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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 © 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 ·
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 – <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 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 functions to be called by Lua code.
62 1.1 mbalmer Through the use of C 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 – <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 – <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">§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">§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 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 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">§2.4</a>).
171 1.1 mbalmer Userdata values cannot be created or modified in Lua,
172 1.1 mbalmer only through the C 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">§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">§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">§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">§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">§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 – <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">§3.2</a> and <a href="#3.3.3">§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">§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">§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">§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 – <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 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 – <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">§6.10</a>));
398 1.2 lneto you must use the C 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">§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">§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>&</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">§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><<</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>>></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">§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><</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><=</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 <= b</code> is equivalent to <code>not (b < 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 – <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 – <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 API,
738 1.2 lneto for full userdata (see <a href="#2.4">§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 – <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 '<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 – <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 – <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>} means 0 or more <em>a</em>'s, and
1026 1.2 lneto [<em>a</em>] 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 ‘<b>=</b>’.
1030 1.2 lneto The complete syntax of Lua can be found in <a href="#9">§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 – <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 & ~ | << >> //
1081 1.2 lneto == ~= <= >= < > =
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 0 is written as <code>[[</code>,
1140 1.2 lneto an opening long bracket of level 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 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 97,
1174 1.2 lneto newline is coded as 10, and '<code>1</code>' is coded as 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 – <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">§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">§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">§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 ‘<b>[</b>’ exp ‘<b>]</b>’
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">§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 ‘<b>.</b>’ 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">§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 – <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 – <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 ::= ‘<b>;</b>’
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">§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 – <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">§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">§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 – <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 ‘<b>=</b>’ explist
1418 1.2 lneto varlist ::= var {‘<b>,</b>’ var}
1419 1.2 lneto explist ::= exp {‘<b>,</b>’ exp}
1420 1.1 mbalmer </pre><p>
1421 1.2 lneto Expressions are discussed in <a href="#3.4">§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">§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 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">§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">§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 – <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">§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>–<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 ::= ‘<b>::</b>’ Name ‘<b>::</b>’
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] [‘<b>;</b>’]
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 – <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 ‘<b>=</b>’ exp ‘<b>,</b>’ exp [‘<b>,</b>’ 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> >= 0 and <em>var</em> > <em>limit</em>) or (<em>step</em> < 0 and <em>var</em> < <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 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 {‘<b>,</b>’ 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>, ···, <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>, ···, <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 – <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">§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 – <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 [‘<b>=</b>’ 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">§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">§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">§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 – <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 ::= ‘<b>...</b>’
1768 1.2 lneto exp ::= exp binop exp
1769 1.2 lneto exp ::= unop exp
1770 1.2 lneto prefixexp ::= var | functioncall | ‘<b>(</b>’ exp ‘<b>)</b>’
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">§3.1</a>;
1775 1.2 lneto variables are explained in <a href="#3.2">§3.2</a>;
1776 1.2 lneto function definitions are explained in <a href="#3.4.11">§3.4.11</a>;
1777 1.2 lneto function calls are explained in <a href="#3.4.10">§3.4.10</a>;
1778 1.2 lneto table constructors are explained in <a href="#3.4.9">§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">§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">§3.4.1</a>),
1787 1.2 lneto bitwise operators (see <a href="#3.4.2">§3.4.2</a>),
1788 1.2 lneto relational operators (see <a href="#3.4.4">§3.4.4</a>), logical operators (see <a href="#3.4.5">§3.4.5</a>),
1789 1.2 lneto and the concatenation operator (see <a href="#3.4.6">§3.4.6</a>).
1790 1.2 lneto Unary operators comprise the unary minus (see <a href="#3.4.1">§3.4.1</a>),
1791 1.2 lneto the unary bitwise not (see <a href="#3.4.2">§3.4.2</a>),
1792 1.3 lneto the unary logical <b>not</b> (see <a href="#3.4.5">§3.4.5</a>),
1793 1.2 lneto and the unary <em>length operator</em> (see <a href="#3.4.7">§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">§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 – <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">§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 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 – <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>&</code>: </b>bitwise and</li>
1906 1.3 lneto <li><b><code>|</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>>></code>: </b>right shift</li>
1909 1.3 lneto <li><b><code><<</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">§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 – <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 – <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><</code>: </b>less than</li>
1997 1.3 lneto <li><b><code>></code>: </b>greater than</li>
1998 1.3 lneto <li><b><code><=</code>: </b>less or equal</li>
1999 1.3 lneto <li><b><code>>=</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">§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">§2.4</a>).
2054 1.2 lneto A comparison <code>a > b</code> is translated to <code>b < a</code>
2055 1.2 lneto and <code>a >= b</code> is translated to <code>b <= 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 – <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">§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 --> 10
2084 1.2 lneto 10 or error() --> 10
2085 1.2 lneto nil or "a" --> "a"
2086 1.2 lneto nil and 10 --> nil
2087 1.2 lneto false and error() --> false
2088 1.2 lneto false and nil --> false
2089 1.2 lneto false or nil --> nil
2090 1.2 lneto 10 and 20 --> 20
2091 1.2 lneto </pre><p>
2092 1.2 lneto (In this manual,
2093 1.2 lneto <code>--></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 – <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">§3.4.3</a>.
2104 1.2 lneto Otherwise, the <code>__concat</code> metamethod is called (see <a href="#2.4">§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 – <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">§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 – <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 < > <= >= ~= ==
2156 1.2 lneto |
2157 1.2 lneto ~
2158 1.2 lneto &
2159 1.2 lneto << >>
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 – <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 ::= ‘<b>{</b>’ [fieldlist] ‘<b>}</b>’
2185 1.2 lneto fieldlist ::= field {fieldsep field} [fieldsep]
2186 1.2 lneto field ::= ‘<b>[</b>’ exp ‘<b>]</b>’ ‘<b>=</b>’ exp | Name ‘<b>=</b>’ exp | exp
2187 1.2 lneto fieldsep ::= ‘<b>,</b>’ | ‘<b>;</b>’
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">§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 – <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">§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 ‘<b>:</b>’ 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 ::= ‘<b>(</b>’ [explist] ‘<b>)</b>’
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 – <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 ::= ‘<b>(</b>’ [parlist] ‘<b>)</b>’ 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 {‘<b>.</b>’ Name} [‘<b>:</b>’ 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 [‘<b>,</b>’ ‘<b>...</b>’] | ‘<b>...</b>’
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, ... --> (nothing)
2431 1.2 lneto g(3, 4) a=3, b=4, ... --> (nothing)
2432 1.2 lneto g(3, 4, 5, 8) a=3, b=4, ... --> 5 8
2433 1.2 lneto g(5, r()) a=5, b=1, ... --> 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">§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 – <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) --> 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) --> 12
2489 1.2 lneto end
2490 1.2 lneto print(x) --> 11
2491 1.2 lneto end
2492 1.2 lneto print(x) --> 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 – <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 API for Lua, that is,
2537 1.1 mbalmer the set of C 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 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 – <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 functions that are still active.
2572 1.1 mbalmer This stack initially contains any arguments to the C function
2573 1.1 mbalmer and it is where the C 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 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 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 <em>n</em> represents the last element;
2590 1.1 mbalmer index -1 also represents the last element
2591 1.1 mbalmer (that is, the element at the 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 – <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 – <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 1 and the stack top
2641 1.2 lneto (<code>1 ≤ abs(index) ≤ 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 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 function (see <a href="#4.4">§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 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 – <a name="4.4">C Closures</a></h2>
2689 1.1 mbalmer
2690 1.1 mbalmer <p>
2691 1.1 mbalmer When a C 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 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 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 – <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 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 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 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 – <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">§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">§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 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 – <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 – <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 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, –]</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 >= 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 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 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>&</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><<</code>)</li>
3105 1.2 lneto <li><b><a name="pdf-LUA_OPSHR"><code>LUA_OPSHR</code></a>: </b> performs right shift (<code>>></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, –]</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">§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 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">§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 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 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 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 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 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 <= 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, –]</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, –]</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 0.
3298 1.3 lneto Also returns 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><</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><=</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> is 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">§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, –]</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 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">§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">§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, –]</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">§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, –]</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">§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), –]</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 1.
3577 1.3 lneto Otherwise,
3578 1.1 mbalmer the function returns 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">§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, –]</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 1,
3615 1.3 lneto this result is equal to the number of elements in the stack;
3616 1.3 lneto in particular, 0 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, –]</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, –]</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, –]</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 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, –]</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 function,
3694 1.1 mbalmer and 0 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, –]</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 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, –]</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 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, –]</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 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, –]</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 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, –]</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 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, –]</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 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, –]</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 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, –]</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 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, –]</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 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, –]</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 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, –]</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 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, –]</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 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">§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">§3.4.7</a>) and
3880 1.3 lneto may trigger a metamethod for the "length" event (see <a href="#2.4">§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, –]</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">§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">§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">§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, –]</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–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), –]</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), –]</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">§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, –]</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, –]</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 closure onto the stack.
4227 1.1 mbalmer
4228 1.1 mbalmer
4229 1.1 mbalmer <p>
4230 1.1 mbalmer When a C function is created,
4231 1.1 mbalmer it is possible to associate some values with it,
4232 1.2 lneto thus creating a C closure (see <a href="#4.4">§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 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 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 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, –]</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 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 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 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, –]</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, –]</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, –]</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 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 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, –]</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, –]</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, –]</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, –]</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, –]</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 0.
4493 1.3 lneto Also returns 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, –]</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, –]</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, –]</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, –]</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 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, –]</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, –]</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">[-?, +?, –]</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, –]</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, –]</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">§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">§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, –]</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">§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">[-?, +?, –]</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 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 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, –]</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, –]</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, –]</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">§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, –]</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 boolean
4938 1.1 mbalmer value (0 or 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, –]</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 function.
4956 1.1 mbalmer That value must be a C 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, –]</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, –]</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">§3.4.3</a>);
4983 1.2 lneto otherwise, <code>lua_tointegerx</code> returns 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 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 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, –]</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, –]</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 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">§3.4.3</a>);
5049 1.2 lneto otherwise, <a href="#lua_tonumberx"><code>lua_tonumberx</code></a> returns 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, –]</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 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, –]</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, –]</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, –]</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, –]</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, –]</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">§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 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">[-?, +?, –]</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">§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 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">§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">§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 – <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 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 for C 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 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, –]</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, –]</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, –]</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>></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, ">S", &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), –]</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, –]</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 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), –]</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 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, –]</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, –]</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, –]</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, –]</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, –]</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 – <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 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 – <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 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, &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(&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, &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(&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, –]</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 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, –]</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, +?, –]</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 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, –]</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">§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, –]</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, –]</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, –]</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, –]</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 C <code>realloc</code> function
6603 1.2 lneto and then sets a panic function (see <a href="#4.6">§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, –]</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 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, –]</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, –]</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 0 is the running function,
6990 1.1 mbalmer level 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 – <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 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 API
7018 1.1 mbalmer and are provided as separate C 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">§6.1</a>);</li>
7024 1.1 mbalmer
7025 1.2 lneto <li>coroutine library (<a href="#6.2">§6.2</a>);</li>
7026 1.1 mbalmer
7027 1.2 lneto <li>package library (<a href="#6.3">§6.3</a>);</li>
7028 1.1 mbalmer
7029 1.2 lneto <li>string manipulation (<a href="#6.4">§6.4</a>);</li>
7030 1.1 mbalmer
7031 1.2 lneto <li>basic UTF-8 support (<a href="#6.5">§6.5</a>);</li>
7032 1.1 mbalmer
7033 1.2 lneto <li>table manipulation (<a href="#6.6">§6.6</a>);</li>
7034 1.1 mbalmer
7035 1.2 lneto <li>mathematical functions (<a href="#6.7">§6.7</a>) (sin, log, etc.);</li>
7036 1.1 mbalmer
7037 1.2 lneto <li>input and output (<a href="#6.8">§6.8</a>);</li>
7038 1.2 lneto
7039 1.2 lneto <li>operating system facilities (<a href="#6.9">§6.9</a>);</li>
7040 1.2 lneto
7041 1.2 lneto <li>debug facilities (<a href="#6.10">§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 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 – <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">§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">§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 1 (the default), the error position is where the
7183 1.1 mbalmer <code>error</code> function was called.
7184 1.1 mbalmer Level 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 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">§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–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">§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">§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–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, ···])</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 <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 (···)</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, ···)</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 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">§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 10, the letter '<code>A</code>' (in either upper or lower case)
7513 1.1 mbalmer represents 10, '<code>B</code>' represents 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, ···])</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 – <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">§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, ···])</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 (···)</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 – <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 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 loader.
7807 1.1 mbalmer
7808 1.1 mbalmer
7809 1.1 mbalmer <p>
7810 1.1 mbalmer Lua initializes the C 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 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 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 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 library
7868 1.2 lneto (which may depend on the C 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 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 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 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 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 function inside the library to
7970 1.1 mbalmer be used as the loader.
7971 1.1 mbalmer The name of this C 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 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 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 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 – <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 1
8054 1.1 mbalmer (not at 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 1;
8079 1.1 mbalmer the default value for <code>j</code> is <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 (···)</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">§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 <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 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, ···)</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 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">§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">§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 <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 <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 --> 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 --> 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 --> 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 --> 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 --> 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 --> 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">§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 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, ···)</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">§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">§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">§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 – <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 <em>x</em>, end with <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 1);
8638 1.1 mbalmer the character matching "<code>.</code>" is captured with number 2,
8639 1.1 mbalmer and the part matching "<code>%s*</code>" has number 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 and 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 – <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><</code>: </b>sets little endian</li>
8669 1.3 lneto <li><b><code>></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 <=>!</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 – <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 (···)</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">§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 – <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">§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] ··· 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], ···, 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],··· = a1[f],···,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 (···)</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], ···, 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><</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], ···, list[j]
8982 1.2 lneto </pre><p>
8983 1.2 lneto By default, <code>i</code> is 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 – <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, ···)</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><</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, ···)</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><</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>π</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 – <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 ···])</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(···)</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 (···)</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(···)</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 (···)</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(···)</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 (···)</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 (···)</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 (···)</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 – <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> (1–12), <code>day</code> (1–31),
9772 1.2 lneto <code>hour</code> (0–23), <code>min</code> (0–59), <code>sec</code> (0–61),
9773 1.1 mbalmer <code>wday</code> (weekday, Sunday is 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 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 function <code>gmtime</code> and C 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 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 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 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 – <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">§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 0 is the current function (<code>getinfo</code> itself);
10073 1.2 lneto level 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 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">§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 2 to get more information about
10229 1.1 mbalmer the running function
10230 1.1 mbalmer (level 0 is the <code>getinfo</code> function,
10231 1.2 lneto and level 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 – <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 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>, ···, <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 <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 – <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 5.2 to Lua 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 – <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 5.2 and Lua 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 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 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 – <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 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 – <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 – <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">§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">§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 ::= ‘<b>;</b>’ |
10709 1.2 lneto varlist ‘<b>=</b>’ 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 ‘<b>=</b>’ exp ‘<b>,</b>’ exp [‘<b>,</b>’ 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 [‘<b>=</b>’ explist]
10723 1.1 mbalmer
10724 1.2 lneto retstat ::= <b>return</b> [explist] [‘<b>;</b>’]
10725 1.1 mbalmer
10726 1.2 lneto label ::= ‘<b>::</b>’ Name ‘<b>::</b>’
10727 1.1 mbalmer
10728 1.2 lneto funcname ::= Name {‘<b>.</b>’ Name} [‘<b>:</b>’ Name]
10729 1.1 mbalmer
10730 1.2 lneto varlist ::= var {‘<b>,</b>’ var}
10731 1.1 mbalmer
10732 1.2 lneto var ::= Name | prefixexp ‘<b>[</b>’ exp ‘<b>]</b>’ | prefixexp ‘<b>.</b>’ Name
10733 1.1 mbalmer
10734 1.2 lneto namelist ::= Name {‘<b>,</b>’ Name}
10735 1.1 mbalmer
10736 1.2 lneto explist ::= exp {‘<b>,</b>’ exp}
10737 1.2 lneto
10738 1.3 lneto exp ::= <b>nil</b> | <b>false</b> | <b>true</b> | Numeral | LiteralString | ‘<b>...</b>’ | functiondef |
10739 1.1 mbalmer prefixexp | tableconstructor | exp binop exp | unop exp
10740 1.1 mbalmer
10741 1.2 lneto prefixexp ::= var | functioncall | ‘<b>(</b>’ exp ‘<b>)</b>’
10742 1.1 mbalmer
10743 1.2 lneto functioncall ::= prefixexp args | prefixexp ‘<b>:</b>’ Name args
10744 1.1 mbalmer
10745 1.3 lneto args ::= ‘<b>(</b>’ [explist] ‘<b>)</b>’ | tableconstructor | LiteralString
10746 1.1 mbalmer
10747 1.2 lneto functiondef ::= <b>function</b> funcbody
10748 1.1 mbalmer
10749 1.2 lneto funcbody ::= ‘<b>(</b>’ [parlist] ‘<b>)</b>’ block <b>end</b>
10750 1.1 mbalmer
10751 1.2 lneto parlist ::= namelist [‘<b>,</b>’ ‘<b>...</b>’] | ‘<b>...</b>’
10752 1.1 mbalmer
10753 1.2 lneto tableconstructor ::= ‘<b>{</b>’ [fieldlist] ‘<b>}</b>’
10754 1.1 mbalmer
10755 1.1 mbalmer fieldlist ::= field {fieldsep field} [fieldsep]
10756 1.1 mbalmer
10757 1.2 lneto field ::= ‘<b>[</b>’ exp ‘<b>]</b>’ ‘<b>=</b>’ exp | Name ‘<b>=</b>’ exp | exp
10758 1.1 mbalmer
10759 1.2 lneto fieldsep ::= ‘<b>,</b>’ | ‘<b>;</b>’
10760 1.1 mbalmer
10761 1.2 lneto binop ::= ‘<b>+</b>’ | ‘<b>-</b>’ | ‘<b>*</b>’ | ‘<b>/</b>’ | ‘<b>//</b>’ | ‘<b>^</b>’ | ‘<b>%</b>’ |
10762 1.2 lneto ‘<b>&</b>’ | ‘<b>~</b>’ | ‘<b>|</b>’ | ‘<b>>></b>’ | ‘<b><<</b>’ | ‘<b>..</b>’ |
10763 1.2 lneto ‘<b><</b>’ | ‘<b><=</b>’ | ‘<b>></b>’ | ‘<b>>=</b>’ | ‘<b>==</b>’ | ‘<b>~=</b>’ |
10764 1.1 mbalmer <b>and</b> | <b>or</b>
10765 1.1 mbalmer
10766 1.2 lneto unop ::= ‘<b>-</b>’ | <b>not</b> | ‘<b>#</b>’ | ‘<b>~</b>’
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