lsquo;<b>)</b>&rsquo; | tableconstructor | LiteralString 
   10746  1.1  mbalmer 
   10747  1.2    lneto 	functiondef ::= <b>function</b> funcbody
   10748  1.1  mbalmer 
   10749  1.2    lneto 	funcbody ::= &lsquo;<b>(</b>&rsquo; [parlist] &lsquo;<b>)</b>&rsquo; block <b>end</b>
   10750  1.1  mbalmer 
   10751  1.2    lneto 	parlist ::= namelist [&lsquo;<b>,</b>&rsquo; &lsquo;<b>...</b>&rsquo;] | &lsquo;<b>...</b>&rsquo;
   10752  1.1  mbalmer 
   10753  1.2    lneto 	tableconstructor ::= &lsquo;<b>{</b>&rsquo; [fieldlist] &lsquo;<b>}</b>&rsquo;
   10754  1.1  mbalmer 
   10755  1.1  mbalmer 	fieldlist ::= field {fieldsep field} [fieldsep]
   10756  1.1  mbalmer 
   10757  1.2    lneto 	field ::= &lsquo;<b>[</b>&rsquo; exp &lsquo;<b>]</b>&rsquo; &lsquo;<b>=</b>&rsquo; exp | Name &lsquo;<b>=</b>&rsquo; exp | exp
   10758  1.1  mbalmer 
   10759  1.2    lneto 	fieldsep ::= &lsquo;<b>,</b>&rsquo; | &lsquo;<b>;</b>&rsquo;
   10760  1.1  mbalmer 
   10761  1.2    lneto 	binop ::=  &lsquo;<b>+</b>&rsquo; | &lsquo;<b>-</b>&rsquo; | &lsquo;<b>*</b>&rsquo; | &lsquo;<b>/</b>&rsquo; | &lsquo;<b>//</b>&rsquo; | &lsquo;<b>^</b>&rsquo; | &lsquo;<b>%</b>&rsquo; | 
   10762  1.2    lneto 		 &lsquo;<b>&amp;</b>&rsquo; | &lsquo;<b>~</b>&rsquo; | &lsquo;<b>|</b>&rsquo; | &lsquo;<b>&gt;&gt;</b>&rsquo; | &lsquo;<b>&lt;&lt;</b>&rsquo; | &lsquo;<b>..</b>&rsquo; | 
   10763  1.2    lneto 		 &lsquo;<b>&lt;</b>&rsquo; | &lsquo;<b>&lt;=</b>&rsquo; | &lsquo;<b>&gt;</b>&rsquo; | &lsquo;<b>&gt;=</b>&rsquo; | &lsquo;<b>==</b>&rsquo; | &lsquo;<b>~=</b>&rsquo; | 
   10764  1.1  mbalmer 		 <b>and</b> | <b>or</b>
   10765  1.1  mbalmer 
   10766  1.2    lneto 	unop ::= &lsquo;<b>-</b>&rsquo; | <b>not</b> | &lsquo;<b>#</b>&rsquo; | &lsquo;<b>~</b>&rsquo;
   10767  1.1  mbalmer 
   10768  1.1  mbalmer </pre>
   10769  1.1  mbalmer 
   10770  1.1  mbalmer <p>
   10771  1.1  mbalmer 
   10772  1.1  mbalmer 
   10773  1.1  mbalmer 
   10774  1.1  mbalmer 
   10775  1.1  mbalmer 
   10776  1.1  mbalmer 
   10777  1.1  mbalmer 
   10778  1.2    lneto 
   10779  1.1  mbalmer <HR>
   10780  1.2    lneto <SMALL CLASS="footer">
   10781  1.1  mbalmer Last update:
   10782  1.3    lneto Tue Jan  6 10:10:50 BRST 2015
   10783  1.1  mbalmer </SMALL>
   10784  1.1  mbalmer <!--
   10785  1.3    lneto Last change: revised for Lua 5.3.0 (final)
   10786  1.1  mbalmer -->
   10787  1.1  mbalmer 
   10788  1.1  mbalmer </body></html>
   10789  1.1  mbalmer 
   10790