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1 1.1 mbalmer <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2 1.4 mbalmer <HTML> 3 1.4 mbalmer <HEAD> 4 1.4 mbalmer <TITLE>Lua 5.3 Reference Manual</TITLE> 5 1.4 mbalmer <LINK REL="stylesheet" TYPE="text/css" HREF="lua.css"> 6 1.4 mbalmer <LINK REL="stylesheet" TYPE="text/css" HREF="manual.css"> 7 1.1 mbalmer <META HTTP-EQUIV="content-type" CONTENT="text/html; charset=iso-8859-1"> 8 1.4 mbalmer </HEAD> 9 1.1 mbalmer 10 1.4 mbalmer <BODY> 11 1.1 mbalmer 12 1.4 mbalmer <H1> 13 1.4 mbalmer <A HREF="http://www.lua.org/"><IMG SRC="logo.gif" ALT="Lua"></A> 14 1.2 lneto Lua 5.3 Reference Manual 15 1.4 mbalmer </H1> 16 1.1 mbalmer 17 1.4 mbalmer <P> 18 1.1 mbalmer by Roberto Ierusalimschy, Luiz Henrique de Figueiredo, Waldemar Celes 19 1.4 mbalmer 20 1.4 mbalmer <P> 21 1.4 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 1.4 mbalmer </SMALL> 26 1.1 mbalmer 27 1.4 mbalmer <DIV CLASS="menubar"> 28 1.4 mbalmer <A HREF="contents.html#contents">contents</A> 29 1.4 mbalmer · 30 1.4 mbalmer <A HREF="contents.html#index">index</A> 31 1.1 mbalmer · 32 1.4 mbalmer <A HREF="http://www.lua.org/manual/">other versions</A> 33 1.4 mbalmer </DIV> 34 1.1 mbalmer 35 1.1 mbalmer <!-- ====================================================================== --> 36 1.1 mbalmer <p> 37 1.1 mbalmer 38 1.5 lneto <!-- Id: manual.of,v 1.153 2015/11/25 16:57:42 roberto Exp --> 39 1.1 mbalmer 40 1.1 mbalmer 41 1.1 mbalmer 42 1.1 mbalmer 43 1.2 lneto <h1>1 – <a name="1">Introduction</a></h1> 44 1.1 mbalmer 45 1.1 mbalmer <p> 46 1.1 mbalmer Lua is an extension programming language designed to support 47 1.1 mbalmer general procedural programming with data description 48 1.1 mbalmer facilities. 49 1.3 lneto Lua also offers good support for object-oriented programming, 50 1.1 mbalmer functional programming, and data-driven programming. 51 1.2 lneto Lua is intended to be used as a powerful, lightweight, 52 1.2 lneto embeddable scripting language for any program that needs one. 53 1.2 lneto Lua is implemented as a library, written in <em>clean C</em>, 54 1.2 lneto the common subset of Standard C and C++. 55 1.1 mbalmer 56 1.1 mbalmer 57 1.1 mbalmer <p> 58 1.3 lneto As an extension language, Lua has no notion of a "main" program: 59 1.1 mbalmer it only works <em>embedded</em> in a host client, 60 1.1 mbalmer called the <em>embedding program</em> or simply the <em>host</em>. 61 1.2 lneto The host program can invoke functions to execute a piece of Lua code, 62 1.1 mbalmer can write and read Lua variables, 63 1.1 mbalmer and can register C functions to be called by Lua code. 64 1.1 mbalmer Through the use of C functions, Lua can be augmented to cope with 65 1.1 mbalmer a wide range of different domains, 66 1.1 mbalmer thus creating customized programming languages sharing a syntactical framework. 67 1.1 mbalmer The Lua distribution includes a sample host program called <code>lua</code>, 68 1.2 lneto which uses the Lua library to offer a complete, standalone Lua interpreter, 69 1.2 lneto for interactive or batch use. 70 1.1 mbalmer 71 1.1 mbalmer 72 1.1 mbalmer <p> 73 1.1 mbalmer Lua is free software, 74 1.1 mbalmer and is provided as usual with no guarantees, 75 1.1 mbalmer as stated in its license. 76 1.1 mbalmer The implementation described in this manual is available 77 1.1 mbalmer at Lua's official web site, <code>www.lua.org</code>. 78 1.1 mbalmer 79 1.1 mbalmer 80 1.1 mbalmer <p> 81 1.1 mbalmer Like any other reference manual, 82 1.1 mbalmer this document is dry in places. 83 1.1 mbalmer For a discussion of the decisions behind the design of Lua, 84 1.1 mbalmer see the technical papers available at Lua's web site. 85 1.1 mbalmer For a detailed introduction to programming in Lua, 86 1.2 lneto see Roberto's book, <em>Programming in Lua</em>. 87 1.1 mbalmer 88 1.1 mbalmer 89 1.1 mbalmer 90 1.2 lneto <h1>2 – <a name="2">Basic Concepts</a></h1> 91 1.1 mbalmer 92 1.1 mbalmer <p> 93 1.2 lneto This section describes the basic concepts of the language. 94 1.1 mbalmer 95 1.1 mbalmer 96 1.1 mbalmer 97 1.2 lneto <h2>2.1 – <a name="2.1">Values and Types</a></h2> 98 1.1 mbalmer 99 1.1 mbalmer <p> 100 1.1 mbalmer Lua is a <em>dynamically typed language</em>. 101 1.1 mbalmer This means that 102 1.1 mbalmer variables do not have types; only values do. 103 1.1 mbalmer There are no type definitions in the language. 104 1.1 mbalmer All values carry their own type. 105 1.1 mbalmer 106 1.1 mbalmer 107 1.1 mbalmer <p> 108 1.1 mbalmer All values in Lua are <em>first-class values</em>. 109 1.1 mbalmer This means that all values can be stored in variables, 110 1.1 mbalmer passed as arguments to other functions, and returned as results. 111 1.1 mbalmer 112 1.1 mbalmer 113 1.1 mbalmer <p> 114 1.1 mbalmer There are eight basic types in Lua: 115 1.1 mbalmer <em>nil</em>, <em>boolean</em>, <em>number</em>, 116 1.1 mbalmer <em>string</em>, <em>function</em>, <em>userdata</em>, 117 1.1 mbalmer <em>thread</em>, and <em>table</em>. 118 1.4 mbalmer The type <em>nil</em> has one single value, <b>nil</b>, 119 1.1 mbalmer whose main property is to be different from any other value; 120 1.1 mbalmer it usually represents the absence of a useful value. 121 1.4 mbalmer The type <em>boolean</em> has two values, <b>false</b> and <b>true</b>. 122 1.1 mbalmer Both <b>nil</b> and <b>false</b> make a condition false; 123 1.1 mbalmer any other value makes it true. 124 1.4 mbalmer The type <em>number</em> represents both 125 1.3 lneto integer numbers and real (floating-point) numbers. 126 1.4 mbalmer The type <em>string</em> represents immutable sequences of bytes. 127 1.1 mbalmer 128 1.1 mbalmer Lua is 8-bit clean: 129 1.2 lneto strings can contain any 8-bit value, 130 1.2 lneto including embedded zeros ('<code>\0</code>'). 131 1.3 lneto Lua is also encoding-agnostic; 132 1.3 lneto it makes no assumptions about the contents of a string. 133 1.2 lneto 134 1.2 lneto 135 1.2 lneto <p> 136 1.2 lneto The type <em>number</em> uses two internal representations, 137 1.4 mbalmer or two subtypes, 138 1.2 lneto one called <em>integer</em> and the other called <em>float</em>. 139 1.2 lneto Lua has explicit rules about when each representation is used, 140 1.2 lneto but it also converts between them automatically as needed (see <a href="#3.4.3">§3.4.3</a>). 141 1.2 lneto Therefore, 142 1.3 lneto the programmer may choose to mostly ignore the difference 143 1.2 lneto between integers and floats 144 1.3 lneto or to assume complete control over the representation of each number. 145 1.2 lneto Standard Lua uses 64-bit integers and double-precision (64-bit) floats, 146 1.2 lneto but you can also compile Lua so that it 147 1.2 lneto uses 32-bit integers and/or single-precision (32-bit) floats. 148 1.4 mbalmer The option with 32 bits for both integers and floats 149 1.3 lneto is particularly attractive 150 1.3 lneto for small machines and embedded systems. 151 1.3 lneto (See macro <code>LUA_32BITS</code> in file <code>luaconf.h</code>.) 152 1.1 mbalmer 153 1.1 mbalmer 154 1.1 mbalmer <p> 155 1.1 mbalmer Lua can call (and manipulate) functions written in Lua and 156 1.3 lneto functions written in C (see <a href="#3.4.10">§3.4.10</a>). 157 1.3 lneto Both are represented by the type <em>function</em>. 158 1.1 mbalmer 159 1.1 mbalmer 160 1.1 mbalmer <p> 161 1.1 mbalmer The type <em>userdata</em> is provided to allow arbitrary C data to 162 1.1 mbalmer be stored in Lua variables. 163 1.3 lneto A userdata value represents a block of raw memory. 164 1.2 lneto There are two kinds of userdata: 165 1.3 lneto <em>full userdata</em>, 166 1.3 lneto which is an object with a block of memory managed by Lua, 167 1.3 lneto and <em>light userdata</em>, 168 1.3 lneto which is simply a C pointer value. 169 1.2 lneto Userdata has no predefined operations in Lua, 170 1.1 mbalmer except assignment and identity test. 171 1.2 lneto By using <em>metatables</em>, 172 1.2 lneto the programmer can define operations for full userdata values 173 1.2 lneto (see <a href="#2.4">§2.4</a>). 174 1.1 mbalmer Userdata values cannot be created or modified in Lua, 175 1.1 mbalmer only through the C API. 176 1.1 mbalmer This guarantees the integrity of data owned by the host program. 177 1.1 mbalmer 178 1.1 mbalmer 179 1.1 mbalmer <p> 180 1.1 mbalmer The type <em>thread</em> represents independent threads of execution 181 1.2 lneto and it is used to implement coroutines (see <a href="#2.6">§2.6</a>). 182 1.3 lneto Lua threads are not related to operating-system threads. 183 1.1 mbalmer Lua supports coroutines on all systems, 184 1.3 lneto even those that do not support threads natively. 185 1.1 mbalmer 186 1.1 mbalmer 187 1.1 mbalmer <p> 188 1.1 mbalmer The type <em>table</em> implements associative arrays, 189 1.1 mbalmer that is, arrays that can be indexed not only with numbers, 190 1.3 lneto but with any Lua value except <b>nil</b> and NaN. 191 1.4 mbalmer (<em>Not a Number</em> is a special value used to represent 192 1.4 mbalmer undefined or unrepresentable numerical results, such as <code>0/0</code>.) 193 1.1 mbalmer Tables can be <em>heterogeneous</em>; 194 1.1 mbalmer that is, they can contain values of all types (except <b>nil</b>). 195 1.2 lneto Any key with value <b>nil</b> is not considered part of the table. 196 1.2 lneto Conversely, any key that is not part of a table has 197 1.2 lneto an associated value <b>nil</b>. 198 1.2 lneto 199 1.2 lneto 200 1.2 lneto <p> 201 1.3 lneto Tables are the sole data-structuring mechanism in Lua; 202 1.2 lneto they can be used to represent ordinary arrays, sequences, 203 1.1 mbalmer symbol tables, sets, records, graphs, trees, etc. 204 1.1 mbalmer To represent records, Lua uses the field name as an index. 205 1.1 mbalmer The language supports this representation by 206 1.1 mbalmer providing <code>a.name</code> as syntactic sugar for <code>a["name"]</code>. 207 1.1 mbalmer There are several convenient ways to create tables in Lua 208 1.2 lneto (see <a href="#3.4.9">§3.4.9</a>). 209 1.2 lneto 210 1.2 lneto 211 1.2 lneto <p> 212 1.2 lneto We use the term <em>sequence</em> to denote a table where 213 1.3 lneto the set of all positive numeric keys is equal to {1..<em>n</em>} 214 1.3 lneto for some non-negative integer <em>n</em>, 215 1.2 lneto which is called the length of the sequence (see <a href="#3.4.7">§3.4.7</a>). 216 1.1 mbalmer 217 1.1 mbalmer 218 1.1 mbalmer <p> 219 1.1 mbalmer Like indices, 220 1.2 lneto the values of table fields can be of any type. 221 1.1 mbalmer In particular, 222 1.1 mbalmer because functions are first-class values, 223 1.1 mbalmer table fields can contain functions. 224 1.2 lneto Thus tables can also carry <em>methods</em> (see <a href="#3.4.11">§3.4.11</a>). 225 1.2 lneto 226 1.2 lneto 227 1.2 lneto <p> 228 1.2 lneto The indexing of tables follows 229 1.2 lneto the definition of raw equality in the language. 230 1.2 lneto The expressions <code>a[i]</code> and <code>a[j]</code> 231 1.2 lneto denote the same table element 232 1.2 lneto if and only if <code>i</code> and <code>j</code> are raw equal 233 1.2 lneto (that is, equal without metamethods). 234 1.2 lneto In particular, floats with integral values 235 1.2 lneto are equal to their respective integers 236 1.2 lneto (e.g., <code>1.0 == 1</code>). 237 1.2 lneto To avoid ambiguities, 238 1.2 lneto any float with integral value used as a key 239 1.2 lneto is converted to its respective integer. 240 1.2 lneto For instance, if you write <code>a[2.0] = true</code>, 241 1.2 lneto the actual key inserted into the table will be the 242 1.2 lneto integer <code>2</code>. 243 1.3 lneto (On the other hand, 244 1.3 lneto 2 and "<code>2</code>" are different Lua values and therefore 245 1.3 lneto denote different table entries.) 246 1.1 mbalmer 247 1.1 mbalmer 248 1.1 mbalmer <p> 249 1.1 mbalmer Tables, functions, threads, and (full) userdata values are <em>objects</em>: 250 1.1 mbalmer variables do not actually <em>contain</em> these values, 251 1.1 mbalmer only <em>references</em> to them. 252 1.1 mbalmer Assignment, parameter passing, and function returns 253 1.1 mbalmer always manipulate references to such values; 254 1.1 mbalmer these operations do not imply any kind of copy. 255 1.1 mbalmer 256 1.1 mbalmer 257 1.1 mbalmer <p> 258 1.1 mbalmer The library function <a href="#pdf-type"><code>type</code></a> returns a string describing the type 259 1.2 lneto of a given value (see <a href="#6.1">§6.1</a>). 260 1.2 lneto 261 1.1 mbalmer 262 1.1 mbalmer 263 1.1 mbalmer 264 1.2 lneto 265 1.2 lneto <h2>2.2 – <a name="2.2">Environments and the Global Environment</a></h2> 266 1.1 mbalmer 267 1.1 mbalmer <p> 268 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>, 269 1.3 lneto any reference to a free name 270 1.3 lneto (that is, a name not bound to any declaration) <code>var</code> 271 1.3 lneto is syntactically translated to <code>_ENV.var</code>. 272 1.2 lneto Moreover, every chunk is compiled in the scope of 273 1.3 lneto an external local variable named <code>_ENV</code> (see <a href="#3.3.2">§3.3.2</a>), 274 1.3 lneto so <code>_ENV</code> itself is never a free name in a chunk. 275 1.1 mbalmer 276 1.1 mbalmer 277 1.2 lneto <p> 278 1.2 lneto Despite the existence of this external <code>_ENV</code> variable and 279 1.3 lneto the translation of free names, 280 1.2 lneto <code>_ENV</code> is a completely regular name. 281 1.2 lneto In particular, 282 1.2 lneto you can define new variables and parameters with that name. 283 1.3 lneto Each reference to a free name uses the <code>_ENV</code> that is 284 1.2 lneto visible at that point in the program, 285 1.2 lneto following the usual visibility rules of Lua (see <a href="#3.5">§3.5</a>). 286 1.1 mbalmer 287 1.1 mbalmer 288 1.2 lneto <p> 289 1.2 lneto Any table used as the value of <code>_ENV</code> is called an <em>environment</em>. 290 1.1 mbalmer 291 1.1 mbalmer 292 1.2 lneto <p> 293 1.2 lneto Lua keeps a distinguished environment called the <em>global environment</em>. 294 1.2 lneto This value is kept at a special index in the C registry (see <a href="#4.5">§4.5</a>). 295 1.3 lneto In Lua, the global variable <a href="#pdf-_G"><code>_G</code></a> is initialized with this same value. 296 1.3 lneto (<a href="#pdf-_G"><code>_G</code></a> is never used internally.) 297 1.1 mbalmer 298 1.1 mbalmer 299 1.1 mbalmer <p> 300 1.3 lneto When Lua loads a chunk, 301 1.3 lneto the default value for its <code>_ENV</code> upvalue 302 1.3 lneto is the global environment (see <a href="#pdf-load"><code>load</code></a>). 303 1.2 lneto Therefore, by default, 304 1.3 lneto free names in Lua code refer to entries in the global environment 305 1.3 lneto (and, therefore, they are also called <em>global variables</em>). 306 1.2 lneto Moreover, all standard libraries are loaded in the global environment 307 1.3 lneto and some functions there operate on that environment. 308 1.2 lneto You can use <a href="#pdf-load"><code>load</code></a> (or <a href="#pdf-loadfile"><code>loadfile</code></a>) 309 1.2 lneto to load a chunk with a different environment. 310 1.2 lneto (In C, you have to load the chunk and then change the value 311 1.2 lneto of its first upvalue.) 312 1.1 mbalmer 313 1.1 mbalmer 314 1.1 mbalmer 315 1.1 mbalmer 316 1.1 mbalmer 317 1.2 lneto <h2>2.3 – <a name="2.3">Error Handling</a></h2> 318 1.1 mbalmer 319 1.1 mbalmer <p> 320 1.2 lneto Because Lua is an embedded extension language, 321 1.2 lneto all Lua actions start from C code in the host program 322 1.3 lneto calling a function from the Lua library. 323 1.3 lneto (When you use Lua standalone, 324 1.3 lneto the <code>lua</code> application is the host program.) 325 1.2 lneto Whenever an error occurs during 326 1.2 lneto the compilation or execution of a Lua chunk, 327 1.2 lneto control returns to the host, 328 1.2 lneto which can take appropriate measures 329 1.2 lneto (such as printing an error message). 330 1.1 mbalmer 331 1.1 mbalmer 332 1.1 mbalmer <p> 333 1.2 lneto Lua code can explicitly generate an error by calling the 334 1.2 lneto <a href="#pdf-error"><code>error</code></a> function. 335 1.2 lneto If you need to catch errors in Lua, 336 1.2 lneto you can use <a href="#pdf-pcall"><code>pcall</code></a> or <a href="#pdf-xpcall"><code>xpcall</code></a> 337 1.2 lneto to call a given function in <em>protected mode</em>. 338 1.1 mbalmer 339 1.1 mbalmer 340 1.1 mbalmer <p> 341 1.2 lneto Whenever there is an error, 342 1.2 lneto an <em>error object</em> (also called an <em>error message</em>) 343 1.2 lneto is propagated with information about the error. 344 1.3 lneto Lua itself only generates errors whose error object is a string, 345 1.2 lneto but programs may generate errors with 346 1.3 lneto any value as the error object. 347 1.3 lneto It is up to the Lua program or its host to handle such error objects. 348 1.1 mbalmer 349 1.1 mbalmer 350 1.1 mbalmer <p> 351 1.2 lneto When you use <a href="#pdf-xpcall"><code>xpcall</code></a> or <a href="#lua_pcall"><code>lua_pcall</code></a>, 352 1.2 lneto you may give a <em>message handler</em> 353 1.2 lneto to be called in case of errors. 354 1.2 lneto This function is called with the original error message 355 1.2 lneto and returns a new error message. 356 1.2 lneto It is called before the error unwinds the stack, 357 1.2 lneto so that it can gather more information about the error, 358 1.2 lneto for instance by inspecting the stack and creating a stack traceback. 359 1.2 lneto This message handler is still protected by the protected call; 360 1.2 lneto so, an error inside the message handler 361 1.2 lneto will call the message handler again. 362 1.3 lneto If this loop goes on for too long, 363 1.3 lneto Lua breaks it and returns an appropriate message. 364 1.1 mbalmer 365 1.1 mbalmer 366 1.1 mbalmer 367 1.1 mbalmer 368 1.1 mbalmer 369 1.2 lneto <h2>2.4 – <a name="2.4">Metatables and Metamethods</a></h2> 370 1.1 mbalmer 371 1.2 lneto <p> 372 1.2 lneto Every value in Lua can have a <em>metatable</em>. 373 1.2 lneto This <em>metatable</em> is an ordinary Lua table 374 1.2 lneto that defines the behavior of the original value 375 1.2 lneto under certain special operations. 376 1.2 lneto You can change several aspects of the behavior 377 1.2 lneto of operations over a value by setting specific fields in its metatable. 378 1.2 lneto For instance, when a non-numeric value is the operand of an addition, 379 1.2 lneto Lua checks for a function in the field "<code>__add</code>" of the value's metatable. 380 1.2 lneto If it finds one, 381 1.2 lneto Lua calls this function to perform the addition. 382 1.1 mbalmer 383 1.1 mbalmer 384 1.1 mbalmer <p> 385 1.2 lneto The keys in a metatable are derived from the <em>event</em> names; 386 1.2 lneto the corresponding values are called <em>metamethods</em>. 387 1.2 lneto In the previous example, the event is <code>"add"</code> 388 1.2 lneto and the metamethod is the function that performs the addition. 389 1.1 mbalmer 390 1.1 mbalmer 391 1.2 lneto <p> 392 1.2 lneto You can query the metatable of any value 393 1.2 lneto using the <a href="#pdf-getmetatable"><code>getmetatable</code></a> function. 394 1.1 mbalmer 395 1.1 mbalmer 396 1.1 mbalmer <p> 397 1.2 lneto You can replace the metatable of tables 398 1.2 lneto using the <a href="#pdf-setmetatable"><code>setmetatable</code></a> function. 399 1.4 mbalmer You cannot change the metatable of other types from Lua code 400 1.3 lneto (except by using the debug library (<a href="#6.10">§6.10</a>)); 401 1.5 lneto you should use the C API for that. 402 1.1 mbalmer 403 1.1 mbalmer 404 1.1 mbalmer <p> 405 1.2 lneto Tables and full userdata have individual metatables 406 1.2 lneto (although multiple tables and userdata can share their metatables). 407 1.2 lneto Values of all other types share one single metatable per type; 408 1.2 lneto that is, there is one single metatable for all numbers, 409 1.2 lneto one for all strings, etc. 410 1.2 lneto By default, a value has no metatable, 411 1.2 lneto but the string library sets a metatable for the string type (see <a href="#6.4">§6.4</a>). 412 1.1 mbalmer 413 1.1 mbalmer 414 1.1 mbalmer <p> 415 1.2 lneto A metatable controls how an object behaves in 416 1.3 lneto arithmetic operations, bitwise operations, 417 1.2 lneto order comparisons, concatenation, length operation, calls, and indexing. 418 1.2 lneto A metatable also can define a function to be called 419 1.3 lneto when a userdata or a table is garbage collected (<a href="#2.5">§2.5</a>). 420 1.1 mbalmer 421 1.1 mbalmer 422 1.1 mbalmer <p> 423 1.2 lneto A detailed list of events controlled by metatables is given next. 424 1.2 lneto Each operation is identified by its corresponding event name. 425 1.2 lneto The key for each event is a string with its name prefixed by 426 1.2 lneto two underscores, '<code>__</code>'; 427 1.2 lneto for instance, the key for operation "add" is the 428 1.2 lneto string "<code>__add</code>". 429 1.2 lneto Note that queries for metamethods are always raw; 430 1.2 lneto the access to a metamethod does not invoke other metamethods. 431 1.1 mbalmer 432 1.1 mbalmer 433 1.2 lneto <p> 434 1.2 lneto For the unary operators (negation, length, and bitwise not), 435 1.2 lneto the metamethod is computed and called with a dummy second operand, 436 1.2 lneto equal to the first one. 437 1.2 lneto This extra operand is only to simplify Lua's internals 438 1.2 lneto (by making these operators behave like a binary operation) 439 1.2 lneto and may be removed in future versions. 440 1.2 lneto (For most uses this extra operand is irrelevant.) 441 1.1 mbalmer 442 1.1 mbalmer 443 1.1 mbalmer 444 1.2 lneto <ul> 445 1.1 mbalmer 446 1.2 lneto <li><b>"add": </b> 447 1.2 lneto the <code>+</code> operation. 448 1.1 mbalmer 449 1.2 lneto If any operand for an addition is not a number 450 1.2 lneto (nor a string coercible to a number), 451 1.2 lneto Lua will try to call a metamethod. 452 1.2 lneto First, Lua will check the first operand (even if it is valid). 453 1.2 lneto If that operand does not define a metamethod for the "<code>__add</code>" event, 454 1.2 lneto then Lua will check the second operand. 455 1.3 lneto If Lua can find a metamethod, 456 1.2 lneto it calls the metamethod with the two operands as arguments, 457 1.2 lneto and the result of the call 458 1.2 lneto (adjusted to one value) 459 1.2 lneto is the result of the operation. 460 1.3 lneto Otherwise, 461 1.3 lneto it raises an error. 462 1.2 lneto </li> 463 1.1 mbalmer 464 1.2 lneto <li><b>"sub": </b> 465 1.2 lneto the <code>-</code> operation. 466 1.1 mbalmer 467 1.2 lneto Behavior similar to the "add" operation. 468 1.2 lneto </li> 469 1.1 mbalmer 470 1.2 lneto <li><b>"mul": </b> 471 1.2 lneto the <code>*</code> operation. 472 1.1 mbalmer 473 1.2 lneto Behavior similar to the "add" operation. 474 1.2 lneto </li> 475 1.1 mbalmer 476 1.2 lneto <li><b>"div": </b> 477 1.2 lneto the <code>/</code> operation. 478 1.1 mbalmer 479 1.2 lneto Behavior similar to the "add" operation. 480 1.2 lneto </li> 481 1.1 mbalmer 482 1.2 lneto <li><b>"mod": </b> 483 1.2 lneto the <code>%</code> operation. 484 1.1 mbalmer 485 1.2 lneto Behavior similar to the "add" operation. 486 1.2 lneto </li> 487 1.1 mbalmer 488 1.2 lneto <li><b>"pow": </b> 489 1.2 lneto the <code>^</code> (exponentiation) operation. 490 1.1 mbalmer 491 1.2 lneto Behavior similar to the "add" operation. 492 1.2 lneto </li> 493 1.1 mbalmer 494 1.2 lneto <li><b>"unm": </b> 495 1.2 lneto the <code>-</code> (unary minus) operation. 496 1.1 mbalmer 497 1.2 lneto Behavior similar to the "add" operation. 498 1.2 lneto </li> 499 1.1 mbalmer 500 1.2 lneto <li><b>"idiv": </b> 501 1.3 lneto the <code>//</code> (floor division) operation. 502 1.1 mbalmer 503 1.3 lneto Behavior similar to the "add" operation. 504 1.2 lneto </li> 505 1.1 mbalmer 506 1.2 lneto <li><b>"band": </b> 507 1.2 lneto the <code>&</code> (bitwise and) operation. 508 1.1 mbalmer 509 1.3 lneto Behavior similar to the "add" operation, 510 1.3 lneto except that Lua will try a metamethod 511 1.4 mbalmer if any operand is neither an integer 512 1.3 lneto nor a value coercible to an integer (see <a href="#3.4.3">§3.4.3</a>). 513 1.2 lneto </li> 514 1.1 mbalmer 515 1.2 lneto <li><b>"bor": </b> 516 1.2 lneto the <code>|</code> (bitwise or) operation. 517 1.1 mbalmer 518 1.2 lneto Behavior similar to the "band" operation. 519 1.2 lneto </li> 520 1.1 mbalmer 521 1.2 lneto <li><b>"bxor": </b> 522 1.2 lneto the <code>~</code> (bitwise exclusive or) operation. 523 1.1 mbalmer 524 1.2 lneto Behavior similar to the "band" operation. 525 1.2 lneto </li> 526 1.1 mbalmer 527 1.2 lneto <li><b>"bnot": </b> 528 1.2 lneto the <code>~</code> (bitwise unary not) operation. 529 1.1 mbalmer 530 1.2 lneto Behavior similar to the "band" operation. 531 1.2 lneto </li> 532 1.1 mbalmer 533 1.2 lneto <li><b>"shl": </b> 534 1.2 lneto the <code><<</code> (bitwise left shift) operation. 535 1.1 mbalmer 536 1.2 lneto Behavior similar to the "band" operation. 537 1.2 lneto </li> 538 1.1 mbalmer 539 1.2 lneto <li><b>"shr": </b> 540 1.2 lneto the <code>>></code> (bitwise right shift) operation. 541 1.1 mbalmer 542 1.2 lneto Behavior similar to the "band" operation. 543 1.2 lneto </li> 544 1.1 mbalmer 545 1.2 lneto <li><b>"concat": </b> 546 1.2 lneto the <code>..</code> (concatenation) operation. 547 1.1 mbalmer 548 1.2 lneto Behavior similar to the "add" operation, 549 1.2 lneto except that Lua will try a metamethod 550 1.4 mbalmer if any operand is neither a string nor a number 551 1.2 lneto (which is always coercible to a string). 552 1.2 lneto </li> 553 1.2 lneto 554 1.2 lneto <li><b>"len": </b> 555 1.2 lneto the <code>#</code> (length) operation. 556 1.2 lneto 557 1.2 lneto If the object is not a string, 558 1.2 lneto Lua will try its metamethod. 559 1.2 lneto If there is a metamethod, 560 1.2 lneto Lua calls it with the object as argument, 561 1.2 lneto and the result of the call 562 1.2 lneto (always adjusted to one value) 563 1.2 lneto is the result of the operation. 564 1.2 lneto If there is no metamethod but the object is a table, 565 1.2 lneto then Lua uses the table length operation (see <a href="#3.4.7">§3.4.7</a>). 566 1.2 lneto Otherwise, Lua raises an error. 567 1.2 lneto </li> 568 1.1 mbalmer 569 1.2 lneto <li><b>"eq": </b> 570 1.2 lneto the <code>==</code> (equal) operation. 571 1.1 mbalmer 572 1.2 lneto Behavior similar to the "add" operation, 573 1.2 lneto except that Lua will try a metamethod only when the values 574 1.2 lneto being compared are either both tables or both full userdata 575 1.2 lneto and they are not primitively equal. 576 1.2 lneto The result of the call is always converted to a boolean. 577 1.2 lneto </li> 578 1.1 mbalmer 579 1.2 lneto <li><b>"lt": </b> 580 1.2 lneto the <code><</code> (less than) operation. 581 1.1 mbalmer 582 1.2 lneto Behavior similar to the "add" operation, 583 1.2 lneto except that Lua will try a metamethod only when the values 584 1.2 lneto being compared are neither both numbers nor both strings. 585 1.2 lneto The result of the call is always converted to a boolean. 586 1.2 lneto </li> 587 1.2 lneto 588 1.2 lneto <li><b>"le": </b> 589 1.2 lneto the <code><=</code> (less equal) operation. 590 1.2 lneto 591 1.2 lneto Unlike other operations, 592 1.5 lneto the less-equal operation can use two different events. 593 1.2 lneto First, Lua looks for the "<code>__le</code>" metamethod in both operands, 594 1.2 lneto like in the "lt" operation. 595 1.2 lneto If it cannot find such a metamethod, 596 1.2 lneto then it will try the "<code>__lt</code>" event, 597 1.2 lneto assuming that <code>a <= b</code> is equivalent to <code>not (b < a)</code>. 598 1.2 lneto As with the other comparison operators, 599 1.2 lneto the result is always a boolean. 600 1.4 mbalmer (This use of the "<code>__lt</code>" event can be removed in future versions; 601 1.4 mbalmer it is also slower than a real "<code>__le</code>" metamethod.) 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 1.4 mbalmer <p> 665 1.4 mbalmer It is a good practice to add all needed metamethods to a table 666 1.4 mbalmer before setting it as a metatable of some object. 667 1.4 mbalmer In particular, the "<code>__gc</code>" metamethod works only when this order 668 1.4 mbalmer is followed (see <a href="#2.5.1">§2.5.1</a>). 669 1.4 mbalmer 670 1.4 mbalmer 671 1.1 mbalmer 672 1.1 mbalmer 673 1.1 mbalmer 674 1.2 lneto <h2>2.5 – <a name="2.5">Garbage Collection</a></h2> 675 1.1 mbalmer 676 1.1 mbalmer <p> 677 1.2 lneto Lua performs automatic memory management. 678 1.2 lneto This means that 679 1.3 lneto you do not have to worry about allocating memory for new objects 680 1.3 lneto or freeing it when the objects are no longer needed. 681 1.2 lneto Lua manages memory automatically by running 682 1.2 lneto a <em>garbage collector</em> to collect all <em>dead objects</em> 683 1.2 lneto (that is, objects that are no longer accessible from Lua). 684 1.2 lneto All memory used by Lua is subject to automatic management: 685 1.2 lneto strings, tables, userdata, functions, threads, internal structures, etc. 686 1.1 mbalmer 687 1.2 lneto 688 1.2 lneto <p> 689 1.2 lneto Lua implements an incremental mark-and-sweep collector. 690 1.2 lneto It uses two numbers to control its garbage-collection cycles: 691 1.2 lneto the <em>garbage-collector pause</em> and 692 1.2 lneto the <em>garbage-collector step multiplier</em>. 693 1.2 lneto Both use percentage points as units 694 1.2 lneto (e.g., a value of 100 means an internal value of 1). 695 1.1 mbalmer 696 1.1 mbalmer 697 1.1 mbalmer <p> 698 1.2 lneto The garbage-collector pause 699 1.2 lneto controls how long the collector waits before starting a new cycle. 700 1.2 lneto Larger values make the collector less aggressive. 701 1.2 lneto Values smaller than 100 mean the collector will not wait to 702 1.2 lneto start a new cycle. 703 1.2 lneto A value of 200 means that the collector waits for the total memory in use 704 1.2 lneto to double before starting a new cycle. 705 1.2 lneto 706 1.1 mbalmer 707 1.2 lneto <p> 708 1.2 lneto The garbage-collector step multiplier 709 1.2 lneto controls the relative speed of the collector relative to 710 1.2 lneto memory allocation. 711 1.2 lneto Larger values make the collector more aggressive but also increase 712 1.2 lneto the size of each incremental step. 713 1.2 lneto You should not use values smaller than 100, 714 1.3 lneto because they make the collector too slow and 715 1.2 lneto can result in the collector never finishing a cycle. 716 1.2 lneto The default is 200, 717 1.2 lneto which means that the collector runs at "twice" 718 1.2 lneto the speed of memory allocation. 719 1.1 mbalmer 720 1.1 mbalmer 721 1.2 lneto <p> 722 1.2 lneto If you set the step multiplier to a very large number 723 1.2 lneto (larger than 10% of the maximum number of 724 1.2 lneto bytes that the program may use), 725 1.2 lneto the collector behaves like a stop-the-world collector. 726 1.2 lneto If you then set the pause to 200, 727 1.2 lneto the collector behaves as in old Lua versions, 728 1.2 lneto doing a complete collection every time Lua doubles its 729 1.2 lneto memory usage. 730 1.1 mbalmer 731 1.1 mbalmer 732 1.2 lneto <p> 733 1.2 lneto You can change these numbers by calling <a href="#lua_gc"><code>lua_gc</code></a> in C 734 1.2 lneto or <a href="#pdf-collectgarbage"><code>collectgarbage</code></a> in Lua. 735 1.2 lneto You can also use these functions to control 736 1.2 lneto the collector directly (e.g., stop and restart it). 737 1.1 mbalmer 738 1.1 mbalmer 739 1.1 mbalmer 740 1.2 lneto <h3>2.5.1 – <a name="2.5.1">Garbage-Collection Metamethods</a></h3> 741 1.1 mbalmer 742 1.2 lneto <p> 743 1.2 lneto You can set garbage-collector metamethods for tables 744 1.2 lneto and, using the C API, 745 1.2 lneto for full userdata (see <a href="#2.4">§2.4</a>). 746 1.2 lneto These metamethods are also called <em>finalizers</em>. 747 1.2 lneto Finalizers allow you to coordinate Lua's garbage collection 748 1.2 lneto with external resource management 749 1.2 lneto (such as closing files, network or database connections, 750 1.2 lneto or freeing your own memory). 751 1.1 mbalmer 752 1.1 mbalmer 753 1.1 mbalmer <p> 754 1.2 lneto For an object (table or userdata) to be finalized when collected, 755 1.2 lneto you must <em>mark</em> it for finalization. 756 1.1 mbalmer 757 1.2 lneto You mark an object for finalization when you set its metatable 758 1.2 lneto and the metatable has a field indexed by the string "<code>__gc</code>". 759 1.2 lneto Note that if you set a metatable without a <code>__gc</code> field 760 1.2 lneto and later create that field in the metatable, 761 1.2 lneto the object will not be marked for finalization. 762 1.1 mbalmer 763 1.1 mbalmer 764 1.2 lneto <p> 765 1.2 lneto When a marked object becomes garbage, 766 1.2 lneto it is not collected immediately by the garbage collector. 767 1.2 lneto Instead, Lua puts it in a list. 768 1.2 lneto After the collection, 769 1.3 lneto Lua goes through that list. 770 1.3 lneto For each object in the list, 771 1.3 lneto it checks the object's <code>__gc</code> metamethod: 772 1.3 lneto If it is a function, 773 1.3 lneto Lua calls it with the object as its single argument; 774 1.3 lneto if the metamethod is not a function, 775 1.3 lneto Lua simply ignores it. 776 1.1 mbalmer 777 1.1 mbalmer 778 1.2 lneto <p> 779 1.2 lneto At the end of each garbage-collection cycle, 780 1.2 lneto the finalizers for objects are called in 781 1.3 lneto the reverse order that the objects were marked for finalization, 782 1.2 lneto among those collected in that cycle; 783 1.2 lneto that is, the first finalizer to be called is the one associated 784 1.2 lneto with the object marked last in the program. 785 1.2 lneto The execution of each finalizer may occur at any point during 786 1.2 lneto the execution of the regular code. 787 1.1 mbalmer 788 1.1 mbalmer 789 1.2 lneto <p> 790 1.2 lneto Because the object being collected must still be used by the finalizer, 791 1.3 lneto that object (and other objects accessible only through it) 792 1.2 lneto must be <em>resurrected</em> by Lua. 793 1.2 lneto Usually, this resurrection is transient, 794 1.2 lneto and the object memory is freed in the next garbage-collection cycle. 795 1.2 lneto However, if the finalizer stores the object in some global place 796 1.2 lneto (e.g., a global variable), 797 1.3 lneto then the resurrection is permanent. 798 1.2 lneto Moreover, if the finalizer marks a finalizing object for finalization again, 799 1.2 lneto its finalizer will be called again in the next cycle where the 800 1.2 lneto object is unreachable. 801 1.2 lneto In any case, 802 1.4 mbalmer the object memory is freed only in a GC cycle where 803 1.2 lneto the object is unreachable and not marked for finalization. 804 1.1 mbalmer 805 1.1 mbalmer 806 1.2 lneto <p> 807 1.2 lneto When you close a state (see <a href="#lua_close"><code>lua_close</code></a>), 808 1.2 lneto Lua calls the finalizers of all objects marked for finalization, 809 1.2 lneto following the reverse order that they were marked. 810 1.2 lneto If any finalizer marks objects for collection during that phase, 811 1.2 lneto these marks have no effect. 812 1.1 mbalmer 813 1.1 mbalmer 814 1.1 mbalmer 815 1.1 mbalmer 816 1.1 mbalmer 817 1.2 lneto <h3>2.5.2 – <a name="2.5.2">Weak Tables</a></h3> 818 1.2 lneto 819 1.2 lneto <p> 820 1.2 lneto A <em>weak table</em> is a table whose elements are 821 1.2 lneto <em>weak references</em>. 822 1.2 lneto A weak reference is ignored by the garbage collector. 823 1.2 lneto In other words, 824 1.2 lneto if the only references to an object are weak references, 825 1.2 lneto then the garbage collector will collect that object. 826 1.2 lneto 827 1.2 lneto 828 1.2 lneto <p> 829 1.2 lneto A weak table can have weak keys, weak values, or both. 830 1.4 mbalmer A table with weak values allows the collection of its values, 831 1.4 mbalmer but prevents the collection of its keys. 832 1.2 lneto A table with both weak keys and weak values allows the collection of 833 1.2 lneto both keys and values. 834 1.2 lneto In any case, if either the key or the value is collected, 835 1.2 lneto the whole pair is removed from the table. 836 1.2 lneto The weakness of a table is controlled by the 837 1.2 lneto <code>__mode</code> field of its metatable. 838 1.2 lneto If the <code>__mode</code> field is a string containing the character '<code>k</code>', 839 1.2 lneto the keys in the table are weak. 840 1.2 lneto If <code>__mode</code> contains '<code>v</code>', 841 1.2 lneto the values in the table are weak. 842 1.1 mbalmer 843 1.1 mbalmer 844 1.2 lneto <p> 845 1.2 lneto A table with weak keys and strong values 846 1.2 lneto is also called an <em>ephemeron table</em>. 847 1.2 lneto In an ephemeron table, 848 1.2 lneto a value is considered reachable only if its key is reachable. 849 1.2 lneto In particular, 850 1.2 lneto if the only reference to a key comes through its value, 851 1.2 lneto the pair is removed. 852 1.1 mbalmer 853 1.1 mbalmer 854 1.2 lneto <p> 855 1.2 lneto Any change in the weakness of a table may take effect only 856 1.2 lneto at the next collect cycle. 857 1.2 lneto In particular, if you change the weakness to a stronger mode, 858 1.2 lneto Lua may still collect some items from that table 859 1.2 lneto before the change takes effect. 860 1.1 mbalmer 861 1.1 mbalmer 862 1.2 lneto <p> 863 1.2 lneto Only objects that have an explicit construction 864 1.2 lneto are removed from weak tables. 865 1.2 lneto Values, such as numbers and light C functions, 866 1.2 lneto are not subject to garbage collection, 867 1.2 lneto and therefore are not removed from weak tables 868 1.3 lneto (unless their associated values are collected). 869 1.2 lneto Although strings are subject to garbage collection, 870 1.2 lneto they do not have an explicit construction, 871 1.2 lneto and therefore are not removed from weak tables. 872 1.1 mbalmer 873 1.1 mbalmer 874 1.1 mbalmer <p> 875 1.2 lneto Resurrected objects 876 1.2 lneto (that is, objects being finalized 877 1.2 lneto and objects accessible only through objects being finalized) 878 1.2 lneto have a special behavior in weak tables. 879 1.2 lneto They are removed from weak values before running their finalizers, 880 1.2 lneto but are removed from weak keys only in the next collection 881 1.2 lneto after running their finalizers, when such objects are actually freed. 882 1.2 lneto This behavior allows the finalizer to access properties 883 1.2 lneto associated with the object through weak tables. 884 1.1 mbalmer 885 1.1 mbalmer 886 1.1 mbalmer <p> 887 1.2 lneto If a weak table is among the resurrected objects in a collection cycle, 888 1.2 lneto it may not be properly cleared until the next cycle. 889 1.1 mbalmer 890 1.1 mbalmer 891 1.1 mbalmer 892 1.1 mbalmer 893 1.1 mbalmer 894 1.1 mbalmer 895 1.1 mbalmer 896 1.2 lneto <h2>2.6 – <a name="2.6">Coroutines</a></h2> 897 1.1 mbalmer 898 1.1 mbalmer <p> 899 1.2 lneto Lua supports coroutines, 900 1.2 lneto also called <em>collaborative multithreading</em>. 901 1.2 lneto A coroutine in Lua represents an independent thread of execution. 902 1.2 lneto Unlike threads in multithread systems, however, 903 1.2 lneto a coroutine only suspends its execution by explicitly calling 904 1.2 lneto a yield function. 905 1.1 mbalmer 906 1.1 mbalmer 907 1.1 mbalmer <p> 908 1.2 lneto You create a coroutine by calling <a href="#pdf-coroutine.create"><code>coroutine.create</code></a>. 909 1.2 lneto Its sole argument is a function 910 1.2 lneto that is the main function of the coroutine. 911 1.2 lneto The <code>create</code> function only creates a new coroutine and 912 1.2 lneto returns a handle to it (an object of type <em>thread</em>); 913 1.2 lneto it does not start the coroutine. 914 1.1 mbalmer 915 1.1 mbalmer 916 1.1 mbalmer <p> 917 1.2 lneto You execute a coroutine by calling <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>. 918 1.2 lneto When you first call <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>, 919 1.2 lneto passing as its first argument 920 1.2 lneto a thread returned by <a href="#pdf-coroutine.create"><code>coroutine.create</code></a>, 921 1.4 mbalmer the coroutine starts its execution by 922 1.4 mbalmer calling its main function. 923 1.3 lneto Extra arguments passed to <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> are passed 924 1.4 mbalmer as arguments to that function. 925 1.2 lneto After the coroutine starts running, 926 1.2 lneto it runs until it terminates or <em>yields</em>. 927 1.1 mbalmer 928 1.1 mbalmer 929 1.1 mbalmer <p> 930 1.2 lneto A coroutine can terminate its execution in two ways: 931 1.2 lneto normally, when its main function returns 932 1.2 lneto (explicitly or implicitly, after the last instruction); 933 1.2 lneto and abnormally, if there is an unprotected error. 934 1.3 lneto In case of normal termination, 935 1.3 lneto <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> returns <b>true</b>, 936 1.2 lneto plus any values returned by the coroutine main function. 937 1.2 lneto In case of errors, <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> returns <b>false</b> 938 1.2 lneto plus an error message. 939 1.1 mbalmer 940 1.1 mbalmer 941 1.1 mbalmer <p> 942 1.2 lneto A coroutine yields by calling <a href="#pdf-coroutine.yield"><code>coroutine.yield</code></a>. 943 1.2 lneto When a coroutine yields, 944 1.2 lneto the corresponding <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> returns immediately, 945 1.2 lneto even if the yield happens inside nested function calls 946 1.2 lneto (that is, not in the main function, 947 1.2 lneto but in a function directly or indirectly called by the main function). 948 1.2 lneto In the case of a yield, <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> also returns <b>true</b>, 949 1.2 lneto plus any values passed to <a href="#pdf-coroutine.yield"><code>coroutine.yield</code></a>. 950 1.2 lneto The next time you resume the same coroutine, 951 1.2 lneto it continues its execution from the point where it yielded, 952 1.2 lneto with the call to <a href="#pdf-coroutine.yield"><code>coroutine.yield</code></a> returning any extra 953 1.2 lneto arguments passed to <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>. 954 1.1 mbalmer 955 1.1 mbalmer 956 1.1 mbalmer <p> 957 1.2 lneto Like <a href="#pdf-coroutine.create"><code>coroutine.create</code></a>, 958 1.2 lneto the <a href="#pdf-coroutine.wrap"><code>coroutine.wrap</code></a> function also creates a coroutine, 959 1.2 lneto but instead of returning the coroutine itself, 960 1.2 lneto it returns a function that, when called, resumes the coroutine. 961 1.2 lneto Any arguments passed to this function 962 1.2 lneto go as extra arguments to <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>. 963 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>, 964 1.2 lneto except the first one (the boolean error code). 965 1.2 lneto Unlike <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>, 966 1.2 lneto <a href="#pdf-coroutine.wrap"><code>coroutine.wrap</code></a> does not catch errors; 967 1.2 lneto any error is propagated to the caller. 968 1.1 mbalmer 969 1.1 mbalmer 970 1.2 lneto <p> 971 1.2 lneto As an example of how coroutines work, 972 1.2 lneto consider the following code: 973 1.1 mbalmer 974 1.1 mbalmer <pre> 975 1.2 lneto function foo (a) 976 1.2 lneto print("foo", a) 977 1.2 lneto return coroutine.yield(2*a) 978 1.2 lneto end 979 1.2 lneto 980 1.2 lneto co = coroutine.create(function (a,b) 981 1.2 lneto print("co-body", a, b) 982 1.2 lneto local r = foo(a+1) 983 1.2 lneto print("co-body", r) 984 1.2 lneto local r, s = coroutine.yield(a+b, a-b) 985 1.2 lneto print("co-body", r, s) 986 1.2 lneto return b, "end" 987 1.2 lneto end) 988 1.2 lneto 989 1.2 lneto print("main", coroutine.resume(co, 1, 10)) 990 1.2 lneto print("main", coroutine.resume(co, "r")) 991 1.2 lneto print("main", coroutine.resume(co, "x", "y")) 992 1.2 lneto print("main", coroutine.resume(co, "x", "y")) 993 1.1 mbalmer </pre><p> 994 1.2 lneto When you run it, it produces the following output: 995 1.1 mbalmer 996 1.2 lneto <pre> 997 1.2 lneto co-body 1 10 998 1.2 lneto foo 2 999 1.2 lneto main true 4 1000 1.2 lneto co-body r 1001 1.2 lneto main true 11 -9 1002 1.2 lneto co-body x y 1003 1.2 lneto main true 10 end 1004 1.2 lneto main false cannot resume dead coroutine 1005 1.2 lneto </pre> 1006 1.1 mbalmer 1007 1.2 lneto <p> 1008 1.2 lneto You can also create and manipulate coroutines through the C API: 1009 1.2 lneto see functions <a href="#lua_newthread"><code>lua_newthread</code></a>, <a href="#lua_resume"><code>lua_resume</code></a>, 1010 1.2 lneto and <a href="#lua_yield"><code>lua_yield</code></a>. 1011 1.1 mbalmer 1012 1.1 mbalmer 1013 1.1 mbalmer 1014 1.1 mbalmer 1015 1.1 mbalmer 1016 1.2 lneto <h1>3 – <a name="3">The Language</a></h1> 1017 1.1 mbalmer 1018 1.1 mbalmer <p> 1019 1.2 lneto This section describes the lexis, the syntax, and the semantics of Lua. 1020 1.2 lneto In other words, 1021 1.2 lneto this section describes 1022 1.2 lneto which tokens are valid, 1023 1.2 lneto how they can be combined, 1024 1.2 lneto and what their combinations mean. 1025 1.1 mbalmer 1026 1.1 mbalmer 1027 1.1 mbalmer <p> 1028 1.2 lneto Language constructs will be explained using the usual extended BNF notation, 1029 1.2 lneto in which 1030 1.2 lneto {<em>a</em>} means 0 or more <em>a</em>'s, and 1031 1.2 lneto [<em>a</em>] means an optional <em>a</em>. 1032 1.2 lneto Non-terminals are shown like non-terminal, 1033 1.2 lneto keywords are shown like <b>kword</b>, 1034 1.2 lneto and other terminal symbols are shown like ‘<b>=</b>’. 1035 1.2 lneto The complete syntax of Lua can be found in <a href="#9">§9</a> 1036 1.2 lneto at the end of this manual. 1037 1.1 mbalmer 1038 1.1 mbalmer 1039 1.1 mbalmer 1040 1.2 lneto <h2>3.1 – <a name="3.1">Lexical Conventions</a></h2> 1041 1.1 mbalmer 1042 1.1 mbalmer <p> 1043 1.2 lneto Lua is a free-form language. 1044 1.2 lneto It ignores spaces (including new lines) and comments 1045 1.2 lneto between lexical elements (tokens), 1046 1.2 lneto except as delimiters between names and keywords. 1047 1.1 mbalmer 1048 1.1 mbalmer 1049 1.1 mbalmer <p> 1050 1.2 lneto <em>Names</em> 1051 1.2 lneto (also called <em>identifiers</em>) 1052 1.2 lneto in Lua can be any string of letters, 1053 1.2 lneto digits, and underscores, 1054 1.5 lneto not beginning with a digit and 1055 1.5 lneto not being a reserved word. 1056 1.2 lneto Identifiers are used to name variables, table fields, and labels. 1057 1.1 mbalmer 1058 1.1 mbalmer 1059 1.2 lneto <p> 1060 1.2 lneto The following <em>keywords</em> are reserved 1061 1.2 lneto and cannot be used as names: 1062 1.1 mbalmer 1063 1.1 mbalmer 1064 1.2 lneto <pre> 1065 1.2 lneto and break do else elseif end 1066 1.2 lneto false for function goto if in 1067 1.2 lneto local nil not or repeat return 1068 1.2 lneto then true until while 1069 1.2 lneto </pre> 1070 1.1 mbalmer 1071 1.2 lneto <p> 1072 1.2 lneto Lua is a case-sensitive language: 1073 1.2 lneto <code>and</code> is a reserved word, but <code>And</code> and <code>AND</code> 1074 1.2 lneto are two different, valid names. 1075 1.2 lneto As a convention, 1076 1.2 lneto programs should avoid creating 1077 1.2 lneto names that start with an underscore followed by 1078 1.2 lneto one or more uppercase letters (such as <a href="#pdf-_VERSION"><code>_VERSION</code></a>). 1079 1.1 mbalmer 1080 1.1 mbalmer 1081 1.1 mbalmer <p> 1082 1.2 lneto The following strings denote other tokens: 1083 1.1 mbalmer 1084 1.1 mbalmer <pre> 1085 1.2 lneto + - * / % ^ # 1086 1.2 lneto & ~ | << >> // 1087 1.2 lneto == ~= <= >= < > = 1088 1.2 lneto ( ) { } [ ] :: 1089 1.2 lneto ; : , . .. ... 1090 1.2 lneto </pre> 1091 1.1 mbalmer 1092 1.1 mbalmer <p> 1093 1.2 lneto <em>Literal strings</em> 1094 1.2 lneto can be delimited by matching single or double quotes, 1095 1.2 lneto and can contain the following C-like escape sequences: 1096 1.2 lneto '<code>\a</code>' (bell), 1097 1.2 lneto '<code>\b</code>' (backspace), 1098 1.2 lneto '<code>\f</code>' (form feed), 1099 1.2 lneto '<code>\n</code>' (newline), 1100 1.2 lneto '<code>\r</code>' (carriage return), 1101 1.2 lneto '<code>\t</code>' (horizontal tab), 1102 1.2 lneto '<code>\v</code>' (vertical tab), 1103 1.2 lneto '<code>\\</code>' (backslash), 1104 1.2 lneto '<code>\"</code>' (quotation mark [double quote]), 1105 1.2 lneto and '<code>\'</code>' (apostrophe [single quote]). 1106 1.2 lneto A backslash followed by a real newline 1107 1.2 lneto results in a newline in the string. 1108 1.2 lneto The escape sequence '<code>\z</code>' skips the following span 1109 1.2 lneto of white-space characters, 1110 1.2 lneto including line breaks; 1111 1.2 lneto it is particularly useful to break and indent a long literal string 1112 1.2 lneto into multiple lines without adding the newlines and spaces 1113 1.2 lneto into the string contents. 1114 1.1 mbalmer 1115 1.1 mbalmer 1116 1.1 mbalmer <p> 1117 1.3 lneto Strings in Lua can contain any 8-bit value, including embedded zeros, 1118 1.3 lneto which can be specified as '<code>\0</code>'. 1119 1.3 lneto More generally, 1120 1.4 mbalmer we can specify any byte in a literal string by its numeric value. 1121 1.3 lneto This can be done 1122 1.3 lneto with the escape sequence <code>\x<em>XX</em></code>, 1123 1.2 lneto where <em>XX</em> is a sequence of exactly two hexadecimal digits, 1124 1.2 lneto or with the escape sequence <code>\<em>ddd</em></code>, 1125 1.2 lneto where <em>ddd</em> is a sequence of up to three decimal digits. 1126 1.3 lneto (Note that if a decimal escape sequence is to be followed by a digit, 1127 1.2 lneto it must be expressed using exactly three digits.) 1128 1.1 mbalmer 1129 1.1 mbalmer 1130 1.2 lneto <p> 1131 1.2 lneto The UTF-8 encoding of a Unicode character 1132 1.2 lneto can be inserted in a literal string with 1133 1.2 lneto the escape sequence <code>\u{<em>XXX</em>}</code> 1134 1.2 lneto (note the mandatory enclosing brackets), 1135 1.2 lneto where <em>XXX</em> is a sequence of one or more hexadecimal digits 1136 1.2 lneto representing the character code point. 1137 1.1 mbalmer 1138 1.1 mbalmer 1139 1.2 lneto <p> 1140 1.2 lneto Literal strings can also be defined using a long format 1141 1.2 lneto enclosed by <em>long brackets</em>. 1142 1.2 lneto We define an <em>opening long bracket of level <em>n</em></em> as an opening 1143 1.2 lneto square bracket followed by <em>n</em> equal signs followed by another 1144 1.2 lneto opening square bracket. 1145 1.2 lneto So, an opening long bracket of level 0 is written as <code>[[</code>, 1146 1.2 lneto an opening long bracket of level 1 is written as <code>[=[</code>, 1147 1.2 lneto and so on. 1148 1.2 lneto A <em>closing long bracket</em> is defined similarly; 1149 1.2 lneto for instance, 1150 1.2 lneto a closing long bracket of level 4 is written as <code>]====]</code>. 1151 1.2 lneto A <em>long literal</em> starts with an opening long bracket of any level and 1152 1.2 lneto ends at the first closing long bracket of the same level. 1153 1.3 lneto It can contain any text except a closing bracket of the same level. 1154 1.2 lneto Literals in this bracketed form can run for several lines, 1155 1.2 lneto do not interpret any escape sequences, 1156 1.2 lneto and ignore long brackets of any other level. 1157 1.2 lneto Any kind of end-of-line sequence 1158 1.2 lneto (carriage return, newline, carriage return followed by newline, 1159 1.2 lneto or newline followed by carriage return) 1160 1.2 lneto is converted to a simple newline. 1161 1.1 mbalmer 1162 1.1 mbalmer 1163 1.2 lneto <p> 1164 1.2 lneto Any byte in a literal string not 1165 1.2 lneto explicitly affected by the previous rules represents itself. 1166 1.2 lneto However, Lua opens files for parsing in text mode, 1167 1.2 lneto and the system file functions may have problems with 1168 1.2 lneto some control characters. 1169 1.2 lneto So, it is safer to represent 1170 1.2 lneto non-text data as a quoted literal with 1171 1.2 lneto explicit escape sequences for non-text characters. 1172 1.1 mbalmer 1173 1.1 mbalmer 1174 1.2 lneto <p> 1175 1.2 lneto For convenience, 1176 1.2 lneto when the opening long bracket is immediately followed by a newline, 1177 1.2 lneto the newline is not included in the string. 1178 1.2 lneto As an example, in a system using ASCII 1179 1.2 lneto (in which '<code>a</code>' is coded as 97, 1180 1.2 lneto newline is coded as 10, and '<code>1</code>' is coded as 49), 1181 1.2 lneto the five literal strings below denote the same string: 1182 1.1 mbalmer 1183 1.1 mbalmer <pre> 1184 1.2 lneto a = 'alo\n123"' 1185 1.2 lneto a = "alo\n123\"" 1186 1.2 lneto a = '\97lo\10\04923"' 1187 1.2 lneto a = [[alo 1188 1.2 lneto 123"]] 1189 1.2 lneto a = [==[ 1190 1.2 lneto alo 1191 1.2 lneto 123"]==] 1192 1.1 mbalmer </pre> 1193 1.1 mbalmer 1194 1.1 mbalmer <p> 1195 1.4 mbalmer A <em>numeric constant</em> (or <em>numeral</em>) 1196 1.3 lneto can be written with an optional fractional part 1197 1.2 lneto and an optional decimal exponent, 1198 1.2 lneto marked by a letter '<code>e</code>' or '<code>E</code>'. 1199 1.2 lneto Lua also accepts hexadecimal constants, 1200 1.2 lneto which start with <code>0x</code> or <code>0X</code>. 1201 1.2 lneto Hexadecimal constants also accept an optional fractional part 1202 1.2 lneto plus an optional binary exponent, 1203 1.2 lneto marked by a letter '<code>p</code>' or '<code>P</code>'. 1204 1.2 lneto A numeric constant with a fractional dot or an exponent 1205 1.2 lneto denotes a float; 1206 1.2 lneto otherwise it denotes an integer. 1207 1.2 lneto Examples of valid integer constants are 1208 1.1 mbalmer 1209 1.1 mbalmer <pre> 1210 1.2 lneto 3 345 0xff 0xBEBADA 1211 1.1 mbalmer </pre><p> 1212 1.2 lneto Examples of valid float constants are 1213 1.1 mbalmer 1214 1.1 mbalmer <pre> 1215 1.2 lneto 3.0 3.1416 314.16e-2 0.31416E1 34e1 1216 1.2 lneto 0x0.1E 0xA23p-4 0X1.921FB54442D18P+1 1217 1.1 mbalmer </pre> 1218 1.1 mbalmer 1219 1.1 mbalmer <p> 1220 1.2 lneto A <em>comment</em> starts with a double hyphen (<code>--</code>) 1221 1.2 lneto anywhere outside a string. 1222 1.2 lneto If the text immediately after <code>--</code> is not an opening long bracket, 1223 1.2 lneto the comment is a <em>short comment</em>, 1224 1.2 lneto which runs until the end of the line. 1225 1.2 lneto Otherwise, it is a <em>long comment</em>, 1226 1.2 lneto which runs until the corresponding closing long bracket. 1227 1.2 lneto Long comments are frequently used to disable code temporarily. 1228 1.2 lneto 1229 1.1 mbalmer 1230 1.1 mbalmer 1231 1.1 mbalmer 1232 1.1 mbalmer 1233 1.2 lneto <h2>3.2 – <a name="3.2">Variables</a></h2> 1234 1.1 mbalmer 1235 1.2 lneto <p> 1236 1.2 lneto Variables are places that store values. 1237 1.2 lneto There are three kinds of variables in Lua: 1238 1.2 lneto global variables, local variables, and table fields. 1239 1.1 mbalmer 1240 1.1 mbalmer 1241 1.2 lneto <p> 1242 1.2 lneto A single name can denote a global variable or a local variable 1243 1.2 lneto (or a function's formal parameter, 1244 1.2 lneto which is a particular kind of local variable): 1245 1.1 mbalmer 1246 1.1 mbalmer <pre> 1247 1.2 lneto var ::= Name 1248 1.1 mbalmer </pre><p> 1249 1.2 lneto Name denotes identifiers, as defined in <a href="#3.1">§3.1</a>. 1250 1.1 mbalmer 1251 1.1 mbalmer 1252 1.1 mbalmer <p> 1253 1.2 lneto Any variable name is assumed to be global unless explicitly declared 1254 1.2 lneto as a local (see <a href="#3.3.7">§3.3.7</a>). 1255 1.2 lneto Local variables are <em>lexically scoped</em>: 1256 1.2 lneto local variables can be freely accessed by functions 1257 1.2 lneto defined inside their scope (see <a href="#3.5">§3.5</a>). 1258 1.2 lneto 1259 1.1 mbalmer 1260 1.2 lneto <p> 1261 1.2 lneto Before the first assignment to a variable, its value is <b>nil</b>. 1262 1.1 mbalmer 1263 1.1 mbalmer 1264 1.1 mbalmer <p> 1265 1.2 lneto Square brackets are used to index a table: 1266 1.1 mbalmer 1267 1.1 mbalmer <pre> 1268 1.2 lneto var ::= prefixexp ‘<b>[</b>’ exp ‘<b>]</b>’ 1269 1.1 mbalmer </pre><p> 1270 1.2 lneto The meaning of accesses to table fields can be changed via metatables. 1271 1.2 lneto An access to an indexed variable <code>t[i]</code> is equivalent to 1272 1.2 lneto a call <code>gettable_event(t,i)</code>. 1273 1.2 lneto (See <a href="#2.4">§2.4</a> for a complete description of the 1274 1.2 lneto <code>gettable_event</code> function. 1275 1.2 lneto This function is not defined or callable in Lua. 1276 1.2 lneto We use it here only for explanatory purposes.) 1277 1.1 mbalmer 1278 1.1 mbalmer 1279 1.1 mbalmer <p> 1280 1.2 lneto The syntax <code>var.Name</code> is just syntactic sugar for 1281 1.2 lneto <code>var["Name"]</code>: 1282 1.1 mbalmer 1283 1.1 mbalmer <pre> 1284 1.2 lneto var ::= prefixexp ‘<b>.</b>’ Name 1285 1.2 lneto </pre> 1286 1.1 mbalmer 1287 1.1 mbalmer <p> 1288 1.2 lneto An access to a global variable <code>x</code> 1289 1.2 lneto is equivalent to <code>_ENV.x</code>. 1290 1.2 lneto Due to the way that chunks are compiled, 1291 1.2 lneto <code>_ENV</code> is never a global name (see <a href="#2.2">§2.2</a>). 1292 1.1 mbalmer 1293 1.1 mbalmer 1294 1.1 mbalmer 1295 1.1 mbalmer 1296 1.1 mbalmer 1297 1.2 lneto <h2>3.3 – <a name="3.3">Statements</a></h2> 1298 1.1 mbalmer 1299 1.1 mbalmer <p> 1300 1.2 lneto Lua supports an almost conventional set of statements, 1301 1.2 lneto similar to those in Pascal or C. 1302 1.2 lneto This set includes 1303 1.2 lneto assignments, control structures, function calls, 1304 1.2 lneto and variable declarations. 1305 1.2 lneto 1306 1.2 lneto 1307 1.1 mbalmer 1308 1.2 lneto <h3>3.3.1 – <a name="3.3.1">Blocks</a></h3> 1309 1.1 mbalmer 1310 1.1 mbalmer <p> 1311 1.2 lneto A block is a list of statements, 1312 1.2 lneto which are executed sequentially: 1313 1.1 mbalmer 1314 1.1 mbalmer <pre> 1315 1.2 lneto block ::= {stat} 1316 1.1 mbalmer </pre><p> 1317 1.2 lneto Lua has <em>empty statements</em> 1318 1.2 lneto that allow you to separate statements with semicolons, 1319 1.2 lneto start a block with a semicolon 1320 1.2 lneto or write two semicolons in sequence: 1321 1.1 mbalmer 1322 1.1 mbalmer <pre> 1323 1.2 lneto stat ::= ‘<b>;</b>’ 1324 1.2 lneto </pre> 1325 1.2 lneto 1326 1.2 lneto <p> 1327 1.2 lneto Function calls and assignments 1328 1.2 lneto can start with an open parenthesis. 1329 1.2 lneto This possibility leads to an ambiguity in Lua's grammar. 1330 1.2 lneto Consider the following fragment: 1331 1.1 mbalmer 1332 1.1 mbalmer <pre> 1333 1.2 lneto a = b + c 1334 1.2 lneto (print or io.write)('done') 1335 1.1 mbalmer </pre><p> 1336 1.2 lneto The grammar could see it in two ways: 1337 1.1 mbalmer 1338 1.1 mbalmer <pre> 1339 1.2 lneto a = b + c(print or io.write)('done') 1340 1.2 lneto 1341 1.2 lneto a = b + c; (print or io.write)('done') 1342 1.1 mbalmer </pre><p> 1343 1.2 lneto The current parser always sees such constructions 1344 1.2 lneto in the first way, 1345 1.2 lneto interpreting the open parenthesis 1346 1.2 lneto as the start of the arguments to a call. 1347 1.2 lneto To avoid this ambiguity, 1348 1.2 lneto it is a good practice to always precede with a semicolon 1349 1.2 lneto statements that start with a parenthesis: 1350 1.1 mbalmer 1351 1.1 mbalmer <pre> 1352 1.2 lneto ;(print or io.write)('done') 1353 1.2 lneto </pre> 1354 1.2 lneto 1355 1.2 lneto <p> 1356 1.2 lneto A block can be explicitly delimited to produce a single statement: 1357 1.1 mbalmer 1358 1.1 mbalmer <pre> 1359 1.2 lneto stat ::= <b>do</b> block <b>end</b> 1360 1.1 mbalmer </pre><p> 1361 1.2 lneto Explicit blocks are useful 1362 1.2 lneto to control the scope of variable declarations. 1363 1.2 lneto Explicit blocks are also sometimes used to 1364 1.2 lneto add a <b>return</b> statement in the middle 1365 1.2 lneto of another block (see <a href="#3.3.4">§3.3.4</a>). 1366 1.2 lneto 1367 1.2 lneto 1368 1.2 lneto 1369 1.2 lneto 1370 1.2 lneto 1371 1.2 lneto <h3>3.3.2 – <a name="3.3.2">Chunks</a></h3> 1372 1.2 lneto 1373 1.2 lneto <p> 1374 1.2 lneto The unit of compilation of Lua is called a <em>chunk</em>. 1375 1.2 lneto Syntactically, 1376 1.2 lneto a chunk is simply a block: 1377 1.1 mbalmer 1378 1.1 mbalmer <pre> 1379 1.2 lneto chunk ::= block 1380 1.2 lneto </pre> 1381 1.1 mbalmer 1382 1.2 lneto <p> 1383 1.2 lneto Lua handles a chunk as the body of an anonymous function 1384 1.2 lneto with a variable number of arguments 1385 1.2 lneto (see <a href="#3.4.11">§3.4.11</a>). 1386 1.2 lneto As such, chunks can define local variables, 1387 1.2 lneto receive arguments, and return values. 1388 1.2 lneto Moreover, such anonymous function is compiled as in the 1389 1.2 lneto scope of an external local variable called <code>_ENV</code> (see <a href="#2.2">§2.2</a>). 1390 1.2 lneto The resulting function always has <code>_ENV</code> as its only upvalue, 1391 1.2 lneto even if it does not use that variable. 1392 1.1 mbalmer 1393 1.1 mbalmer 1394 1.1 mbalmer <p> 1395 1.2 lneto A chunk can be stored in a file or in a string inside the host program. 1396 1.2 lneto To execute a chunk, 1397 1.3 lneto Lua first <em>loads</em> it, 1398 1.3 lneto precompiling the chunk's code into instructions for a virtual machine, 1399 1.3 lneto and then Lua executes the compiled code 1400 1.2 lneto with an interpreter for the virtual machine. 1401 1.1 mbalmer 1402 1.1 mbalmer 1403 1.1 mbalmer <p> 1404 1.2 lneto Chunks can also be precompiled into binary form; 1405 1.2 lneto see program <code>luac</code> and function <a href="#pdf-string.dump"><code>string.dump</code></a> for details. 1406 1.2 lneto Programs in source and compiled forms are interchangeable; 1407 1.2 lneto Lua automatically detects the file type and acts accordingly (see <a href="#pdf-load"><code>load</code></a>). 1408 1.2 lneto 1409 1.2 lneto 1410 1.2 lneto 1411 1.1 mbalmer 1412 1.1 mbalmer 1413 1.2 lneto <h3>3.3.3 – <a name="3.3.3">Assignment</a></h3> 1414 1.1 mbalmer 1415 1.1 mbalmer <p> 1416 1.2 lneto Lua allows multiple assignments. 1417 1.2 lneto Therefore, the syntax for assignment 1418 1.2 lneto defines a list of variables on the left side 1419 1.2 lneto and a list of expressions on the right side. 1420 1.2 lneto The elements in both lists are separated by commas: 1421 1.1 mbalmer 1422 1.1 mbalmer <pre> 1423 1.2 lneto stat ::= varlist ‘<b>=</b>’ explist 1424 1.2 lneto varlist ::= var {‘<b>,</b>’ var} 1425 1.2 lneto explist ::= exp {‘<b>,</b>’ exp} 1426 1.1 mbalmer </pre><p> 1427 1.2 lneto Expressions are discussed in <a href="#3.4">§3.4</a>. 1428 1.1 mbalmer 1429 1.1 mbalmer 1430 1.1 mbalmer <p> 1431 1.2 lneto Before the assignment, 1432 1.2 lneto the list of values is <em>adjusted</em> to the length of 1433 1.2 lneto the list of variables. 1434 1.2 lneto If there are more values than needed, 1435 1.2 lneto the excess values are thrown away. 1436 1.2 lneto If there are fewer values than needed, 1437 1.2 lneto the list is extended with as many <b>nil</b>'s as needed. 1438 1.2 lneto If the list of expressions ends with a function call, 1439 1.2 lneto then all values returned by that call enter the list of values, 1440 1.2 lneto before the adjustment 1441 1.2 lneto (except when the call is enclosed in parentheses; see <a href="#3.4">§3.4</a>). 1442 1.1 mbalmer 1443 1.1 mbalmer 1444 1.1 mbalmer <p> 1445 1.2 lneto The assignment statement first evaluates all its expressions 1446 1.3 lneto and only then the assignments are performed. 1447 1.2 lneto Thus the code 1448 1.1 mbalmer 1449 1.1 mbalmer <pre> 1450 1.2 lneto i = 3 1451 1.2 lneto i, a[i] = i+1, 20 1452 1.1 mbalmer </pre><p> 1453 1.2 lneto sets <code>a[3]</code> to 20, without affecting <code>a[4]</code> 1454 1.2 lneto because the <code>i</code> in <code>a[i]</code> is evaluated (to 3) 1455 1.2 lneto before it is assigned 4. 1456 1.2 lneto Similarly, the line 1457 1.1 mbalmer 1458 1.1 mbalmer <pre> 1459 1.2 lneto x, y = y, x 1460 1.2 lneto </pre><p> 1461 1.2 lneto exchanges the values of <code>x</code> and <code>y</code>, 1462 1.2 lneto and 1463 1.1 mbalmer 1464 1.2 lneto <pre> 1465 1.2 lneto x, y, z = y, z, x 1466 1.2 lneto </pre><p> 1467 1.2 lneto cyclically permutes the values of <code>x</code>, <code>y</code>, and <code>z</code>. 1468 1.1 mbalmer 1469 1.1 mbalmer 1470 1.2 lneto <p> 1471 1.2 lneto The meaning of assignments to global variables 1472 1.2 lneto and table fields can be changed via metatables. 1473 1.2 lneto An assignment to an indexed variable <code>t[i] = val</code> is equivalent to 1474 1.2 lneto <code>settable_event(t,i,val)</code>. 1475 1.2 lneto (See <a href="#2.4">§2.4</a> for a complete description of the 1476 1.2 lneto <code>settable_event</code> function. 1477 1.2 lneto This function is not defined or callable in Lua. 1478 1.2 lneto We use it here only for explanatory purposes.) 1479 1.1 mbalmer 1480 1.1 mbalmer 1481 1.2 lneto <p> 1482 1.3 lneto An assignment to a global name <code>x = val</code> 1483 1.2 lneto is equivalent to the assignment 1484 1.2 lneto <code>_ENV.x = val</code> (see <a href="#2.2">§2.2</a>). 1485 1.1 mbalmer 1486 1.1 mbalmer 1487 1.1 mbalmer 1488 1.1 mbalmer 1489 1.1 mbalmer 1490 1.2 lneto <h3>3.3.4 – <a name="3.3.4">Control Structures</a></h3><p> 1491 1.2 lneto The control structures 1492 1.2 lneto <b>if</b>, <b>while</b>, and <b>repeat</b> have the usual meaning and 1493 1.2 lneto familiar syntax: 1494 1.1 mbalmer 1495 1.1 mbalmer 1496 1.1 mbalmer 1497 1.1 mbalmer 1498 1.1 mbalmer <pre> 1499 1.2 lneto stat ::= <b>while</b> exp <b>do</b> block <b>end</b> 1500 1.2 lneto stat ::= <b>repeat</b> block <b>until</b> exp 1501 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> 1502 1.1 mbalmer </pre><p> 1503 1.2 lneto Lua also has a <b>for</b> statement, in two flavors (see <a href="#3.3.5">§3.3.5</a>). 1504 1.1 mbalmer 1505 1.1 mbalmer 1506 1.2 lneto <p> 1507 1.2 lneto The condition expression of a 1508 1.2 lneto control structure can return any value. 1509 1.2 lneto Both <b>false</b> and <b>nil</b> are considered false. 1510 1.2 lneto All values different from <b>nil</b> and <b>false</b> are considered true 1511 1.2 lneto (in particular, the number 0 and the empty string are also true). 1512 1.1 mbalmer 1513 1.1 mbalmer 1514 1.1 mbalmer <p> 1515 1.2 lneto In the <b>repeat</b>–<b>until</b> loop, 1516 1.2 lneto the inner block does not end at the <b>until</b> keyword, 1517 1.2 lneto but only after the condition. 1518 1.2 lneto So, the condition can refer to local variables 1519 1.2 lneto declared inside the loop block. 1520 1.1 mbalmer 1521 1.1 mbalmer 1522 1.1 mbalmer <p> 1523 1.2 lneto The <b>goto</b> statement transfers the program control to a label. 1524 1.2 lneto For syntactical reasons, 1525 1.2 lneto labels in Lua are considered statements too: 1526 1.1 mbalmer 1527 1.1 mbalmer 1528 1.1 mbalmer 1529 1.2 lneto <pre> 1530 1.2 lneto stat ::= <b>goto</b> Name 1531 1.2 lneto stat ::= label 1532 1.2 lneto label ::= ‘<b>::</b>’ Name ‘<b>::</b>’ 1533 1.2 lneto </pre> 1534 1.1 mbalmer 1535 1.1 mbalmer <p> 1536 1.2 lneto A label is visible in the entire block where it is defined, 1537 1.2 lneto except 1538 1.2 lneto inside nested blocks where a label with the same name is defined and 1539 1.2 lneto inside nested functions. 1540 1.2 lneto A goto may jump to any visible label as long as it does not 1541 1.2 lneto enter into the scope of a local variable. 1542 1.1 mbalmer 1543 1.1 mbalmer 1544 1.1 mbalmer <p> 1545 1.2 lneto Labels and empty statements are called <em>void statements</em>, 1546 1.2 lneto as they perform no actions. 1547 1.1 mbalmer 1548 1.1 mbalmer 1549 1.1 mbalmer <p> 1550 1.2 lneto The <b>break</b> statement terminates the execution of a 1551 1.2 lneto <b>while</b>, <b>repeat</b>, or <b>for</b> loop, 1552 1.2 lneto skipping to the next statement after the loop: 1553 1.1 mbalmer 1554 1.1 mbalmer 1555 1.2 lneto <pre> 1556 1.2 lneto stat ::= <b>break</b> 1557 1.2 lneto </pre><p> 1558 1.2 lneto A <b>break</b> ends the innermost enclosing loop. 1559 1.1 mbalmer 1560 1.1 mbalmer 1561 1.1 mbalmer <p> 1562 1.2 lneto The <b>return</b> statement is used to return values 1563 1.3 lneto from a function or a chunk 1564 1.3 lneto (which is an anonymous function). 1565 1.1 mbalmer 1566 1.2 lneto Functions can return more than one value, 1567 1.2 lneto so the syntax for the <b>return</b> statement is 1568 1.1 mbalmer 1569 1.2 lneto <pre> 1570 1.2 lneto stat ::= <b>return</b> [explist] [‘<b>;</b>’] 1571 1.2 lneto </pre> 1572 1.1 mbalmer 1573 1.1 mbalmer <p> 1574 1.2 lneto The <b>return</b> statement can only be written 1575 1.2 lneto as the last statement of a block. 1576 1.2 lneto If it is really necessary to <b>return</b> in the middle of a block, 1577 1.2 lneto then an explicit inner block can be used, 1578 1.2 lneto as in the idiom <code>do return end</code>, 1579 1.2 lneto because now <b>return</b> is the last statement in its (inner) block. 1580 1.1 mbalmer 1581 1.1 mbalmer 1582 1.1 mbalmer 1583 1.1 mbalmer 1584 1.1 mbalmer 1585 1.2 lneto <h3>3.3.5 – <a name="3.3.5">For Statement</a></h3> 1586 1.1 mbalmer 1587 1.2 lneto <p> 1588 1.1 mbalmer 1589 1.2 lneto The <b>for</b> statement has two forms: 1590 1.4 mbalmer one numerical and one generic. 1591 1.1 mbalmer 1592 1.1 mbalmer 1593 1.2 lneto <p> 1594 1.4 mbalmer The numerical <b>for</b> loop repeats a block of code while a 1595 1.2 lneto control variable runs through an arithmetic progression. 1596 1.2 lneto It has the following syntax: 1597 1.1 mbalmer 1598 1.2 lneto <pre> 1599 1.2 lneto stat ::= <b>for</b> Name ‘<b>=</b>’ exp ‘<b>,</b>’ exp [‘<b>,</b>’ exp] <b>do</b> block <b>end</b> 1600 1.2 lneto </pre><p> 1601 1.2 lneto The <em>block</em> is repeated for <em>name</em> starting at the value of 1602 1.2 lneto the first <em>exp</em>, until it passes the second <em>exp</em> by steps of the 1603 1.2 lneto third <em>exp</em>. 1604 1.2 lneto More precisely, a <b>for</b> statement like 1605 1.1 mbalmer 1606 1.1 mbalmer <pre> 1607 1.2 lneto for v = <em>e1</em>, <em>e2</em>, <em>e3</em> do <em>block</em> end 1608 1.1 mbalmer </pre><p> 1609 1.2 lneto is equivalent to the code: 1610 1.1 mbalmer 1611 1.1 mbalmer <pre> 1612 1.2 lneto do 1613 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>) 1614 1.2 lneto if not (<em>var</em> and <em>limit</em> and <em>step</em>) then error() end 1615 1.2 lneto <em>var</em> = <em>var</em> - <em>step</em> 1616 1.2 lneto while true do 1617 1.2 lneto <em>var</em> = <em>var</em> + <em>step</em> 1618 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 1619 1.2 lneto break 1620 1.1 mbalmer end 1621 1.2 lneto local v = <em>var</em> 1622 1.2 lneto <em>block</em> 1623 1.1 mbalmer end 1624 1.1 mbalmer end 1625 1.2 lneto </pre> 1626 1.2 lneto 1627 1.2 lneto <p> 1628 1.2 lneto Note the following: 1629 1.1 mbalmer 1630 1.2 lneto <ul> 1631 1.1 mbalmer 1632 1.2 lneto <li> 1633 1.2 lneto All three control expressions are evaluated only once, 1634 1.2 lneto before the loop starts. 1635 1.2 lneto They must all result in numbers. 1636 1.1 mbalmer </li> 1637 1.1 mbalmer 1638 1.2 lneto <li> 1639 1.2 lneto <code><em>var</em></code>, <code><em>limit</em></code>, and <code><em>step</em></code> are invisible variables. 1640 1.2 lneto The names shown here are for explanatory purposes only. 1641 1.1 mbalmer </li> 1642 1.1 mbalmer 1643 1.2 lneto <li> 1644 1.2 lneto If the third expression (the step) is absent, 1645 1.2 lneto then a step of 1 is used. 1646 1.2 lneto </li> 1647 1.1 mbalmer 1648 1.2 lneto <li> 1649 1.2 lneto You can use <b>break</b> and <b>goto</b> to exit a <b>for</b> loop. 1650 1.1 mbalmer </li> 1651 1.1 mbalmer 1652 1.2 lneto <li> 1653 1.2 lneto The loop variable <code>v</code> is local to the loop body. 1654 1.2 lneto If you need its value after the loop, 1655 1.2 lneto assign it to another variable before exiting the loop. 1656 1.1 mbalmer </li> 1657 1.1 mbalmer 1658 1.2 lneto </ul> 1659 1.1 mbalmer 1660 1.2 lneto <p> 1661 1.2 lneto The generic <b>for</b> statement works over functions, 1662 1.2 lneto called <em>iterators</em>. 1663 1.2 lneto On each iteration, the iterator function is called to produce a new value, 1664 1.2 lneto stopping when this new value is <b>nil</b>. 1665 1.2 lneto The generic <b>for</b> loop has the following syntax: 1666 1.1 mbalmer 1667 1.2 lneto <pre> 1668 1.2 lneto stat ::= <b>for</b> namelist <b>in</b> explist <b>do</b> block <b>end</b> 1669 1.2 lneto namelist ::= Name {‘<b>,</b>’ Name} 1670 1.2 lneto </pre><p> 1671 1.2 lneto A <b>for</b> statement like 1672 1.1 mbalmer 1673 1.2 lneto <pre> 1674 1.2 lneto for <em>var_1</em>, ···, <em>var_n</em> in <em>explist</em> do <em>block</em> end 1675 1.2 lneto </pre><p> 1676 1.2 lneto is equivalent to the code: 1677 1.1 mbalmer 1678 1.1 mbalmer <pre> 1679 1.2 lneto do 1680 1.2 lneto local <em>f</em>, <em>s</em>, <em>var</em> = <em>explist</em> 1681 1.2 lneto while true do 1682 1.2 lneto local <em>var_1</em>, ···, <em>var_n</em> = <em>f</em>(<em>s</em>, <em>var</em>) 1683 1.2 lneto if <em>var_1</em> == nil then break end 1684 1.2 lneto <em>var</em> = <em>var_1</em> 1685 1.2 lneto <em>block</em> 1686 1.1 mbalmer end 1687 1.1 mbalmer end 1688 1.1 mbalmer </pre><p> 1689 1.2 lneto Note the following: 1690 1.2 lneto 1691 1.2 lneto <ul> 1692 1.2 lneto 1693 1.2 lneto <li> 1694 1.2 lneto <code><em>explist</em></code> is evaluated only once. 1695 1.2 lneto Its results are an <em>iterator</em> function, 1696 1.2 lneto a <em>state</em>, 1697 1.2 lneto and an initial value for the first <em>iterator variable</em>. 1698 1.1 mbalmer </li> 1699 1.1 mbalmer 1700 1.2 lneto <li> 1701 1.2 lneto <code><em>f</em></code>, <code><em>s</em></code>, and <code><em>var</em></code> are invisible variables. 1702 1.2 lneto The names are here for explanatory purposes only. 1703 1.2 lneto </li> 1704 1.1 mbalmer 1705 1.2 lneto <li> 1706 1.2 lneto You can use <b>break</b> to exit a <b>for</b> loop. 1707 1.2 lneto </li> 1708 1.1 mbalmer 1709 1.2 lneto <li> 1710 1.2 lneto The loop variables <code><em>var_i</em></code> are local to the loop; 1711 1.2 lneto you cannot use their values after the <b>for</b> ends. 1712 1.2 lneto If you need these values, 1713 1.2 lneto then assign them to other variables before breaking or exiting the loop. 1714 1.1 mbalmer </li> 1715 1.1 mbalmer 1716 1.2 lneto </ul> 1717 1.2 lneto 1718 1.2 lneto 1719 1.1 mbalmer 1720 1.1 mbalmer 1721 1.2 lneto <h3>3.3.6 – <a name="3.3.6">Function Calls as Statements</a></h3><p> 1722 1.2 lneto To allow possible side-effects, 1723 1.2 lneto function calls can be executed as statements: 1724 1.2 lneto 1725 1.1 mbalmer <pre> 1726 1.2 lneto stat ::= functioncall 1727 1.1 mbalmer </pre><p> 1728 1.2 lneto In this case, all returned values are thrown away. 1729 1.2 lneto Function calls are explained in <a href="#3.4.10">§3.4.10</a>. 1730 1.2 lneto 1731 1.2 lneto 1732 1.2 lneto 1733 1.1 mbalmer 1734 1.1 mbalmer 1735 1.2 lneto <h3>3.3.7 – <a name="3.3.7">Local Declarations</a></h3><p> 1736 1.2 lneto Local variables can be declared anywhere inside a block. 1737 1.2 lneto The declaration can include an initial assignment: 1738 1.1 mbalmer 1739 1.1 mbalmer <pre> 1740 1.2 lneto stat ::= <b>local</b> namelist [‘<b>=</b>’ explist] 1741 1.1 mbalmer </pre><p> 1742 1.2 lneto If present, an initial assignment has the same semantics 1743 1.2 lneto of a multiple assignment (see <a href="#3.3.3">§3.3.3</a>). 1744 1.2 lneto Otherwise, all variables are initialized with <b>nil</b>. 1745 1.2 lneto 1746 1.2 lneto 1747 1.2 lneto <p> 1748 1.2 lneto A chunk is also a block (see <a href="#3.3.2">§3.3.2</a>), 1749 1.2 lneto and so local variables can be declared in a chunk outside any explicit block. 1750 1.1 mbalmer 1751 1.1 mbalmer 1752 1.2 lneto <p> 1753 1.2 lneto The visibility rules for local variables are explained in <a href="#3.5">§3.5</a>. 1754 1.2 lneto 1755 1.1 mbalmer 1756 1.1 mbalmer 1757 1.1 mbalmer 1758 1.1 mbalmer 1759 1.1 mbalmer 1760 1.1 mbalmer 1761 1.2 lneto <h2>3.4 – <a name="3.4">Expressions</a></h2> 1762 1.1 mbalmer 1763 1.2 lneto <p> 1764 1.2 lneto The basic expressions in Lua are the following: 1765 1.1 mbalmer 1766 1.1 mbalmer <pre> 1767 1.2 lneto exp ::= prefixexp 1768 1.2 lneto exp ::= <b>nil</b> | <b>false</b> | <b>true</b> 1769 1.3 lneto exp ::= Numeral 1770 1.3 lneto exp ::= LiteralString 1771 1.2 lneto exp ::= functiondef 1772 1.2 lneto exp ::= tableconstructor 1773 1.2 lneto exp ::= ‘<b>...</b>’ 1774 1.2 lneto exp ::= exp binop exp 1775 1.2 lneto exp ::= unop exp 1776 1.2 lneto prefixexp ::= var | functioncall | ‘<b>(</b>’ exp ‘<b>)</b>’ 1777 1.2 lneto </pre> 1778 1.2 lneto 1779 1.2 lneto <p> 1780 1.3 lneto Numerals and literal strings are explained in <a href="#3.1">§3.1</a>; 1781 1.2 lneto variables are explained in <a href="#3.2">§3.2</a>; 1782 1.2 lneto function definitions are explained in <a href="#3.4.11">§3.4.11</a>; 1783 1.2 lneto function calls are explained in <a href="#3.4.10">§3.4.10</a>; 1784 1.2 lneto table constructors are explained in <a href="#3.4.9">§3.4.9</a>. 1785 1.2 lneto Vararg expressions, 1786 1.2 lneto denoted by three dots ('<code>...</code>'), can only be used when 1787 1.2 lneto directly inside a vararg function; 1788 1.2 lneto they are explained in <a href="#3.4.11">§3.4.11</a>. 1789 1.2 lneto 1790 1.1 mbalmer 1791 1.2 lneto <p> 1792 1.2 lneto Binary operators comprise arithmetic operators (see <a href="#3.4.1">§3.4.1</a>), 1793 1.2 lneto bitwise operators (see <a href="#3.4.2">§3.4.2</a>), 1794 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>), 1795 1.2 lneto and the concatenation operator (see <a href="#3.4.6">§3.4.6</a>). 1796 1.2 lneto Unary operators comprise the unary minus (see <a href="#3.4.1">§3.4.1</a>), 1797 1.2 lneto the unary bitwise not (see <a href="#3.4.2">§3.4.2</a>), 1798 1.3 lneto the unary logical <b>not</b> (see <a href="#3.4.5">§3.4.5</a>), 1799 1.2 lneto and the unary <em>length operator</em> (see <a href="#3.4.7">§3.4.7</a>). 1800 1.1 mbalmer 1801 1.1 mbalmer 1802 1.2 lneto <p> 1803 1.2 lneto Both function calls and vararg expressions can result in multiple values. 1804 1.2 lneto If a function call is used as a statement (see <a href="#3.3.6">§3.3.6</a>), 1805 1.2 lneto then its return list is adjusted to zero elements, 1806 1.2 lneto thus discarding all returned values. 1807 1.2 lneto If an expression is used as the last (or the only) element 1808 1.2 lneto of a list of expressions, 1809 1.2 lneto then no adjustment is made 1810 1.2 lneto (unless the expression is enclosed in parentheses). 1811 1.2 lneto In all other contexts, 1812 1.2 lneto Lua adjusts the result list to one element, 1813 1.2 lneto either discarding all values except the first one 1814 1.2 lneto or adding a single <b>nil</b> if there are no values. 1815 1.1 mbalmer 1816 1.1 mbalmer 1817 1.2 lneto <p> 1818 1.2 lneto Here are some examples: 1819 1.1 mbalmer 1820 1.1 mbalmer <pre> 1821 1.2 lneto f() -- adjusted to 0 results 1822 1.2 lneto g(f(), x) -- f() is adjusted to 1 result 1823 1.2 lneto g(x, f()) -- g gets x plus all results from f() 1824 1.2 lneto a,b,c = f(), x -- f() is adjusted to 1 result (c gets nil) 1825 1.2 lneto a,b = ... -- a gets the first vararg parameter, b gets 1826 1.2 lneto -- the second (both a and b can get nil if there 1827 1.2 lneto -- is no corresponding vararg parameter) 1828 1.2 lneto 1829 1.2 lneto a,b,c = x, f() -- f() is adjusted to 2 results 1830 1.2 lneto a,b,c = f() -- f() is adjusted to 3 results 1831 1.2 lneto return f() -- returns all results from f() 1832 1.2 lneto return ... -- returns all received vararg parameters 1833 1.2 lneto return x,y,f() -- returns x, y, and all results from f() 1834 1.2 lneto {f()} -- creates a list with all results from f() 1835 1.2 lneto {...} -- creates a list with all vararg parameters 1836 1.2 lneto {f(), nil} -- f() is adjusted to 1 result 1837 1.2 lneto </pre> 1838 1.2 lneto 1839 1.2 lneto <p> 1840 1.2 lneto Any expression enclosed in parentheses always results in only one value. 1841 1.2 lneto Thus, 1842 1.2 lneto <code>(f(x,y,z))</code> is always a single value, 1843 1.2 lneto even if <code>f</code> returns several values. 1844 1.2 lneto (The value of <code>(f(x,y,z))</code> is the first value returned by <code>f</code> 1845 1.2 lneto or <b>nil</b> if <code>f</code> does not return any values.) 1846 1.2 lneto 1847 1.1 mbalmer 1848 1.1 mbalmer 1849 1.2 lneto <h3>3.4.1 – <a name="3.4.1">Arithmetic Operators</a></h3><p> 1850 1.2 lneto Lua supports the following arithmetic operators: 1851 1.1 mbalmer 1852 1.3 lneto <ul> 1853 1.3 lneto <li><b><code>+</code>: </b>addition</li> 1854 1.3 lneto <li><b><code>-</code>: </b>subtraction</li> 1855 1.3 lneto <li><b><code>*</code>: </b>multiplication</li> 1856 1.3 lneto <li><b><code>/</code>: </b>float division</li> 1857 1.3 lneto <li><b><code>//</code>: </b>floor division</li> 1858 1.3 lneto <li><b><code>%</code>: </b>modulo</li> 1859 1.3 lneto <li><b><code>^</code>: </b>exponentiation</li> 1860 1.3 lneto <li><b><code>-</code>: </b>unary minus</li> 1861 1.3 lneto </ul> 1862 1.1 mbalmer 1863 1.2 lneto <p> 1864 1.3 lneto With the exception of exponentiation and float division, 1865 1.2 lneto the arithmetic operators work as follows: 1866 1.2 lneto If both operands are integers, 1867 1.2 lneto the operation is performed over integers and the result is an integer. 1868 1.2 lneto Otherwise, if both operands are numbers 1869 1.2 lneto or strings that can be converted to 1870 1.2 lneto numbers (see <a href="#3.4.3">§3.4.3</a>), 1871 1.2 lneto then they are converted to floats, 1872 1.2 lneto the operation is performed following the usual rules 1873 1.2 lneto for floating-point arithmetic 1874 1.2 lneto (usually the IEEE 754 standard), 1875 1.2 lneto and the result is a float. 1876 1.1 mbalmer 1877 1.1 mbalmer 1878 1.1 mbalmer <p> 1879 1.3 lneto Exponentiation and float division (<code>/</code>) 1880 1.2 lneto always convert their operands to floats 1881 1.2 lneto and the result is always a float. 1882 1.3 lneto Exponentiation uses the ISO C function <code>pow</code>, 1883 1.2 lneto so that it works for non-integer exponents too. 1884 1.1 mbalmer 1885 1.1 mbalmer 1886 1.1 mbalmer <p> 1887 1.3 lneto Floor division (<code>//</code>) is a division 1888 1.4 mbalmer that rounds the quotient towards minus infinity, 1889 1.3 lneto that is, the floor of the division of its operands. 1890 1.1 mbalmer 1891 1.1 mbalmer 1892 1.1 mbalmer <p> 1893 1.2 lneto Modulo is defined as the remainder of a division 1894 1.4 mbalmer that rounds the quotient towards minus infinity (floor division). 1895 1.1 mbalmer 1896 1.1 mbalmer 1897 1.1 mbalmer <p> 1898 1.2 lneto In case of overflows in integer arithmetic, 1899 1.2 lneto all operations <em>wrap around</em>, 1900 1.2 lneto according to the usual rules of two-complement arithmetic. 1901 1.3 lneto (In other words, 1902 1.3 lneto they return the unique representable integer 1903 1.3 lneto that is equal modulo <em>2<sup>64</sup></em> to the mathematical result.) 1904 1.2 lneto 1905 1.2 lneto 1906 1.2 lneto 1907 1.2 lneto <h3>3.4.2 – <a name="3.4.2">Bitwise Operators</a></h3><p> 1908 1.2 lneto Lua supports the following bitwise operators: 1909 1.1 mbalmer 1910 1.3 lneto <ul> 1911 1.3 lneto <li><b><code>&</code>: </b>bitwise and</li> 1912 1.3 lneto <li><b><code>|</code>: </b>bitwise or</li> 1913 1.3 lneto <li><b><code>~</code>: </b>bitwise exclusive or</li> 1914 1.3 lneto <li><b><code>>></code>: </b>right shift</li> 1915 1.3 lneto <li><b><code><<</code>: </b>left shift</li> 1916 1.3 lneto <li><b><code>~</code>: </b>unary bitwise not</li> 1917 1.3 lneto </ul> 1918 1.1 mbalmer 1919 1.1 mbalmer <p> 1920 1.2 lneto All bitwise operations convert its operands to integers 1921 1.2 lneto (see <a href="#3.4.3">§3.4.3</a>), 1922 1.2 lneto operate on all bits of those integers, 1923 1.2 lneto and result in an integer. 1924 1.1 mbalmer 1925 1.1 mbalmer 1926 1.1 mbalmer <p> 1927 1.2 lneto Both right and left shifts fill the vacant bits with zeros. 1928 1.2 lneto Negative displacements shift to the other direction; 1929 1.2 lneto displacements with absolute values equal to or higher than 1930 1.2 lneto the number of bits in an integer 1931 1.3 lneto result in zero (as all bits are shifted out). 1932 1.2 lneto 1933 1.2 lneto 1934 1.2 lneto 1935 1.2 lneto 1936 1.2 lneto 1937 1.2 lneto <h3>3.4.3 – <a name="3.4.3">Coercions and Conversions</a></h3><p> 1938 1.2 lneto Lua provides some automatic conversions between some 1939 1.2 lneto types and representations at run time. 1940 1.3 lneto Bitwise operators always convert float operands to integers. 1941 1.3 lneto Exponentiation and float division 1942 1.3 lneto always convert integer operands to floats. 1943 1.3 lneto All other arithmetic operations applied to mixed numbers 1944 1.2 lneto (integers and floats) convert the integer operand to a float; 1945 1.2 lneto this is called the <em>usual rule</em>. 1946 1.2 lneto The C API also converts both integers to floats and 1947 1.2 lneto floats to integers, as needed. 1948 1.2 lneto Moreover, string concatenation accepts numbers as arguments, 1949 1.2 lneto besides strings. 1950 1.1 mbalmer 1951 1.1 mbalmer 1952 1.1 mbalmer <p> 1953 1.2 lneto Lua also converts strings to numbers, 1954 1.2 lneto whenever a number is expected. 1955 1.1 mbalmer 1956 1.1 mbalmer 1957 1.2 lneto <p> 1958 1.2 lneto In a conversion from integer to float, 1959 1.2 lneto if the integer value has an exact representation as a float, 1960 1.2 lneto that is the result. 1961 1.2 lneto Otherwise, 1962 1.3 lneto the conversion gets the nearest higher or 1963 1.3 lneto the nearest lower representable value. 1964 1.2 lneto This kind of conversion never fails. 1965 1.1 mbalmer 1966 1.1 mbalmer 1967 1.2 lneto <p> 1968 1.2 lneto The conversion from float to integer 1969 1.3 lneto checks whether the float has an exact representation as an integer 1970 1.3 lneto (that is, the float has an integral value and 1971 1.3 lneto it is in the range of integer representation). 1972 1.3 lneto If it does, that representation is the result. 1973 1.2 lneto Otherwise, the conversion fails. 1974 1.1 mbalmer 1975 1.1 mbalmer 1976 1.1 mbalmer <p> 1977 1.2 lneto The conversion from strings to numbers goes as follows: 1978 1.2 lneto First, the string is converted to an integer or a float, 1979 1.2 lneto following its syntax and the rules of the Lua lexer. 1980 1.2 lneto (The string may have also leading and trailing spaces and a sign.) 1981 1.4 mbalmer Then, the resulting number (float or integer) 1982 1.4 mbalmer is converted to the type (float or integer) required by the context 1983 1.4 mbalmer (e.g., the operation that forced the conversion). 1984 1.1 mbalmer 1985 1.1 mbalmer 1986 1.1 mbalmer <p> 1987 1.3 lneto The conversion from numbers to strings uses a 1988 1.3 lneto non-specified human-readable format. 1989 1.2 lneto For complete control over how numbers are converted to strings, 1990 1.2 lneto use the <code>format</code> function from the string library 1991 1.2 lneto (see <a href="#pdf-string.format"><code>string.format</code></a>). 1992 1.2 lneto 1993 1.2 lneto 1994 1.2 lneto 1995 1.2 lneto 1996 1.2 lneto 1997 1.2 lneto <h3>3.4.4 – <a name="3.4.4">Relational Operators</a></h3><p> 1998 1.2 lneto Lua supports the following relational operators: 1999 1.3 lneto 2000 1.3 lneto <ul> 2001 1.3 lneto <li><b><code>==</code>: </b>equality</li> 2002 1.3 lneto <li><b><code>~=</code>: </b>inequality</li> 2003 1.3 lneto <li><b><code><</code>: </b>less than</li> 2004 1.3 lneto <li><b><code>></code>: </b>greater than</li> 2005 1.3 lneto <li><b><code><=</code>: </b>less or equal</li> 2006 1.3 lneto <li><b><code>>=</code>: </b>greater or equal</li> 2007 1.3 lneto </ul><p> 2008 1.2 lneto These operators always result in <b>false</b> or <b>true</b>. 2009 1.1 mbalmer 2010 1.1 mbalmer 2011 1.1 mbalmer <p> 2012 1.2 lneto Equality (<code>==</code>) first compares the type of its operands. 2013 1.2 lneto If the types are different, then the result is <b>false</b>. 2014 1.2 lneto Otherwise, the values of the operands are compared. 2015 1.2 lneto Strings are compared in the obvious way. 2016 1.4 mbalmer Numbers are equal if they denote the same mathematical value. 2017 1.1 mbalmer 2018 1.1 mbalmer 2019 1.1 mbalmer <p> 2020 1.2 lneto Tables, userdata, and threads 2021 1.2 lneto are compared by reference: 2022 1.2 lneto two objects are considered equal only if they are the same object. 2023 1.2 lneto Every time you create a new object 2024 1.2 lneto (a table, userdata, or thread), 2025 1.2 lneto this new object is different from any previously existing object. 2026 1.2 lneto Closures with the same reference are always equal. 2027 1.2 lneto Closures with any detectable difference 2028 1.2 lneto (different behavior, different definition) are always different. 2029 1.1 mbalmer 2030 1.1 mbalmer 2031 1.1 mbalmer <p> 2032 1.2 lneto You can change the way that Lua compares tables and userdata 2033 1.2 lneto by using the "eq" metamethod (see <a href="#2.4">§2.4</a>). 2034 1.1 mbalmer 2035 1.1 mbalmer 2036 1.2 lneto <p> 2037 1.3 lneto Equality comparisons do not convert strings to numbers 2038 1.2 lneto or vice versa. 2039 1.2 lneto Thus, <code>"0"==0</code> evaluates to <b>false</b>, 2040 1.2 lneto and <code>t[0]</code> and <code>t["0"]</code> denote different 2041 1.2 lneto entries in a table. 2042 1.1 mbalmer 2043 1.1 mbalmer 2044 1.1 mbalmer <p> 2045 1.2 lneto The operator <code>~=</code> is exactly the negation of equality (<code>==</code>). 2046 1.1 mbalmer 2047 1.1 mbalmer 2048 1.2 lneto <p> 2049 1.2 lneto The order operators work as follows. 2050 1.2 lneto If both arguments are numbers, 2051 1.4 mbalmer then they are compared according to their mathematical values 2052 1.4 mbalmer (regardless of their subtypes). 2053 1.2 lneto Otherwise, if both arguments are strings, 2054 1.2 lneto then their values are compared according to the current locale. 2055 1.2 lneto Otherwise, Lua tries to call the "lt" or the "le" 2056 1.2 lneto metamethod (see <a href="#2.4">§2.4</a>). 2057 1.2 lneto A comparison <code>a > b</code> is translated to <code>b < a</code> 2058 1.2 lneto and <code>a >= b</code> is translated to <code>b <= a</code>. 2059 1.2 lneto 2060 1.2 lneto 2061 1.4 mbalmer <p> 2062 1.4 mbalmer Following the IEEE 754 standard, 2063 1.4 mbalmer NaN is considered neither smaller than, 2064 1.4 mbalmer nor equal to, nor greater than any value (including itself). 2065 1.4 mbalmer 2066 1.4 mbalmer 2067 1.2 lneto 2068 1.2 lneto 2069 1.2 lneto 2070 1.2 lneto <h3>3.4.5 – <a name="3.4.5">Logical Operators</a></h3><p> 2071 1.2 lneto The logical operators in Lua are 2072 1.2 lneto <b>and</b>, <b>or</b>, and <b>not</b>. 2073 1.2 lneto Like the control structures (see <a href="#3.3.4">§3.3.4</a>), 2074 1.2 lneto all logical operators consider both <b>false</b> and <b>nil</b> as false 2075 1.2 lneto and anything else as true. 2076 1.2 lneto 2077 1.2 lneto 2078 1.2 lneto <p> 2079 1.2 lneto The negation operator <b>not</b> always returns <b>false</b> or <b>true</b>. 2080 1.2 lneto The conjunction operator <b>and</b> returns its first argument 2081 1.2 lneto if this value is <b>false</b> or <b>nil</b>; 2082 1.2 lneto otherwise, <b>and</b> returns its second argument. 2083 1.2 lneto The disjunction operator <b>or</b> returns its first argument 2084 1.2 lneto if this value is different from <b>nil</b> and <b>false</b>; 2085 1.2 lneto otherwise, <b>or</b> returns its second argument. 2086 1.2 lneto Both <b>and</b> and <b>or</b> use short-circuit evaluation; 2087 1.2 lneto that is, 2088 1.2 lneto the second operand is evaluated only if necessary. 2089 1.2 lneto Here are some examples: 2090 1.2 lneto 2091 1.2 lneto <pre> 2092 1.2 lneto 10 or 20 --> 10 2093 1.2 lneto 10 or error() --> 10 2094 1.2 lneto nil or "a" --> "a" 2095 1.2 lneto nil and 10 --> nil 2096 1.2 lneto false and error() --> false 2097 1.2 lneto false and nil --> false 2098 1.2 lneto false or nil --> nil 2099 1.2 lneto 10 and 20 --> 20 2100 1.2 lneto </pre><p> 2101 1.2 lneto (In this manual, 2102 1.2 lneto <code>--></code> indicates the result of the preceding expression.) 2103 1.2 lneto 2104 1.2 lneto 2105 1.2 lneto 2106 1.2 lneto 2107 1.2 lneto 2108 1.2 lneto <h3>3.4.6 – <a name="3.4.6">Concatenation</a></h3><p> 2109 1.2 lneto The string concatenation operator in Lua is 2110 1.2 lneto denoted by two dots ('<code>..</code>'). 2111 1.2 lneto If both operands are strings or numbers, then they are converted to 2112 1.2 lneto strings according to the rules described in <a href="#3.4.3">§3.4.3</a>. 2113 1.2 lneto Otherwise, the <code>__concat</code> metamethod is called (see <a href="#2.4">§2.4</a>). 2114 1.2 lneto 2115 1.2 lneto 2116 1.2 lneto 2117 1.2 lneto 2118 1.2 lneto 2119 1.2 lneto <h3>3.4.7 – <a name="3.4.7">The Length Operator</a></h3> 2120 1.2 lneto 2121 1.2 lneto <p> 2122 1.2 lneto The length operator is denoted by the unary prefix operator <code>#</code>. 2123 1.2 lneto The length of a string is its number of bytes 2124 1.2 lneto (that is, the usual meaning of string length when each 2125 1.2 lneto character is one byte). 2126 1.2 lneto 2127 1.2 lneto 2128 1.2 lneto <p> 2129 1.2 lneto A program can modify the behavior of the length operator for 2130 1.2 lneto any value but strings through the <code>__len</code> metamethod (see <a href="#2.4">§2.4</a>). 2131 1.2 lneto 2132 1.2 lneto 2133 1.2 lneto <p> 2134 1.2 lneto Unless a <code>__len</code> metamethod is given, 2135 1.2 lneto the length of a table <code>t</code> is only defined if the 2136 1.2 lneto table is a <em>sequence</em>, 2137 1.2 lneto that is, 2138 1.2 lneto the set of its positive numeric keys is equal to <em>{1..n}</em> 2139 1.2 lneto for some non-negative integer <em>n</em>. 2140 1.2 lneto In that case, <em>n</em> is its length. 2141 1.2 lneto Note that a table like 2142 1.2 lneto 2143 1.2 lneto <pre> 2144 1.2 lneto {10, 20, nil, 40} 2145 1.2 lneto </pre><p> 2146 1.2 lneto is not a sequence, because it has the key <code>4</code> 2147 1.2 lneto but does not have the key <code>3</code>. 2148 1.2 lneto (So, there is no <em>n</em> such that the set <em>{1..n}</em> is equal 2149 1.2 lneto to the set of positive numeric keys of that table.) 2150 1.2 lneto Note, however, that non-numeric keys do not interfere 2151 1.2 lneto with whether a table is a sequence. 2152 1.2 lneto 2153 1.2 lneto 2154 1.2 lneto 2155 1.2 lneto 2156 1.2 lneto 2157 1.2 lneto <h3>3.4.8 – <a name="3.4.8">Precedence</a></h3><p> 2158 1.2 lneto Operator precedence in Lua follows the table below, 2159 1.2 lneto from lower to higher priority: 2160 1.2 lneto 2161 1.2 lneto <pre> 2162 1.2 lneto or 2163 1.2 lneto and 2164 1.2 lneto < > <= >= ~= == 2165 1.2 lneto | 2166 1.2 lneto ~ 2167 1.2 lneto & 2168 1.2 lneto << >> 2169 1.2 lneto .. 2170 1.2 lneto + - 2171 1.2 lneto * / // % 2172 1.2 lneto unary operators (not # - ~) 2173 1.2 lneto ^ 2174 1.2 lneto </pre><p> 2175 1.2 lneto As usual, 2176 1.2 lneto you can use parentheses to change the precedences of an expression. 2177 1.2 lneto The concatenation ('<code>..</code>') and exponentiation ('<code>^</code>') 2178 1.2 lneto operators are right associative. 2179 1.2 lneto All other binary operators are left associative. 2180 1.2 lneto 2181 1.2 lneto 2182 1.2 lneto 2183 1.2 lneto 2184 1.2 lneto 2185 1.2 lneto <h3>3.4.9 – <a name="3.4.9">Table Constructors</a></h3><p> 2186 1.2 lneto Table constructors are expressions that create tables. 2187 1.2 lneto Every time a constructor is evaluated, a new table is created. 2188 1.2 lneto A constructor can be used to create an empty table 2189 1.2 lneto or to create a table and initialize some of its fields. 2190 1.2 lneto The general syntax for constructors is 2191 1.2 lneto 2192 1.2 lneto <pre> 2193 1.2 lneto tableconstructor ::= ‘<b>{</b>’ [fieldlist] ‘<b>}</b>’ 2194 1.2 lneto fieldlist ::= field {fieldsep field} [fieldsep] 2195 1.2 lneto field ::= ‘<b>[</b>’ exp ‘<b>]</b>’ ‘<b>=</b>’ exp | Name ‘<b>=</b>’ exp | exp 2196 1.2 lneto fieldsep ::= ‘<b>,</b>’ | ‘<b>;</b>’ 2197 1.2 lneto </pre> 2198 1.2 lneto 2199 1.2 lneto <p> 2200 1.2 lneto Each field of the form <code>[exp1] = exp2</code> adds to the new table an entry 2201 1.2 lneto with key <code>exp1</code> and value <code>exp2</code>. 2202 1.2 lneto A field of the form <code>name = exp</code> is equivalent to 2203 1.2 lneto <code>["name"] = exp</code>. 2204 1.2 lneto Finally, fields of the form <code>exp</code> are equivalent to 2205 1.3 lneto <code>[i] = exp</code>, where <code>i</code> are consecutive integers 2206 1.2 lneto starting with 1. 2207 1.2 lneto Fields in the other formats do not affect this counting. 2208 1.2 lneto For example, 2209 1.2 lneto 2210 1.2 lneto <pre> 2211 1.2 lneto a = { [f(1)] = g; "x", "y"; x = 1, f(x), [30] = 23; 45 } 2212 1.2 lneto </pre><p> 2213 1.2 lneto is equivalent to 2214 1.2 lneto 2215 1.2 lneto <pre> 2216 1.2 lneto do 2217 1.2 lneto local t = {} 2218 1.2 lneto t[f(1)] = g 2219 1.2 lneto t[1] = "x" -- 1st exp 2220 1.2 lneto t[2] = "y" -- 2nd exp 2221 1.2 lneto t.x = 1 -- t["x"] = 1 2222 1.2 lneto t[3] = f(x) -- 3rd exp 2223 1.2 lneto t[30] = 23 2224 1.2 lneto t[4] = 45 -- 4th exp 2225 1.2 lneto a = t 2226 1.2 lneto end 2227 1.2 lneto </pre> 2228 1.2 lneto 2229 1.2 lneto <p> 2230 1.3 lneto The order of the assignments in a constructor is undefined. 2231 1.3 lneto (This order would be relevant only when there are repeated keys.) 2232 1.3 lneto 2233 1.3 lneto 2234 1.3 lneto <p> 2235 1.2 lneto If the last field in the list has the form <code>exp</code> 2236 1.2 lneto and the expression is a function call or a vararg expression, 2237 1.2 lneto then all values returned by this expression enter the list consecutively 2238 1.2 lneto (see <a href="#3.4.10">§3.4.10</a>). 2239 1.2 lneto 2240 1.2 lneto 2241 1.2 lneto <p> 2242 1.2 lneto The field list can have an optional trailing separator, 2243 1.2 lneto as a convenience for machine-generated code. 2244 1.2 lneto 2245 1.2 lneto 2246 1.2 lneto 2247 1.2 lneto 2248 1.2 lneto 2249 1.2 lneto <h3>3.4.10 – <a name="3.4.10">Function Calls</a></h3><p> 2250 1.2 lneto A function call in Lua has the following syntax: 2251 1.2 lneto 2252 1.2 lneto <pre> 2253 1.2 lneto functioncall ::= prefixexp args 2254 1.2 lneto </pre><p> 2255 1.2 lneto In a function call, 2256 1.2 lneto first prefixexp and args are evaluated. 2257 1.2 lneto If the value of prefixexp has type <em>function</em>, 2258 1.2 lneto then this function is called 2259 1.2 lneto with the given arguments. 2260 1.2 lneto Otherwise, the prefixexp "call" metamethod is called, 2261 1.2 lneto having as first parameter the value of prefixexp, 2262 1.2 lneto followed by the original call arguments 2263 1.2 lneto (see <a href="#2.4">§2.4</a>). 2264 1.2 lneto 2265 1.2 lneto 2266 1.2 lneto <p> 2267 1.2 lneto The form 2268 1.2 lneto 2269 1.2 lneto <pre> 2270 1.2 lneto functioncall ::= prefixexp ‘<b>:</b>’ Name args 2271 1.2 lneto </pre><p> 2272 1.2 lneto can be used to call "methods". 2273 1.2 lneto A call <code>v:name(<em>args</em>)</code> 2274 1.2 lneto is syntactic sugar for <code>v.name(v,<em>args</em>)</code>, 2275 1.2 lneto except that <code>v</code> is evaluated only once. 2276 1.2 lneto 2277 1.2 lneto 2278 1.2 lneto <p> 2279 1.2 lneto Arguments have the following syntax: 2280 1.2 lneto 2281 1.2 lneto <pre> 2282 1.2 lneto args ::= ‘<b>(</b>’ [explist] ‘<b>)</b>’ 2283 1.2 lneto args ::= tableconstructor 2284 1.3 lneto args ::= LiteralString 2285 1.2 lneto </pre><p> 2286 1.2 lneto All argument expressions are evaluated before the call. 2287 1.2 lneto A call of the form <code>f{<em>fields</em>}</code> is 2288 1.2 lneto syntactic sugar for <code>f({<em>fields</em>})</code>; 2289 1.2 lneto that is, the argument list is a single new table. 2290 1.2 lneto A call of the form <code>f'<em>string</em>'</code> 2291 1.2 lneto (or <code>f"<em>string</em>"</code> or <code>f[[<em>string</em>]]</code>) 2292 1.2 lneto is syntactic sugar for <code>f('<em>string</em>')</code>; 2293 1.2 lneto that is, the argument list is a single literal string. 2294 1.2 lneto 2295 1.2 lneto 2296 1.2 lneto <p> 2297 1.2 lneto A call of the form <code>return <em>functioncall</em></code> is called 2298 1.2 lneto a <em>tail call</em>. 2299 1.2 lneto Lua implements <em>proper tail calls</em> 2300 1.2 lneto (or <em>proper tail recursion</em>): 2301 1.2 lneto in a tail call, 2302 1.2 lneto the called function reuses the stack entry of the calling function. 2303 1.2 lneto Therefore, there is no limit on the number of nested tail calls that 2304 1.2 lneto a program can execute. 2305 1.2 lneto However, a tail call erases any debug information about the 2306 1.2 lneto calling function. 2307 1.2 lneto Note that a tail call only happens with a particular syntax, 2308 1.2 lneto where the <b>return</b> has one single function call as argument; 2309 1.2 lneto this syntax makes the calling function return exactly 2310 1.2 lneto the returns of the called function. 2311 1.2 lneto So, none of the following examples are tail calls: 2312 1.2 lneto 2313 1.2 lneto <pre> 2314 1.2 lneto return (f(x)) -- results adjusted to 1 2315 1.2 lneto return 2 * f(x) 2316 1.2 lneto return x, f(x) -- additional results 2317 1.2 lneto f(x); return -- results discarded 2318 1.2 lneto return x or f(x) -- results adjusted to 1 2319 1.2 lneto </pre> 2320 1.2 lneto 2321 1.2 lneto 2322 1.2 lneto 2323 1.2 lneto 2324 1.2 lneto <h3>3.4.11 – <a name="3.4.11">Function Definitions</a></h3> 2325 1.2 lneto 2326 1.2 lneto <p> 2327 1.2 lneto The syntax for function definition is 2328 1.2 lneto 2329 1.2 lneto <pre> 2330 1.2 lneto functiondef ::= <b>function</b> funcbody 2331 1.2 lneto funcbody ::= ‘<b>(</b>’ [parlist] ‘<b>)</b>’ block <b>end</b> 2332 1.2 lneto </pre> 2333 1.2 lneto 2334 1.2 lneto <p> 2335 1.2 lneto The following syntactic sugar simplifies function definitions: 2336 1.2 lneto 2337 1.2 lneto <pre> 2338 1.2 lneto stat ::= <b>function</b> funcname funcbody 2339 1.2 lneto stat ::= <b>local</b> <b>function</b> Name funcbody 2340 1.2 lneto funcname ::= Name {‘<b>.</b>’ Name} [‘<b>:</b>’ Name] 2341 1.2 lneto </pre><p> 2342 1.2 lneto The statement 2343 1.2 lneto 2344 1.2 lneto <pre> 2345 1.2 lneto function f () <em>body</em> end 2346 1.2 lneto </pre><p> 2347 1.2 lneto translates to 2348 1.2 lneto 2349 1.2 lneto <pre> 2350 1.2 lneto f = function () <em>body</em> end 2351 1.2 lneto </pre><p> 2352 1.2 lneto The statement 2353 1.2 lneto 2354 1.2 lneto <pre> 2355 1.2 lneto function t.a.b.c.f () <em>body</em> end 2356 1.2 lneto </pre><p> 2357 1.2 lneto translates to 2358 1.2 lneto 2359 1.2 lneto <pre> 2360 1.2 lneto t.a.b.c.f = function () <em>body</em> end 2361 1.2 lneto </pre><p> 2362 1.2 lneto The statement 2363 1.2 lneto 2364 1.2 lneto <pre> 2365 1.2 lneto local function f () <em>body</em> end 2366 1.2 lneto </pre><p> 2367 1.2 lneto translates to 2368 1.2 lneto 2369 1.2 lneto <pre> 2370 1.2 lneto local f; f = function () <em>body</em> end 2371 1.2 lneto </pre><p> 2372 1.2 lneto not to 2373 1.2 lneto 2374 1.2 lneto <pre> 2375 1.2 lneto local f = function () <em>body</em> end 2376 1.2 lneto </pre><p> 2377 1.2 lneto (This only makes a difference when the body of the function 2378 1.2 lneto contains references to <code>f</code>.) 2379 1.2 lneto 2380 1.2 lneto 2381 1.2 lneto <p> 2382 1.2 lneto A function definition is an executable expression, 2383 1.2 lneto whose value has type <em>function</em>. 2384 1.2 lneto When Lua precompiles a chunk, 2385 1.2 lneto all its function bodies are precompiled too. 2386 1.2 lneto Then, whenever Lua executes the function definition, 2387 1.2 lneto the function is <em>instantiated</em> (or <em>closed</em>). 2388 1.2 lneto This function instance (or <em>closure</em>) 2389 1.2 lneto is the final value of the expression. 2390 1.2 lneto 2391 1.2 lneto 2392 1.2 lneto <p> 2393 1.2 lneto Parameters act as local variables that are 2394 1.2 lneto initialized with the argument values: 2395 1.2 lneto 2396 1.2 lneto <pre> 2397 1.2 lneto parlist ::= namelist [‘<b>,</b>’ ‘<b>...</b>’] | ‘<b>...</b>’ 2398 1.2 lneto </pre><p> 2399 1.2 lneto When a function is called, 2400 1.2 lneto the list of arguments is adjusted to 2401 1.2 lneto the length of the list of parameters, 2402 1.2 lneto unless the function is a <em>vararg function</em>, 2403 1.2 lneto which is indicated by three dots ('<code>...</code>') 2404 1.2 lneto at the end of its parameter list. 2405 1.2 lneto A vararg function does not adjust its argument list; 2406 1.2 lneto instead, it collects all extra arguments and supplies them 2407 1.2 lneto to the function through a <em>vararg expression</em>, 2408 1.2 lneto which is also written as three dots. 2409 1.2 lneto The value of this expression is a list of all actual extra arguments, 2410 1.2 lneto similar to a function with multiple results. 2411 1.2 lneto If a vararg expression is used inside another expression 2412 1.2 lneto or in the middle of a list of expressions, 2413 1.2 lneto then its return list is adjusted to one element. 2414 1.2 lneto If the expression is used as the last element of a list of expressions, 2415 1.2 lneto then no adjustment is made 2416 1.2 lneto (unless that last expression is enclosed in parentheses). 2417 1.2 lneto 2418 1.2 lneto 2419 1.2 lneto <p> 2420 1.2 lneto As an example, consider the following definitions: 2421 1.2 lneto 2422 1.2 lneto <pre> 2423 1.2 lneto function f(a, b) end 2424 1.2 lneto function g(a, b, ...) end 2425 1.2 lneto function r() return 1,2,3 end 2426 1.2 lneto </pre><p> 2427 1.2 lneto Then, we have the following mapping from arguments to parameters and 2428 1.2 lneto to the vararg expression: 2429 1.1 mbalmer 2430 1.1 mbalmer <pre> 2431 1.2 lneto CALL PARAMETERS 2432 1.2 lneto 2433 1.2 lneto f(3) a=3, b=nil 2434 1.2 lneto f(3, 4) a=3, b=4 2435 1.2 lneto f(3, 4, 5) a=3, b=4 2436 1.2 lneto f(r(), 10) a=1, b=10 2437 1.2 lneto f(r()) a=1, b=2 2438 1.2 lneto 2439 1.2 lneto g(3) a=3, b=nil, ... --> (nothing) 2440 1.2 lneto g(3, 4) a=3, b=4, ... --> (nothing) 2441 1.2 lneto g(3, 4, 5, 8) a=3, b=4, ... --> 5 8 2442 1.2 lneto g(5, r()) a=5, b=1, ... --> 2 3 2443 1.1 mbalmer </pre> 2444 1.1 mbalmer 2445 1.1 mbalmer <p> 2446 1.2 lneto Results are returned using the <b>return</b> statement (see <a href="#3.3.4">§3.3.4</a>). 2447 1.2 lneto If control reaches the end of a function 2448 1.2 lneto without encountering a <b>return</b> statement, 2449 1.2 lneto then the function returns with no results. 2450 1.1 mbalmer 2451 1.1 mbalmer 2452 1.1 mbalmer <p> 2453 1.1 mbalmer 2454 1.2 lneto There is a system-dependent limit on the number of values 2455 1.2 lneto that a function may return. 2456 1.2 lneto This limit is guaranteed to be larger than 1000. 2457 1.1 mbalmer 2458 1.1 mbalmer 2459 1.1 mbalmer <p> 2460 1.2 lneto The <em>colon</em> syntax 2461 1.2 lneto is used for defining <em>methods</em>, 2462 1.2 lneto that is, functions that have an implicit extra parameter <code>self</code>. 2463 1.2 lneto Thus, the statement 2464 1.1 mbalmer 2465 1.2 lneto <pre> 2466 1.2 lneto function t.a.b.c:f (<em>params</em>) <em>body</em> end 2467 1.2 lneto </pre><p> 2468 1.2 lneto is syntactic sugar for 2469 1.1 mbalmer 2470 1.2 lneto <pre> 2471 1.2 lneto t.a.b.c.f = function (self, <em>params</em>) <em>body</em> end 2472 1.2 lneto </pre> 2473 1.1 mbalmer 2474 1.1 mbalmer 2475 1.1 mbalmer 2476 1.1 mbalmer 2477 1.1 mbalmer 2478 1.1 mbalmer 2479 1.2 lneto <h2>3.5 – <a name="3.5">Visibility Rules</a></h2> 2480 1.1 mbalmer 2481 1.1 mbalmer <p> 2482 1.1 mbalmer 2483 1.2 lneto Lua is a lexically scoped language. 2484 1.2 lneto The scope of a local variable begins at the first statement after 2485 1.2 lneto its declaration and lasts until the last non-void statement 2486 1.2 lneto of the innermost block that includes the declaration. 2487 1.2 lneto Consider the following example: 2488 1.1 mbalmer 2489 1.2 lneto <pre> 2490 1.2 lneto x = 10 -- global variable 2491 1.2 lneto do -- new block 2492 1.2 lneto local x = x -- new 'x', with value 10 2493 1.2 lneto print(x) --> 10 2494 1.2 lneto x = x+1 2495 1.2 lneto do -- another block 2496 1.2 lneto local x = x+1 -- another 'x' 2497 1.2 lneto print(x) --> 12 2498 1.2 lneto end 2499 1.2 lneto print(x) --> 11 2500 1.2 lneto end 2501 1.2 lneto print(x) --> 10 (the global one) 2502 1.2 lneto </pre> 2503 1.1 mbalmer 2504 1.1 mbalmer <p> 2505 1.2 lneto Notice that, in a declaration like <code>local x = x</code>, 2506 1.2 lneto the new <code>x</code> being declared is not in scope yet, 2507 1.2 lneto and so the second <code>x</code> refers to the outside variable. 2508 1.1 mbalmer 2509 1.1 mbalmer 2510 1.1 mbalmer <p> 2511 1.2 lneto Because of the lexical scoping rules, 2512 1.2 lneto local variables can be freely accessed by functions 2513 1.2 lneto defined inside their scope. 2514 1.2 lneto A local variable used by an inner function is called 2515 1.2 lneto an <em>upvalue</em>, or <em>external local variable</em>, 2516 1.2 lneto inside the inner function. 2517 1.1 mbalmer 2518 1.1 mbalmer 2519 1.1 mbalmer <p> 2520 1.2 lneto Notice that each execution of a <b>local</b> statement 2521 1.2 lneto defines new local variables. 2522 1.2 lneto Consider the following example: 2523 1.1 mbalmer 2524 1.1 mbalmer <pre> 2525 1.2 lneto a = {} 2526 1.2 lneto local x = 20 2527 1.2 lneto for i=1,10 do 2528 1.2 lneto local y = 0 2529 1.2 lneto a[i] = function () y=y+1; return x+y end 2530 1.1 mbalmer end 2531 1.1 mbalmer </pre><p> 2532 1.2 lneto The loop creates ten closures 2533 1.2 lneto (that is, ten instances of the anonymous function). 2534 1.2 lneto Each of these closures uses a different <code>y</code> variable, 2535 1.2 lneto while all of them share the same <code>x</code>. 2536 1.1 mbalmer 2537 1.1 mbalmer 2538 1.1 mbalmer 2539 1.1 mbalmer 2540 1.1 mbalmer 2541 1.2 lneto <h1>4 – <a name="4">The Application Program Interface</a></h1> 2542 1.1 mbalmer 2543 1.1 mbalmer <p> 2544 1.1 mbalmer 2545 1.1 mbalmer This section describes the C API for Lua, that is, 2546 1.1 mbalmer the set of C functions available to the host program to communicate 2547 1.1 mbalmer with Lua. 2548 1.1 mbalmer All API functions and related types and constants 2549 1.1 mbalmer are declared in the header file <a name="pdf-lua.h"><code>lua.h</code></a>. 2550 1.1 mbalmer 2551 1.1 mbalmer 2552 1.1 mbalmer <p> 2553 1.1 mbalmer Even when we use the term "function", 2554 1.1 mbalmer any facility in the API may be provided as a macro instead. 2555 1.2 lneto Except where stated otherwise, 2556 1.2 lneto all such macros use each of their arguments exactly once 2557 1.1 mbalmer (except for the first argument, which is always a Lua state), 2558 1.1 mbalmer and so do not generate any hidden side-effects. 2559 1.1 mbalmer 2560 1.1 mbalmer 2561 1.1 mbalmer <p> 2562 1.1 mbalmer As in most C libraries, 2563 1.1 mbalmer the Lua API functions do not check their arguments for validity or consistency. 2564 1.1 mbalmer However, you can change this behavior by compiling Lua 2565 1.2 lneto with the macro <a name="pdf-LUA_USE_APICHECK"><code>LUA_USE_APICHECK</code></a> defined. 2566 1.1 mbalmer 2567 1.1 mbalmer 2568 1.1 mbalmer 2569 1.2 lneto <h2>4.1 – <a name="4.1">The Stack</a></h2> 2570 1.1 mbalmer 2571 1.1 mbalmer <p> 2572 1.1 mbalmer Lua uses a <em>virtual stack</em> to pass values to and from C. 2573 1.1 mbalmer Each element in this stack represents a Lua value 2574 1.1 mbalmer (<b>nil</b>, number, string, etc.). 2575 1.1 mbalmer 2576 1.1 mbalmer 2577 1.1 mbalmer <p> 2578 1.1 mbalmer Whenever Lua calls C, the called function gets a new stack, 2579 1.1 mbalmer which is independent of previous stacks and of stacks of 2580 1.1 mbalmer C functions that are still active. 2581 1.1 mbalmer This stack initially contains any arguments to the C function 2582 1.1 mbalmer and it is where the C function pushes its results 2583 1.1 mbalmer to be returned to the caller (see <a href="#lua_CFunction"><code>lua_CFunction</code></a>). 2584 1.1 mbalmer 2585 1.1 mbalmer 2586 1.1 mbalmer <p> 2587 1.1 mbalmer For convenience, 2588 1.1 mbalmer most query operations in the API do not follow a strict stack discipline. 2589 1.1 mbalmer Instead, they can refer to any element in the stack 2590 1.1 mbalmer by using an <em>index</em>: 2591 1.2 lneto A positive index represents an absolute stack position 2592 1.1 mbalmer (starting at 1); 2593 1.2 lneto a negative index represents an offset relative to the top of the stack. 2594 1.1 mbalmer More specifically, if the stack has <em>n</em> elements, 2595 1.1 mbalmer then index 1 represents the first element 2596 1.1 mbalmer (that is, the element that was pushed onto the stack first) 2597 1.1 mbalmer and 2598 1.1 mbalmer index <em>n</em> represents the last element; 2599 1.1 mbalmer index -1 also represents the last element 2600 1.1 mbalmer (that is, the element at the top) 2601 1.1 mbalmer and index <em>-n</em> represents the first element. 2602 1.1 mbalmer 2603 1.1 mbalmer 2604 1.1 mbalmer 2605 1.1 mbalmer 2606 1.1 mbalmer 2607 1.2 lneto <h2>4.2 – <a name="4.2">Stack Size</a></h2> 2608 1.1 mbalmer 2609 1.1 mbalmer <p> 2610 1.2 lneto When you interact with the Lua API, 2611 1.1 mbalmer you are responsible for ensuring consistency. 2612 1.1 mbalmer In particular, 2613 1.1 mbalmer <em>you are responsible for controlling stack overflow</em>. 2614 1.1 mbalmer You can use the function <a href="#lua_checkstack"><code>lua_checkstack</code></a> 2615 1.3 lneto to ensure that the stack has enough space for pushing new elements. 2616 1.1 mbalmer 2617 1.1 mbalmer 2618 1.1 mbalmer <p> 2619 1.1 mbalmer Whenever Lua calls C, 2620 1.3 lneto it ensures that the stack has space for 2621 1.3 lneto at least <a name="pdf-LUA_MINSTACK"><code>LUA_MINSTACK</code></a> extra slots. 2622 1.1 mbalmer <code>LUA_MINSTACK</code> is defined as 20, 2623 1.1 mbalmer so that usually you do not have to worry about stack space 2624 1.1 mbalmer unless your code has loops pushing elements onto the stack. 2625 1.1 mbalmer 2626 1.1 mbalmer 2627 1.1 mbalmer <p> 2628 1.2 lneto When you call a Lua function 2629 1.2 lneto without a fixed number of results (see <a href="#lua_call"><code>lua_call</code></a>), 2630 1.3 lneto Lua ensures that the stack has enough space for all results, 2631 1.2 lneto but it does not ensure any extra space. 2632 1.2 lneto So, before pushing anything in the stack after such a call 2633 1.2 lneto you should use <a href="#lua_checkstack"><code>lua_checkstack</code></a>. 2634 1.2 lneto 2635 1.2 lneto 2636 1.2 lneto 2637 1.2 lneto 2638 1.1 mbalmer 2639 1.2 lneto <h2>4.3 – <a name="4.3">Valid and Acceptable Indices</a></h2> 2640 1.1 mbalmer 2641 1.2 lneto <p> 2642 1.2 lneto Any function in the API that receives stack indices 2643 1.2 lneto works only with <em>valid indices</em> or <em>acceptable indices</em>. 2644 1.1 mbalmer 2645 1.1 mbalmer 2646 1.2 lneto <p> 2647 1.2 lneto A <em>valid index</em> is an index that refers to a 2648 1.4 mbalmer position that stores a modifiable Lua value. 2649 1.4 mbalmer It comprises stack indices between 1 and the stack top 2650 1.4 mbalmer (<code>1 ≤ abs(index) ≤ top</code>) 2651 1.4 mbalmer 2652 1.4 mbalmer plus <em>pseudo-indices</em>, 2653 1.4 mbalmer which represent some positions that are accessible to C code 2654 1.4 mbalmer but that are not in the stack. 2655 1.4 mbalmer Pseudo-indices are used to access the registry (see <a href="#4.5">§4.5</a>) 2656 1.2 lneto and the upvalues of a C function (see <a href="#4.4">§4.4</a>). 2657 1.2 lneto 2658 1.2 lneto 2659 1.2 lneto <p> 2660 1.4 mbalmer Functions that do not need a specific mutable position, 2661 1.4 mbalmer but only a value (e.g., query functions), 2662 1.2 lneto can be called with acceptable indices. 2663 1.2 lneto An <em>acceptable index</em> can be any valid index, 2664 1.2 lneto but it also can be any positive index after the stack top 2665 1.2 lneto within the space allocated for the stack, 2666 1.2 lneto that is, indices up to the stack size. 2667 1.2 lneto (Note that 0 is never an acceptable index.) 2668 1.2 lneto Except when noted otherwise, 2669 1.2 lneto functions in the API work with acceptable indices. 2670 1.1 mbalmer 2671 1.1 mbalmer 2672 1.1 mbalmer <p> 2673 1.2 lneto Acceptable indices serve to avoid extra tests 2674 1.2 lneto against the stack top when querying the stack. 2675 1.2 lneto For instance, a C function can query its third argument 2676 1.2 lneto without the need to first check whether there is a third argument, 2677 1.2 lneto that is, without the need to check whether 3 is a valid index. 2678 1.1 mbalmer 2679 1.1 mbalmer 2680 1.1 mbalmer <p> 2681 1.2 lneto For functions that can be called with acceptable indices, 2682 1.2 lneto any non-valid index is treated as if it 2683 1.2 lneto contains a value of a virtual type <a name="pdf-LUA_TNONE"><code>LUA_TNONE</code></a>, 2684 1.2 lneto which behaves like a nil value. 2685 1.1 mbalmer 2686 1.1 mbalmer 2687 1.1 mbalmer 2688 1.1 mbalmer 2689 1.1 mbalmer 2690 1.2 lneto <h2>4.4 – <a name="4.4">C Closures</a></h2> 2691 1.1 mbalmer 2692 1.1 mbalmer <p> 2693 1.1 mbalmer When a C function is created, 2694 1.1 mbalmer it is possible to associate some values with it, 2695 1.2 lneto thus creating a <em>C closure</em> 2696 1.2 lneto (see <a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a>); 2697 1.1 mbalmer these values are called <em>upvalues</em> and are 2698 1.2 lneto accessible to the function whenever it is called. 2699 1.1 mbalmer 2700 1.1 mbalmer 2701 1.1 mbalmer <p> 2702 1.1 mbalmer Whenever a C function is called, 2703 1.1 mbalmer its upvalues are located at specific pseudo-indices. 2704 1.1 mbalmer These pseudo-indices are produced by the macro 2705 1.2 lneto <a href="#lua_upvalueindex"><code>lua_upvalueindex</code></a>. 2706 1.4 mbalmer The first upvalue associated with a function is at index 2707 1.1 mbalmer <code>lua_upvalueindex(1)</code>, and so on. 2708 1.1 mbalmer Any access to <code>lua_upvalueindex(<em>n</em>)</code>, 2709 1.1 mbalmer where <em>n</em> is greater than the number of upvalues of the 2710 1.5 lneto current function 2711 1.5 lneto (but not greater than 256, 2712 1.5 lneto which is one plus the maximum number of upvalues in a closure), 2713 1.2 lneto produces an acceptable but invalid index. 2714 1.1 mbalmer 2715 1.1 mbalmer 2716 1.1 mbalmer 2717 1.1 mbalmer 2718 1.1 mbalmer 2719 1.2 lneto <h2>4.5 – <a name="4.5">Registry</a></h2> 2720 1.1 mbalmer 2721 1.1 mbalmer <p> 2722 1.1 mbalmer Lua provides a <em>registry</em>, 2723 1.2 lneto a predefined table that can be used by any C code to 2724 1.2 lneto store whatever Lua values it needs to store. 2725 1.2 lneto The registry table is always located at pseudo-index 2726 1.4 mbalmer <a name="pdf-LUA_REGISTRYINDEX"><code>LUA_REGISTRYINDEX</code></a>. 2727 1.1 mbalmer Any C library can store data into this table, 2728 1.2 lneto but it must take care to choose keys 2729 1.2 lneto that are different from those used 2730 1.1 mbalmer by other libraries, to avoid collisions. 2731 1.2 lneto Typically, you should use as key a string containing your library name, 2732 1.2 lneto or a light userdata with the address of a C object in your code, 2733 1.2 lneto or any Lua object created by your code. 2734 1.3 lneto As with variable names, 2735 1.2 lneto string keys starting with an underscore followed by 2736 1.2 lneto uppercase letters are reserved for Lua. 2737 1.1 mbalmer 2738 1.1 mbalmer 2739 1.1 mbalmer <p> 2740 1.3 lneto The integer keys in the registry are used 2741 1.3 lneto by the reference mechanism (see <a href="#luaL_ref"><code>luaL_ref</code></a>) 2742 1.2 lneto and by some predefined values. 2743 1.2 lneto Therefore, integer keys must not be used for other purposes. 2744 1.2 lneto 2745 1.1 mbalmer 2746 1.2 lneto <p> 2747 1.2 lneto When you create a new Lua state, 2748 1.2 lneto its registry comes with some predefined values. 2749 1.2 lneto These predefined values are indexed with integer keys 2750 1.2 lneto defined as constants in <code>lua.h</code>. 2751 1.2 lneto The following constants are defined: 2752 1.2 lneto 2753 1.2 lneto <ul> 2754 1.2 lneto <li><b><a name="pdf-LUA_RIDX_MAINTHREAD"><code>LUA_RIDX_MAINTHREAD</code></a>: </b> At this index the registry has 2755 1.2 lneto the main thread of the state. 2756 1.2 lneto (The main thread is the one created together with the state.) 2757 1.2 lneto </li> 2758 1.1 mbalmer 2759 1.2 lneto <li><b><a name="pdf-LUA_RIDX_GLOBALS"><code>LUA_RIDX_GLOBALS</code></a>: </b> At this index the registry has 2760 1.2 lneto the global environment. 2761 1.2 lneto </li> 2762 1.2 lneto </ul> 2763 1.1 mbalmer 2764 1.1 mbalmer 2765 1.1 mbalmer 2766 1.2 lneto 2767 1.2 lneto <h2>4.6 – <a name="4.6">Error Handling in C</a></h2> 2768 1.1 mbalmer 2769 1.1 mbalmer <p> 2770 1.1 mbalmer Internally, Lua uses the C <code>longjmp</code> facility to handle errors. 2771 1.3 lneto (Lua will use exceptions if you compile it as C++; 2772 1.3 lneto search for <code>LUAI_THROW</code> in the source code for details.) 2773 1.1 mbalmer When Lua faces any error 2774 1.2 lneto (such as a memory allocation error, type errors, syntax errors, 2775 1.1 mbalmer and runtime errors) 2776 1.1 mbalmer it <em>raises</em> an error; 2777 1.1 mbalmer that is, it does a long jump. 2778 1.1 mbalmer A <em>protected environment</em> uses <code>setjmp</code> 2779 1.2 lneto to set a recovery point; 2780 1.2 lneto any error jumps to the most recent active recovery point. 2781 1.2 lneto 2782 1.2 lneto 2783 1.2 lneto <p> 2784 1.2 lneto If an error happens outside any protected environment, 2785 1.2 lneto Lua calls a <em>panic function</em> (see <a href="#lua_atpanic"><code>lua_atpanic</code></a>) 2786 1.2 lneto and then calls <code>abort</code>, 2787 1.2 lneto thus exiting the host application. 2788 1.2 lneto Your panic function can avoid this exit by 2789 1.2 lneto never returning 2790 1.2 lneto (e.g., doing a long jump to your own recovery point outside Lua). 2791 1.2 lneto 2792 1.2 lneto 2793 1.2 lneto <p> 2794 1.2 lneto The panic function runs as if it were a message handler (see <a href="#2.3">§2.3</a>); 2795 1.2 lneto in particular, the error message is at the top of the stack. 2796 1.3 lneto However, there is no guarantee about stack space. 2797 1.2 lneto To push anything on the stack, 2798 1.2 lneto the panic function must first check the available space (see <a href="#4.2">§4.2</a>). 2799 1.1 mbalmer 2800 1.1 mbalmer 2801 1.1 mbalmer <p> 2802 1.2 lneto Most functions in the API can raise an error, 2803 1.1 mbalmer for instance due to a memory allocation error. 2804 1.2 lneto The documentation for each function indicates whether 2805 1.2 lneto it can raise errors. 2806 1.2 lneto 2807 1.2 lneto 2808 1.2 lneto <p> 2809 1.2 lneto Inside a C function you can raise an error by calling <a href="#lua_error"><code>lua_error</code></a>. 2810 1.2 lneto 2811 1.2 lneto 2812 1.2 lneto 2813 1.2 lneto 2814 1.2 lneto 2815 1.2 lneto <h2>4.7 – <a name="4.7">Handling Yields in C</a></h2> 2816 1.2 lneto 2817 1.2 lneto <p> 2818 1.2 lneto Internally, Lua uses the C <code>longjmp</code> facility to yield a coroutine. 2819 1.2 lneto Therefore, if a C function <code>foo</code> calls an API function 2820 1.2 lneto and this API function yields 2821 1.2 lneto (directly or indirectly by calling another function that yields), 2822 1.2 lneto Lua cannot return to <code>foo</code> any more, 2823 1.2 lneto because the <code>longjmp</code> removes its frame from the C stack. 2824 1.2 lneto 2825 1.2 lneto 2826 1.2 lneto <p> 2827 1.2 lneto To avoid this kind of problem, 2828 1.2 lneto Lua raises an error whenever it tries to yield across an API call, 2829 1.2 lneto except for three functions: 2830 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>. 2831 1.2 lneto All those functions receive a <em>continuation function</em> 2832 1.3 lneto (as a parameter named <code>k</code>) to continue execution after a yield. 2833 1.2 lneto 2834 1.2 lneto 2835 1.2 lneto <p> 2836 1.2 lneto We need to set some terminology to explain continuations. 2837 1.2 lneto We have a C function called from Lua which we will call 2838 1.2 lneto the <em>original function</em>. 2839 1.2 lneto This original function then calls one of those three functions in the C API, 2840 1.2 lneto which we will call the <em>callee function</em>, 2841 1.2 lneto that then yields the current thread. 2842 1.2 lneto (This can happen when the callee function is <a href="#lua_yieldk"><code>lua_yieldk</code></a>, 2843 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> 2844 1.2 lneto and the function called by them yields.) 2845 1.2 lneto 2846 1.2 lneto 2847 1.2 lneto <p> 2848 1.2 lneto Suppose the running thread yields while executing the callee function. 2849 1.2 lneto After the thread resumes, 2850 1.2 lneto it eventually will finish running the callee function. 2851 1.2 lneto However, 2852 1.2 lneto the callee function cannot return to the original function, 2853 1.2 lneto because its frame in the C stack was destroyed by the yield. 2854 1.2 lneto Instead, Lua calls a <em>continuation function</em>, 2855 1.2 lneto which was given as an argument to the callee function. 2856 1.2 lneto As the name implies, 2857 1.2 lneto the continuation function should continue the task 2858 1.2 lneto of the original function. 2859 1.2 lneto 2860 1.2 lneto 2861 1.2 lneto <p> 2862 1.2 lneto As an illustration, consider the following function: 2863 1.2 lneto 2864 1.2 lneto <pre> 2865 1.2 lneto int original_function (lua_State *L) { 2866 1.2 lneto ... /* code 1 */ 2867 1.2 lneto status = lua_pcall(L, n, m, h); /* calls Lua */ 2868 1.2 lneto ... /* code 2 */ 2869 1.2 lneto } 2870 1.2 lneto </pre><p> 2871 1.2 lneto Now we want to allow 2872 1.3 lneto the Lua code being run by <a href="#lua_pcall"><code>lua_pcall</code></a> to yield. 2873 1.2 lneto First, we can rewrite our function like here: 2874 1.2 lneto 2875 1.2 lneto <pre> 2876 1.3 lneto int k (lua_State *L, int status, lua_KContext ctx) { 2877 1.2 lneto ... /* code 2 */ 2878 1.2 lneto } 2879 1.2 lneto 2880 1.2 lneto int original_function (lua_State *L) { 2881 1.2 lneto ... /* code 1 */ 2882 1.2 lneto return k(L, lua_pcall(L, n, m, h), ctx); 2883 1.2 lneto } 2884 1.2 lneto </pre><p> 2885 1.2 lneto In the above code, 2886 1.2 lneto the new function <code>k</code> is a 2887 1.2 lneto <em>continuation function</em> (with type <a href="#lua_KFunction"><code>lua_KFunction</code></a>), 2888 1.2 lneto which should do all the work that the original function 2889 1.2 lneto was doing after calling <a href="#lua_pcall"><code>lua_pcall</code></a>. 2890 1.2 lneto Now, we must inform Lua that it must call <code>k</code> if the Lua code 2891 1.3 lneto being executed by <a href="#lua_pcall"><code>lua_pcall</code></a> gets interrupted in some way 2892 1.2 lneto (errors or yielding), 2893 1.2 lneto so we rewrite the code as here, 2894 1.2 lneto replacing <a href="#lua_pcall"><code>lua_pcall</code></a> by <a href="#lua_pcallk"><code>lua_pcallk</code></a>: 2895 1.2 lneto 2896 1.2 lneto <pre> 2897 1.2 lneto int original_function (lua_State *L) { 2898 1.2 lneto ... /* code 1 */ 2899 1.2 lneto return k(L, lua_pcallk(L, n, m, h, ctx2, k), ctx1); 2900 1.2 lneto } 2901 1.3 lneto </pre><p> 2902 1.3 lneto Note the external, explicit call to the continuation: 2903 1.3 lneto Lua will call the continuation only if needed, that is, 2904 1.3 lneto in case of errors or resuming after a yield. 2905 1.3 lneto If the called function returns normally without ever yielding, 2906 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. 2907 1.3 lneto (Of course, instead of calling the continuation in that case, 2908 1.3 lneto you can do the equivalent work directly inside the original function.) 2909 1.3 lneto 2910 1.2 lneto 2911 1.2 lneto <p> 2912 1.2 lneto Besides the Lua state, 2913 1.2 lneto the continuation function has two other parameters: 2914 1.2 lneto the final status of the call plus the context value (<code>ctx</code>) that 2915 1.2 lneto was passed originally to <a href="#lua_pcallk"><code>lua_pcallk</code></a>. 2916 1.2 lneto (Lua does not use this context value; 2917 1.2 lneto it only passes this value from the original function to the 2918 1.2 lneto continuation function.) 2919 1.2 lneto For <a href="#lua_pcallk"><code>lua_pcallk</code></a>, 2920 1.2 lneto the status is the same value that would be returned by <a href="#lua_pcallk"><code>lua_pcallk</code></a>, 2921 1.3 lneto except that it is <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a> when being executed after a yield 2922 1.2 lneto (instead of <a href="#pdf-LUA_OK"><code>LUA_OK</code></a>). 2923 1.2 lneto For <a href="#lua_yieldk"><code>lua_yieldk</code></a> and <a href="#lua_callk"><code>lua_callk</code></a>, 2924 1.2 lneto the status is always <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a> when Lua calls the continuation. 2925 1.2 lneto (For these two functions, 2926 1.2 lneto Lua will not call the continuation in case of errors, 2927 1.2 lneto because they do not handle errors.) 2928 1.3 lneto Similarly, when using <a href="#lua_callk"><code>lua_callk</code></a>, 2929 1.3 lneto you should call the continuation function 2930 1.3 lneto with <a href="#pdf-LUA_OK"><code>LUA_OK</code></a> as the status. 2931 1.3 lneto (For <a href="#lua_yieldk"><code>lua_yieldk</code></a>, there is not much point in calling 2932 1.3 lneto directly the continuation function, 2933 1.3 lneto because <a href="#lua_yieldk"><code>lua_yieldk</code></a> usually does not return.) 2934 1.1 mbalmer 2935 1.1 mbalmer 2936 1.1 mbalmer <p> 2937 1.2 lneto Lua treats the continuation function as if it were the original function. 2938 1.2 lneto The continuation function receives the same Lua stack 2939 1.2 lneto from the original function, 2940 1.2 lneto in the same state it would be if the callee function had returned. 2941 1.2 lneto (For instance, 2942 1.2 lneto after a <a href="#lua_callk"><code>lua_callk</code></a> the function and its arguments are 2943 1.2 lneto removed from the stack and replaced by the results from the call.) 2944 1.2 lneto It also has the same upvalues. 2945 1.2 lneto Whatever it returns is handled by Lua as if it were the return 2946 1.2 lneto of the original function. 2947 1.1 mbalmer 2948 1.1 mbalmer 2949 1.1 mbalmer 2950 1.1 mbalmer 2951 1.1 mbalmer 2952 1.2 lneto <h2>4.8 – <a name="4.8">Functions and Types</a></h2> 2953 1.1 mbalmer 2954 1.1 mbalmer <p> 2955 1.1 mbalmer Here we list all functions and types from the C API in 2956 1.1 mbalmer alphabetical order. 2957 1.1 mbalmer Each function has an indicator like this: 2958 1.1 mbalmer <span class="apii">[-o, +p, <em>x</em>]</span> 2959 1.1 mbalmer 2960 1.1 mbalmer 2961 1.1 mbalmer <p> 2962 1.1 mbalmer The first field, <code>o</code>, 2963 1.1 mbalmer is how many elements the function pops from the stack. 2964 1.1 mbalmer The second field, <code>p</code>, 2965 1.1 mbalmer is how many elements the function pushes onto the stack. 2966 1.1 mbalmer (Any function always pushes its results after popping its arguments.) 2967 1.1 mbalmer A field in the form <code>x|y</code> means the function can push (or pop) 2968 1.1 mbalmer <code>x</code> or <code>y</code> elements, 2969 1.1 mbalmer depending on the situation; 2970 1.1 mbalmer an interrogation mark '<code>?</code>' means that 2971 1.1 mbalmer we cannot know how many elements the function pops/pushes 2972 1.1 mbalmer by looking only at its arguments 2973 1.1 mbalmer (e.g., they may depend on what is on the stack). 2974 1.1 mbalmer The third field, <code>x</code>, 2975 1.2 lneto tells whether the function may raise errors: 2976 1.2 lneto '<code>-</code>' means the function never raises any error; 2977 1.5 lneto '<code>m</code>' means the function may raise memory errors; 2978 1.2 lneto '<code>e</code>' means the function may raise errors; 2979 1.2 lneto '<code>v</code>' means the function may raise an error on purpose. 2980 1.2 lneto 2981 1.2 lneto 2982 1.2 lneto 2983 1.2 lneto <hr><h3><a name="lua_absindex"><code>lua_absindex</code></a></h3><p> 2984 1.2 lneto <span class="apii">[-0, +0, –]</span> 2985 1.2 lneto <pre>int lua_absindex (lua_State *L, int idx);</pre> 2986 1.2 lneto 2987 1.2 lneto <p> 2988 1.4 mbalmer Converts the acceptable index <code>idx</code> 2989 1.4 mbalmer into an equivalent absolute index 2990 1.2 lneto (that is, one that does not depend on the stack top). 2991 1.2 lneto 2992 1.2 lneto 2993 1.1 mbalmer 2994 1.1 mbalmer 2995 1.1 mbalmer 2996 1.1 mbalmer <hr><h3><a name="lua_Alloc"><code>lua_Alloc</code></a></h3> 2997 1.1 mbalmer <pre>typedef void * (*lua_Alloc) (void *ud, 2998 1.1 mbalmer void *ptr, 2999 1.1 mbalmer size_t osize, 3000 1.1 mbalmer size_t nsize);</pre> 3001 1.1 mbalmer 3002 1.1 mbalmer <p> 3003 1.1 mbalmer The type of the memory-allocation function used by Lua states. 3004 1.1 mbalmer The allocator function must provide a 3005 1.1 mbalmer functionality similar to <code>realloc</code>, 3006 1.1 mbalmer but not exactly the same. 3007 1.1 mbalmer Its arguments are 3008 1.1 mbalmer <code>ud</code>, an opaque pointer passed to <a href="#lua_newstate"><code>lua_newstate</code></a>; 3009 1.1 mbalmer <code>ptr</code>, a pointer to the block being allocated/reallocated/freed; 3010 1.2 lneto <code>osize</code>, the original size of the block or some code about what 3011 1.2 lneto is being allocated; 3012 1.3 lneto and <code>nsize</code>, the new size of the block. 3013 1.2 lneto 3014 1.2 lneto 3015 1.2 lneto <p> 3016 1.2 lneto When <code>ptr</code> is not <code>NULL</code>, 3017 1.2 lneto <code>osize</code> is the size of the block pointed by <code>ptr</code>, 3018 1.2 lneto that is, the size given when it was allocated or reallocated. 3019 1.2 lneto 3020 1.2 lneto 3021 1.2 lneto <p> 3022 1.2 lneto When <code>ptr</code> is <code>NULL</code>, 3023 1.2 lneto <code>osize</code> encodes the kind of object that Lua is allocating. 3024 1.2 lneto <code>osize</code> is any of 3025 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>, 3026 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) 3027 1.2 lneto Lua is creating a new object of that type. 3028 1.2 lneto When <code>osize</code> is some other value, 3029 1.2 lneto Lua is allocating memory for something else. 3030 1.2 lneto 3031 1.2 lneto 3032 1.2 lneto <p> 3033 1.2 lneto Lua assumes the following behavior from the allocator function: 3034 1.2 lneto 3035 1.2 lneto 3036 1.2 lneto <p> 3037 1.2 lneto When <code>nsize</code> is zero, 3038 1.2 lneto the allocator must behave like <code>free</code> 3039 1.2 lneto and return <code>NULL</code>. 3040 1.2 lneto 3041 1.2 lneto 3042 1.2 lneto <p> 3043 1.2 lneto When <code>nsize</code> is not zero, 3044 1.2 lneto the allocator must behave like <code>realloc</code>. 3045 1.2 lneto The allocator returns <code>NULL</code> 3046 1.2 lneto if and only if it cannot fulfill the request. 3047 1.1 mbalmer Lua assumes that the allocator never fails when 3048 1.1 mbalmer <code>osize >= nsize</code>. 3049 1.1 mbalmer 3050 1.1 mbalmer 3051 1.1 mbalmer <p> 3052 1.1 mbalmer Here is a simple implementation for the allocator function. 3053 1.1 mbalmer It is used in the auxiliary library by <a href="#luaL_newstate"><code>luaL_newstate</code></a>. 3054 1.1 mbalmer 3055 1.1 mbalmer <pre> 3056 1.1 mbalmer static void *l_alloc (void *ud, void *ptr, size_t osize, 3057 1.1 mbalmer size_t nsize) { 3058 1.1 mbalmer (void)ud; (void)osize; /* not used */ 3059 1.1 mbalmer if (nsize == 0) { 3060 1.1 mbalmer free(ptr); 3061 1.1 mbalmer return NULL; 3062 1.1 mbalmer } 3063 1.1 mbalmer else 3064 1.1 mbalmer return realloc(ptr, nsize); 3065 1.1 mbalmer } 3066 1.1 mbalmer </pre><p> 3067 1.2 lneto Note that Standard C ensures 3068 1.1 mbalmer that <code>free(NULL)</code> has no effect and that 3069 1.3 lneto <code>realloc(NULL,size)</code> is equivalent to <code>malloc(size)</code>. 3070 1.2 lneto This code assumes that <code>realloc</code> does not fail when shrinking a block. 3071 1.2 lneto (Although Standard C does not ensure this behavior, 3072 1.2 lneto it seems to be a safe assumption.) 3073 1.1 mbalmer 3074 1.1 mbalmer 3075 1.1 mbalmer 3076 1.1 mbalmer 3077 1.1 mbalmer 3078 1.2 lneto <hr><h3><a name="lua_arith"><code>lua_arith</code></a></h3><p> 3079 1.2 lneto <span class="apii">[-(2|1), +1, <em>e</em>]</span> 3080 1.2 lneto <pre>void lua_arith (lua_State *L, int op);</pre> 3081 1.1 mbalmer 3082 1.1 mbalmer <p> 3083 1.2 lneto Performs an arithmetic or bitwise operation over the two values 3084 1.2 lneto (or one, in the case of negations) 3085 1.2 lneto at the top of the stack, 3086 1.2 lneto with the value at the top being the second operand, 3087 1.2 lneto pops these values, and pushes the result of the operation. 3088 1.2 lneto The function follows the semantics of the corresponding Lua operator 3089 1.2 lneto (that is, it may call metamethods). 3090 1.1 mbalmer 3091 1.1 mbalmer 3092 1.1 mbalmer <p> 3093 1.2 lneto The value of <code>op</code> must be one of the following constants: 3094 1.2 lneto 3095 1.2 lneto <ul> 3096 1.2 lneto 3097 1.2 lneto <li><b><a name="pdf-LUA_OPADD"><code>LUA_OPADD</code></a>: </b> performs addition (<code>+</code>)</li> 3098 1.2 lneto <li><b><a name="pdf-LUA_OPSUB"><code>LUA_OPSUB</code></a>: </b> performs subtraction (<code>-</code>)</li> 3099 1.2 lneto <li><b><a name="pdf-LUA_OPMUL"><code>LUA_OPMUL</code></a>: </b> performs multiplication (<code>*</code>)</li> 3100 1.2 lneto <li><b><a name="pdf-LUA_OPDIV"><code>LUA_OPDIV</code></a>: </b> performs float division (<code>/</code>)</li> 3101 1.3 lneto <li><b><a name="pdf-LUA_OPIDIV"><code>LUA_OPIDIV</code></a>: </b> performs floor division (<code>//</code>)</li> 3102 1.2 lneto <li><b><a name="pdf-LUA_OPMOD"><code>LUA_OPMOD</code></a>: </b> performs modulo (<code>%</code>)</li> 3103 1.2 lneto <li><b><a name="pdf-LUA_OPPOW"><code>LUA_OPPOW</code></a>: </b> performs exponentiation (<code>^</code>)</li> 3104 1.2 lneto <li><b><a name="pdf-LUA_OPUNM"><code>LUA_OPUNM</code></a>: </b> performs mathematical negation (unary <code>-</code>)</li> 3105 1.2 lneto <li><b><a name="pdf-LUA_OPBNOT"><code>LUA_OPBNOT</code></a>: </b> performs bitwise negation (<code>~</code>)</li> 3106 1.2 lneto <li><b><a name="pdf-LUA_OPBAND"><code>LUA_OPBAND</code></a>: </b> performs bitwise and (<code>&</code>)</li> 3107 1.2 lneto <li><b><a name="pdf-LUA_OPBOR"><code>LUA_OPBOR</code></a>: </b> performs bitwise or (<code>|</code>)</li> 3108 1.2 lneto <li><b><a name="pdf-LUA_OPBXOR"><code>LUA_OPBXOR</code></a>: </b> performs bitwise exclusive or (<code>~</code>)</li> 3109 1.2 lneto <li><b><a name="pdf-LUA_OPSHL"><code>LUA_OPSHL</code></a>: </b> performs left shift (<code><<</code>)</li> 3110 1.2 lneto <li><b><a name="pdf-LUA_OPSHR"><code>LUA_OPSHR</code></a>: </b> performs right shift (<code>>></code>)</li> 3111 1.2 lneto 3112 1.2 lneto </ul> 3113 1.2 lneto 3114 1.2 lneto 3115 1.2 lneto 3116 1.1 mbalmer 3117 1.2 lneto <hr><h3><a name="lua_atpanic"><code>lua_atpanic</code></a></h3><p> 3118 1.2 lneto <span class="apii">[-0, +0, –]</span> 3119 1.2 lneto <pre>lua_CFunction lua_atpanic (lua_State *L, lua_CFunction panicf);</pre> 3120 1.1 mbalmer 3121 1.1 mbalmer <p> 3122 1.2 lneto Sets a new panic function and returns the old one (see <a href="#4.6">§4.6</a>). 3123 1.1 mbalmer 3124 1.1 mbalmer 3125 1.1 mbalmer 3126 1.1 mbalmer 3127 1.1 mbalmer 3128 1.1 mbalmer <hr><h3><a name="lua_call"><code>lua_call</code></a></h3><p> 3129 1.2 lneto <span class="apii">[-(nargs+1), +nresults, <em>e</em>]</span> 3130 1.1 mbalmer <pre>void lua_call (lua_State *L, int nargs, int nresults);</pre> 3131 1.1 mbalmer 3132 1.1 mbalmer <p> 3133 1.1 mbalmer Calls a function. 3134 1.1 mbalmer 3135 1.1 mbalmer 3136 1.1 mbalmer <p> 3137 1.1 mbalmer To call a function you must use the following protocol: 3138 1.1 mbalmer first, the function to be called is pushed onto the stack; 3139 1.1 mbalmer then, the arguments to the function are pushed 3140 1.1 mbalmer in direct order; 3141 1.1 mbalmer that is, the first argument is pushed first. 3142 1.1 mbalmer Finally you call <a href="#lua_call"><code>lua_call</code></a>; 3143 1.1 mbalmer <code>nargs</code> is the number of arguments that you pushed onto the stack. 3144 1.1 mbalmer All arguments and the function value are popped from the stack 3145 1.1 mbalmer when the function is called. 3146 1.1 mbalmer The function results are pushed onto the stack when the function returns. 3147 1.1 mbalmer The number of results is adjusted to <code>nresults</code>, 3148 1.1 mbalmer unless <code>nresults</code> is <a name="pdf-LUA_MULTRET"><code>LUA_MULTRET</code></a>. 3149 1.2 lneto In this case, all results from the function are pushed. 3150 1.5 lneto Lua takes care that the returned values fit into the stack space, 3151 1.5 lneto but it does not ensure any extra space in the stack. 3152 1.1 mbalmer The function results are pushed onto the stack in direct order 3153 1.1 mbalmer (the first result is pushed first), 3154 1.1 mbalmer so that after the call the last result is on the top of the stack. 3155 1.1 mbalmer 3156 1.1 mbalmer 3157 1.1 mbalmer <p> 3158 1.1 mbalmer Any error inside the called function is propagated upwards 3159 1.1 mbalmer (with a <code>longjmp</code>). 3160 1.1 mbalmer 3161 1.1 mbalmer 3162 1.1 mbalmer <p> 3163 1.1 mbalmer The following example shows how the host program can do the 3164 1.1 mbalmer equivalent to this Lua code: 3165 1.1 mbalmer 3166 1.1 mbalmer <pre> 3167 1.1 mbalmer a = f("how", t.x, 14) 3168 1.1 mbalmer </pre><p> 3169 1.1 mbalmer Here it is in C: 3170 1.1 mbalmer 3171 1.1 mbalmer <pre> 3172 1.2 lneto lua_getglobal(L, "f"); /* function to be called */ 3173 1.3 lneto lua_pushliteral(L, "how"); /* 1st argument */ 3174 1.2 lneto lua_getglobal(L, "t"); /* table to be indexed */ 3175 1.1 mbalmer lua_getfield(L, -1, "x"); /* push result of t.x (2nd arg) */ 3176 1.1 mbalmer lua_remove(L, -2); /* remove 't' from the stack */ 3177 1.1 mbalmer lua_pushinteger(L, 14); /* 3rd argument */ 3178 1.1 mbalmer lua_call(L, 3, 1); /* call 'f' with 3 arguments and 1 result */ 3179 1.2 lneto lua_setglobal(L, "a"); /* set global 'a' */ 3180 1.1 mbalmer </pre><p> 3181 1.3 lneto Note that the code above is <em>balanced</em>: 3182 1.1 mbalmer at its end, the stack is back to its original configuration. 3183 1.1 mbalmer This is considered good programming practice. 3184 1.1 mbalmer 3185 1.1 mbalmer 3186 1.1 mbalmer 3187 1.1 mbalmer 3188 1.1 mbalmer 3189 1.2 lneto <hr><h3><a name="lua_callk"><code>lua_callk</code></a></h3><p> 3190 1.2 lneto <span class="apii">[-(nargs + 1), +nresults, <em>e</em>]</span> 3191 1.3 lneto <pre>void lua_callk (lua_State *L, 3192 1.3 lneto int nargs, 3193 1.3 lneto int nresults, 3194 1.3 lneto lua_KContext ctx, 3195 1.2 lneto lua_KFunction k);</pre> 3196 1.2 lneto 3197 1.2 lneto <p> 3198 1.2 lneto This function behaves exactly like <a href="#lua_call"><code>lua_call</code></a>, 3199 1.2 lneto but allows the called function to yield (see <a href="#4.7">§4.7</a>). 3200 1.2 lneto 3201 1.2 lneto 3202 1.2 lneto 3203 1.2 lneto 3204 1.2 lneto 3205 1.1 mbalmer <hr><h3><a name="lua_CFunction"><code>lua_CFunction</code></a></h3> 3206 1.1 mbalmer <pre>typedef int (*lua_CFunction) (lua_State *L);</pre> 3207 1.1 mbalmer 3208 1.1 mbalmer <p> 3209 1.1 mbalmer Type for C functions. 3210 1.1 mbalmer 3211 1.1 mbalmer 3212 1.1 mbalmer <p> 3213 1.1 mbalmer In order to communicate properly with Lua, 3214 1.1 mbalmer a C function must use the following protocol, 3215 1.1 mbalmer which defines the way parameters and results are passed: 3216 1.1 mbalmer a C function receives its arguments from Lua in its stack 3217 1.1 mbalmer in direct order (the first argument is pushed first). 3218 1.1 mbalmer So, when the function starts, 3219 1.1 mbalmer <code>lua_gettop(L)</code> returns the number of arguments received by the function. 3220 1.1 mbalmer The first argument (if any) is at index 1 3221 1.1 mbalmer and its last argument is at index <code>lua_gettop(L)</code>. 3222 1.1 mbalmer To return values to Lua, a C function just pushes them onto the stack, 3223 1.1 mbalmer in direct order (the first result is pushed first), 3224 1.1 mbalmer and returns the number of results. 3225 1.1 mbalmer Any other value in the stack below the results will be properly 3226 1.1 mbalmer discarded by Lua. 3227 1.1 mbalmer Like a Lua function, a C function called by Lua can also return 3228 1.1 mbalmer many results. 3229 1.1 mbalmer 3230 1.1 mbalmer 3231 1.1 mbalmer <p> 3232 1.1 mbalmer As an example, the following function receives a variable number 3233 1.4 mbalmer of numeric arguments and returns their average and their sum: 3234 1.1 mbalmer 3235 1.1 mbalmer <pre> 3236 1.1 mbalmer static int foo (lua_State *L) { 3237 1.1 mbalmer int n = lua_gettop(L); /* number of arguments */ 3238 1.3 lneto lua_Number sum = 0.0; 3239 1.1 mbalmer int i; 3240 1.1 mbalmer for (i = 1; i <= n; i++) { 3241 1.1 mbalmer if (!lua_isnumber(L, i)) { 3242 1.3 lneto lua_pushliteral(L, "incorrect argument"); 3243 1.1 mbalmer lua_error(L); 3244 1.1 mbalmer } 3245 1.1 mbalmer sum += lua_tonumber(L, i); 3246 1.1 mbalmer } 3247 1.1 mbalmer lua_pushnumber(L, sum/n); /* first result */ 3248 1.1 mbalmer lua_pushnumber(L, sum); /* second result */ 3249 1.1 mbalmer return 2; /* number of results */ 3250 1.1 mbalmer } 3251 1.1 mbalmer </pre> 3252 1.1 mbalmer 3253 1.1 mbalmer 3254 1.1 mbalmer 3255 1.1 mbalmer 3256 1.1 mbalmer <hr><h3><a name="lua_checkstack"><code>lua_checkstack</code></a></h3><p> 3257 1.2 lneto <span class="apii">[-0, +0, –]</span> 3258 1.3 lneto <pre>int lua_checkstack (lua_State *L, int n);</pre> 3259 1.1 mbalmer 3260 1.1 mbalmer <p> 3261 1.5 lneto Ensures that the stack has space for at least <code>n</code> extra slots 3262 1.5 lneto (that is, that you can safely push up to <code>n</code> values into it). 3263 1.2 lneto It returns false if it cannot fulfill the request, 3264 1.3 lneto either because it would cause the stack 3265 1.3 lneto to be larger than a fixed maximum size 3266 1.3 lneto (typically at least several thousand elements) or 3267 1.3 lneto because it cannot allocate memory for the extra space. 3268 1.1 mbalmer This function never shrinks the stack; 3269 1.5 lneto if the stack already has space for the extra slots, 3270 1.1 mbalmer it is left unchanged. 3271 1.1 mbalmer 3272 1.1 mbalmer 3273 1.1 mbalmer 3274 1.1 mbalmer 3275 1.1 mbalmer 3276 1.1 mbalmer <hr><h3><a name="lua_close"><code>lua_close</code></a></h3><p> 3277 1.2 lneto <span class="apii">[-0, +0, –]</span> 3278 1.1 mbalmer <pre>void lua_close (lua_State *L);</pre> 3279 1.1 mbalmer 3280 1.1 mbalmer <p> 3281 1.1 mbalmer Destroys all objects in the given Lua state 3282 1.1 mbalmer (calling the corresponding garbage-collection metamethods, if any) 3283 1.1 mbalmer and frees all dynamic memory used by this state. 3284 1.1 mbalmer On several platforms, you may not need to call this function, 3285 1.1 mbalmer because all resources are naturally released when the host program ends. 3286 1.2 lneto On the other hand, long-running programs that create multiple states, 3287 1.2 lneto such as daemons or web servers, 3288 1.3 lneto will probably need to close states as soon as they are not needed. 3289 1.2 lneto 3290 1.1 mbalmer 3291 1.1 mbalmer 3292 1.1 mbalmer 3293 1.1 mbalmer 3294 1.2 lneto <hr><h3><a name="lua_compare"><code>lua_compare</code></a></h3><p> 3295 1.2 lneto <span class="apii">[-0, +0, <em>e</em>]</span> 3296 1.2 lneto <pre>int lua_compare (lua_State *L, int index1, int index2, int op);</pre> 3297 1.2 lneto 3298 1.2 lneto <p> 3299 1.2 lneto Compares two Lua values. 3300 1.2 lneto Returns 1 if the value at index <code>index1</code> satisfies <code>op</code> 3301 1.2 lneto when compared with the value at index <code>index2</code>, 3302 1.2 lneto following the semantics of the corresponding Lua operator 3303 1.2 lneto (that is, it may call metamethods). 3304 1.2 lneto Otherwise returns 0. 3305 1.3 lneto Also returns 0 if any of the indices is not valid. 3306 1.2 lneto 3307 1.2 lneto 3308 1.2 lneto <p> 3309 1.2 lneto The value of <code>op</code> must be one of the following constants: 3310 1.2 lneto 3311 1.2 lneto <ul> 3312 1.2 lneto 3313 1.2 lneto <li><b><a name="pdf-LUA_OPEQ"><code>LUA_OPEQ</code></a>: </b> compares for equality (<code>==</code>)</li> 3314 1.2 lneto <li><b><a name="pdf-LUA_OPLT"><code>LUA_OPLT</code></a>: </b> compares for less than (<code><</code>)</li> 3315 1.2 lneto <li><b><a name="pdf-LUA_OPLE"><code>LUA_OPLE</code></a>: </b> compares for less or equal (<code><=</code>)</li> 3316 1.2 lneto 3317 1.2 lneto </ul> 3318 1.2 lneto 3319 1.2 lneto 3320 1.2 lneto 3321 1.1 mbalmer 3322 1.1 mbalmer <hr><h3><a name="lua_concat"><code>lua_concat</code></a></h3><p> 3323 1.1 mbalmer <span class="apii">[-n, +1, <em>e</em>]</span> 3324 1.1 mbalmer <pre>void lua_concat (lua_State *L, int n);</pre> 3325 1.1 mbalmer 3326 1.1 mbalmer <p> 3327 1.1 mbalmer Concatenates the <code>n</code> values at the top of the stack, 3328 1.1 mbalmer pops them, and leaves the result at the top. 3329 1.1 mbalmer If <code>n</code> is 1, the result is the single value on the stack 3330 1.1 mbalmer (that is, the function does nothing); 3331 1.1 mbalmer if <code>n</code> is 0, the result is the empty string. 3332 1.1 mbalmer Concatenation is performed following the usual semantics of Lua 3333 1.2 lneto (see <a href="#3.4.6">§3.4.6</a>). 3334 1.1 mbalmer 3335 1.1 mbalmer 3336 1.1 mbalmer 3337 1.1 mbalmer 3338 1.1 mbalmer 3339 1.2 lneto <hr><h3><a name="lua_copy"><code>lua_copy</code></a></h3><p> 3340 1.2 lneto <span class="apii">[-0, +0, –]</span> 3341 1.2 lneto <pre>void lua_copy (lua_State *L, int fromidx, int toidx);</pre> 3342 1.1 mbalmer 3343 1.1 mbalmer <p> 3344 1.3 lneto Copies the element at index <code>fromidx</code> 3345 1.3 lneto into the valid index <code>toidx</code>, 3346 1.3 lneto replacing the value at that position. 3347 1.3 lneto Values at other positions are not affected. 3348 1.1 mbalmer 3349 1.1 mbalmer 3350 1.1 mbalmer 3351 1.1 mbalmer 3352 1.1 mbalmer 3353 1.1 mbalmer <hr><h3><a name="lua_createtable"><code>lua_createtable</code></a></h3><p> 3354 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 3355 1.1 mbalmer <pre>void lua_createtable (lua_State *L, int narr, int nrec);</pre> 3356 1.1 mbalmer 3357 1.1 mbalmer <p> 3358 1.1 mbalmer Creates a new empty table and pushes it onto the stack. 3359 1.2 lneto Parameter <code>narr</code> is a hint for how many elements the table 3360 1.2 lneto will have as a sequence; 3361 1.2 lneto parameter <code>nrec</code> is a hint for how many other elements 3362 1.1 mbalmer the table will have. 3363 1.2 lneto Lua may use these hints to preallocate memory for the new table. 3364 1.5 lneto This preallocation is useful for performance when you know in advance 3365 1.2 lneto how many elements the table will have. 3366 1.1 mbalmer Otherwise you can use the function <a href="#lua_newtable"><code>lua_newtable</code></a>. 3367 1.1 mbalmer 3368 1.1 mbalmer 3369 1.1 mbalmer 3370 1.1 mbalmer 3371 1.1 mbalmer 3372 1.1 mbalmer <hr><h3><a name="lua_dump"><code>lua_dump</code></a></h3><p> 3373 1.5 lneto <span class="apii">[-0, +0, –]</span> 3374 1.2 lneto <pre>int lua_dump (lua_State *L, 3375 1.2 lneto lua_Writer writer, 3376 1.2 lneto void *data, 3377 1.2 lneto int strip);</pre> 3378 1.1 mbalmer 3379 1.1 mbalmer <p> 3380 1.1 mbalmer Dumps a function as a binary chunk. 3381 1.1 mbalmer Receives a Lua function on the top of the stack 3382 1.1 mbalmer and produces a binary chunk that, 3383 1.1 mbalmer if loaded again, 3384 1.1 mbalmer results in a function equivalent to the one dumped. 3385 1.1 mbalmer As it produces parts of the chunk, 3386 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>) 3387 1.1 mbalmer with the given <code>data</code> 3388 1.1 mbalmer to write them. 3389 1.1 mbalmer 3390 1.1 mbalmer 3391 1.1 mbalmer <p> 3392 1.2 lneto If <code>strip</code> is true, 3393 1.4 mbalmer the binary representation may not include all debug information 3394 1.4 mbalmer about the function, 3395 1.4 mbalmer to save space. 3396 1.2 lneto 3397 1.2 lneto 3398 1.2 lneto <p> 3399 1.1 mbalmer The value returned is the error code returned by the last 3400 1.1 mbalmer call to the writer; 3401 1.1 mbalmer 0 means no errors. 3402 1.1 mbalmer 3403 1.1 mbalmer 3404 1.1 mbalmer <p> 3405 1.1 mbalmer This function does not pop the Lua function from the stack. 3406 1.1 mbalmer 3407 1.1 mbalmer 3408 1.1 mbalmer 3409 1.1 mbalmer 3410 1.1 mbalmer 3411 1.1 mbalmer <hr><h3><a name="lua_error"><code>lua_error</code></a></h3><p> 3412 1.1 mbalmer <span class="apii">[-1, +0, <em>v</em>]</span> 3413 1.1 mbalmer <pre>int lua_error (lua_State *L);</pre> 3414 1.1 mbalmer 3415 1.1 mbalmer <p> 3416 1.3 lneto Generates a Lua error, 3417 1.3 lneto using the value at the top of the stack as the error object. 3418 1.1 mbalmer This function does a long jump, 3419 1.2 lneto and therefore never returns 3420 1.1 mbalmer (see <a href="#luaL_error"><code>luaL_error</code></a>). 3421 1.1 mbalmer 3422 1.1 mbalmer 3423 1.1 mbalmer 3424 1.1 mbalmer 3425 1.1 mbalmer 3426 1.1 mbalmer <hr><h3><a name="lua_gc"><code>lua_gc</code></a></h3><p> 3427 1.1 mbalmer <span class="apii">[-0, +0, <em>e</em>]</span> 3428 1.1 mbalmer <pre>int lua_gc (lua_State *L, int what, int data);</pre> 3429 1.1 mbalmer 3430 1.1 mbalmer <p> 3431 1.1 mbalmer Controls the garbage collector. 3432 1.1 mbalmer 3433 1.1 mbalmer 3434 1.1 mbalmer <p> 3435 1.1 mbalmer This function performs several tasks, 3436 1.1 mbalmer according to the value of the parameter <code>what</code>: 3437 1.1 mbalmer 3438 1.1 mbalmer <ul> 3439 1.1 mbalmer 3440 1.2 lneto <li><b><code>LUA_GCSTOP</code>: </b> 3441 1.1 mbalmer stops the garbage collector. 3442 1.1 mbalmer </li> 3443 1.1 mbalmer 3444 1.2 lneto <li><b><code>LUA_GCRESTART</code>: </b> 3445 1.1 mbalmer restarts the garbage collector. 3446 1.1 mbalmer </li> 3447 1.1 mbalmer 3448 1.2 lneto <li><b><code>LUA_GCCOLLECT</code>: </b> 3449 1.1 mbalmer performs a full garbage-collection cycle. 3450 1.1 mbalmer </li> 3451 1.1 mbalmer 3452 1.2 lneto <li><b><code>LUA_GCCOUNT</code>: </b> 3453 1.1 mbalmer returns the current amount of memory (in Kbytes) in use by Lua. 3454 1.1 mbalmer </li> 3455 1.1 mbalmer 3456 1.2 lneto <li><b><code>LUA_GCCOUNTB</code>: </b> 3457 1.1 mbalmer returns the remainder of dividing the current amount of bytes of 3458 1.1 mbalmer memory in use by Lua by 1024. 3459 1.1 mbalmer </li> 3460 1.1 mbalmer 3461 1.2 lneto <li><b><code>LUA_GCSTEP</code>: </b> 3462 1.1 mbalmer performs an incremental step of garbage collection. 3463 1.1 mbalmer </li> 3464 1.1 mbalmer 3465 1.2 lneto <li><b><code>LUA_GCSETPAUSE</code>: </b> 3466 1.1 mbalmer sets <code>data</code> as the new value 3467 1.2 lneto for the <em>pause</em> of the collector (see <a href="#2.5">§2.5</a>) 3468 1.2 lneto and returns the previous value of the pause. 3469 1.1 mbalmer </li> 3470 1.1 mbalmer 3471 1.2 lneto <li><b><code>LUA_GCSETSTEPMUL</code>: </b> 3472 1.1 mbalmer sets <code>data</code> as the new value for the <em>step multiplier</em> of 3473 1.2 lneto the collector (see <a href="#2.5">§2.5</a>) 3474 1.2 lneto and returns the previous value of the step multiplier. 3475 1.2 lneto </li> 3476 1.2 lneto 3477 1.2 lneto <li><b><code>LUA_GCISRUNNING</code>: </b> 3478 1.2 lneto returns a boolean that tells whether the collector is running 3479 1.2 lneto (i.e., not stopped). 3480 1.1 mbalmer </li> 3481 1.1 mbalmer 3482 1.1 mbalmer </ul> 3483 1.1 mbalmer 3484 1.2 lneto <p> 3485 1.2 lneto For more details about these options, 3486 1.2 lneto see <a href="#pdf-collectgarbage"><code>collectgarbage</code></a>. 3487 1.2 lneto 3488 1.2 lneto 3489 1.1 mbalmer 3490 1.1 mbalmer 3491 1.1 mbalmer 3492 1.1 mbalmer <hr><h3><a name="lua_getallocf"><code>lua_getallocf</code></a></h3><p> 3493 1.2 lneto <span class="apii">[-0, +0, –]</span> 3494 1.1 mbalmer <pre>lua_Alloc lua_getallocf (lua_State *L, void **ud);</pre> 3495 1.1 mbalmer 3496 1.1 mbalmer <p> 3497 1.1 mbalmer Returns the memory-allocation function of a given state. 3498 1.1 mbalmer If <code>ud</code> is not <code>NULL</code>, Lua stores in <code>*ud</code> the 3499 1.3 lneto opaque pointer given when the memory-allocator function was set. 3500 1.1 mbalmer 3501 1.1 mbalmer 3502 1.1 mbalmer 3503 1.1 mbalmer 3504 1.1 mbalmer 3505 1.1 mbalmer <hr><h3><a name="lua_getfield"><code>lua_getfield</code></a></h3><p> 3506 1.1 mbalmer <span class="apii">[-0, +1, <em>e</em>]</span> 3507 1.2 lneto <pre>int lua_getfield (lua_State *L, int index, const char *k);</pre> 3508 1.1 mbalmer 3509 1.1 mbalmer <p> 3510 1.1 mbalmer Pushes onto the stack the value <code>t[k]</code>, 3511 1.2 lneto where <code>t</code> is the value at the given index. 3512 1.1 mbalmer As in Lua, this function may trigger a metamethod 3513 1.2 lneto for the "index" event (see <a href="#2.4">§2.4</a>). 3514 1.2 lneto 3515 1.2 lneto 3516 1.2 lneto <p> 3517 1.2 lneto Returns the type of the pushed value. 3518 1.1 mbalmer 3519 1.1 mbalmer 3520 1.1 mbalmer 3521 1.1 mbalmer 3522 1.1 mbalmer 3523 1.3 lneto <hr><h3><a name="lua_getextraspace"><code>lua_getextraspace</code></a></h3><p> 3524 1.3 lneto <span class="apii">[-0, +0, –]</span> 3525 1.3 lneto <pre>void *lua_getextraspace (lua_State *L);</pre> 3526 1.3 lneto 3527 1.3 lneto <p> 3528 1.3 lneto Returns a pointer to a raw memory area associated with the 3529 1.3 lneto given Lua state. 3530 1.3 lneto The application can use this area for any purpose; 3531 1.3 lneto Lua does not use it for anything. 3532 1.3 lneto 3533 1.3 lneto 3534 1.3 lneto <p> 3535 1.3 lneto Each new thread has this area initialized with a copy 3536 1.3 lneto of the area of the main thread. 3537 1.3 lneto 3538 1.3 lneto 3539 1.3 lneto <p> 3540 1.3 lneto By default, this area has the size of a pointer to void, 3541 1.3 lneto but you can recompile Lua with a different size for this area. 3542 1.3 lneto (See <code>LUA_EXTRASPACE</code> in <code>luaconf.h</code>.) 3543 1.3 lneto 3544 1.3 lneto 3545 1.3 lneto 3546 1.3 lneto 3547 1.3 lneto 3548 1.1 mbalmer <hr><h3><a name="lua_getglobal"><code>lua_getglobal</code></a></h3><p> 3549 1.1 mbalmer <span class="apii">[-0, +1, <em>e</em>]</span> 3550 1.2 lneto <pre>int lua_getglobal (lua_State *L, const char *name);</pre> 3551 1.1 mbalmer 3552 1.1 mbalmer <p> 3553 1.1 mbalmer Pushes onto the stack the value of the global <code>name</code>. 3554 1.2 lneto Returns the type of that value. 3555 1.1 mbalmer 3556 1.1 mbalmer 3557 1.1 mbalmer 3558 1.1 mbalmer 3559 1.1 mbalmer 3560 1.3 lneto <hr><h3><a name="lua_geti"><code>lua_geti</code></a></h3><p> 3561 1.3 lneto <span class="apii">[-0, +1, <em>e</em>]</span> 3562 1.3 lneto <pre>int lua_geti (lua_State *L, int index, lua_Integer i);</pre> 3563 1.3 lneto 3564 1.3 lneto <p> 3565 1.3 lneto Pushes onto the stack the value <code>t[i]</code>, 3566 1.3 lneto where <code>t</code> is the value at the given index. 3567 1.3 lneto As in Lua, this function may trigger a metamethod 3568 1.3 lneto for the "index" event (see <a href="#2.4">§2.4</a>). 3569 1.3 lneto 3570 1.3 lneto 3571 1.3 lneto <p> 3572 1.3 lneto Returns the type of the pushed value. 3573 1.3 lneto 3574 1.3 lneto 3575 1.3 lneto 3576 1.3 lneto 3577 1.3 lneto 3578 1.1 mbalmer <hr><h3><a name="lua_getmetatable"><code>lua_getmetatable</code></a></h3><p> 3579 1.2 lneto <span class="apii">[-0, +(0|1), –]</span> 3580 1.1 mbalmer <pre>int lua_getmetatable (lua_State *L, int index);</pre> 3581 1.1 mbalmer 3582 1.1 mbalmer <p> 3583 1.3 lneto If the value at the given index has a metatable, 3584 1.3 lneto the function pushes that metatable onto the stack and returns 1. 3585 1.3 lneto Otherwise, 3586 1.1 mbalmer the function returns 0 and pushes nothing on the stack. 3587 1.1 mbalmer 3588 1.1 mbalmer 3589 1.1 mbalmer 3590 1.1 mbalmer 3591 1.1 mbalmer 3592 1.1 mbalmer <hr><h3><a name="lua_gettable"><code>lua_gettable</code></a></h3><p> 3593 1.1 mbalmer <span class="apii">[-1, +1, <em>e</em>]</span> 3594 1.2 lneto <pre>int lua_gettable (lua_State *L, int index);</pre> 3595 1.1 mbalmer 3596 1.1 mbalmer <p> 3597 1.1 mbalmer Pushes onto the stack the value <code>t[k]</code>, 3598 1.2 lneto where <code>t</code> is the value at the given index 3599 1.1 mbalmer and <code>k</code> is the value at the top of the stack. 3600 1.1 mbalmer 3601 1.1 mbalmer 3602 1.1 mbalmer <p> 3603 1.3 lneto This function pops the key from the stack, 3604 1.3 lneto pushing the resulting value in its place. 3605 1.1 mbalmer As in Lua, this function may trigger a metamethod 3606 1.2 lneto for the "index" event (see <a href="#2.4">§2.4</a>). 3607 1.2 lneto 3608 1.2 lneto 3609 1.2 lneto <p> 3610 1.2 lneto Returns the type of the pushed value. 3611 1.1 mbalmer 3612 1.1 mbalmer 3613 1.1 mbalmer 3614 1.1 mbalmer 3615 1.1 mbalmer 3616 1.1 mbalmer <hr><h3><a name="lua_gettop"><code>lua_gettop</code></a></h3><p> 3617 1.2 lneto <span class="apii">[-0, +0, –]</span> 3618 1.1 mbalmer <pre>int lua_gettop (lua_State *L);</pre> 3619 1.1 mbalmer 3620 1.1 mbalmer <p> 3621 1.1 mbalmer Returns the index of the top element in the stack. 3622 1.1 mbalmer Because indices start at 1, 3623 1.3 lneto this result is equal to the number of elements in the stack; 3624 1.3 lneto in particular, 0 means an empty stack. 3625 1.1 mbalmer 3626 1.1 mbalmer 3627 1.1 mbalmer 3628 1.1 mbalmer 3629 1.1 mbalmer 3630 1.2 lneto <hr><h3><a name="lua_getuservalue"><code>lua_getuservalue</code></a></h3><p> 3631 1.2 lneto <span class="apii">[-0, +1, –]</span> 3632 1.2 lneto <pre>int lua_getuservalue (lua_State *L, int index);</pre> 3633 1.2 lneto 3634 1.2 lneto <p> 3635 1.2 lneto Pushes onto the stack the Lua value associated with the userdata 3636 1.2 lneto at the given index. 3637 1.2 lneto 3638 1.2 lneto 3639 1.2 lneto <p> 3640 1.2 lneto Returns the type of the pushed value. 3641 1.2 lneto 3642 1.2 lneto 3643 1.2 lneto 3644 1.2 lneto 3645 1.2 lneto 3646 1.1 mbalmer <hr><h3><a name="lua_insert"><code>lua_insert</code></a></h3><p> 3647 1.2 lneto <span class="apii">[-1, +1, –]</span> 3648 1.1 mbalmer <pre>void lua_insert (lua_State *L, int index);</pre> 3649 1.1 mbalmer 3650 1.1 mbalmer <p> 3651 1.1 mbalmer Moves the top element into the given valid index, 3652 1.1 mbalmer shifting up the elements above this index to open space. 3653 1.2 lneto This function cannot be called with a pseudo-index, 3654 1.1 mbalmer because a pseudo-index is not an actual stack position. 3655 1.1 mbalmer 3656 1.1 mbalmer 3657 1.1 mbalmer 3658 1.1 mbalmer 3659 1.1 mbalmer 3660 1.1 mbalmer <hr><h3><a name="lua_Integer"><code>lua_Integer</code></a></h3> 3661 1.2 lneto <pre>typedef ... lua_Integer;</pre> 3662 1.1 mbalmer 3663 1.1 mbalmer <p> 3664 1.2 lneto The type of integers in Lua. 3665 1.1 mbalmer 3666 1.1 mbalmer 3667 1.1 mbalmer <p> 3668 1.3 lneto By default this type is <code>long long</code>, 3669 1.2 lneto (usually a 64-bit two-complement integer), 3670 1.3 lneto but that can be changed to <code>long</code> or <code>int</code> 3671 1.2 lneto (usually a 32-bit two-complement integer). 3672 1.4 mbalmer (See <code>LUA_INT_TYPE</code> in <code>luaconf.h</code>.) 3673 1.2 lneto 3674 1.2 lneto 3675 1.2 lneto <p> 3676 1.2 lneto Lua also defines the constants 3677 1.2 lneto <a name="pdf-LUA_MININTEGER"><code>LUA_MININTEGER</code></a> and <a name="pdf-LUA_MAXINTEGER"><code>LUA_MAXINTEGER</code></a>, 3678 1.2 lneto with the minimum and the maximum values that fit in this type. 3679 1.1 mbalmer 3680 1.1 mbalmer 3681 1.1 mbalmer 3682 1.1 mbalmer 3683 1.1 mbalmer 3684 1.1 mbalmer <hr><h3><a name="lua_isboolean"><code>lua_isboolean</code></a></h3><p> 3685 1.2 lneto <span class="apii">[-0, +0, –]</span> 3686 1.1 mbalmer <pre>int lua_isboolean (lua_State *L, int index);</pre> 3687 1.1 mbalmer 3688 1.1 mbalmer <p> 3689 1.2 lneto Returns 1 if the value at the given index is a boolean, 3690 1.1 mbalmer and 0 otherwise. 3691 1.1 mbalmer 3692 1.1 mbalmer 3693 1.1 mbalmer 3694 1.1 mbalmer 3695 1.1 mbalmer 3696 1.1 mbalmer <hr><h3><a name="lua_iscfunction"><code>lua_iscfunction</code></a></h3><p> 3697 1.2 lneto <span class="apii">[-0, +0, –]</span> 3698 1.1 mbalmer <pre>int lua_iscfunction (lua_State *L, int index);</pre> 3699 1.1 mbalmer 3700 1.1 mbalmer <p> 3701 1.2 lneto Returns 1 if the value at the given index is a C function, 3702 1.1 mbalmer and 0 otherwise. 3703 1.1 mbalmer 3704 1.1 mbalmer 3705 1.1 mbalmer 3706 1.1 mbalmer 3707 1.1 mbalmer 3708 1.1 mbalmer <hr><h3><a name="lua_isfunction"><code>lua_isfunction</code></a></h3><p> 3709 1.2 lneto <span class="apii">[-0, +0, –]</span> 3710 1.1 mbalmer <pre>int lua_isfunction (lua_State *L, int index);</pre> 3711 1.1 mbalmer 3712 1.1 mbalmer <p> 3713 1.2 lneto Returns 1 if the value at the given index is a function 3714 1.1 mbalmer (either C or Lua), and 0 otherwise. 3715 1.1 mbalmer 3716 1.1 mbalmer 3717 1.1 mbalmer 3718 1.1 mbalmer 3719 1.1 mbalmer 3720 1.2 lneto <hr><h3><a name="lua_isinteger"><code>lua_isinteger</code></a></h3><p> 3721 1.2 lneto <span class="apii">[-0, +0, –]</span> 3722 1.2 lneto <pre>int lua_isinteger (lua_State *L, int index);</pre> 3723 1.2 lneto 3724 1.2 lneto <p> 3725 1.2 lneto Returns 1 if the value at the given index is an integer 3726 1.2 lneto (that is, the value is a number and is represented as an integer), 3727 1.2 lneto and 0 otherwise. 3728 1.2 lneto 3729 1.2 lneto 3730 1.2 lneto 3731 1.2 lneto 3732 1.2 lneto 3733 1.1 mbalmer <hr><h3><a name="lua_islightuserdata"><code>lua_islightuserdata</code></a></h3><p> 3734 1.2 lneto <span class="apii">[-0, +0, –]</span> 3735 1.1 mbalmer <pre>int lua_islightuserdata (lua_State *L, int index);</pre> 3736 1.1 mbalmer 3737 1.1 mbalmer <p> 3738 1.2 lneto Returns 1 if the value at the given index is a light userdata, 3739 1.1 mbalmer and 0 otherwise. 3740 1.1 mbalmer 3741 1.1 mbalmer 3742 1.1 mbalmer 3743 1.1 mbalmer 3744 1.1 mbalmer 3745 1.1 mbalmer <hr><h3><a name="lua_isnil"><code>lua_isnil</code></a></h3><p> 3746 1.2 lneto <span class="apii">[-0, +0, –]</span> 3747 1.1 mbalmer <pre>int lua_isnil (lua_State *L, int index);</pre> 3748 1.1 mbalmer 3749 1.1 mbalmer <p> 3750 1.2 lneto Returns 1 if the value at the given index is <b>nil</b>, 3751 1.1 mbalmer and 0 otherwise. 3752 1.1 mbalmer 3753 1.1 mbalmer 3754 1.1 mbalmer 3755 1.1 mbalmer 3756 1.1 mbalmer 3757 1.1 mbalmer <hr><h3><a name="lua_isnone"><code>lua_isnone</code></a></h3><p> 3758 1.2 lneto <span class="apii">[-0, +0, –]</span> 3759 1.1 mbalmer <pre>int lua_isnone (lua_State *L, int index);</pre> 3760 1.1 mbalmer 3761 1.1 mbalmer <p> 3762 1.2 lneto Returns 1 if the given index is not valid, 3763 1.1 mbalmer and 0 otherwise. 3764 1.1 mbalmer 3765 1.1 mbalmer 3766 1.1 mbalmer 3767 1.1 mbalmer 3768 1.1 mbalmer 3769 1.1 mbalmer <hr><h3><a name="lua_isnoneornil"><code>lua_isnoneornil</code></a></h3><p> 3770 1.2 lneto <span class="apii">[-0, +0, –]</span> 3771 1.1 mbalmer <pre>int lua_isnoneornil (lua_State *L, int index);</pre> 3772 1.1 mbalmer 3773 1.1 mbalmer <p> 3774 1.2 lneto Returns 1 if the given index is not valid 3775 1.1 mbalmer or if the value at this index is <b>nil</b>, 3776 1.1 mbalmer and 0 otherwise. 3777 1.1 mbalmer 3778 1.1 mbalmer 3779 1.1 mbalmer 3780 1.1 mbalmer 3781 1.1 mbalmer 3782 1.1 mbalmer <hr><h3><a name="lua_isnumber"><code>lua_isnumber</code></a></h3><p> 3783 1.2 lneto <span class="apii">[-0, +0, –]</span> 3784 1.1 mbalmer <pre>int lua_isnumber (lua_State *L, int index);</pre> 3785 1.1 mbalmer 3786 1.1 mbalmer <p> 3787 1.2 lneto Returns 1 if the value at the given index is a number 3788 1.1 mbalmer or a string convertible to a number, 3789 1.1 mbalmer and 0 otherwise. 3790 1.1 mbalmer 3791 1.1 mbalmer 3792 1.1 mbalmer 3793 1.1 mbalmer 3794 1.1 mbalmer 3795 1.1 mbalmer <hr><h3><a name="lua_isstring"><code>lua_isstring</code></a></h3><p> 3796 1.2 lneto <span class="apii">[-0, +0, –]</span> 3797 1.1 mbalmer <pre>int lua_isstring (lua_State *L, int index);</pre> 3798 1.1 mbalmer 3799 1.1 mbalmer <p> 3800 1.2 lneto Returns 1 if the value at the given index is a string 3801 1.1 mbalmer or a number (which is always convertible to a string), 3802 1.1 mbalmer and 0 otherwise. 3803 1.1 mbalmer 3804 1.1 mbalmer 3805 1.1 mbalmer 3806 1.1 mbalmer 3807 1.1 mbalmer 3808 1.1 mbalmer <hr><h3><a name="lua_istable"><code>lua_istable</code></a></h3><p> 3809 1.2 lneto <span class="apii">[-0, +0, –]</span> 3810 1.1 mbalmer <pre>int lua_istable (lua_State *L, int index);</pre> 3811 1.1 mbalmer 3812 1.1 mbalmer <p> 3813 1.2 lneto Returns 1 if the value at the given index is a table, 3814 1.1 mbalmer and 0 otherwise. 3815 1.1 mbalmer 3816 1.1 mbalmer 3817 1.1 mbalmer 3818 1.1 mbalmer 3819 1.1 mbalmer 3820 1.1 mbalmer <hr><h3><a name="lua_isthread"><code>lua_isthread</code></a></h3><p> 3821 1.2 lneto <span class="apii">[-0, +0, –]</span> 3822 1.1 mbalmer <pre>int lua_isthread (lua_State *L, int index);</pre> 3823 1.1 mbalmer 3824 1.1 mbalmer <p> 3825 1.2 lneto Returns 1 if the value at the given index is a thread, 3826 1.1 mbalmer and 0 otherwise. 3827 1.1 mbalmer 3828 1.1 mbalmer 3829 1.1 mbalmer 3830 1.1 mbalmer 3831 1.1 mbalmer 3832 1.1 mbalmer <hr><h3><a name="lua_isuserdata"><code>lua_isuserdata</code></a></h3><p> 3833 1.2 lneto <span class="apii">[-0, +0, –]</span> 3834 1.1 mbalmer <pre>int lua_isuserdata (lua_State *L, int index);</pre> 3835 1.1 mbalmer 3836 1.1 mbalmer <p> 3837 1.2 lneto Returns 1 if the value at the given index is a userdata 3838 1.1 mbalmer (either full or light), and 0 otherwise. 3839 1.1 mbalmer 3840 1.1 mbalmer 3841 1.1 mbalmer 3842 1.1 mbalmer 3843 1.1 mbalmer 3844 1.2 lneto <hr><h3><a name="lua_isyieldable"><code>lua_isyieldable</code></a></h3><p> 3845 1.2 lneto <span class="apii">[-0, +0, –]</span> 3846 1.2 lneto <pre>int lua_isyieldable (lua_State *L);</pre> 3847 1.2 lneto 3848 1.2 lneto <p> 3849 1.2 lneto Returns 1 if the given coroutine can yield, 3850 1.2 lneto and 0 otherwise. 3851 1.2 lneto 3852 1.2 lneto 3853 1.2 lneto 3854 1.2 lneto 3855 1.2 lneto 3856 1.3 lneto <hr><h3><a name="lua_KContext"><code>lua_KContext</code></a></h3> 3857 1.3 lneto <pre>typedef ... lua_KContext;</pre> 3858 1.3 lneto 3859 1.3 lneto <p> 3860 1.3 lneto The type for continuation-function contexts. 3861 1.4 mbalmer It must be a numeric type. 3862 1.3 lneto This type is defined as <code>intptr_t</code> 3863 1.3 lneto when <code>intptr_t</code> is available, 3864 1.3 lneto so that it can store pointers too. 3865 1.3 lneto Otherwise, it is defined as <code>ptrdiff_t</code>. 3866 1.3 lneto 3867 1.3 lneto 3868 1.3 lneto 3869 1.3 lneto 3870 1.3 lneto 3871 1.2 lneto <hr><h3><a name="lua_KFunction"><code>lua_KFunction</code></a></h3> 3872 1.3 lneto <pre>typedef int (*lua_KFunction) (lua_State *L, int status, lua_KContext ctx);</pre> 3873 1.2 lneto 3874 1.2 lneto <p> 3875 1.2 lneto Type for continuation functions (see <a href="#4.7">§4.7</a>). 3876 1.2 lneto 3877 1.2 lneto 3878 1.2 lneto 3879 1.2 lneto 3880 1.2 lneto 3881 1.2 lneto <hr><h3><a name="lua_len"><code>lua_len</code></a></h3><p> 3882 1.2 lneto <span class="apii">[-0, +1, <em>e</em>]</span> 3883 1.2 lneto <pre>void lua_len (lua_State *L, int index);</pre> 3884 1.1 mbalmer 3885 1.1 mbalmer <p> 3886 1.3 lneto Returns the length of the value at the given index. 3887 1.3 lneto It is equivalent to the '<code>#</code>' operator in Lua (see <a href="#3.4.7">§3.4.7</a>) and 3888 1.3 lneto may trigger a metamethod for the "length" event (see <a href="#2.4">§2.4</a>). 3889 1.2 lneto The result is pushed on the stack. 3890 1.1 mbalmer 3891 1.1 mbalmer 3892 1.1 mbalmer 3893 1.1 mbalmer 3894 1.1 mbalmer 3895 1.1 mbalmer <hr><h3><a name="lua_load"><code>lua_load</code></a></h3><p> 3896 1.2 lneto <span class="apii">[-0, +1, –]</span> 3897 1.1 mbalmer <pre>int lua_load (lua_State *L, 3898 1.1 mbalmer lua_Reader reader, 3899 1.1 mbalmer void *data, 3900 1.3 lneto const char *chunkname, 3901 1.2 lneto const char *mode);</pre> 3902 1.1 mbalmer 3903 1.1 mbalmer <p> 3904 1.3 lneto Loads a Lua chunk without running it. 3905 1.1 mbalmer If there are no errors, 3906 1.2 lneto <code>lua_load</code> pushes the compiled chunk as a Lua 3907 1.1 mbalmer function on top of the stack. 3908 1.1 mbalmer Otherwise, it pushes an error message. 3909 1.2 lneto 3910 1.2 lneto 3911 1.2 lneto <p> 3912 1.2 lneto The return values of <code>lua_load</code> are: 3913 1.1 mbalmer 3914 1.1 mbalmer <ul> 3915 1.1 mbalmer 3916 1.2 lneto <li><b><a href="#pdf-LUA_OK"><code>LUA_OK</code></a>: </b> no errors;</li> 3917 1.2 lneto 3918 1.2 lneto <li><b><a name="pdf-LUA_ERRSYNTAX"><code>LUA_ERRSYNTAX</code></a>: </b> 3919 1.2 lneto syntax error during precompilation;</li> 3920 1.1 mbalmer 3921 1.2 lneto <li><b><a href="#pdf-LUA_ERRMEM"><code>LUA_ERRMEM</code></a>: </b> 3922 1.2 lneto memory allocation error;</li> 3923 1.1 mbalmer 3924 1.2 lneto <li><b><a href="#pdf-LUA_ERRGCMM"><code>LUA_ERRGCMM</code></a>: </b> 3925 1.2 lneto error while running a <code>__gc</code> metamethod. 3926 1.2 lneto (This error has no relation with the chunk being loaded. 3927 1.2 lneto It is generated by the garbage collector.) 3928 1.2 lneto </li> 3929 1.1 mbalmer 3930 1.1 mbalmer </ul> 3931 1.1 mbalmer 3932 1.1 mbalmer <p> 3933 1.2 lneto The <code>lua_load</code> function uses a user-supplied <code>reader</code> function 3934 1.2 lneto to read the chunk (see <a href="#lua_Reader"><code>lua_Reader</code></a>). 3935 1.2 lneto The <code>data</code> argument is an opaque value passed to the reader function. 3936 1.2 lneto 3937 1.2 lneto 3938 1.2 lneto <p> 3939 1.3 lneto The <code>chunkname</code> argument gives a name to the chunk, 3940 1.2 lneto which is used for error messages and in debug information (see <a href="#4.9">§4.9</a>). 3941 1.1 mbalmer 3942 1.1 mbalmer 3943 1.1 mbalmer <p> 3944 1.2 lneto <code>lua_load</code> automatically detects whether the chunk is text or binary 3945 1.1 mbalmer and loads it accordingly (see program <code>luac</code>). 3946 1.2 lneto The string <code>mode</code> works as in function <a href="#pdf-load"><code>load</code></a>, 3947 1.2 lneto with the addition that 3948 1.2 lneto a <code>NULL</code> value is equivalent to the string "<code>bt</code>". 3949 1.1 mbalmer 3950 1.1 mbalmer 3951 1.1 mbalmer <p> 3952 1.2 lneto <code>lua_load</code> uses the stack internally, 3953 1.2 lneto so the reader function must always leave the stack 3954 1.2 lneto unmodified when returning. 3955 1.1 mbalmer 3956 1.1 mbalmer 3957 1.1 mbalmer <p> 3958 1.3 lneto If the resulting function has upvalues, 3959 1.3 lneto its first upvalue is set to the value of the global environment 3960 1.2 lneto stored at index <code>LUA_RIDX_GLOBALS</code> in the registry (see <a href="#4.5">§4.5</a>). 3961 1.2 lneto When loading main chunks, 3962 1.2 lneto this upvalue will be the <code>_ENV</code> variable (see <a href="#2.2">§2.2</a>). 3963 1.3 lneto Other upvalues are initialized with <b>nil</b>. 3964 1.1 mbalmer 3965 1.1 mbalmer 3966 1.1 mbalmer 3967 1.1 mbalmer 3968 1.1 mbalmer 3969 1.1 mbalmer <hr><h3><a name="lua_newstate"><code>lua_newstate</code></a></h3><p> 3970 1.2 lneto <span class="apii">[-0, +0, –]</span> 3971 1.1 mbalmer <pre>lua_State *lua_newstate (lua_Alloc f, void *ud);</pre> 3972 1.1 mbalmer 3973 1.1 mbalmer <p> 3974 1.2 lneto Creates a new thread running in a new, independent state. 3975 1.2 lneto Returns <code>NULL</code> if it cannot create the thread or the state 3976 1.1 mbalmer (due to lack of memory). 3977 1.1 mbalmer The argument <code>f</code> is the allocator function; 3978 1.1 mbalmer Lua does all memory allocation for this state through this function. 3979 1.1 mbalmer The second argument, <code>ud</code>, is an opaque pointer that Lua 3980 1.2 lneto passes to the allocator in every call. 3981 1.1 mbalmer 3982 1.1 mbalmer 3983 1.1 mbalmer 3984 1.1 mbalmer 3985 1.1 mbalmer 3986 1.1 mbalmer <hr><h3><a name="lua_newtable"><code>lua_newtable</code></a></h3><p> 3987 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 3988 1.1 mbalmer <pre>void lua_newtable (lua_State *L);</pre> 3989 1.1 mbalmer 3990 1.1 mbalmer <p> 3991 1.1 mbalmer Creates a new empty table and pushes it onto the stack. 3992 1.1 mbalmer It is equivalent to <code>lua_createtable(L, 0, 0)</code>. 3993 1.1 mbalmer 3994 1.1 mbalmer 3995 1.1 mbalmer 3996 1.1 mbalmer 3997 1.1 mbalmer 3998 1.1 mbalmer <hr><h3><a name="lua_newthread"><code>lua_newthread</code></a></h3><p> 3999 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 4000 1.1 mbalmer <pre>lua_State *lua_newthread (lua_State *L);</pre> 4001 1.1 mbalmer 4002 1.1 mbalmer <p> 4003 1.1 mbalmer Creates a new thread, pushes it on the stack, 4004 1.1 mbalmer and returns a pointer to a <a href="#lua_State"><code>lua_State</code></a> that represents this new thread. 4005 1.2 lneto The new thread returned by this function shares with the original thread 4006 1.2 lneto its global environment, 4007 1.1 mbalmer but has an independent execution stack. 4008 1.1 mbalmer 4009 1.1 mbalmer 4010 1.1 mbalmer <p> 4011 1.1 mbalmer There is no explicit function to close or to destroy a thread. 4012 1.1 mbalmer Threads are subject to garbage collection, 4013 1.1 mbalmer like any Lua object. 4014 1.1 mbalmer 4015 1.1 mbalmer 4016 1.1 mbalmer 4017 1.1 mbalmer 4018 1.1 mbalmer 4019 1.1 mbalmer <hr><h3><a name="lua_newuserdata"><code>lua_newuserdata</code></a></h3><p> 4020 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 4021 1.1 mbalmer <pre>void *lua_newuserdata (lua_State *L, size_t size);</pre> 4022 1.1 mbalmer 4023 1.1 mbalmer <p> 4024 1.1 mbalmer This function allocates a new block of memory with the given size, 4025 1.1 mbalmer pushes onto the stack a new full userdata with the block address, 4026 1.1 mbalmer and returns this address. 4027 1.2 lneto The host program can freely use this memory. 4028 1.1 mbalmer 4029 1.1 mbalmer 4030 1.1 mbalmer 4031 1.1 mbalmer 4032 1.1 mbalmer 4033 1.1 mbalmer <hr><h3><a name="lua_next"><code>lua_next</code></a></h3><p> 4034 1.1 mbalmer <span class="apii">[-1, +(2|0), <em>e</em>]</span> 4035 1.1 mbalmer <pre>int lua_next (lua_State *L, int index);</pre> 4036 1.1 mbalmer 4037 1.1 mbalmer <p> 4038 1.1 mbalmer Pops a key from the stack, 4039 1.2 lneto and pushes a key–value pair from the table at the given index 4040 1.1 mbalmer (the "next" pair after the given key). 4041 1.1 mbalmer If there are no more elements in the table, 4042 1.1 mbalmer then <a href="#lua_next"><code>lua_next</code></a> returns 0 (and pushes nothing). 4043 1.1 mbalmer 4044 1.1 mbalmer 4045 1.1 mbalmer <p> 4046 1.1 mbalmer A typical traversal looks like this: 4047 1.1 mbalmer 4048 1.1 mbalmer <pre> 4049 1.1 mbalmer /* table is in the stack at index 't' */ 4050 1.1 mbalmer lua_pushnil(L); /* first key */ 4051 1.1 mbalmer while (lua_next(L, t) != 0) { 4052 1.1 mbalmer /* uses 'key' (at index -2) and 'value' (at index -1) */ 4053 1.1 mbalmer printf("%s - %s\n", 4054 1.1 mbalmer lua_typename(L, lua_type(L, -2)), 4055 1.1 mbalmer lua_typename(L, lua_type(L, -1))); 4056 1.1 mbalmer /* removes 'value'; keeps 'key' for next iteration */ 4057 1.1 mbalmer lua_pop(L, 1); 4058 1.1 mbalmer } 4059 1.1 mbalmer </pre> 4060 1.1 mbalmer 4061 1.1 mbalmer <p> 4062 1.1 mbalmer While traversing a table, 4063 1.1 mbalmer do not call <a href="#lua_tolstring"><code>lua_tolstring</code></a> directly on a key, 4064 1.1 mbalmer unless you know that the key is actually a string. 4065 1.2 lneto Recall that <a href="#lua_tolstring"><code>lua_tolstring</code></a> may change 4066 1.1 mbalmer the value at the given index; 4067 1.1 mbalmer this confuses the next call to <a href="#lua_next"><code>lua_next</code></a>. 4068 1.1 mbalmer 4069 1.1 mbalmer 4070 1.2 lneto <p> 4071 1.2 lneto See function <a href="#pdf-next"><code>next</code></a> for the caveats of modifying 4072 1.2 lneto the table during its traversal. 4073 1.2 lneto 4074 1.2 lneto 4075 1.1 mbalmer 4076 1.1 mbalmer 4077 1.1 mbalmer 4078 1.1 mbalmer <hr><h3><a name="lua_Number"><code>lua_Number</code></a></h3> 4079 1.4 mbalmer <pre>typedef ... lua_Number;</pre> 4080 1.1 mbalmer 4081 1.1 mbalmer <p> 4082 1.2 lneto The type of floats in Lua. 4083 1.1 mbalmer 4084 1.1 mbalmer 4085 1.1 mbalmer <p> 4086 1.2 lneto By default this type is double, 4087 1.4 mbalmer but that can be changed to a single float or a long double. 4088 1.4 mbalmer (See <code>LUA_FLOAT_TYPE</code> in <code>luaconf.h</code>.) 4089 1.2 lneto 4090 1.2 lneto 4091 1.1 mbalmer 4092 1.1 mbalmer 4093 1.1 mbalmer 4094 1.3 lneto <hr><h3><a name="lua_numbertointeger"><code>lua_numbertointeger</code></a></h3> 4095 1.3 lneto <pre>int lua_numbertointeger (lua_Number n, lua_Integer *p);</pre> 4096 1.1 mbalmer 4097 1.2 lneto <p> 4098 1.2 lneto Converts a Lua float to a Lua integer. 4099 1.2 lneto This macro assumes that <code>n</code> has an integral value. 4100 1.2 lneto If that value is within the range of Lua integers, 4101 1.2 lneto it is converted to an integer and assigned to <code>*p</code>. 4102 1.2 lneto The macro results in a boolean indicating whether the 4103 1.2 lneto conversion was successful. 4104 1.2 lneto (Note that this range test can be tricky to do 4105 1.2 lneto correctly without this macro, 4106 1.2 lneto due to roundings.) 4107 1.1 mbalmer 4108 1.1 mbalmer 4109 1.1 mbalmer <p> 4110 1.2 lneto This macro may evaluate its arguments more than once. 4111 1.1 mbalmer 4112 1.1 mbalmer 4113 1.1 mbalmer 4114 1.1 mbalmer 4115 1.1 mbalmer 4116 1.1 mbalmer <hr><h3><a name="lua_pcall"><code>lua_pcall</code></a></h3><p> 4117 1.2 lneto <span class="apii">[-(nargs + 1), +(nresults|1), –]</span> 4118 1.2 lneto <pre>int lua_pcall (lua_State *L, int nargs, int nresults, int msgh);</pre> 4119 1.1 mbalmer 4120 1.1 mbalmer <p> 4121 1.1 mbalmer Calls a function in protected mode. 4122 1.1 mbalmer 4123 1.1 mbalmer 4124 1.1 mbalmer <p> 4125 1.1 mbalmer Both <code>nargs</code> and <code>nresults</code> have the same meaning as 4126 1.1 mbalmer in <a href="#lua_call"><code>lua_call</code></a>. 4127 1.1 mbalmer If there are no errors during the call, 4128 1.1 mbalmer <a href="#lua_pcall"><code>lua_pcall</code></a> behaves exactly like <a href="#lua_call"><code>lua_call</code></a>. 4129 1.1 mbalmer However, if there is any error, 4130 1.1 mbalmer <a href="#lua_pcall"><code>lua_pcall</code></a> catches it, 4131 1.1 mbalmer pushes a single value on the stack (the error message), 4132 1.1 mbalmer and returns an error code. 4133 1.1 mbalmer Like <a href="#lua_call"><code>lua_call</code></a>, 4134 1.1 mbalmer <a href="#lua_pcall"><code>lua_pcall</code></a> always removes the function 4135 1.1 mbalmer and its arguments from the stack. 4136 1.1 mbalmer 4137 1.1 mbalmer 4138 1.1 mbalmer <p> 4139 1.2 lneto If <code>msgh</code> is 0, 4140 1.1 mbalmer then the error message returned on the stack 4141 1.1 mbalmer is exactly the original error message. 4142 1.2 lneto Otherwise, <code>msgh</code> is the stack index of a 4143 1.2 lneto <em>message handler</em>. 4144 1.4 mbalmer (This index cannot be a pseudo-index.) 4145 1.1 mbalmer In case of runtime errors, 4146 1.1 mbalmer this function will be called with the error message 4147 1.2 lneto and its return value will be the message 4148 1.2 lneto returned on the stack by <a href="#lua_pcall"><code>lua_pcall</code></a>. 4149 1.1 mbalmer 4150 1.1 mbalmer 4151 1.1 mbalmer <p> 4152 1.2 lneto Typically, the message handler is used to add more debug 4153 1.1 mbalmer information to the error message, such as a stack traceback. 4154 1.1 mbalmer Such information cannot be gathered after the return of <a href="#lua_pcall"><code>lua_pcall</code></a>, 4155 1.1 mbalmer since by then the stack has unwound. 4156 1.1 mbalmer 4157 1.1 mbalmer 4158 1.1 mbalmer <p> 4159 1.2 lneto The <a href="#lua_pcall"><code>lua_pcall</code></a> function returns one of the following constants 4160 1.1 mbalmer (defined in <code>lua.h</code>): 4161 1.1 mbalmer 4162 1.1 mbalmer <ul> 4163 1.1 mbalmer 4164 1.2 lneto <li><b><a name="pdf-LUA_OK"><code>LUA_OK</code></a> (0): </b> 4165 1.2 lneto success.</li> 4166 1.2 lneto 4167 1.2 lneto <li><b><a name="pdf-LUA_ERRRUN"><code>LUA_ERRRUN</code></a>: </b> 4168 1.1 mbalmer a runtime error. 4169 1.1 mbalmer </li> 4170 1.1 mbalmer 4171 1.2 lneto <li><b><a name="pdf-LUA_ERRMEM"><code>LUA_ERRMEM</code></a>: </b> 4172 1.1 mbalmer memory allocation error. 4173 1.2 lneto For such errors, Lua does not call the message handler. 4174 1.2 lneto </li> 4175 1.2 lneto 4176 1.2 lneto <li><b><a name="pdf-LUA_ERRERR"><code>LUA_ERRERR</code></a>: </b> 4177 1.2 lneto error while running the message handler. 4178 1.1 mbalmer </li> 4179 1.1 mbalmer 4180 1.2 lneto <li><b><a name="pdf-LUA_ERRGCMM"><code>LUA_ERRGCMM</code></a>: </b> 4181 1.2 lneto error while running a <code>__gc</code> metamethod. 4182 1.2 lneto (This error typically has no relation with the function being called.) 4183 1.1 mbalmer </li> 4184 1.1 mbalmer 4185 1.1 mbalmer </ul> 4186 1.1 mbalmer 4187 1.1 mbalmer 4188 1.1 mbalmer 4189 1.1 mbalmer 4190 1.2 lneto <hr><h3><a name="lua_pcallk"><code>lua_pcallk</code></a></h3><p> 4191 1.2 lneto <span class="apii">[-(nargs + 1), +(nresults|1), –]</span> 4192 1.2 lneto <pre>int lua_pcallk (lua_State *L, 4193 1.2 lneto int nargs, 4194 1.2 lneto int nresults, 4195 1.3 lneto int msgh, 4196 1.3 lneto lua_KContext ctx, 4197 1.2 lneto lua_KFunction k);</pre> 4198 1.2 lneto 4199 1.2 lneto <p> 4200 1.2 lneto This function behaves exactly like <a href="#lua_pcall"><code>lua_pcall</code></a>, 4201 1.2 lneto but allows the called function to yield (see <a href="#4.7">§4.7</a>). 4202 1.2 lneto 4203 1.2 lneto 4204 1.2 lneto 4205 1.2 lneto 4206 1.2 lneto 4207 1.1 mbalmer <hr><h3><a name="lua_pop"><code>lua_pop</code></a></h3><p> 4208 1.2 lneto <span class="apii">[-n, +0, –]</span> 4209 1.1 mbalmer <pre>void lua_pop (lua_State *L, int n);</pre> 4210 1.1 mbalmer 4211 1.1 mbalmer <p> 4212 1.1 mbalmer Pops <code>n</code> elements from the stack. 4213 1.1 mbalmer 4214 1.1 mbalmer 4215 1.1 mbalmer 4216 1.1 mbalmer 4217 1.1 mbalmer 4218 1.1 mbalmer <hr><h3><a name="lua_pushboolean"><code>lua_pushboolean</code></a></h3><p> 4219 1.2 lneto <span class="apii">[-0, +1, –]</span> 4220 1.1 mbalmer <pre>void lua_pushboolean (lua_State *L, int b);</pre> 4221 1.1 mbalmer 4222 1.1 mbalmer <p> 4223 1.1 mbalmer Pushes a boolean value with value <code>b</code> onto the stack. 4224 1.1 mbalmer 4225 1.1 mbalmer 4226 1.1 mbalmer 4227 1.1 mbalmer 4228 1.1 mbalmer 4229 1.1 mbalmer <hr><h3><a name="lua_pushcclosure"><code>lua_pushcclosure</code></a></h3><p> 4230 1.5 lneto <span class="apii">[-n, +1, <em>m</em>]</span> 4231 1.1 mbalmer <pre>void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n);</pre> 4232 1.1 mbalmer 4233 1.1 mbalmer <p> 4234 1.1 mbalmer Pushes a new C closure onto the stack. 4235 1.1 mbalmer 4236 1.1 mbalmer 4237 1.1 mbalmer <p> 4238 1.1 mbalmer When a C function is created, 4239 1.1 mbalmer it is possible to associate some values with it, 4240 1.2 lneto thus creating a C closure (see <a href="#4.4">§4.4</a>); 4241 1.1 mbalmer these values are then accessible to the function whenever it is called. 4242 1.1 mbalmer To associate values with a C function, 4243 1.2 lneto first these values must be pushed onto the stack 4244 1.1 mbalmer (when there are multiple values, the first value is pushed first). 4245 1.1 mbalmer Then <a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a> 4246 1.1 mbalmer is called to create and push the C function onto the stack, 4247 1.2 lneto with the argument <code>n</code> telling how many values will be 4248 1.1 mbalmer associated with the function. 4249 1.1 mbalmer <a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a> also pops these values from the stack. 4250 1.1 mbalmer 4251 1.1 mbalmer 4252 1.1 mbalmer <p> 4253 1.1 mbalmer The maximum value for <code>n</code> is 255. 4254 1.1 mbalmer 4255 1.1 mbalmer 4256 1.2 lneto <p> 4257 1.2 lneto When <code>n</code> is zero, 4258 1.2 lneto this function creates a <em>light C function</em>, 4259 1.2 lneto which is just a pointer to the C function. 4260 1.2 lneto In that case, it never raises a memory error. 4261 1.2 lneto 4262 1.2 lneto 4263 1.1 mbalmer 4264 1.1 mbalmer 4265 1.1 mbalmer 4266 1.1 mbalmer <hr><h3><a name="lua_pushcfunction"><code>lua_pushcfunction</code></a></h3><p> 4267 1.2 lneto <span class="apii">[-0, +1, –]</span> 4268 1.1 mbalmer <pre>void lua_pushcfunction (lua_State *L, lua_CFunction f);</pre> 4269 1.1 mbalmer 4270 1.1 mbalmer <p> 4271 1.1 mbalmer Pushes a C function onto the stack. 4272 1.1 mbalmer This function receives a pointer to a C function 4273 1.1 mbalmer and pushes onto the stack a Lua value of type <code>function</code> that, 4274 1.1 mbalmer when called, invokes the corresponding C function. 4275 1.1 mbalmer 4276 1.1 mbalmer 4277 1.1 mbalmer <p> 4278 1.4 mbalmer Any function to be callable by Lua must 4279 1.1 mbalmer follow the correct protocol to receive its parameters 4280 1.1 mbalmer and return its results (see <a href="#lua_CFunction"><code>lua_CFunction</code></a>). 4281 1.1 mbalmer 4282 1.1 mbalmer 4283 1.1 mbalmer 4284 1.1 mbalmer 4285 1.1 mbalmer 4286 1.1 mbalmer <hr><h3><a name="lua_pushfstring"><code>lua_pushfstring</code></a></h3><p> 4287 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 4288 1.1 mbalmer <pre>const char *lua_pushfstring (lua_State *L, const char *fmt, ...);</pre> 4289 1.1 mbalmer 4290 1.1 mbalmer <p> 4291 1.1 mbalmer Pushes onto the stack a formatted string 4292 1.1 mbalmer and returns a pointer to this string. 4293 1.3 lneto It is similar to the ISO C function <code>sprintf</code>, 4294 1.1 mbalmer but has some important differences: 4295 1.1 mbalmer 4296 1.1 mbalmer <ul> 4297 1.1 mbalmer 4298 1.1 mbalmer <li> 4299 1.1 mbalmer You do not have to allocate space for the result: 4300 1.1 mbalmer the result is a Lua string and Lua takes care of memory allocation 4301 1.1 mbalmer (and deallocation, through garbage collection). 4302 1.1 mbalmer </li> 4303 1.1 mbalmer 4304 1.1 mbalmer <li> 4305 1.1 mbalmer The conversion specifiers are quite restricted. 4306 1.1 mbalmer There are no flags, widths, or precisions. 4307 1.1 mbalmer The conversion specifiers can only be 4308 1.2 lneto '<code>%%</code>' (inserts the character '<code>%</code>'), 4309 1.1 mbalmer '<code>%s</code>' (inserts a zero-terminated string, with no size restrictions), 4310 1.1 mbalmer '<code>%f</code>' (inserts a <a href="#lua_Number"><code>lua_Number</code></a>), 4311 1.4 mbalmer '<code>%I</code>' (inserts a <a href="#lua_Integer"><code>lua_Integer</code></a>), 4312 1.1 mbalmer '<code>%p</code>' (inserts a pointer as a hexadecimal numeral), 4313 1.2 lneto '<code>%d</code>' (inserts an <code>int</code>), 4314 1.2 lneto '<code>%c</code>' (inserts an <code>int</code> as a one-byte character), and 4315 1.3 lneto '<code>%U</code>' (inserts a <code>long int</code> as a UTF-8 byte sequence). 4316 1.1 mbalmer </li> 4317 1.1 mbalmer 4318 1.1 mbalmer </ul> 4319 1.1 mbalmer 4320 1.1 mbalmer 4321 1.1 mbalmer 4322 1.1 mbalmer 4323 1.2 lneto <hr><h3><a name="lua_pushglobaltable"><code>lua_pushglobaltable</code></a></h3><p> 4324 1.2 lneto <span class="apii">[-0, +1, –]</span> 4325 1.2 lneto <pre>void lua_pushglobaltable (lua_State *L);</pre> 4326 1.2 lneto 4327 1.2 lneto <p> 4328 1.2 lneto Pushes the global environment onto the stack. 4329 1.2 lneto 4330 1.2 lneto 4331 1.2 lneto 4332 1.2 lneto 4333 1.2 lneto 4334 1.1 mbalmer <hr><h3><a name="lua_pushinteger"><code>lua_pushinteger</code></a></h3><p> 4335 1.2 lneto <span class="apii">[-0, +1, –]</span> 4336 1.1 mbalmer <pre>void lua_pushinteger (lua_State *L, lua_Integer n);</pre> 4337 1.1 mbalmer 4338 1.1 mbalmer <p> 4339 1.2 lneto Pushes an integer with value <code>n</code> onto the stack. 4340 1.1 mbalmer 4341 1.1 mbalmer 4342 1.1 mbalmer 4343 1.1 mbalmer 4344 1.1 mbalmer 4345 1.1 mbalmer <hr><h3><a name="lua_pushlightuserdata"><code>lua_pushlightuserdata</code></a></h3><p> 4346 1.2 lneto <span class="apii">[-0, +1, –]</span> 4347 1.1 mbalmer <pre>void lua_pushlightuserdata (lua_State *L, void *p);</pre> 4348 1.1 mbalmer 4349 1.1 mbalmer <p> 4350 1.1 mbalmer Pushes a light userdata onto the stack. 4351 1.1 mbalmer 4352 1.1 mbalmer 4353 1.1 mbalmer <p> 4354 1.1 mbalmer Userdata represent C values in Lua. 4355 1.2 lneto A <em>light userdata</em> represents a pointer, a <code>void*</code>. 4356 1.1 mbalmer It is a value (like a number): 4357 1.1 mbalmer you do not create it, it has no individual metatable, 4358 1.1 mbalmer and it is not collected (as it was never created). 4359 1.1 mbalmer A light userdata is equal to "any" 4360 1.1 mbalmer light userdata with the same C address. 4361 1.1 mbalmer 4362 1.1 mbalmer 4363 1.1 mbalmer 4364 1.1 mbalmer 4365 1.1 mbalmer 4366 1.1 mbalmer <hr><h3><a name="lua_pushliteral"><code>lua_pushliteral</code></a></h3><p> 4367 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 4368 1.2 lneto <pre>const char *lua_pushliteral (lua_State *L, const char *s);</pre> 4369 1.1 mbalmer 4370 1.1 mbalmer <p> 4371 1.4 mbalmer This macro is equivalent to <a href="#lua_pushstring"><code>lua_pushstring</code></a>, 4372 1.4 mbalmer but should be used only when <code>s</code> is a literal string. 4373 1.1 mbalmer 4374 1.1 mbalmer 4375 1.1 mbalmer 4376 1.1 mbalmer 4377 1.1 mbalmer 4378 1.1 mbalmer <hr><h3><a name="lua_pushlstring"><code>lua_pushlstring</code></a></h3><p> 4379 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 4380 1.2 lneto <pre>const char *lua_pushlstring (lua_State *L, const char *s, size_t len);</pre> 4381 1.1 mbalmer 4382 1.1 mbalmer <p> 4383 1.1 mbalmer Pushes the string pointed to by <code>s</code> with size <code>len</code> 4384 1.1 mbalmer onto the stack. 4385 1.1 mbalmer Lua makes (or reuses) an internal copy of the given string, 4386 1.1 mbalmer so the memory at <code>s</code> can be freed or reused immediately after 4387 1.1 mbalmer the function returns. 4388 1.2 lneto The string can contain any binary data, 4389 1.2 lneto including embedded zeros. 4390 1.2 lneto 4391 1.2 lneto 4392 1.2 lneto <p> 4393 1.2 lneto Returns a pointer to the internal copy of the string. 4394 1.1 mbalmer 4395 1.1 mbalmer 4396 1.1 mbalmer 4397 1.1 mbalmer 4398 1.1 mbalmer 4399 1.1 mbalmer <hr><h3><a name="lua_pushnil"><code>lua_pushnil</code></a></h3><p> 4400 1.2 lneto <span class="apii">[-0, +1, –]</span> 4401 1.1 mbalmer <pre>void lua_pushnil (lua_State *L);</pre> 4402 1.1 mbalmer 4403 1.1 mbalmer <p> 4404 1.1 mbalmer Pushes a nil value onto the stack. 4405 1.1 mbalmer 4406 1.1 mbalmer 4407 1.1 mbalmer 4408 1.1 mbalmer 4409 1.1 mbalmer 4410 1.1 mbalmer <hr><h3><a name="lua_pushnumber"><code>lua_pushnumber</code></a></h3><p> 4411 1.2 lneto <span class="apii">[-0, +1, –]</span> 4412 1.1 mbalmer <pre>void lua_pushnumber (lua_State *L, lua_Number n);</pre> 4413 1.1 mbalmer 4414 1.1 mbalmer <p> 4415 1.2 lneto Pushes a float with value <code>n</code> onto the stack. 4416 1.1 mbalmer 4417 1.1 mbalmer 4418 1.1 mbalmer 4419 1.1 mbalmer 4420 1.1 mbalmer 4421 1.1 mbalmer <hr><h3><a name="lua_pushstring"><code>lua_pushstring</code></a></h3><p> 4422 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 4423 1.2 lneto <pre>const char *lua_pushstring (lua_State *L, const char *s);</pre> 4424 1.1 mbalmer 4425 1.1 mbalmer <p> 4426 1.1 mbalmer Pushes the zero-terminated string pointed to by <code>s</code> 4427 1.1 mbalmer onto the stack. 4428 1.1 mbalmer Lua makes (or reuses) an internal copy of the given string, 4429 1.1 mbalmer so the memory at <code>s</code> can be freed or reused immediately after 4430 1.1 mbalmer the function returns. 4431 1.2 lneto 4432 1.2 lneto 4433 1.2 lneto <p> 4434 1.2 lneto Returns a pointer to the internal copy of the string. 4435 1.2 lneto 4436 1.2 lneto 4437 1.2 lneto <p> 4438 1.2 lneto If <code>s</code> is <code>NULL</code>, pushes <b>nil</b> and returns <code>NULL</code>. 4439 1.1 mbalmer 4440 1.1 mbalmer 4441 1.1 mbalmer 4442 1.1 mbalmer 4443 1.1 mbalmer 4444 1.1 mbalmer <hr><h3><a name="lua_pushthread"><code>lua_pushthread</code></a></h3><p> 4445 1.2 lneto <span class="apii">[-0, +1, –]</span> 4446 1.1 mbalmer <pre>int lua_pushthread (lua_State *L);</pre> 4447 1.1 mbalmer 4448 1.1 mbalmer <p> 4449 1.1 mbalmer Pushes the thread represented by <code>L</code> onto the stack. 4450 1.1 mbalmer Returns 1 if this thread is the main thread of its state. 4451 1.1 mbalmer 4452 1.1 mbalmer 4453 1.1 mbalmer 4454 1.1 mbalmer 4455 1.1 mbalmer 4456 1.1 mbalmer <hr><h3><a name="lua_pushvalue"><code>lua_pushvalue</code></a></h3><p> 4457 1.2 lneto <span class="apii">[-0, +1, –]</span> 4458 1.1 mbalmer <pre>void lua_pushvalue (lua_State *L, int index);</pre> 4459 1.1 mbalmer 4460 1.1 mbalmer <p> 4461 1.2 lneto Pushes a copy of the element at the given index 4462 1.1 mbalmer onto the stack. 4463 1.1 mbalmer 4464 1.1 mbalmer 4465 1.1 mbalmer 4466 1.1 mbalmer 4467 1.1 mbalmer 4468 1.1 mbalmer <hr><h3><a name="lua_pushvfstring"><code>lua_pushvfstring</code></a></h3><p> 4469 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 4470 1.1 mbalmer <pre>const char *lua_pushvfstring (lua_State *L, 4471 1.1 mbalmer const char *fmt, 4472 1.1 mbalmer va_list argp);</pre> 4473 1.1 mbalmer 4474 1.1 mbalmer <p> 4475 1.1 mbalmer Equivalent to <a href="#lua_pushfstring"><code>lua_pushfstring</code></a>, except that it receives a <code>va_list</code> 4476 1.1 mbalmer instead of a variable number of arguments. 4477 1.1 mbalmer 4478 1.1 mbalmer 4479 1.1 mbalmer 4480 1.1 mbalmer 4481 1.1 mbalmer 4482 1.1 mbalmer <hr><h3><a name="lua_rawequal"><code>lua_rawequal</code></a></h3><p> 4483 1.2 lneto <span class="apii">[-0, +0, –]</span> 4484 1.1 mbalmer <pre>int lua_rawequal (lua_State *L, int index1, int index2);</pre> 4485 1.1 mbalmer 4486 1.1 mbalmer <p> 4487 1.2 lneto Returns 1 if the two values in indices <code>index1</code> and 4488 1.1 mbalmer <code>index2</code> are primitively equal 4489 1.1 mbalmer (that is, without calling metamethods). 4490 1.1 mbalmer Otherwise returns 0. 4491 1.3 lneto Also returns 0 if any of the indices are not valid. 4492 1.1 mbalmer 4493 1.1 mbalmer 4494 1.1 mbalmer 4495 1.1 mbalmer 4496 1.1 mbalmer 4497 1.1 mbalmer <hr><h3><a name="lua_rawget"><code>lua_rawget</code></a></h3><p> 4498 1.2 lneto <span class="apii">[-1, +1, –]</span> 4499 1.2 lneto <pre>int lua_rawget (lua_State *L, int index);</pre> 4500 1.1 mbalmer 4501 1.1 mbalmer <p> 4502 1.1 mbalmer Similar to <a href="#lua_gettable"><code>lua_gettable</code></a>, but does a raw access 4503 1.1 mbalmer (i.e., without metamethods). 4504 1.1 mbalmer 4505 1.1 mbalmer 4506 1.1 mbalmer 4507 1.1 mbalmer 4508 1.1 mbalmer 4509 1.2 lneto <hr><h3><a name="lua_rawgeti"><code>lua_rawgeti</code></a></h3><p> 4510 1.2 lneto <span class="apii">[-0, +1, –]</span> 4511 1.2 lneto <pre>int lua_rawgeti (lua_State *L, int index, lua_Integer n);</pre> 4512 1.2 lneto 4513 1.2 lneto <p> 4514 1.2 lneto Pushes onto the stack the value <code>t[n]</code>, 4515 1.2 lneto where <code>t</code> is the table at the given index. 4516 1.2 lneto The access is raw; 4517 1.2 lneto that is, it does not invoke metamethods. 4518 1.2 lneto 4519 1.2 lneto 4520 1.2 lneto <p> 4521 1.2 lneto Returns the type of the pushed value. 4522 1.2 lneto 4523 1.2 lneto 4524 1.2 lneto 4525 1.2 lneto 4526 1.2 lneto 4527 1.2 lneto <hr><h3><a name="lua_rawgetp"><code>lua_rawgetp</code></a></h3><p> 4528 1.2 lneto <span class="apii">[-0, +1, –]</span> 4529 1.2 lneto <pre>int lua_rawgetp (lua_State *L, int index, const void *p);</pre> 4530 1.2 lneto 4531 1.2 lneto <p> 4532 1.2 lneto Pushes onto the stack the value <code>t[k]</code>, 4533 1.2 lneto where <code>t</code> is the table at the given index and 4534 1.2 lneto <code>k</code> is the pointer <code>p</code> represented as a light userdata. 4535 1.2 lneto The access is raw; 4536 1.2 lneto that is, it does not invoke metamethods. 4537 1.2 lneto 4538 1.2 lneto 4539 1.2 lneto <p> 4540 1.2 lneto Returns the type of the pushed value. 4541 1.2 lneto 4542 1.2 lneto 4543 1.2 lneto 4544 1.2 lneto 4545 1.2 lneto 4546 1.2 lneto <hr><h3><a name="lua_rawlen"><code>lua_rawlen</code></a></h3><p> 4547 1.2 lneto <span class="apii">[-0, +0, –]</span> 4548 1.2 lneto <pre>size_t lua_rawlen (lua_State *L, int index);</pre> 4549 1.2 lneto 4550 1.2 lneto <p> 4551 1.2 lneto Returns the raw "length" of the value at the given index: 4552 1.2 lneto for strings, this is the string length; 4553 1.2 lneto for tables, this is the result of the length operator ('<code>#</code>') 4554 1.2 lneto with no metamethods; 4555 1.2 lneto for userdata, this is the size of the block of memory allocated 4556 1.2 lneto for the userdata; 4557 1.2 lneto for other values, it is 0. 4558 1.1 mbalmer 4559 1.1 mbalmer 4560 1.1 mbalmer 4561 1.1 mbalmer 4562 1.1 mbalmer 4563 1.1 mbalmer <hr><h3><a name="lua_rawset"><code>lua_rawset</code></a></h3><p> 4564 1.5 lneto <span class="apii">[-2, +0, <em>m</em>]</span> 4565 1.1 mbalmer <pre>void lua_rawset (lua_State *L, int index);</pre> 4566 1.1 mbalmer 4567 1.1 mbalmer <p> 4568 1.1 mbalmer Similar to <a href="#lua_settable"><code>lua_settable</code></a>, but does a raw assignment 4569 1.1 mbalmer (i.e., without metamethods). 4570 1.1 mbalmer 4571 1.1 mbalmer 4572 1.1 mbalmer 4573 1.1 mbalmer 4574 1.1 mbalmer 4575 1.1 mbalmer <hr><h3><a name="lua_rawseti"><code>lua_rawseti</code></a></h3><p> 4576 1.5 lneto <span class="apii">[-1, +0, <em>m</em>]</span> 4577 1.3 lneto <pre>void lua_rawseti (lua_State *L, int index, lua_Integer i);</pre> 4578 1.1 mbalmer 4579 1.1 mbalmer <p> 4580 1.3 lneto Does the equivalent of <code>t[i] = v</code>, 4581 1.2 lneto where <code>t</code> is the table at the given index 4582 1.2 lneto and <code>v</code> is the value at the top of the stack. 4583 1.2 lneto 4584 1.2 lneto 4585 1.2 lneto <p> 4586 1.2 lneto This function pops the value from the stack. 4587 1.2 lneto The assignment is raw; 4588 1.2 lneto that is, it does not invoke metamethods. 4589 1.2 lneto 4590 1.2 lneto 4591 1.2 lneto 4592 1.2 lneto 4593 1.2 lneto 4594 1.2 lneto <hr><h3><a name="lua_rawsetp"><code>lua_rawsetp</code></a></h3><p> 4595 1.5 lneto <span class="apii">[-1, +0, <em>m</em>]</span> 4596 1.2 lneto <pre>void lua_rawsetp (lua_State *L, int index, const void *p);</pre> 4597 1.2 lneto 4598 1.2 lneto <p> 4599 1.4 mbalmer Does the equivalent of <code>t[p] = v</code>, 4600 1.2 lneto where <code>t</code> is the table at the given index, 4601 1.4 mbalmer <code>p</code> is encoded as a light userdata, 4602 1.1 mbalmer and <code>v</code> is the value at the top of the stack. 4603 1.1 mbalmer 4604 1.1 mbalmer 4605 1.1 mbalmer <p> 4606 1.1 mbalmer This function pops the value from the stack. 4607 1.1 mbalmer The assignment is raw; 4608 1.1 mbalmer that is, it does not invoke metamethods. 4609 1.1 mbalmer 4610 1.1 mbalmer 4611 1.1 mbalmer 4612 1.1 mbalmer 4613 1.1 mbalmer 4614 1.1 mbalmer <hr><h3><a name="lua_Reader"><code>lua_Reader</code></a></h3> 4615 1.1 mbalmer <pre>typedef const char * (*lua_Reader) (lua_State *L, 4616 1.1 mbalmer void *data, 4617 1.1 mbalmer size_t *size);</pre> 4618 1.1 mbalmer 4619 1.1 mbalmer <p> 4620 1.1 mbalmer The reader function used by <a href="#lua_load"><code>lua_load</code></a>. 4621 1.1 mbalmer Every time it needs another piece of the chunk, 4622 1.1 mbalmer <a href="#lua_load"><code>lua_load</code></a> calls the reader, 4623 1.1 mbalmer passing along its <code>data</code> parameter. 4624 1.1 mbalmer The reader must return a pointer to a block of memory 4625 1.1 mbalmer with a new piece of the chunk 4626 1.1 mbalmer and set <code>size</code> to the block size. 4627 1.1 mbalmer The block must exist until the reader function is called again. 4628 1.1 mbalmer To signal the end of the chunk, 4629 1.1 mbalmer the reader must return <code>NULL</code> or set <code>size</code> to zero. 4630 1.1 mbalmer The reader function may return pieces of any size greater than zero. 4631 1.1 mbalmer 4632 1.1 mbalmer 4633 1.1 mbalmer 4634 1.1 mbalmer 4635 1.1 mbalmer 4636 1.1 mbalmer <hr><h3><a name="lua_register"><code>lua_register</code></a></h3><p> 4637 1.1 mbalmer <span class="apii">[-0, +0, <em>e</em>]</span> 4638 1.2 lneto <pre>void lua_register (lua_State *L, const char *name, lua_CFunction f);</pre> 4639 1.1 mbalmer 4640 1.1 mbalmer <p> 4641 1.1 mbalmer Sets the C function <code>f</code> as the new value of global <code>name</code>. 4642 1.1 mbalmer It is defined as a macro: 4643 1.1 mbalmer 4644 1.1 mbalmer <pre> 4645 1.1 mbalmer #define lua_register(L,n,f) \ 4646 1.1 mbalmer (lua_pushcfunction(L, f), lua_setglobal(L, n)) 4647 1.1 mbalmer </pre> 4648 1.1 mbalmer 4649 1.1 mbalmer 4650 1.1 mbalmer 4651 1.1 mbalmer 4652 1.1 mbalmer <hr><h3><a name="lua_remove"><code>lua_remove</code></a></h3><p> 4653 1.2 lneto <span class="apii">[-1, +0, –]</span> 4654 1.1 mbalmer <pre>void lua_remove (lua_State *L, int index);</pre> 4655 1.1 mbalmer 4656 1.1 mbalmer <p> 4657 1.1 mbalmer Removes the element at the given valid index, 4658 1.1 mbalmer shifting down the elements above this index to fill the gap. 4659 1.2 lneto This function cannot be called with a pseudo-index, 4660 1.1 mbalmer because a pseudo-index is not an actual stack position. 4661 1.1 mbalmer 4662 1.1 mbalmer 4663 1.1 mbalmer 4664 1.1 mbalmer 4665 1.1 mbalmer 4666 1.1 mbalmer <hr><h3><a name="lua_replace"><code>lua_replace</code></a></h3><p> 4667 1.2 lneto <span class="apii">[-1, +0, –]</span> 4668 1.1 mbalmer <pre>void lua_replace (lua_State *L, int index);</pre> 4669 1.1 mbalmer 4670 1.1 mbalmer <p> 4671 1.2 lneto Moves the top element into the given valid index 4672 1.1 mbalmer without shifting any element 4673 1.4 mbalmer (therefore replacing the value at that given index), 4674 1.2 lneto and then pops the top element. 4675 1.1 mbalmer 4676 1.1 mbalmer 4677 1.1 mbalmer 4678 1.1 mbalmer 4679 1.1 mbalmer 4680 1.1 mbalmer <hr><h3><a name="lua_resume"><code>lua_resume</code></a></h3><p> 4681 1.2 lneto <span class="apii">[-?, +?, –]</span> 4682 1.2 lneto <pre>int lua_resume (lua_State *L, lua_State *from, int nargs);</pre> 4683 1.1 mbalmer 4684 1.1 mbalmer <p> 4685 1.4 mbalmer Starts and resumes a coroutine in the given thread <code>L</code>. 4686 1.1 mbalmer 4687 1.1 mbalmer 4688 1.1 mbalmer <p> 4689 1.2 lneto To start a coroutine, 4690 1.2 lneto you push onto the thread stack the main function plus any arguments; 4691 1.1 mbalmer then you call <a href="#lua_resume"><code>lua_resume</code></a>, 4692 1.2 lneto with <code>nargs</code> being the number of arguments. 4693 1.1 mbalmer This call returns when the coroutine suspends or finishes its execution. 4694 1.1 mbalmer When it returns, the stack contains all values passed to <a href="#lua_yield"><code>lua_yield</code></a>, 4695 1.1 mbalmer or all values returned by the body function. 4696 1.1 mbalmer <a href="#lua_resume"><code>lua_resume</code></a> returns 4697 1.1 mbalmer <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a> if the coroutine yields, 4698 1.2 lneto <a href="#pdf-LUA_OK"><code>LUA_OK</code></a> if the coroutine finishes its execution 4699 1.1 mbalmer without errors, 4700 1.1 mbalmer or an error code in case of errors (see <a href="#lua_pcall"><code>lua_pcall</code></a>). 4701 1.2 lneto 4702 1.2 lneto 4703 1.2 lneto <p> 4704 1.1 mbalmer In case of errors, 4705 1.1 mbalmer the stack is not unwound, 4706 1.1 mbalmer so you can use the debug API over it. 4707 1.1 mbalmer The error message is on the top of the stack. 4708 1.2 lneto 4709 1.2 lneto 4710 1.2 lneto <p> 4711 1.2 lneto To resume a coroutine, 4712 1.2 lneto you remove any results from the last <a href="#lua_yield"><code>lua_yield</code></a>, 4713 1.2 lneto put on its stack only the values to 4714 1.1 mbalmer be passed as results from <code>yield</code>, 4715 1.1 mbalmer and then call <a href="#lua_resume"><code>lua_resume</code></a>. 4716 1.1 mbalmer 4717 1.1 mbalmer 4718 1.2 lneto <p> 4719 1.2 lneto The parameter <code>from</code> represents the coroutine that is resuming <code>L</code>. 4720 1.2 lneto If there is no such coroutine, 4721 1.2 lneto this parameter can be <code>NULL</code>. 4722 1.2 lneto 4723 1.2 lneto 4724 1.1 mbalmer 4725 1.1 mbalmer 4726 1.1 mbalmer 4727 1.2 lneto <hr><h3><a name="lua_rotate"><code>lua_rotate</code></a></h3><p> 4728 1.2 lneto <span class="apii">[-0, +0, –]</span> 4729 1.2 lneto <pre>void lua_rotate (lua_State *L, int idx, int n);</pre> 4730 1.1 mbalmer 4731 1.1 mbalmer <p> 4732 1.4 mbalmer Rotates the stack elements between the valid index <code>idx</code> 4733 1.4 mbalmer and the top of the stack. 4734 1.4 mbalmer The elements are rotated <code>n</code> positions in the direction of the top, 4735 1.4 mbalmer 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 1.4 mbalmer This function cannot be called with a pseudo-index, 4741 1.4 mbalmer because a pseudo-index is not an actual stack position. 4742 1.1 mbalmer 4743 1.1 mbalmer 4744 1.1 mbalmer 4745 1.1 mbalmer 4746 1.1 mbalmer 4747 1.2 lneto <hr><h3><a name="lua_setallocf"><code>lua_setallocf</code></a></h3><p> 4748 1.2 lneto <span class="apii">[-0, +0, –]</span> 4749 1.2 lneto <pre>void lua_setallocf (lua_State *L, lua_Alloc f, void *ud);</pre> 4750 1.1 mbalmer 4751 1.1 mbalmer <p> 4752 1.2 lneto Changes the allocator function of a given state to <code>f</code> 4753 1.2 lneto with user data <code>ud</code>. 4754 1.1 mbalmer 4755 1.1 mbalmer 4756 1.1 mbalmer 4757 1.1 mbalmer 4758 1.1 mbalmer 4759 1.1 mbalmer <hr><h3><a name="lua_setfield"><code>lua_setfield</code></a></h3><p> 4760 1.1 mbalmer <span class="apii">[-1, +0, <em>e</em>]</span> 4761 1.1 mbalmer <pre>void lua_setfield (lua_State *L, int index, const char *k);</pre> 4762 1.1 mbalmer 4763 1.1 mbalmer <p> 4764 1.1 mbalmer Does the equivalent to <code>t[k] = v</code>, 4765 1.2 lneto where <code>t</code> is the value at the given index 4766 1.1 mbalmer and <code>v</code> is the value at the top of the stack. 4767 1.1 mbalmer 4768 1.1 mbalmer 4769 1.1 mbalmer <p> 4770 1.1 mbalmer This function pops the value from the stack. 4771 1.1 mbalmer As in Lua, this function may trigger a metamethod 4772 1.2 lneto for the "newindex" event (see <a href="#2.4">§2.4</a>). 4773 1.1 mbalmer 4774 1.1 mbalmer 4775 1.1 mbalmer 4776 1.1 mbalmer 4777 1.1 mbalmer 4778 1.1 mbalmer <hr><h3><a name="lua_setglobal"><code>lua_setglobal</code></a></h3><p> 4779 1.1 mbalmer <span class="apii">[-1, +0, <em>e</em>]</span> 4780 1.1 mbalmer <pre>void lua_setglobal (lua_State *L, const char *name);</pre> 4781 1.1 mbalmer 4782 1.1 mbalmer <p> 4783 1.1 mbalmer Pops a value from the stack and 4784 1.1 mbalmer sets it as the new value of global <code>name</code>. 4785 1.1 mbalmer 4786 1.1 mbalmer 4787 1.1 mbalmer 4788 1.1 mbalmer 4789 1.1 mbalmer 4790 1.3 lneto <hr><h3><a name="lua_seti"><code>lua_seti</code></a></h3><p> 4791 1.3 lneto <span class="apii">[-1, +0, <em>e</em>]</span> 4792 1.3 lneto <pre>void lua_seti (lua_State *L, int index, lua_Integer n);</pre> 4793 1.3 lneto 4794 1.3 lneto <p> 4795 1.3 lneto Does the equivalent to <code>t[n] = v</code>, 4796 1.3 lneto where <code>t</code> is the value at the given index 4797 1.3 lneto and <code>v</code> is the value at the top of the stack. 4798 1.3 lneto 4799 1.3 lneto 4800 1.3 lneto <p> 4801 1.3 lneto This function pops the value from the stack. 4802 1.3 lneto As in Lua, this function may trigger a metamethod 4803 1.3 lneto for the "newindex" event (see <a href="#2.4">§2.4</a>). 4804 1.3 lneto 4805 1.3 lneto 4806 1.3 lneto 4807 1.3 lneto 4808 1.3 lneto 4809 1.1 mbalmer <hr><h3><a name="lua_setmetatable"><code>lua_setmetatable</code></a></h3><p> 4810 1.2 lneto <span class="apii">[-1, +0, –]</span> 4811 1.2 lneto <pre>void lua_setmetatable (lua_State *L, int index);</pre> 4812 1.1 mbalmer 4813 1.1 mbalmer <p> 4814 1.1 mbalmer Pops a table from the stack and 4815 1.2 lneto sets it as the new metatable for the value at the given index. 4816 1.1 mbalmer 4817 1.1 mbalmer 4818 1.1 mbalmer 4819 1.1 mbalmer 4820 1.1 mbalmer 4821 1.1 mbalmer <hr><h3><a name="lua_settable"><code>lua_settable</code></a></h3><p> 4822 1.1 mbalmer <span class="apii">[-2, +0, <em>e</em>]</span> 4823 1.1 mbalmer <pre>void lua_settable (lua_State *L, int index);</pre> 4824 1.1 mbalmer 4825 1.1 mbalmer <p> 4826 1.1 mbalmer Does the equivalent to <code>t[k] = v</code>, 4827 1.2 lneto where <code>t</code> is the value at the given index, 4828 1.1 mbalmer <code>v</code> is the value at the top of the stack, 4829 1.1 mbalmer and <code>k</code> is the value just below the top. 4830 1.1 mbalmer 4831 1.1 mbalmer 4832 1.1 mbalmer <p> 4833 1.1 mbalmer This function pops both the key and the value from the stack. 4834 1.1 mbalmer As in Lua, this function may trigger a metamethod 4835 1.2 lneto for the "newindex" event (see <a href="#2.4">§2.4</a>). 4836 1.1 mbalmer 4837 1.1 mbalmer 4838 1.1 mbalmer 4839 1.1 mbalmer 4840 1.1 mbalmer 4841 1.1 mbalmer <hr><h3><a name="lua_settop"><code>lua_settop</code></a></h3><p> 4842 1.2 lneto <span class="apii">[-?, +?, –]</span> 4843 1.1 mbalmer <pre>void lua_settop (lua_State *L, int index);</pre> 4844 1.1 mbalmer 4845 1.1 mbalmer <p> 4846 1.2 lneto Accepts any index, or 0, 4847 1.1 mbalmer and sets the stack top to this index. 4848 1.1 mbalmer If the new top is larger than the old one, 4849 1.1 mbalmer then the new elements are filled with <b>nil</b>. 4850 1.1 mbalmer If <code>index</code> is 0, then all stack elements are removed. 4851 1.1 mbalmer 4852 1.1 mbalmer 4853 1.1 mbalmer 4854 1.1 mbalmer 4855 1.1 mbalmer 4856 1.2 lneto <hr><h3><a name="lua_setuservalue"><code>lua_setuservalue</code></a></h3><p> 4857 1.2 lneto <span class="apii">[-1, +0, –]</span> 4858 1.2 lneto <pre>void lua_setuservalue (lua_State *L, int index);</pre> 4859 1.2 lneto 4860 1.2 lneto <p> 4861 1.2 lneto Pops a value from the stack and sets it as 4862 1.2 lneto the new value associated to the userdata at the given index. 4863 1.2 lneto 4864 1.2 lneto 4865 1.2 lneto 4866 1.2 lneto 4867 1.2 lneto 4868 1.1 mbalmer <hr><h3><a name="lua_State"><code>lua_State</code></a></h3> 4869 1.1 mbalmer <pre>typedef struct lua_State lua_State;</pre> 4870 1.1 mbalmer 4871 1.1 mbalmer <p> 4872 1.2 lneto An opaque structure that points to a thread and indirectly 4873 1.2 lneto (through the thread) to the whole state of a Lua interpreter. 4874 1.1 mbalmer The Lua library is fully reentrant: 4875 1.1 mbalmer it has no global variables. 4876 1.2 lneto All information about a state is accessible through this structure. 4877 1.1 mbalmer 4878 1.1 mbalmer 4879 1.1 mbalmer <p> 4880 1.2 lneto A pointer to this structure must be passed as the first argument to 4881 1.1 mbalmer every function in the library, except to <a href="#lua_newstate"><code>lua_newstate</code></a>, 4882 1.1 mbalmer which creates a Lua state from scratch. 4883 1.1 mbalmer 4884 1.1 mbalmer 4885 1.1 mbalmer 4886 1.1 mbalmer 4887 1.1 mbalmer 4888 1.1 mbalmer <hr><h3><a name="lua_status"><code>lua_status</code></a></h3><p> 4889 1.2 lneto <span class="apii">[-0, +0, –]</span> 4890 1.1 mbalmer <pre>int lua_status (lua_State *L);</pre> 4891 1.1 mbalmer 4892 1.1 mbalmer <p> 4893 1.1 mbalmer Returns the status of the thread <code>L</code>. 4894 1.1 mbalmer 4895 1.1 mbalmer 4896 1.1 mbalmer <p> 4897 1.2 lneto The status can be 0 (<a href="#pdf-LUA_OK"><code>LUA_OK</code></a>) for a normal thread, 4898 1.2 lneto an error code if the thread finished the execution 4899 1.2 lneto of a <a href="#lua_resume"><code>lua_resume</code></a> with an error, 4900 1.1 mbalmer or <a name="pdf-LUA_YIELD"><code>LUA_YIELD</code></a> if the thread is suspended. 4901 1.1 mbalmer 4902 1.1 mbalmer 4903 1.2 lneto <p> 4904 1.2 lneto You can only call functions in threads with status <a href="#pdf-LUA_OK"><code>LUA_OK</code></a>. 4905 1.2 lneto You can resume threads with status <a href="#pdf-LUA_OK"><code>LUA_OK</code></a> 4906 1.2 lneto (to start a new coroutine) or <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a> 4907 1.2 lneto (to resume a coroutine). 4908 1.2 lneto 4909 1.2 lneto 4910 1.2 lneto 4911 1.2 lneto 4912 1.2 lneto 4913 1.3 lneto <hr><h3><a name="lua_stringtonumber"><code>lua_stringtonumber</code></a></h3><p> 4914 1.2 lneto <span class="apii">[-0, +1, –]</span> 4915 1.3 lneto <pre>size_t lua_stringtonumber (lua_State *L, const char *s);</pre> 4916 1.2 lneto 4917 1.2 lneto <p> 4918 1.2 lneto Converts the zero-terminated string <code>s</code> to a number, 4919 1.2 lneto pushes that number into the stack, 4920 1.3 lneto and returns the total size of the string, 4921 1.3 lneto that is, its length plus one. 4922 1.2 lneto The conversion can result in an integer or a float, 4923 1.2 lneto according to the lexical conventions of Lua (see <a href="#3.1">§3.1</a>). 4924 1.2 lneto The string may have leading and trailing spaces and a sign. 4925 1.2 lneto If the string is not a valid numeral, 4926 1.2 lneto returns 0 and pushes nothing. 4927 1.3 lneto (Note that the result can be used as a boolean, 4928 1.3 lneto true if the conversion succeeds.) 4929 1.2 lneto 4930 1.2 lneto 4931 1.1 mbalmer 4932 1.1 mbalmer 4933 1.1 mbalmer 4934 1.1 mbalmer <hr><h3><a name="lua_toboolean"><code>lua_toboolean</code></a></h3><p> 4935 1.2 lneto <span class="apii">[-0, +0, –]</span> 4936 1.1 mbalmer <pre>int lua_toboolean (lua_State *L, int index);</pre> 4937 1.1 mbalmer 4938 1.1 mbalmer <p> 4939 1.2 lneto Converts the Lua value at the given index to a C boolean 4940 1.1 mbalmer value (0 or 1). 4941 1.1 mbalmer Like all tests in Lua, 4942 1.2 lneto <a href="#lua_toboolean"><code>lua_toboolean</code></a> returns true for any Lua value 4943 1.1 mbalmer different from <b>false</b> and <b>nil</b>; 4944 1.2 lneto otherwise it returns false. 4945 1.1 mbalmer (If you want to accept only actual boolean values, 4946 1.1 mbalmer use <a href="#lua_isboolean"><code>lua_isboolean</code></a> to test the value's type.) 4947 1.1 mbalmer 4948 1.1 mbalmer 4949 1.1 mbalmer 4950 1.1 mbalmer 4951 1.1 mbalmer 4952 1.1 mbalmer <hr><h3><a name="lua_tocfunction"><code>lua_tocfunction</code></a></h3><p> 4953 1.2 lneto <span class="apii">[-0, +0, –]</span> 4954 1.1 mbalmer <pre>lua_CFunction lua_tocfunction (lua_State *L, int index);</pre> 4955 1.1 mbalmer 4956 1.1 mbalmer <p> 4957 1.2 lneto Converts a value at the given index to a C function. 4958 1.1 mbalmer That value must be a C function; 4959 1.1 mbalmer otherwise, returns <code>NULL</code>. 4960 1.1 mbalmer 4961 1.1 mbalmer 4962 1.1 mbalmer 4963 1.1 mbalmer 4964 1.1 mbalmer 4965 1.1 mbalmer <hr><h3><a name="lua_tointeger"><code>lua_tointeger</code></a></h3><p> 4966 1.2 lneto <span class="apii">[-0, +0, –]</span> 4967 1.1 mbalmer <pre>lua_Integer lua_tointeger (lua_State *L, int index);</pre> 4968 1.1 mbalmer 4969 1.1 mbalmer <p> 4970 1.2 lneto Equivalent to <a href="#lua_tointegerx"><code>lua_tointegerx</code></a> with <code>isnum</code> equal to <code>NULL</code>. 4971 1.2 lneto 4972 1.2 lneto 4973 1.2 lneto 4974 1.2 lneto 4975 1.2 lneto 4976 1.2 lneto <hr><h3><a name="lua_tointegerx"><code>lua_tointegerx</code></a></h3><p> 4977 1.2 lneto <span class="apii">[-0, +0, –]</span> 4978 1.2 lneto <pre>lua_Integer lua_tointegerx (lua_State *L, int index, int *isnum);</pre> 4979 1.2 lneto 4980 1.2 lneto <p> 4981 1.2 lneto Converts the Lua value at the given index 4982 1.1 mbalmer to the signed integral type <a href="#lua_Integer"><code>lua_Integer</code></a>. 4983 1.2 lneto The Lua value must be an integer, 4984 1.2 lneto or a number or string convertible to an integer (see <a href="#3.4.3">§3.4.3</a>); 4985 1.2 lneto otherwise, <code>lua_tointegerx</code> returns 0. 4986 1.1 mbalmer 4987 1.1 mbalmer 4988 1.1 mbalmer <p> 4989 1.2 lneto If <code>isnum</code> is not <code>NULL</code>, 4990 1.2 lneto its referent is assigned a boolean value that 4991 1.2 lneto indicates whether the operation succeeded. 4992 1.1 mbalmer 4993 1.1 mbalmer 4994 1.1 mbalmer 4995 1.1 mbalmer 4996 1.1 mbalmer 4997 1.1 mbalmer <hr><h3><a name="lua_tolstring"><code>lua_tolstring</code></a></h3><p> 4998 1.5 lneto <span class="apii">[-0, +0, <em>m</em>]</span> 4999 1.1 mbalmer <pre>const char *lua_tolstring (lua_State *L, int index, size_t *len);</pre> 5000 1.1 mbalmer 5001 1.1 mbalmer <p> 5002 1.2 lneto Converts the Lua value at the given index to a C string. 5003 1.1 mbalmer If <code>len</code> is not <code>NULL</code>, 5004 1.5 lneto it sets <code>*len</code> with the string length. 5005 1.1 mbalmer The Lua value must be a string or a number; 5006 1.1 mbalmer otherwise, the function returns <code>NULL</code>. 5007 1.1 mbalmer If the value is a number, 5008 1.2 lneto then <code>lua_tolstring</code> also 5009 1.1 mbalmer <em>changes the actual value in the stack to a string</em>. 5010 1.1 mbalmer (This change confuses <a href="#lua_next"><code>lua_next</code></a> 5011 1.2 lneto when <code>lua_tolstring</code> is applied to keys during a table traversal.) 5012 1.1 mbalmer 5013 1.1 mbalmer 5014 1.1 mbalmer <p> 5015 1.5 lneto <code>lua_tolstring</code> returns a pointer 5016 1.1 mbalmer to a string inside the Lua state. 5017 1.1 mbalmer This string always has a zero ('<code>\0</code>') 5018 1.1 mbalmer after its last character (as in C), 5019 1.1 mbalmer but can contain other zeros in its body. 5020 1.3 lneto 5021 1.3 lneto 5022 1.3 lneto <p> 5023 1.1 mbalmer Because Lua has garbage collection, 5024 1.2 lneto there is no guarantee that the pointer returned by <code>lua_tolstring</code> 5025 1.3 lneto will be valid after the corresponding Lua value is removed from the stack. 5026 1.1 mbalmer 5027 1.1 mbalmer 5028 1.1 mbalmer 5029 1.1 mbalmer 5030 1.1 mbalmer 5031 1.1 mbalmer <hr><h3><a name="lua_tonumber"><code>lua_tonumber</code></a></h3><p> 5032 1.2 lneto <span class="apii">[-0, +0, –]</span> 5033 1.1 mbalmer <pre>lua_Number lua_tonumber (lua_State *L, int index);</pre> 5034 1.1 mbalmer 5035 1.1 mbalmer <p> 5036 1.2 lneto Equivalent to <a href="#lua_tonumberx"><code>lua_tonumberx</code></a> with <code>isnum</code> equal to <code>NULL</code>. 5037 1.2 lneto 5038 1.2 lneto 5039 1.2 lneto 5040 1.2 lneto 5041 1.2 lneto 5042 1.2 lneto <hr><h3><a name="lua_tonumberx"><code>lua_tonumberx</code></a></h3><p> 5043 1.2 lneto <span class="apii">[-0, +0, –]</span> 5044 1.2 lneto <pre>lua_Number lua_tonumberx (lua_State *L, int index, int *isnum);</pre> 5045 1.2 lneto 5046 1.2 lneto <p> 5047 1.2 lneto Converts the Lua value at the given index 5048 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>). 5049 1.1 mbalmer The Lua value must be a number or a string convertible to a number 5050 1.2 lneto (see <a href="#3.4.3">§3.4.3</a>); 5051 1.2 lneto otherwise, <a href="#lua_tonumberx"><code>lua_tonumberx</code></a> returns 0. 5052 1.2 lneto 5053 1.2 lneto 5054 1.2 lneto <p> 5055 1.2 lneto If <code>isnum</code> is not <code>NULL</code>, 5056 1.2 lneto its referent is assigned a boolean value that 5057 1.2 lneto indicates whether the operation succeeded. 5058 1.1 mbalmer 5059 1.1 mbalmer 5060 1.1 mbalmer 5061 1.1 mbalmer 5062 1.1 mbalmer 5063 1.1 mbalmer <hr><h3><a name="lua_topointer"><code>lua_topointer</code></a></h3><p> 5064 1.2 lneto <span class="apii">[-0, +0, –]</span> 5065 1.1 mbalmer <pre>const void *lua_topointer (lua_State *L, int index);</pre> 5066 1.1 mbalmer 5067 1.1 mbalmer <p> 5068 1.2 lneto Converts the value at the given index to a generic 5069 1.1 mbalmer C pointer (<code>void*</code>). 5070 1.1 mbalmer The value can be a userdata, a table, a thread, or a function; 5071 1.2 lneto otherwise, <code>lua_topointer</code> returns <code>NULL</code>. 5072 1.1 mbalmer Different objects will give different pointers. 5073 1.1 mbalmer There is no way to convert the pointer back to its original value. 5074 1.1 mbalmer 5075 1.1 mbalmer 5076 1.1 mbalmer <p> 5077 1.4 mbalmer Typically this function is used only for hashing and debug information. 5078 1.1 mbalmer 5079 1.1 mbalmer 5080 1.1 mbalmer 5081 1.1 mbalmer 5082 1.1 mbalmer 5083 1.1 mbalmer <hr><h3><a name="lua_tostring"><code>lua_tostring</code></a></h3><p> 5084 1.5 lneto <span class="apii">[-0, +0, <em>m</em>]</span> 5085 1.1 mbalmer <pre>const char *lua_tostring (lua_State *L, int index);</pre> 5086 1.1 mbalmer 5087 1.1 mbalmer <p> 5088 1.1 mbalmer Equivalent to <a href="#lua_tolstring"><code>lua_tolstring</code></a> with <code>len</code> equal to <code>NULL</code>. 5089 1.1 mbalmer 5090 1.1 mbalmer 5091 1.1 mbalmer 5092 1.1 mbalmer 5093 1.1 mbalmer 5094 1.1 mbalmer <hr><h3><a name="lua_tothread"><code>lua_tothread</code></a></h3><p> 5095 1.2 lneto <span class="apii">[-0, +0, –]</span> 5096 1.1 mbalmer <pre>lua_State *lua_tothread (lua_State *L, int index);</pre> 5097 1.1 mbalmer 5098 1.1 mbalmer <p> 5099 1.2 lneto Converts the value at the given index to a Lua thread 5100 1.1 mbalmer (represented as <code>lua_State*</code>). 5101 1.1 mbalmer This value must be a thread; 5102 1.1 mbalmer otherwise, the function returns <code>NULL</code>. 5103 1.1 mbalmer 5104 1.1 mbalmer 5105 1.1 mbalmer 5106 1.1 mbalmer 5107 1.1 mbalmer 5108 1.1 mbalmer <hr><h3><a name="lua_touserdata"><code>lua_touserdata</code></a></h3><p> 5109 1.2 lneto <span class="apii">[-0, +0, –]</span> 5110 1.1 mbalmer <pre>void *lua_touserdata (lua_State *L, int index);</pre> 5111 1.1 mbalmer 5112 1.1 mbalmer <p> 5113 1.2 lneto If the value at the given index is a full userdata, 5114 1.1 mbalmer returns its block address. 5115 1.1 mbalmer If the value is a light userdata, 5116 1.1 mbalmer returns its pointer. 5117 1.1 mbalmer Otherwise, returns <code>NULL</code>. 5118 1.1 mbalmer 5119 1.1 mbalmer 5120 1.1 mbalmer 5121 1.1 mbalmer 5122 1.1 mbalmer 5123 1.1 mbalmer <hr><h3><a name="lua_type"><code>lua_type</code></a></h3><p> 5124 1.2 lneto <span class="apii">[-0, +0, –]</span> 5125 1.1 mbalmer <pre>int lua_type (lua_State *L, int index);</pre> 5126 1.1 mbalmer 5127 1.1 mbalmer <p> 5128 1.2 lneto Returns the type of the value in the given valid index, 5129 1.2 lneto or <code>LUA_TNONE</code> for a non-valid (but acceptable) index. 5130 1.1 mbalmer The types returned by <a href="#lua_type"><code>lua_type</code></a> are coded by the following constants 5131 1.1 mbalmer defined in <code>lua.h</code>: 5132 1.4 mbalmer <a name="pdf-LUA_TNIL"><code>LUA_TNIL</code></a> (0), 5133 1.2 lneto <a name="pdf-LUA_TNUMBER"><code>LUA_TNUMBER</code></a>, 5134 1.2 lneto <a name="pdf-LUA_TBOOLEAN"><code>LUA_TBOOLEAN</code></a>, 5135 1.2 lneto <a name="pdf-LUA_TSTRING"><code>LUA_TSTRING</code></a>, 5136 1.2 lneto <a name="pdf-LUA_TTABLE"><code>LUA_TTABLE</code></a>, 5137 1.2 lneto <a name="pdf-LUA_TFUNCTION"><code>LUA_TFUNCTION</code></a>, 5138 1.2 lneto <a name="pdf-LUA_TUSERDATA"><code>LUA_TUSERDATA</code></a>, 5139 1.2 lneto <a name="pdf-LUA_TTHREAD"><code>LUA_TTHREAD</code></a>, 5140 1.1 mbalmer and 5141 1.2 lneto <a name="pdf-LUA_TLIGHTUSERDATA"><code>LUA_TLIGHTUSERDATA</code></a>. 5142 1.1 mbalmer 5143 1.1 mbalmer 5144 1.1 mbalmer 5145 1.1 mbalmer 5146 1.1 mbalmer 5147 1.1 mbalmer <hr><h3><a name="lua_typename"><code>lua_typename</code></a></h3><p> 5148 1.2 lneto <span class="apii">[-0, +0, –]</span> 5149 1.2 lneto <pre>const char *lua_typename (lua_State *L, int tp);</pre> 5150 1.1 mbalmer 5151 1.1 mbalmer <p> 5152 1.1 mbalmer Returns the name of the type encoded by the value <code>tp</code>, 5153 1.1 mbalmer which must be one the values returned by <a href="#lua_type"><code>lua_type</code></a>. 5154 1.1 mbalmer 5155 1.1 mbalmer 5156 1.1 mbalmer 5157 1.1 mbalmer 5158 1.1 mbalmer 5159 1.2 lneto <hr><h3><a name="lua_Unsigned"><code>lua_Unsigned</code></a></h3> 5160 1.2 lneto <pre>typedef ... lua_Unsigned;</pre> 5161 1.2 lneto 5162 1.2 lneto <p> 5163 1.2 lneto The unsigned version of <a href="#lua_Integer"><code>lua_Integer</code></a>. 5164 1.2 lneto 5165 1.2 lneto 5166 1.2 lneto 5167 1.2 lneto 5168 1.2 lneto 5169 1.2 lneto <hr><h3><a name="lua_upvalueindex"><code>lua_upvalueindex</code></a></h3><p> 5170 1.2 lneto <span class="apii">[-0, +0, –]</span> 5171 1.2 lneto <pre>int lua_upvalueindex (int i);</pre> 5172 1.2 lneto 5173 1.2 lneto <p> 5174 1.2 lneto Returns the pseudo-index that represents the <code>i</code>-th upvalue of 5175 1.2 lneto the running function (see <a href="#4.4">§4.4</a>). 5176 1.2 lneto 5177 1.2 lneto 5178 1.2 lneto 5179 1.2 lneto 5180 1.2 lneto 5181 1.2 lneto <hr><h3><a name="lua_version"><code>lua_version</code></a></h3><p> 5182 1.2 lneto <span class="apii">[-0, +0, <em>v</em>]</span> 5183 1.2 lneto <pre>const lua_Number *lua_version (lua_State *L);</pre> 5184 1.2 lneto 5185 1.2 lneto <p> 5186 1.2 lneto Returns the address of the version number stored in the Lua core. 5187 1.2 lneto When called with a valid <a href="#lua_State"><code>lua_State</code></a>, 5188 1.2 lneto returns the address of the version used to create that state. 5189 1.2 lneto When called with <code>NULL</code>, 5190 1.2 lneto returns the address of the version running the call. 5191 1.2 lneto 5192 1.2 lneto 5193 1.2 lneto 5194 1.2 lneto 5195 1.2 lneto 5196 1.1 mbalmer <hr><h3><a name="lua_Writer"><code>lua_Writer</code></a></h3> 5197 1.1 mbalmer <pre>typedef int (*lua_Writer) (lua_State *L, 5198 1.1 mbalmer const void* p, 5199 1.1 mbalmer size_t sz, 5200 1.1 mbalmer void* ud);</pre> 5201 1.1 mbalmer 5202 1.1 mbalmer <p> 5203 1.1 mbalmer The type of the writer function used by <a href="#lua_dump"><code>lua_dump</code></a>. 5204 1.1 mbalmer Every time it produces another piece of chunk, 5205 1.1 mbalmer <a href="#lua_dump"><code>lua_dump</code></a> calls the writer, 5206 1.1 mbalmer passing along the buffer to be written (<code>p</code>), 5207 1.1 mbalmer its size (<code>sz</code>), 5208 1.1 mbalmer and the <code>data</code> parameter supplied to <a href="#lua_dump"><code>lua_dump</code></a>. 5209 1.1 mbalmer 5210 1.1 mbalmer 5211 1.1 mbalmer <p> 5212 1.1 mbalmer The writer returns an error code: 5213 1.1 mbalmer 0 means no errors; 5214 1.1 mbalmer any other value means an error and stops <a href="#lua_dump"><code>lua_dump</code></a> from 5215 1.1 mbalmer calling the writer again. 5216 1.1 mbalmer 5217 1.1 mbalmer 5218 1.1 mbalmer 5219 1.1 mbalmer 5220 1.1 mbalmer 5221 1.1 mbalmer <hr><h3><a name="lua_xmove"><code>lua_xmove</code></a></h3><p> 5222 1.2 lneto <span class="apii">[-?, +?, –]</span> 5223 1.1 mbalmer <pre>void lua_xmove (lua_State *from, lua_State *to, int n);</pre> 5224 1.1 mbalmer 5225 1.1 mbalmer <p> 5226 1.2 lneto Exchange values between different threads of the same state. 5227 1.1 mbalmer 5228 1.1 mbalmer 5229 1.1 mbalmer <p> 5230 1.1 mbalmer This function pops <code>n</code> values from the stack <code>from</code>, 5231 1.1 mbalmer and pushes them onto the stack <code>to</code>. 5232 1.1 mbalmer 5233 1.1 mbalmer 5234 1.1 mbalmer 5235 1.1 mbalmer 5236 1.1 mbalmer 5237 1.1 mbalmer <hr><h3><a name="lua_yield"><code>lua_yield</code></a></h3><p> 5238 1.3 lneto <span class="apii">[-?, +?, <em>e</em>]</span> 5239 1.2 lneto <pre>int lua_yield (lua_State *L, int nresults);</pre> 5240 1.2 lneto 5241 1.2 lneto <p> 5242 1.2 lneto This function is equivalent to <a href="#lua_yieldk"><code>lua_yieldk</code></a>, 5243 1.2 lneto but it has no continuation (see <a href="#4.7">§4.7</a>). 5244 1.2 lneto Therefore, when the thread resumes, 5245 1.3 lneto it continues the function that called 5246 1.2 lneto the function calling <code>lua_yield</code>. 5247 1.2 lneto 5248 1.2 lneto 5249 1.2 lneto 5250 1.2 lneto 5251 1.2 lneto 5252 1.2 lneto <hr><h3><a name="lua_yieldk"><code>lua_yieldk</code></a></h3><p> 5253 1.3 lneto <span class="apii">[-?, +?, <em>e</em>]</span> 5254 1.3 lneto <pre>int lua_yieldk (lua_State *L, 5255 1.3 lneto int nresults, 5256 1.3 lneto lua_KContext ctx, 5257 1.3 lneto lua_KFunction k);</pre> 5258 1.1 mbalmer 5259 1.1 mbalmer <p> 5260 1.3 lneto Yields a coroutine (thread). 5261 1.1 mbalmer 5262 1.1 mbalmer 5263 1.1 mbalmer <p> 5264 1.3 lneto When a C function calls <a href="#lua_yieldk"><code>lua_yieldk</code></a>, 5265 1.1 mbalmer the running coroutine suspends its execution, 5266 1.1 mbalmer and the call to <a href="#lua_resume"><code>lua_resume</code></a> that started this coroutine returns. 5267 1.1 mbalmer The parameter <code>nresults</code> is the number of values from the stack 5268 1.2 lneto that will be passed as results to <a href="#lua_resume"><code>lua_resume</code></a>. 5269 1.2 lneto 5270 1.2 lneto 5271 1.2 lneto <p> 5272 1.2 lneto When the coroutine is resumed again, 5273 1.2 lneto Lua calls the given continuation function <code>k</code> to continue 5274 1.2 lneto the execution of the C function that yielded (see <a href="#4.7">§4.7</a>). 5275 1.2 lneto This continuation function receives the same stack 5276 1.2 lneto from the previous function, 5277 1.2 lneto with the <code>n</code> results removed and 5278 1.2 lneto replaced by the arguments passed to <a href="#lua_resume"><code>lua_resume</code></a>. 5279 1.2 lneto Moreover, 5280 1.2 lneto the continuation function receives the value <code>ctx</code> 5281 1.2 lneto that was passed to <a href="#lua_yieldk"><code>lua_yieldk</code></a>. 5282 1.1 mbalmer 5283 1.1 mbalmer 5284 1.3 lneto <p> 5285 1.3 lneto Usually, this function does not return; 5286 1.3 lneto when the coroutine eventually resumes, 5287 1.3 lneto it continues executing the continuation function. 5288 1.3 lneto However, there is one special case, 5289 1.3 lneto which is when this function is called 5290 1.3 lneto from inside a line hook (see <a href="#4.9">§4.9</a>). 5291 1.3 lneto In that case, <code>lua_yieldk</code> should be called with no continuation 5292 1.3 lneto (probably in the form of <a href="#lua_yield"><code>lua_yield</code></a>), 5293 1.3 lneto and the hook should return immediately after the call. 5294 1.3 lneto Lua will yield and, 5295 1.3 lneto when the coroutine resumes again, 5296 1.3 lneto it will continue the normal execution 5297 1.3 lneto of the (Lua) function that triggered the hook. 5298 1.3 lneto 5299 1.3 lneto 5300 1.3 lneto <p> 5301 1.3 lneto This function can raise an error if it is called from a thread 5302 1.3 lneto with a pending C call with no continuation function, 5303 1.3 lneto or it is called from a thread that is not running inside a resume 5304 1.3 lneto (e.g., the main thread). 5305 1.3 lneto 5306 1.3 lneto 5307 1.1 mbalmer 5308 1.1 mbalmer 5309 1.1 mbalmer 5310 1.1 mbalmer 5311 1.1 mbalmer 5312 1.2 lneto <h2>4.9 – <a name="4.9">The Debug Interface</a></h2> 5313 1.1 mbalmer 5314 1.1 mbalmer <p> 5315 1.1 mbalmer Lua has no built-in debugging facilities. 5316 1.1 mbalmer Instead, it offers a special interface 5317 1.1 mbalmer by means of functions and <em>hooks</em>. 5318 1.1 mbalmer This interface allows the construction of different 5319 1.1 mbalmer kinds of debuggers, profilers, and other tools 5320 1.1 mbalmer that need "inside information" from the interpreter. 5321 1.1 mbalmer 5322 1.1 mbalmer 5323 1.1 mbalmer 5324 1.1 mbalmer <hr><h3><a name="lua_Debug"><code>lua_Debug</code></a></h3> 5325 1.1 mbalmer <pre>typedef struct lua_Debug { 5326 1.1 mbalmer int event; 5327 1.1 mbalmer const char *name; /* (n) */ 5328 1.1 mbalmer const char *namewhat; /* (n) */ 5329 1.1 mbalmer const char *what; /* (S) */ 5330 1.1 mbalmer const char *source; /* (S) */ 5331 1.1 mbalmer int currentline; /* (l) */ 5332 1.1 mbalmer int linedefined; /* (S) */ 5333 1.1 mbalmer int lastlinedefined; /* (S) */ 5334 1.2 lneto unsigned char nups; /* (u) number of upvalues */ 5335 1.2 lneto unsigned char nparams; /* (u) number of parameters */ 5336 1.2 lneto char isvararg; /* (u) */ 5337 1.2 lneto char istailcall; /* (t) */ 5338 1.1 mbalmer char short_src[LUA_IDSIZE]; /* (S) */ 5339 1.1 mbalmer /* private part */ 5340 1.1 mbalmer <em>other fields</em> 5341 1.1 mbalmer } lua_Debug;</pre> 5342 1.1 mbalmer 5343 1.1 mbalmer <p> 5344 1.1 mbalmer A structure used to carry different pieces of 5345 1.2 lneto information about a function or an activation record. 5346 1.1 mbalmer <a href="#lua_getstack"><code>lua_getstack</code></a> fills only the private part 5347 1.1 mbalmer of this structure, for later use. 5348 1.1 mbalmer To fill the other fields of <a href="#lua_Debug"><code>lua_Debug</code></a> with useful information, 5349 1.1 mbalmer call <a href="#lua_getinfo"><code>lua_getinfo</code></a>. 5350 1.1 mbalmer 5351 1.1 mbalmer 5352 1.1 mbalmer <p> 5353 1.1 mbalmer The fields of <a href="#lua_Debug"><code>lua_Debug</code></a> have the following meaning: 5354 1.1 mbalmer 5355 1.1 mbalmer <ul> 5356 1.1 mbalmer 5357 1.2 lneto <li><b><code>source</code>: </b> 5358 1.3 lneto the name of the chunk that created the function. 5359 1.2 lneto If <code>source</code> starts with a '<code>@</code>', 5360 1.2 lneto it means that the function was defined in a file where 5361 1.2 lneto the file name follows the '<code>@</code>'. 5362 1.2 lneto If <code>source</code> starts with a '<code>=</code>', 5363 1.2 lneto the remainder of its contents describe the source in a user-dependent manner. 5364 1.2 lneto Otherwise, 5365 1.2 lneto the function was defined in a string where 5366 1.2 lneto <code>source</code> is that string. 5367 1.1 mbalmer </li> 5368 1.1 mbalmer 5369 1.2 lneto <li><b><code>short_src</code>: </b> 5370 1.1 mbalmer a "printable" version of <code>source</code>, to be used in error messages. 5371 1.1 mbalmer </li> 5372 1.1 mbalmer 5373 1.2 lneto <li><b><code>linedefined</code>: </b> 5374 1.1 mbalmer the line number where the definition of the function starts. 5375 1.1 mbalmer </li> 5376 1.1 mbalmer 5377 1.2 lneto <li><b><code>lastlinedefined</code>: </b> 5378 1.1 mbalmer the line number where the definition of the function ends. 5379 1.1 mbalmer </li> 5380 1.1 mbalmer 5381 1.2 lneto <li><b><code>what</code>: </b> 5382 1.1 mbalmer the string <code>"Lua"</code> if the function is a Lua function, 5383 1.1 mbalmer <code>"C"</code> if it is a C function, 5384 1.2 lneto <code>"main"</code> if it is the main part of a chunk. 5385 1.1 mbalmer </li> 5386 1.1 mbalmer 5387 1.2 lneto <li><b><code>currentline</code>: </b> 5388 1.1 mbalmer the current line where the given function is executing. 5389 1.1 mbalmer When no line information is available, 5390 1.1 mbalmer <code>currentline</code> is set to -1. 5391 1.1 mbalmer </li> 5392 1.1 mbalmer 5393 1.2 lneto <li><b><code>name</code>: </b> 5394 1.1 mbalmer a reasonable name for the given function. 5395 1.1 mbalmer Because functions in Lua are first-class values, 5396 1.1 mbalmer they do not have a fixed name: 5397 1.1 mbalmer some functions can be the value of multiple global variables, 5398 1.1 mbalmer while others can be stored only in a table field. 5399 1.1 mbalmer The <code>lua_getinfo</code> function checks how the function was 5400 1.1 mbalmer called to find a suitable name. 5401 1.1 mbalmer If it cannot find a name, 5402 1.1 mbalmer then <code>name</code> is set to <code>NULL</code>. 5403 1.1 mbalmer </li> 5404 1.1 mbalmer 5405 1.2 lneto <li><b><code>namewhat</code>: </b> 5406 1.1 mbalmer explains the <code>name</code> field. 5407 1.1 mbalmer The value of <code>namewhat</code> can be 5408 1.1 mbalmer <code>"global"</code>, <code>"local"</code>, <code>"method"</code>, 5409 1.1 mbalmer <code>"field"</code>, <code>"upvalue"</code>, or <code>""</code> (the empty string), 5410 1.1 mbalmer according to how the function was called. 5411 1.1 mbalmer (Lua uses the empty string when no other option seems to apply.) 5412 1.1 mbalmer </li> 5413 1.1 mbalmer 5414 1.2 lneto <li><b><code>istailcall</code>: </b> 5415 1.2 lneto true if this function invocation was called by a tail call. 5416 1.2 lneto In this case, the caller of this level is not in the stack. 5417 1.2 lneto </li> 5418 1.2 lneto 5419 1.2 lneto <li><b><code>nups</code>: </b> 5420 1.1 mbalmer the number of upvalues of the function. 5421 1.1 mbalmer </li> 5422 1.1 mbalmer 5423 1.2 lneto <li><b><code>nparams</code>: </b> 5424 1.2 lneto the number of fixed parameters of the function 5425 1.2 lneto (always 0 for C functions). 5426 1.2 lneto </li> 5427 1.2 lneto 5428 1.2 lneto <li><b><code>isvararg</code>: </b> 5429 1.2 lneto true if the function is a vararg function 5430 1.2 lneto (always true for C functions). 5431 1.2 lneto </li> 5432 1.2 lneto 5433 1.1 mbalmer </ul> 5434 1.1 mbalmer 5435 1.1 mbalmer 5436 1.1 mbalmer 5437 1.1 mbalmer 5438 1.1 mbalmer <hr><h3><a name="lua_gethook"><code>lua_gethook</code></a></h3><p> 5439 1.2 lneto <span class="apii">[-0, +0, –]</span> 5440 1.1 mbalmer <pre>lua_Hook lua_gethook (lua_State *L);</pre> 5441 1.1 mbalmer 5442 1.1 mbalmer <p> 5443 1.1 mbalmer Returns the current hook function. 5444 1.1 mbalmer 5445 1.1 mbalmer 5446 1.1 mbalmer 5447 1.1 mbalmer 5448 1.1 mbalmer 5449 1.1 mbalmer <hr><h3><a name="lua_gethookcount"><code>lua_gethookcount</code></a></h3><p> 5450 1.2 lneto <span class="apii">[-0, +0, –]</span> 5451 1.1 mbalmer <pre>int lua_gethookcount (lua_State *L);</pre> 5452 1.1 mbalmer 5453 1.1 mbalmer <p> 5454 1.1 mbalmer Returns the current hook count. 5455 1.1 mbalmer 5456 1.1 mbalmer 5457 1.1 mbalmer 5458 1.1 mbalmer 5459 1.1 mbalmer 5460 1.1 mbalmer <hr><h3><a name="lua_gethookmask"><code>lua_gethookmask</code></a></h3><p> 5461 1.2 lneto <span class="apii">[-0, +0, –]</span> 5462 1.1 mbalmer <pre>int lua_gethookmask (lua_State *L);</pre> 5463 1.1 mbalmer 5464 1.1 mbalmer <p> 5465 1.1 mbalmer Returns the current hook mask. 5466 1.1 mbalmer 5467 1.1 mbalmer 5468 1.1 mbalmer 5469 1.1 mbalmer 5470 1.1 mbalmer 5471 1.1 mbalmer <hr><h3><a name="lua_getinfo"><code>lua_getinfo</code></a></h3><p> 5472 1.2 lneto <span class="apii">[-(0|1), +(0|1|2), <em>e</em>]</span> 5473 1.1 mbalmer <pre>int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar);</pre> 5474 1.1 mbalmer 5475 1.1 mbalmer <p> 5476 1.2 lneto Gets information about a specific function or function invocation. 5477 1.1 mbalmer 5478 1.1 mbalmer 5479 1.1 mbalmer <p> 5480 1.1 mbalmer To get information about a function invocation, 5481 1.1 mbalmer the parameter <code>ar</code> must be a valid activation record that was 5482 1.1 mbalmer filled by a previous call to <a href="#lua_getstack"><code>lua_getstack</code></a> or 5483 1.1 mbalmer given as argument to a hook (see <a href="#lua_Hook"><code>lua_Hook</code></a>). 5484 1.1 mbalmer 5485 1.1 mbalmer 5486 1.1 mbalmer <p> 5487 1.1 mbalmer To get information about a function you push it onto the stack 5488 1.1 mbalmer and start the <code>what</code> string with the character '<code>></code>'. 5489 1.1 mbalmer (In that case, 5490 1.2 lneto <code>lua_getinfo</code> pops the function from the top of the stack.) 5491 1.1 mbalmer For instance, to know in which line a function <code>f</code> was defined, 5492 1.1 mbalmer you can write the following code: 5493 1.1 mbalmer 5494 1.1 mbalmer <pre> 5495 1.1 mbalmer lua_Debug ar; 5496 1.2 lneto lua_getglobal(L, "f"); /* get global 'f' */ 5497 1.1 mbalmer lua_getinfo(L, ">S", &ar); 5498 1.1 mbalmer printf("%d\n", ar.linedefined); 5499 1.1 mbalmer </pre> 5500 1.1 mbalmer 5501 1.1 mbalmer <p> 5502 1.1 mbalmer Each character in the string <code>what</code> 5503 1.1 mbalmer selects some fields of the structure <code>ar</code> to be filled or 5504 1.1 mbalmer a value to be pushed on the stack: 5505 1.1 mbalmer 5506 1.1 mbalmer <ul> 5507 1.1 mbalmer 5508 1.2 lneto <li><b>'<code>n</code>': </b> fills in the field <code>name</code> and <code>namewhat</code>; 5509 1.1 mbalmer </li> 5510 1.1 mbalmer 5511 1.2 lneto <li><b>'<code>S</code>': </b> 5512 1.1 mbalmer fills in the fields <code>source</code>, <code>short_src</code>, 5513 1.1 mbalmer <code>linedefined</code>, <code>lastlinedefined</code>, and <code>what</code>; 5514 1.1 mbalmer </li> 5515 1.1 mbalmer 5516 1.2 lneto <li><b>'<code>l</code>': </b> fills in the field <code>currentline</code>; 5517 1.2 lneto </li> 5518 1.2 lneto 5519 1.2 lneto <li><b>'<code>t</code>': </b> fills in the field <code>istailcall</code>; 5520 1.1 mbalmer </li> 5521 1.1 mbalmer 5522 1.2 lneto <li><b>'<code>u</code>': </b> fills in the fields 5523 1.2 lneto <code>nups</code>, <code>nparams</code>, and <code>isvararg</code>; 5524 1.1 mbalmer </li> 5525 1.1 mbalmer 5526 1.2 lneto <li><b>'<code>f</code>': </b> 5527 1.1 mbalmer pushes onto the stack the function that is 5528 1.1 mbalmer running at the given level; 5529 1.1 mbalmer </li> 5530 1.1 mbalmer 5531 1.2 lneto <li><b>'<code>L</code>': </b> 5532 1.1 mbalmer pushes onto the stack a table whose indices are the 5533 1.1 mbalmer numbers of the lines that are valid on the function. 5534 1.1 mbalmer (A <em>valid line</em> is a line with some associated code, 5535 1.1 mbalmer that is, a line where you can put a break point. 5536 1.1 mbalmer Non-valid lines include empty lines and comments.) 5537 1.2 lneto 5538 1.2 lneto 5539 1.2 lneto <p> 5540 1.2 lneto If this option is given together with option '<code>f</code>', 5541 1.2 lneto its table is pushed after the function. 5542 1.1 mbalmer </li> 5543 1.1 mbalmer 5544 1.1 mbalmer </ul> 5545 1.1 mbalmer 5546 1.1 mbalmer <p> 5547 1.1 mbalmer This function returns 0 on error 5548 1.1 mbalmer (for instance, an invalid option in <code>what</code>). 5549 1.1 mbalmer 5550 1.1 mbalmer 5551 1.1 mbalmer 5552 1.1 mbalmer 5553 1.1 mbalmer 5554 1.1 mbalmer <hr><h3><a name="lua_getlocal"><code>lua_getlocal</code></a></h3><p> 5555 1.2 lneto <span class="apii">[-0, +(0|1), –]</span> 5556 1.3 lneto <pre>const char *lua_getlocal (lua_State *L, const lua_Debug *ar, int n);</pre> 5557 1.1 mbalmer 5558 1.1 mbalmer <p> 5559 1.2 lneto Gets information about a local variable of 5560 1.2 lneto a given activation record or a given function. 5561 1.2 lneto 5562 1.2 lneto 5563 1.2 lneto <p> 5564 1.2 lneto In the first case, 5565 1.2 lneto the parameter <code>ar</code> must be a valid activation record that was 5566 1.1 mbalmer filled by a previous call to <a href="#lua_getstack"><code>lua_getstack</code></a> or 5567 1.1 mbalmer given as argument to a hook (see <a href="#lua_Hook"><code>lua_Hook</code></a>). 5568 1.2 lneto The index <code>n</code> selects which local variable to inspect; 5569 1.2 lneto see <a href="#pdf-debug.getlocal"><code>debug.getlocal</code></a> for details about variable indices 5570 1.2 lneto and names. 5571 1.2 lneto 5572 1.2 lneto 5573 1.2 lneto <p> 5574 1.1 mbalmer <a href="#lua_getlocal"><code>lua_getlocal</code></a> pushes the variable's value onto the stack 5575 1.1 mbalmer and returns its name. 5576 1.1 mbalmer 5577 1.1 mbalmer 5578 1.1 mbalmer <p> 5579 1.2 lneto In the second case, <code>ar</code> must be <code>NULL</code> and the function 5580 1.2 lneto to be inspected must be at the top of the stack. 5581 1.2 lneto In this case, only parameters of Lua functions are visible 5582 1.2 lneto (as there is no information about what variables are active) 5583 1.2 lneto and no values are pushed onto the stack. 5584 1.1 mbalmer 5585 1.1 mbalmer 5586 1.1 mbalmer <p> 5587 1.1 mbalmer Returns <code>NULL</code> (and pushes nothing) 5588 1.1 mbalmer when the index is greater than 5589 1.1 mbalmer the number of active local variables. 5590 1.1 mbalmer 5591 1.1 mbalmer 5592 1.1 mbalmer 5593 1.1 mbalmer 5594 1.1 mbalmer 5595 1.1 mbalmer <hr><h3><a name="lua_getstack"><code>lua_getstack</code></a></h3><p> 5596 1.2 lneto <span class="apii">[-0, +0, –]</span> 5597 1.1 mbalmer <pre>int lua_getstack (lua_State *L, int level, lua_Debug *ar);</pre> 5598 1.1 mbalmer 5599 1.1 mbalmer <p> 5600 1.2 lneto Gets information about the interpreter runtime stack. 5601 1.1 mbalmer 5602 1.1 mbalmer 5603 1.1 mbalmer <p> 5604 1.1 mbalmer This function fills parts of a <a href="#lua_Debug"><code>lua_Debug</code></a> structure with 5605 1.1 mbalmer an identification of the <em>activation record</em> 5606 1.1 mbalmer of the function executing at a given level. 5607 1.1 mbalmer Level 0 is the current running function, 5608 1.2 lneto whereas level <em>n+1</em> is the function that has called level <em>n</em> 5609 1.2 lneto (except for tail calls, which do not count on the stack). 5610 1.1 mbalmer When there are no errors, <a href="#lua_getstack"><code>lua_getstack</code></a> returns 1; 5611 1.1 mbalmer when called with a level greater than the stack depth, 5612 1.1 mbalmer it returns 0. 5613 1.1 mbalmer 5614 1.1 mbalmer 5615 1.1 mbalmer 5616 1.1 mbalmer 5617 1.1 mbalmer 5618 1.1 mbalmer <hr><h3><a name="lua_getupvalue"><code>lua_getupvalue</code></a></h3><p> 5619 1.2 lneto <span class="apii">[-0, +(0|1), –]</span> 5620 1.1 mbalmer <pre>const char *lua_getupvalue (lua_State *L, int funcindex, int n);</pre> 5621 1.1 mbalmer 5622 1.1 mbalmer <p> 5623 1.4 mbalmer Gets information about the <code>n</code>-th upvalue 5624 1.4 mbalmer of the closure at index <code>funcindex</code>. 5625 1.4 mbalmer It pushes the upvalue's value onto the stack 5626 1.4 mbalmer and returns its name. 5627 1.4 mbalmer Returns <code>NULL</code> (and pushes nothing) 5628 1.4 mbalmer when the index <code>n</code> is greater than the number of upvalues. 5629 1.4 mbalmer 5630 1.4 mbalmer 5631 1.4 mbalmer <p> 5632 1.4 mbalmer For C functions, this function uses the empty string <code>""</code> 5633 1.4 mbalmer as a name for all upvalues. 5634 1.1 mbalmer (For Lua functions, 5635 1.1 mbalmer upvalues are the external local variables that the function uses, 5636 1.1 mbalmer and that are consequently included in its closure.) 5637 1.1 mbalmer 5638 1.1 mbalmer 5639 1.1 mbalmer <p> 5640 1.4 mbalmer Upvalues have no particular order, 5641 1.4 mbalmer as they are active through the whole function. 5642 1.4 mbalmer They are numbered in an arbitrary order. 5643 1.1 mbalmer 5644 1.1 mbalmer 5645 1.1 mbalmer 5646 1.1 mbalmer 5647 1.1 mbalmer 5648 1.1 mbalmer <hr><h3><a name="lua_Hook"><code>lua_Hook</code></a></h3> 5649 1.1 mbalmer <pre>typedef void (*lua_Hook) (lua_State *L, lua_Debug *ar);</pre> 5650 1.1 mbalmer 5651 1.1 mbalmer <p> 5652 1.1 mbalmer Type for debugging hook functions. 5653 1.1 mbalmer 5654 1.1 mbalmer 5655 1.1 mbalmer <p> 5656 1.1 mbalmer Whenever a hook is called, its <code>ar</code> argument has its field 5657 1.1 mbalmer <code>event</code> set to the specific event that triggered the hook. 5658 1.1 mbalmer Lua identifies these events with the following constants: 5659 1.1 mbalmer <a name="pdf-LUA_HOOKCALL"><code>LUA_HOOKCALL</code></a>, <a name="pdf-LUA_HOOKRET"><code>LUA_HOOKRET</code></a>, 5660 1.2 lneto <a name="pdf-LUA_HOOKTAILCALL"><code>LUA_HOOKTAILCALL</code></a>, <a name="pdf-LUA_HOOKLINE"><code>LUA_HOOKLINE</code></a>, 5661 1.1 mbalmer and <a name="pdf-LUA_HOOKCOUNT"><code>LUA_HOOKCOUNT</code></a>. 5662 1.1 mbalmer Moreover, for line events, the field <code>currentline</code> is also set. 5663 1.1 mbalmer To get the value of any other field in <code>ar</code>, 5664 1.1 mbalmer the hook must call <a href="#lua_getinfo"><code>lua_getinfo</code></a>. 5665 1.2 lneto 5666 1.2 lneto 5667 1.2 lneto <p> 5668 1.2 lneto For call events, <code>event</code> can be <code>LUA_HOOKCALL</code>, 5669 1.2 lneto the normal value, or <code>LUA_HOOKTAILCALL</code>, for a tail call; 5670 1.2 lneto in this case, there will be no corresponding return event. 5671 1.1 mbalmer 5672 1.1 mbalmer 5673 1.1 mbalmer <p> 5674 1.1 mbalmer While Lua is running a hook, it disables other calls to hooks. 5675 1.1 mbalmer Therefore, if a hook calls back Lua to execute a function or a chunk, 5676 1.1 mbalmer this execution occurs without any calls to hooks. 5677 1.1 mbalmer 5678 1.1 mbalmer 5679 1.2 lneto <p> 5680 1.2 lneto Hook functions cannot have continuations, 5681 1.2 lneto that is, they cannot call <a href="#lua_yieldk"><code>lua_yieldk</code></a>, 5682 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>. 5683 1.2 lneto 5684 1.2 lneto 5685 1.2 lneto <p> 5686 1.2 lneto Hook functions can yield under the following conditions: 5687 1.4 mbalmer Only count and line events can yield; 5688 1.4 mbalmer to yield, a hook function must finish its execution 5689 1.4 mbalmer calling <a href="#lua_yield"><code>lua_yield</code></a> with <code>nresults</code> equal to zero 5690 1.4 mbalmer (that is, with no values). 5691 1.2 lneto 5692 1.2 lneto 5693 1.1 mbalmer 5694 1.1 mbalmer 5695 1.1 mbalmer 5696 1.1 mbalmer <hr><h3><a name="lua_sethook"><code>lua_sethook</code></a></h3><p> 5697 1.2 lneto <span class="apii">[-0, +0, –]</span> 5698 1.2 lneto <pre>void lua_sethook (lua_State *L, lua_Hook f, int mask, int count);</pre> 5699 1.1 mbalmer 5700 1.1 mbalmer <p> 5701 1.1 mbalmer Sets the debugging hook function. 5702 1.1 mbalmer 5703 1.1 mbalmer 5704 1.1 mbalmer <p> 5705 1.1 mbalmer Argument <code>f</code> is the hook function. 5706 1.1 mbalmer <code>mask</code> specifies on which events the hook will be called: 5707 1.1 mbalmer it is formed by a bitwise or of the constants 5708 1.1 mbalmer <a name="pdf-LUA_MASKCALL"><code>LUA_MASKCALL</code></a>, 5709 1.1 mbalmer <a name="pdf-LUA_MASKRET"><code>LUA_MASKRET</code></a>, 5710 1.1 mbalmer <a name="pdf-LUA_MASKLINE"><code>LUA_MASKLINE</code></a>, 5711 1.1 mbalmer and <a name="pdf-LUA_MASKCOUNT"><code>LUA_MASKCOUNT</code></a>. 5712 1.1 mbalmer The <code>count</code> argument is only meaningful when the mask 5713 1.1 mbalmer includes <code>LUA_MASKCOUNT</code>. 5714 1.1 mbalmer For each event, the hook is called as explained below: 5715 1.1 mbalmer 5716 1.1 mbalmer <ul> 5717 1.1 mbalmer 5718 1.2 lneto <li><b>The call hook: </b> is called when the interpreter calls a function. 5719 1.1 mbalmer The hook is called just after Lua enters the new function, 5720 1.1 mbalmer before the function gets its arguments. 5721 1.1 mbalmer </li> 5722 1.1 mbalmer 5723 1.2 lneto <li><b>The return hook: </b> is called when the interpreter returns from a function. 5724 1.1 mbalmer The hook is called just before Lua leaves the function. 5725 1.2 lneto There is no standard way to access the values 5726 1.2 lneto to be returned by the function. 5727 1.1 mbalmer </li> 5728 1.1 mbalmer 5729 1.2 lneto <li><b>The line hook: </b> is called when the interpreter is about to 5730 1.1 mbalmer start the execution of a new line of code, 5731 1.1 mbalmer or when it jumps back in the code (even to the same line). 5732 1.1 mbalmer (This event only happens while Lua is executing a Lua function.) 5733 1.1 mbalmer </li> 5734 1.1 mbalmer 5735 1.2 lneto <li><b>The count hook: </b> is called after the interpreter executes every 5736 1.1 mbalmer <code>count</code> instructions. 5737 1.1 mbalmer (This event only happens while Lua is executing a Lua function.) 5738 1.1 mbalmer </li> 5739 1.1 mbalmer 5740 1.1 mbalmer </ul> 5741 1.1 mbalmer 5742 1.1 mbalmer <p> 5743 1.1 mbalmer A hook is disabled by setting <code>mask</code> to zero. 5744 1.1 mbalmer 5745 1.1 mbalmer 5746 1.1 mbalmer 5747 1.1 mbalmer 5748 1.1 mbalmer 5749 1.1 mbalmer <hr><h3><a name="lua_setlocal"><code>lua_setlocal</code></a></h3><p> 5750 1.2 lneto <span class="apii">[-(0|1), +0, –]</span> 5751 1.3 lneto <pre>const char *lua_setlocal (lua_State *L, const lua_Debug *ar, int n);</pre> 5752 1.1 mbalmer 5753 1.1 mbalmer <p> 5754 1.1 mbalmer Sets the value of a local variable of a given activation record. 5755 1.4 mbalmer It assigns the value at the top of the stack 5756 1.1 mbalmer to the variable and returns its name. 5757 1.1 mbalmer It also pops the value from the stack. 5758 1.1 mbalmer 5759 1.1 mbalmer 5760 1.1 mbalmer <p> 5761 1.1 mbalmer Returns <code>NULL</code> (and pops nothing) 5762 1.1 mbalmer when the index is greater than 5763 1.1 mbalmer the number of active local variables. 5764 1.1 mbalmer 5765 1.1 mbalmer 5766 1.4 mbalmer <p> 5767 1.4 mbalmer Parameters <code>ar</code> and <code>n</code> are as in function <a href="#lua_getlocal"><code>lua_getlocal</code></a>. 5768 1.4 mbalmer 5769 1.4 mbalmer 5770 1.1 mbalmer 5771 1.1 mbalmer 5772 1.1 mbalmer 5773 1.1 mbalmer <hr><h3><a name="lua_setupvalue"><code>lua_setupvalue</code></a></h3><p> 5774 1.2 lneto <span class="apii">[-(0|1), +0, –]</span> 5775 1.1 mbalmer <pre>const char *lua_setupvalue (lua_State *L, int funcindex, int n);</pre> 5776 1.1 mbalmer 5777 1.1 mbalmer <p> 5778 1.1 mbalmer Sets the value of a closure's upvalue. 5779 1.1 mbalmer It assigns the value at the top of the stack 5780 1.1 mbalmer to the upvalue and returns its name. 5781 1.1 mbalmer It also pops the value from the stack. 5782 1.1 mbalmer 5783 1.1 mbalmer 5784 1.1 mbalmer <p> 5785 1.1 mbalmer Returns <code>NULL</code> (and pops nothing) 5786 1.4 mbalmer when the index <code>n</code> is greater than the number of upvalues. 5787 1.4 mbalmer 5788 1.4 mbalmer 5789 1.4 mbalmer <p> 5790 1.4 mbalmer Parameters <code>funcindex</code> and <code>n</code> are as in function <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>. 5791 1.1 mbalmer 5792 1.1 mbalmer 5793 1.1 mbalmer 5794 1.1 mbalmer 5795 1.1 mbalmer 5796 1.2 lneto <hr><h3><a name="lua_upvalueid"><code>lua_upvalueid</code></a></h3><p> 5797 1.2 lneto <span class="apii">[-0, +0, –]</span> 5798 1.2 lneto <pre>void *lua_upvalueid (lua_State *L, int funcindex, int n);</pre> 5799 1.2 lneto 5800 1.2 lneto <p> 5801 1.3 lneto Returns a unique identifier for the upvalue numbered <code>n</code> 5802 1.2 lneto from the closure at index <code>funcindex</code>. 5803 1.2 lneto 5804 1.2 lneto 5805 1.2 lneto <p> 5806 1.2 lneto These unique identifiers allow a program to check whether different 5807 1.2 lneto closures share upvalues. 5808 1.2 lneto Lua closures that share an upvalue 5809 1.2 lneto (that is, that access a same external local variable) 5810 1.2 lneto will return identical ids for those upvalue indices. 5811 1.2 lneto 5812 1.2 lneto 5813 1.4 mbalmer <p> 5814 1.4 mbalmer Parameters <code>funcindex</code> and <code>n</code> are as in function <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>, 5815 1.4 mbalmer but <code>n</code> cannot be greater than the number of upvalues. 5816 1.4 mbalmer 5817 1.4 mbalmer 5818 1.2 lneto 5819 1.2 lneto 5820 1.2 lneto 5821 1.2 lneto <hr><h3><a name="lua_upvaluejoin"><code>lua_upvaluejoin</code></a></h3><p> 5822 1.2 lneto <span class="apii">[-0, +0, –]</span> 5823 1.2 lneto <pre>void lua_upvaluejoin (lua_State *L, int funcindex1, int n1, 5824 1.2 lneto int funcindex2, int n2);</pre> 5825 1.2 lneto 5826 1.2 lneto <p> 5827 1.2 lneto Make the <code>n1</code>-th upvalue of the Lua closure at index <code>funcindex1</code> 5828 1.2 lneto refer to the <code>n2</code>-th upvalue of the Lua closure at index <code>funcindex2</code>. 5829 1.2 lneto 5830 1.2 lneto 5831 1.2 lneto 5832 1.2 lneto 5833 1.2 lneto 5834 1.1 mbalmer 5835 1.1 mbalmer 5836 1.2 lneto <h1>5 – <a name="5">The Auxiliary Library</a></h1> 5837 1.1 mbalmer 5838 1.1 mbalmer <p> 5839 1.1 mbalmer 5840 1.1 mbalmer The <em>auxiliary library</em> provides several convenient functions 5841 1.1 mbalmer to interface C with Lua. 5842 1.2 lneto While the basic API provides the primitive functions for all 5843 1.1 mbalmer interactions between C and Lua, 5844 1.1 mbalmer the auxiliary library provides higher-level functions for some 5845 1.1 mbalmer common tasks. 5846 1.1 mbalmer 5847 1.1 mbalmer 5848 1.1 mbalmer <p> 5849 1.2 lneto All functions and types from the auxiliary library 5850 1.1 mbalmer are defined in header file <code>lauxlib.h</code> and 5851 1.1 mbalmer have a prefix <code>luaL_</code>. 5852 1.1 mbalmer 5853 1.1 mbalmer 5854 1.1 mbalmer <p> 5855 1.1 mbalmer All functions in the auxiliary library are built on 5856 1.1 mbalmer top of the basic API, 5857 1.2 lneto and so they provide nothing that cannot be done with that API. 5858 1.2 lneto Nevertheless, the use of the auxiliary library ensures 5859 1.2 lneto more consistency to your code. 5860 1.2 lneto 5861 1.2 lneto 5862 1.2 lneto <p> 5863 1.2 lneto Several functions in the auxiliary library use internally some 5864 1.2 lneto extra stack slots. 5865 1.2 lneto When a function in the auxiliary library uses less than five slots, 5866 1.2 lneto it does not check the stack size; 5867 1.2 lneto it simply assumes that there are enough slots. 5868 1.1 mbalmer 5869 1.1 mbalmer 5870 1.1 mbalmer <p> 5871 1.1 mbalmer Several functions in the auxiliary library are used to 5872 1.1 mbalmer check C function arguments. 5873 1.1 mbalmer Because the error message is formatted for arguments 5874 1.1 mbalmer (e.g., "<code>bad argument #1</code>"), 5875 1.1 mbalmer you should not use these functions for other stack values. 5876 1.1 mbalmer 5877 1.1 mbalmer 5878 1.2 lneto <p> 5879 1.2 lneto Functions called <code>luaL_check*</code> 5880 1.2 lneto always raise an error if the check is not satisfied. 5881 1.2 lneto 5882 1.2 lneto 5883 1.1 mbalmer 5884 1.2 lneto <h2>5.1 – <a name="5.1">Functions and Types</a></h2> 5885 1.1 mbalmer 5886 1.1 mbalmer <p> 5887 1.1 mbalmer Here we list all functions and types from the auxiliary library 5888 1.1 mbalmer in alphabetical order. 5889 1.1 mbalmer 5890 1.1 mbalmer 5891 1.1 mbalmer 5892 1.1 mbalmer <hr><h3><a name="luaL_addchar"><code>luaL_addchar</code></a></h3><p> 5893 1.5 lneto <span class="apii">[-?, +?, <em>m</em>]</span> 5894 1.1 mbalmer <pre>void luaL_addchar (luaL_Buffer *B, char c);</pre> 5895 1.1 mbalmer 5896 1.1 mbalmer <p> 5897 1.2 lneto Adds the byte <code>c</code> to the buffer <code>B</code> 5898 1.1 mbalmer (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>). 5899 1.1 mbalmer 5900 1.1 mbalmer 5901 1.1 mbalmer 5902 1.1 mbalmer 5903 1.1 mbalmer 5904 1.1 mbalmer <hr><h3><a name="luaL_addlstring"><code>luaL_addlstring</code></a></h3><p> 5905 1.5 lneto <span class="apii">[-?, +?, <em>m</em>]</span> 5906 1.1 mbalmer <pre>void luaL_addlstring (luaL_Buffer *B, const char *s, size_t l);</pre> 5907 1.1 mbalmer 5908 1.1 mbalmer <p> 5909 1.1 mbalmer Adds the string pointed to by <code>s</code> with length <code>l</code> to 5910 1.1 mbalmer the buffer <code>B</code> 5911 1.1 mbalmer (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>). 5912 1.2 lneto The string can contain embedded zeros. 5913 1.1 mbalmer 5914 1.1 mbalmer 5915 1.1 mbalmer 5916 1.1 mbalmer 5917 1.1 mbalmer 5918 1.1 mbalmer <hr><h3><a name="luaL_addsize"><code>luaL_addsize</code></a></h3><p> 5919 1.5 lneto <span class="apii">[-?, +?, –]</span> 5920 1.1 mbalmer <pre>void luaL_addsize (luaL_Buffer *B, size_t n);</pre> 5921 1.1 mbalmer 5922 1.1 mbalmer <p> 5923 1.1 mbalmer Adds to the buffer <code>B</code> (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>) 5924 1.1 mbalmer a string of length <code>n</code> previously copied to the 5925 1.1 mbalmer buffer area (see <a href="#luaL_prepbuffer"><code>luaL_prepbuffer</code></a>). 5926 1.1 mbalmer 5927 1.1 mbalmer 5928 1.1 mbalmer 5929 1.1 mbalmer 5930 1.1 mbalmer 5931 1.1 mbalmer <hr><h3><a name="luaL_addstring"><code>luaL_addstring</code></a></h3><p> 5932 1.5 lneto <span class="apii">[-?, +?, <em>m</em>]</span> 5933 1.1 mbalmer <pre>void luaL_addstring (luaL_Buffer *B, const char *s);</pre> 5934 1.1 mbalmer 5935 1.1 mbalmer <p> 5936 1.1 mbalmer Adds the zero-terminated string pointed to by <code>s</code> 5937 1.1 mbalmer to the buffer <code>B</code> 5938 1.1 mbalmer (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>). 5939 1.1 mbalmer 5940 1.1 mbalmer 5941 1.1 mbalmer 5942 1.1 mbalmer 5943 1.1 mbalmer 5944 1.1 mbalmer <hr><h3><a name="luaL_addvalue"><code>luaL_addvalue</code></a></h3><p> 5945 1.5 lneto <span class="apii">[-1, +?, <em>m</em>]</span> 5946 1.1 mbalmer <pre>void luaL_addvalue (luaL_Buffer *B);</pre> 5947 1.1 mbalmer 5948 1.1 mbalmer <p> 5949 1.1 mbalmer Adds the value at the top of the stack 5950 1.1 mbalmer to the buffer <code>B</code> 5951 1.1 mbalmer (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>). 5952 1.1 mbalmer Pops the value. 5953 1.1 mbalmer 5954 1.1 mbalmer 5955 1.1 mbalmer <p> 5956 1.1 mbalmer This is the only function on string buffers that can (and must) 5957 1.1 mbalmer be called with an extra element on the stack, 5958 1.1 mbalmer which is the value to be added to the buffer. 5959 1.1 mbalmer 5960 1.1 mbalmer 5961 1.1 mbalmer 5962 1.1 mbalmer 5963 1.1 mbalmer 5964 1.1 mbalmer <hr><h3><a name="luaL_argcheck"><code>luaL_argcheck</code></a></h3><p> 5965 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 5966 1.1 mbalmer <pre>void luaL_argcheck (lua_State *L, 5967 1.1 mbalmer int cond, 5968 1.2 lneto int arg, 5969 1.1 mbalmer const char *extramsg);</pre> 5970 1.1 mbalmer 5971 1.1 mbalmer <p> 5972 1.1 mbalmer Checks whether <code>cond</code> is true. 5973 1.2 lneto If it is not, raises an error with a standard message (see <a href="#luaL_argerror"><code>luaL_argerror</code></a>). 5974 1.1 mbalmer 5975 1.1 mbalmer 5976 1.1 mbalmer 5977 1.1 mbalmer 5978 1.1 mbalmer 5979 1.1 mbalmer <hr><h3><a name="luaL_argerror"><code>luaL_argerror</code></a></h3><p> 5980 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 5981 1.2 lneto <pre>int luaL_argerror (lua_State *L, int arg, const char *extramsg);</pre> 5982 1.1 mbalmer 5983 1.1 mbalmer <p> 5984 1.2 lneto Raises an error reporting a problem with argument <code>arg</code> 5985 1.2 lneto of the C function that called it, 5986 1.2 lneto using a standard message 5987 1.2 lneto that includes <code>extramsg</code> as a comment: 5988 1.1 mbalmer 5989 1.1 mbalmer <pre> 5990 1.2 lneto bad argument #<em>arg</em> to '<em>funcname</em>' (<em>extramsg</em>) 5991 1.2 lneto </pre><p> 5992 1.2 lneto This function never returns. 5993 1.1 mbalmer 5994 1.1 mbalmer 5995 1.1 mbalmer 5996 1.1 mbalmer 5997 1.1 mbalmer 5998 1.1 mbalmer <hr><h3><a name="luaL_Buffer"><code>luaL_Buffer</code></a></h3> 5999 1.1 mbalmer <pre>typedef struct luaL_Buffer luaL_Buffer;</pre> 6000 1.1 mbalmer 6001 1.1 mbalmer <p> 6002 1.1 mbalmer Type for a <em>string buffer</em>. 6003 1.1 mbalmer 6004 1.1 mbalmer 6005 1.1 mbalmer <p> 6006 1.1 mbalmer A string buffer allows C code to build Lua strings piecemeal. 6007 1.1 mbalmer Its pattern of use is as follows: 6008 1.1 mbalmer 6009 1.1 mbalmer <ul> 6010 1.1 mbalmer 6011 1.2 lneto <li>First declare a variable <code>b</code> of type <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>.</li> 6012 1.1 mbalmer 6013 1.2 lneto <li>Then initialize it with a call <code>luaL_buffinit(L, &b)</code>.</li> 6014 1.1 mbalmer 6015 1.1 mbalmer <li> 6016 1.2 lneto Then add string pieces to the buffer calling any of 6017 1.1 mbalmer the <code>luaL_add*</code> functions. 6018 1.1 mbalmer </li> 6019 1.1 mbalmer 6020 1.1 mbalmer <li> 6021 1.2 lneto Finish by calling <code>luaL_pushresult(&b)</code>. 6022 1.1 mbalmer This call leaves the final string on the top of the stack. 6023 1.1 mbalmer </li> 6024 1.1 mbalmer 6025 1.1 mbalmer </ul> 6026 1.1 mbalmer 6027 1.1 mbalmer <p> 6028 1.2 lneto If you know beforehand the total size of the resulting string, 6029 1.2 lneto you can use the buffer like this: 6030 1.2 lneto 6031 1.2 lneto <ul> 6032 1.2 lneto 6033 1.2 lneto <li>First declare a variable <code>b</code> of type <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>.</li> 6034 1.2 lneto 6035 1.2 lneto <li>Then initialize it and preallocate a space of 6036 1.2 lneto size <code>sz</code> with a call <code>luaL_buffinitsize(L, &b, sz)</code>.</li> 6037 1.2 lneto 6038 1.2 lneto <li>Then copy the string into that space.</li> 6039 1.2 lneto 6040 1.2 lneto <li> 6041 1.2 lneto Finish by calling <code>luaL_pushresultsize(&b, sz)</code>, 6042 1.2 lneto where <code>sz</code> is the total size of the resulting string 6043 1.2 lneto copied into that space. 6044 1.2 lneto </li> 6045 1.2 lneto 6046 1.2 lneto </ul> 6047 1.2 lneto 6048 1.2 lneto <p> 6049 1.1 mbalmer During its normal operation, 6050 1.1 mbalmer a string buffer uses a variable number of stack slots. 6051 1.1 mbalmer So, while using a buffer, you cannot assume that you know where 6052 1.1 mbalmer the top of the stack is. 6053 1.1 mbalmer You can use the stack between successive calls to buffer operations 6054 1.1 mbalmer as long as that use is balanced; 6055 1.1 mbalmer that is, 6056 1.1 mbalmer when you call a buffer operation, 6057 1.1 mbalmer the stack is at the same level 6058 1.1 mbalmer it was immediately after the previous buffer operation. 6059 1.1 mbalmer (The only exception to this rule is <a href="#luaL_addvalue"><code>luaL_addvalue</code></a>.) 6060 1.1 mbalmer After calling <a href="#luaL_pushresult"><code>luaL_pushresult</code></a> the stack is back to its 6061 1.1 mbalmer level when the buffer was initialized, 6062 1.1 mbalmer plus the final string on its top. 6063 1.1 mbalmer 6064 1.1 mbalmer 6065 1.1 mbalmer 6066 1.1 mbalmer 6067 1.1 mbalmer 6068 1.1 mbalmer <hr><h3><a name="luaL_buffinit"><code>luaL_buffinit</code></a></h3><p> 6069 1.2 lneto <span class="apii">[-0, +0, –]</span> 6070 1.1 mbalmer <pre>void luaL_buffinit (lua_State *L, luaL_Buffer *B);</pre> 6071 1.1 mbalmer 6072 1.1 mbalmer <p> 6073 1.1 mbalmer Initializes a buffer <code>B</code>. 6074 1.1 mbalmer This function does not allocate any space; 6075 1.1 mbalmer the buffer must be declared as a variable 6076 1.1 mbalmer (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>). 6077 1.1 mbalmer 6078 1.1 mbalmer 6079 1.1 mbalmer 6080 1.1 mbalmer 6081 1.1 mbalmer 6082 1.2 lneto <hr><h3><a name="luaL_buffinitsize"><code>luaL_buffinitsize</code></a></h3><p> 6083 1.5 lneto <span class="apii">[-?, +?, <em>m</em>]</span> 6084 1.2 lneto <pre>char *luaL_buffinitsize (lua_State *L, luaL_Buffer *B, size_t sz);</pre> 6085 1.2 lneto 6086 1.2 lneto <p> 6087 1.2 lneto Equivalent to the sequence 6088 1.2 lneto <a href="#luaL_buffinit"><code>luaL_buffinit</code></a>, <a href="#luaL_prepbuffsize"><code>luaL_prepbuffsize</code></a>. 6089 1.2 lneto 6090 1.2 lneto 6091 1.2 lneto 6092 1.2 lneto 6093 1.2 lneto 6094 1.1 mbalmer <hr><h3><a name="luaL_callmeta"><code>luaL_callmeta</code></a></h3><p> 6095 1.1 mbalmer <span class="apii">[-0, +(0|1), <em>e</em>]</span> 6096 1.1 mbalmer <pre>int luaL_callmeta (lua_State *L, int obj, const char *e);</pre> 6097 1.1 mbalmer 6098 1.1 mbalmer <p> 6099 1.1 mbalmer Calls a metamethod. 6100 1.1 mbalmer 6101 1.1 mbalmer 6102 1.1 mbalmer <p> 6103 1.1 mbalmer If the object at index <code>obj</code> has a metatable and this 6104 1.1 mbalmer metatable has a field <code>e</code>, 6105 1.2 lneto this function calls this field passing the object as its only argument. 6106 1.2 lneto In this case this function returns true and pushes onto the 6107 1.1 mbalmer stack the value returned by the call. 6108 1.1 mbalmer If there is no metatable or no metamethod, 6109 1.2 lneto this function returns false (without pushing any value on the stack). 6110 1.1 mbalmer 6111 1.1 mbalmer 6112 1.1 mbalmer 6113 1.1 mbalmer 6114 1.1 mbalmer 6115 1.1 mbalmer <hr><h3><a name="luaL_checkany"><code>luaL_checkany</code></a></h3><p> 6116 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6117 1.2 lneto <pre>void luaL_checkany (lua_State *L, int arg);</pre> 6118 1.1 mbalmer 6119 1.1 mbalmer <p> 6120 1.1 mbalmer Checks whether the function has an argument 6121 1.2 lneto of any type (including <b>nil</b>) at position <code>arg</code>. 6122 1.1 mbalmer 6123 1.1 mbalmer 6124 1.1 mbalmer 6125 1.1 mbalmer 6126 1.1 mbalmer 6127 1.1 mbalmer <hr><h3><a name="luaL_checkinteger"><code>luaL_checkinteger</code></a></h3><p> 6128 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6129 1.2 lneto <pre>lua_Integer luaL_checkinteger (lua_State *L, int arg);</pre> 6130 1.1 mbalmer 6131 1.1 mbalmer <p> 6132 1.2 lneto Checks whether the function argument <code>arg</code> is an integer 6133 1.2 lneto (or can be converted to an integer) 6134 1.2 lneto and returns this integer cast to a <a href="#lua_Integer"><code>lua_Integer</code></a>. 6135 1.1 mbalmer 6136 1.1 mbalmer 6137 1.1 mbalmer 6138 1.1 mbalmer 6139 1.1 mbalmer 6140 1.1 mbalmer <hr><h3><a name="luaL_checklstring"><code>luaL_checklstring</code></a></h3><p> 6141 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6142 1.2 lneto <pre>const char *luaL_checklstring (lua_State *L, int arg, size_t *l);</pre> 6143 1.1 mbalmer 6144 1.1 mbalmer <p> 6145 1.2 lneto Checks whether the function argument <code>arg</code> is a string 6146 1.1 mbalmer and returns this string; 6147 1.1 mbalmer if <code>l</code> is not <code>NULL</code> fills <code>*l</code> 6148 1.1 mbalmer with the string's length. 6149 1.1 mbalmer 6150 1.1 mbalmer 6151 1.1 mbalmer <p> 6152 1.1 mbalmer This function uses <a href="#lua_tolstring"><code>lua_tolstring</code></a> to get its result, 6153 1.1 mbalmer so all conversions and caveats of that function apply here. 6154 1.1 mbalmer 6155 1.1 mbalmer 6156 1.1 mbalmer 6157 1.1 mbalmer 6158 1.1 mbalmer 6159 1.1 mbalmer <hr><h3><a name="luaL_checknumber"><code>luaL_checknumber</code></a></h3><p> 6160 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6161 1.2 lneto <pre>lua_Number luaL_checknumber (lua_State *L, int arg);</pre> 6162 1.1 mbalmer 6163 1.1 mbalmer <p> 6164 1.2 lneto Checks whether the function argument <code>arg</code> is a number 6165 1.1 mbalmer and returns this number. 6166 1.1 mbalmer 6167 1.1 mbalmer 6168 1.1 mbalmer 6169 1.1 mbalmer 6170 1.1 mbalmer 6171 1.1 mbalmer <hr><h3><a name="luaL_checkoption"><code>luaL_checkoption</code></a></h3><p> 6172 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6173 1.1 mbalmer <pre>int luaL_checkoption (lua_State *L, 6174 1.2 lneto int arg, 6175 1.1 mbalmer const char *def, 6176 1.1 mbalmer const char *const lst[]);</pre> 6177 1.1 mbalmer 6178 1.1 mbalmer <p> 6179 1.2 lneto Checks whether the function argument <code>arg</code> is a string and 6180 1.1 mbalmer searches for this string in the array <code>lst</code> 6181 1.1 mbalmer (which must be NULL-terminated). 6182 1.1 mbalmer Returns the index in the array where the string was found. 6183 1.1 mbalmer Raises an error if the argument is not a string or 6184 1.1 mbalmer if the string cannot be found. 6185 1.1 mbalmer 6186 1.1 mbalmer 6187 1.1 mbalmer <p> 6188 1.1 mbalmer If <code>def</code> is not <code>NULL</code>, 6189 1.1 mbalmer the function uses <code>def</code> as a default value when 6190 1.2 lneto there is no argument <code>arg</code> or when this argument is <b>nil</b>. 6191 1.1 mbalmer 6192 1.1 mbalmer 6193 1.1 mbalmer <p> 6194 1.1 mbalmer This is a useful function for mapping strings to C enums. 6195 1.1 mbalmer (The usual convention in Lua libraries is 6196 1.1 mbalmer to use strings instead of numbers to select options.) 6197 1.1 mbalmer 6198 1.1 mbalmer 6199 1.1 mbalmer 6200 1.1 mbalmer 6201 1.1 mbalmer 6202 1.1 mbalmer <hr><h3><a name="luaL_checkstack"><code>luaL_checkstack</code></a></h3><p> 6203 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6204 1.1 mbalmer <pre>void luaL_checkstack (lua_State *L, int sz, const char *msg);</pre> 6205 1.1 mbalmer 6206 1.1 mbalmer <p> 6207 1.1 mbalmer Grows the stack size to <code>top + sz</code> elements, 6208 1.1 mbalmer raising an error if the stack cannot grow to that size. 6209 1.2 lneto <code>msg</code> is an additional text to go into the error message 6210 1.2 lneto (or <code>NULL</code> for no additional text). 6211 1.1 mbalmer 6212 1.1 mbalmer 6213 1.1 mbalmer 6214 1.1 mbalmer 6215 1.1 mbalmer 6216 1.1 mbalmer <hr><h3><a name="luaL_checkstring"><code>luaL_checkstring</code></a></h3><p> 6217 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6218 1.2 lneto <pre>const char *luaL_checkstring (lua_State *L, int arg);</pre> 6219 1.1 mbalmer 6220 1.1 mbalmer <p> 6221 1.2 lneto Checks whether the function argument <code>arg</code> is a string 6222 1.1 mbalmer and returns this string. 6223 1.1 mbalmer 6224 1.1 mbalmer 6225 1.1 mbalmer <p> 6226 1.1 mbalmer This function uses <a href="#lua_tolstring"><code>lua_tolstring</code></a> to get its result, 6227 1.1 mbalmer so all conversions and caveats of that function apply here. 6228 1.1 mbalmer 6229 1.1 mbalmer 6230 1.1 mbalmer 6231 1.1 mbalmer 6232 1.1 mbalmer 6233 1.1 mbalmer <hr><h3><a name="luaL_checktype"><code>luaL_checktype</code></a></h3><p> 6234 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6235 1.2 lneto <pre>void luaL_checktype (lua_State *L, int arg, int t);</pre> 6236 1.1 mbalmer 6237 1.1 mbalmer <p> 6238 1.2 lneto Checks whether the function argument <code>arg</code> has type <code>t</code>. 6239 1.1 mbalmer See <a href="#lua_type"><code>lua_type</code></a> for the encoding of types for <code>t</code>. 6240 1.1 mbalmer 6241 1.1 mbalmer 6242 1.1 mbalmer 6243 1.1 mbalmer 6244 1.1 mbalmer 6245 1.1 mbalmer <hr><h3><a name="luaL_checkudata"><code>luaL_checkudata</code></a></h3><p> 6246 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6247 1.2 lneto <pre>void *luaL_checkudata (lua_State *L, int arg, const char *tname);</pre> 6248 1.2 lneto 6249 1.2 lneto <p> 6250 1.2 lneto Checks whether the function argument <code>arg</code> is a userdata 6251 1.2 lneto of the type <code>tname</code> (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>) and 6252 1.2 lneto returns the userdata address (see <a href="#lua_touserdata"><code>lua_touserdata</code></a>). 6253 1.2 lneto 6254 1.2 lneto 6255 1.2 lneto 6256 1.2 lneto 6257 1.2 lneto 6258 1.2 lneto <hr><h3><a name="luaL_checkversion"><code>luaL_checkversion</code></a></h3><p> 6259 1.2 lneto <span class="apii">[-0, +0, –]</span> 6260 1.2 lneto <pre>void luaL_checkversion (lua_State *L);</pre> 6261 1.1 mbalmer 6262 1.1 mbalmer <p> 6263 1.2 lneto Checks whether the core running the call, 6264 1.2 lneto the core that created the Lua state, 6265 1.2 lneto and the code making the call are all using the same version of Lua. 6266 1.2 lneto Also checks whether the core running the call 6267 1.2 lneto and the core that created the Lua state 6268 1.2 lneto are using the same address space. 6269 1.1 mbalmer 6270 1.1 mbalmer 6271 1.1 mbalmer 6272 1.1 mbalmer 6273 1.1 mbalmer 6274 1.1 mbalmer <hr><h3><a name="luaL_dofile"><code>luaL_dofile</code></a></h3><p> 6275 1.2 lneto <span class="apii">[-0, +?, <em>e</em>]</span> 6276 1.1 mbalmer <pre>int luaL_dofile (lua_State *L, const char *filename);</pre> 6277 1.1 mbalmer 6278 1.1 mbalmer <p> 6279 1.1 mbalmer Loads and runs the given file. 6280 1.1 mbalmer It is defined as the following macro: 6281 1.1 mbalmer 6282 1.1 mbalmer <pre> 6283 1.1 mbalmer (luaL_loadfile(L, filename) || lua_pcall(L, 0, LUA_MULTRET, 0)) 6284 1.1 mbalmer </pre><p> 6285 1.2 lneto It returns false if there are no errors 6286 1.2 lneto or true in case of errors. 6287 1.1 mbalmer 6288 1.1 mbalmer 6289 1.1 mbalmer 6290 1.1 mbalmer 6291 1.1 mbalmer 6292 1.1 mbalmer <hr><h3><a name="luaL_dostring"><code>luaL_dostring</code></a></h3><p> 6293 1.2 lneto <span class="apii">[-0, +?, –]</span> 6294 1.1 mbalmer <pre>int luaL_dostring (lua_State *L, const char *str);</pre> 6295 1.1 mbalmer 6296 1.1 mbalmer <p> 6297 1.1 mbalmer Loads and runs the given string. 6298 1.1 mbalmer It is defined as the following macro: 6299 1.1 mbalmer 6300 1.1 mbalmer <pre> 6301 1.1 mbalmer (luaL_loadstring(L, str) || lua_pcall(L, 0, LUA_MULTRET, 0)) 6302 1.1 mbalmer </pre><p> 6303 1.2 lneto It returns false if there are no errors 6304 1.2 lneto or true in case of errors. 6305 1.1 mbalmer 6306 1.1 mbalmer 6307 1.1 mbalmer 6308 1.1 mbalmer 6309 1.1 mbalmer 6310 1.1 mbalmer <hr><h3><a name="luaL_error"><code>luaL_error</code></a></h3><p> 6311 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6312 1.1 mbalmer <pre>int luaL_error (lua_State *L, const char *fmt, ...);</pre> 6313 1.1 mbalmer 6314 1.1 mbalmer <p> 6315 1.1 mbalmer Raises an error. 6316 1.2 lneto The error message format is given by <code>fmt</code> 6317 1.2 lneto plus any extra arguments, 6318 1.2 lneto following the same rules of <a href="#lua_pushfstring"><code>lua_pushfstring</code></a>. 6319 1.2 lneto It also adds at the beginning of the message the file name and 6320 1.2 lneto the line number where the error occurred, 6321 1.2 lneto if this information is available. 6322 1.2 lneto 6323 1.2 lneto 6324 1.2 lneto <p> 6325 1.2 lneto This function never returns, 6326 1.2 lneto but it is an idiom to use it in C functions 6327 1.2 lneto as <code>return luaL_error(<em>args</em>)</code>. 6328 1.2 lneto 6329 1.2 lneto 6330 1.2 lneto 6331 1.2 lneto 6332 1.2 lneto 6333 1.2 lneto <hr><h3><a name="luaL_execresult"><code>luaL_execresult</code></a></h3><p> 6334 1.5 lneto <span class="apii">[-0, +3, <em>m</em>]</span> 6335 1.2 lneto <pre>int luaL_execresult (lua_State *L, int stat);</pre> 6336 1.2 lneto 6337 1.2 lneto <p> 6338 1.2 lneto This function produces the return values for 6339 1.2 lneto process-related functions in the standard library 6340 1.2 lneto (<a href="#pdf-os.execute"><code>os.execute</code></a> and <a href="#pdf-io.close"><code>io.close</code></a>). 6341 1.2 lneto 6342 1.2 lneto 6343 1.2 lneto 6344 1.2 lneto 6345 1.1 mbalmer 6346 1.2 lneto <hr><h3><a name="luaL_fileresult"><code>luaL_fileresult</code></a></h3><p> 6347 1.5 lneto <span class="apii">[-0, +(1|3), <em>m</em>]</span> 6348 1.2 lneto <pre>int luaL_fileresult (lua_State *L, int stat, const char *fname);</pre> 6349 1.1 mbalmer 6350 1.1 mbalmer <p> 6351 1.2 lneto This function produces the return values for 6352 1.2 lneto file-related functions in the standard library 6353 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.). 6354 1.1 mbalmer 6355 1.1 mbalmer 6356 1.1 mbalmer 6357 1.1 mbalmer 6358 1.1 mbalmer 6359 1.1 mbalmer <hr><h3><a name="luaL_getmetafield"><code>luaL_getmetafield</code></a></h3><p> 6360 1.5 lneto <span class="apii">[-0, +(0|1), <em>m</em>]</span> 6361 1.1 mbalmer <pre>int luaL_getmetafield (lua_State *L, int obj, const char *e);</pre> 6362 1.1 mbalmer 6363 1.1 mbalmer <p> 6364 1.1 mbalmer Pushes onto the stack the field <code>e</code> from the metatable 6365 1.3 lneto of the object at index <code>obj</code> and returns the type of pushed value. 6366 1.1 mbalmer If the object does not have a metatable, 6367 1.1 mbalmer or if the metatable does not have this field, 6368 1.3 lneto pushes nothing and returns <code>LUA_TNIL</code>. 6369 1.1 mbalmer 6370 1.1 mbalmer 6371 1.1 mbalmer 6372 1.1 mbalmer 6373 1.1 mbalmer 6374 1.1 mbalmer <hr><h3><a name="luaL_getmetatable"><code>luaL_getmetatable</code></a></h3><p> 6375 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 6376 1.3 lneto <pre>int luaL_getmetatable (lua_State *L, const char *tname);</pre> 6377 1.1 mbalmer 6378 1.1 mbalmer <p> 6379 1.1 mbalmer Pushes onto the stack the metatable associated with name <code>tname</code> 6380 1.4 mbalmer in the registry (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>) 6381 1.4 mbalmer (<b>nil</b> if there is no metatable associated with that name). 6382 1.4 mbalmer Returns the type of the pushed value. 6383 1.1 mbalmer 6384 1.1 mbalmer 6385 1.1 mbalmer 6386 1.1 mbalmer 6387 1.1 mbalmer 6388 1.2 lneto <hr><h3><a name="luaL_getsubtable"><code>luaL_getsubtable</code></a></h3><p> 6389 1.2 lneto <span class="apii">[-0, +1, <em>e</em>]</span> 6390 1.2 lneto <pre>int luaL_getsubtable (lua_State *L, int idx, const char *fname);</pre> 6391 1.2 lneto 6392 1.2 lneto <p> 6393 1.2 lneto Ensures that the value <code>t[fname]</code>, 6394 1.2 lneto where <code>t</code> is the value at index <code>idx</code>, 6395 1.2 lneto is a table, 6396 1.2 lneto and pushes that table onto the stack. 6397 1.2 lneto Returns true if it finds a previous table there 6398 1.2 lneto and false if it creates a new table. 6399 1.2 lneto 6400 1.2 lneto 6401 1.2 lneto 6402 1.2 lneto 6403 1.2 lneto 6404 1.1 mbalmer <hr><h3><a name="luaL_gsub"><code>luaL_gsub</code></a></h3><p> 6405 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 6406 1.1 mbalmer <pre>const char *luaL_gsub (lua_State *L, 6407 1.1 mbalmer const char *s, 6408 1.1 mbalmer const char *p, 6409 1.1 mbalmer const char *r);</pre> 6410 1.1 mbalmer 6411 1.1 mbalmer <p> 6412 1.1 mbalmer Creates a copy of string <code>s</code> by replacing 6413 1.1 mbalmer any occurrence of the string <code>p</code> 6414 1.1 mbalmer with the string <code>r</code>. 6415 1.1 mbalmer Pushes the resulting string on the stack and returns it. 6416 1.1 mbalmer 6417 1.1 mbalmer 6418 1.1 mbalmer 6419 1.1 mbalmer 6420 1.1 mbalmer 6421 1.2 lneto <hr><h3><a name="luaL_len"><code>luaL_len</code></a></h3><p> 6422 1.2 lneto <span class="apii">[-0, +0, <em>e</em>]</span> 6423 1.2 lneto <pre>lua_Integer luaL_len (lua_State *L, int index);</pre> 6424 1.2 lneto 6425 1.2 lneto <p> 6426 1.2 lneto Returns the "length" of the value at the given index 6427 1.2 lneto as a number; 6428 1.2 lneto it is equivalent to the '<code>#</code>' operator in Lua (see <a href="#3.4.7">§3.4.7</a>). 6429 1.2 lneto Raises an error if the result of the operation is not an integer. 6430 1.2 lneto (This case only can happen through metamethods.) 6431 1.2 lneto 6432 1.2 lneto 6433 1.2 lneto 6434 1.2 lneto 6435 1.2 lneto 6436 1.1 mbalmer <hr><h3><a name="luaL_loadbuffer"><code>luaL_loadbuffer</code></a></h3><p> 6437 1.2 lneto <span class="apii">[-0, +1, –]</span> 6438 1.1 mbalmer <pre>int luaL_loadbuffer (lua_State *L, 6439 1.1 mbalmer const char *buff, 6440 1.1 mbalmer size_t sz, 6441 1.1 mbalmer const char *name);</pre> 6442 1.1 mbalmer 6443 1.1 mbalmer <p> 6444 1.2 lneto Equivalent to <a href="#luaL_loadbufferx"><code>luaL_loadbufferx</code></a> with <code>mode</code> equal to <code>NULL</code>. 6445 1.2 lneto 6446 1.2 lneto 6447 1.2 lneto 6448 1.2 lneto 6449 1.2 lneto 6450 1.2 lneto <hr><h3><a name="luaL_loadbufferx"><code>luaL_loadbufferx</code></a></h3><p> 6451 1.2 lneto <span class="apii">[-0, +1, –]</span> 6452 1.2 lneto <pre>int luaL_loadbufferx (lua_State *L, 6453 1.2 lneto const char *buff, 6454 1.2 lneto size_t sz, 6455 1.2 lneto const char *name, 6456 1.2 lneto const char *mode);</pre> 6457 1.2 lneto 6458 1.2 lneto <p> 6459 1.1 mbalmer Loads a buffer as a Lua chunk. 6460 1.1 mbalmer This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chunk in the 6461 1.1 mbalmer buffer pointed to by <code>buff</code> with size <code>sz</code>. 6462 1.1 mbalmer 6463 1.1 mbalmer 6464 1.1 mbalmer <p> 6465 1.1 mbalmer This function returns the same results as <a href="#lua_load"><code>lua_load</code></a>. 6466 1.1 mbalmer <code>name</code> is the chunk name, 6467 1.1 mbalmer used for debug information and error messages. 6468 1.2 lneto The string <code>mode</code> works as in function <a href="#lua_load"><code>lua_load</code></a>. 6469 1.1 mbalmer 6470 1.1 mbalmer 6471 1.1 mbalmer 6472 1.1 mbalmer 6473 1.1 mbalmer 6474 1.1 mbalmer <hr><h3><a name="luaL_loadfile"><code>luaL_loadfile</code></a></h3><p> 6475 1.2 lneto <span class="apii">[-0, +1, <em>e</em>]</span> 6476 1.1 mbalmer <pre>int luaL_loadfile (lua_State *L, const char *filename);</pre> 6477 1.1 mbalmer 6478 1.1 mbalmer <p> 6479 1.2 lneto Equivalent to <a href="#luaL_loadfilex"><code>luaL_loadfilex</code></a> with <code>mode</code> equal to <code>NULL</code>. 6480 1.2 lneto 6481 1.2 lneto 6482 1.2 lneto 6483 1.2 lneto 6484 1.2 lneto 6485 1.2 lneto <hr><h3><a name="luaL_loadfilex"><code>luaL_loadfilex</code></a></h3><p> 6486 1.2 lneto <span class="apii">[-0, +1, <em>e</em>]</span> 6487 1.2 lneto <pre>int luaL_loadfilex (lua_State *L, const char *filename, 6488 1.2 lneto const char *mode);</pre> 6489 1.2 lneto 6490 1.2 lneto <p> 6491 1.1 mbalmer Loads a file as a Lua chunk. 6492 1.1 mbalmer This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chunk in the file 6493 1.1 mbalmer named <code>filename</code>. 6494 1.1 mbalmer If <code>filename</code> is <code>NULL</code>, 6495 1.1 mbalmer then it loads from the standard input. 6496 1.1 mbalmer The first line in the file is ignored if it starts with a <code>#</code>. 6497 1.1 mbalmer 6498 1.1 mbalmer 6499 1.1 mbalmer <p> 6500 1.2 lneto The string <code>mode</code> works as in function <a href="#lua_load"><code>lua_load</code></a>. 6501 1.2 lneto 6502 1.2 lneto 6503 1.2 lneto <p> 6504 1.1 mbalmer This function returns the same results as <a href="#lua_load"><code>lua_load</code></a>, 6505 1.1 mbalmer but it has an extra error code <a name="pdf-LUA_ERRFILE"><code>LUA_ERRFILE</code></a> 6506 1.2 lneto if it cannot open/read the file or the file has a wrong mode. 6507 1.1 mbalmer 6508 1.1 mbalmer 6509 1.1 mbalmer <p> 6510 1.1 mbalmer As <a href="#lua_load"><code>lua_load</code></a>, this function only loads the chunk; 6511 1.1 mbalmer it does not run it. 6512 1.1 mbalmer 6513 1.1 mbalmer 6514 1.1 mbalmer 6515 1.1 mbalmer 6516 1.1 mbalmer 6517 1.1 mbalmer <hr><h3><a name="luaL_loadstring"><code>luaL_loadstring</code></a></h3><p> 6518 1.2 lneto <span class="apii">[-0, +1, –]</span> 6519 1.1 mbalmer <pre>int luaL_loadstring (lua_State *L, const char *s);</pre> 6520 1.1 mbalmer 6521 1.1 mbalmer <p> 6522 1.1 mbalmer Loads a string as a Lua chunk. 6523 1.1 mbalmer This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chunk in 6524 1.1 mbalmer the zero-terminated string <code>s</code>. 6525 1.1 mbalmer 6526 1.1 mbalmer 6527 1.1 mbalmer <p> 6528 1.1 mbalmer This function returns the same results as <a href="#lua_load"><code>lua_load</code></a>. 6529 1.1 mbalmer 6530 1.1 mbalmer 6531 1.1 mbalmer <p> 6532 1.1 mbalmer Also as <a href="#lua_load"><code>lua_load</code></a>, this function only loads the chunk; 6533 1.1 mbalmer it does not run it. 6534 1.1 mbalmer 6535 1.1 mbalmer 6536 1.1 mbalmer 6537 1.1 mbalmer 6538 1.1 mbalmer 6539 1.2 lneto <hr><h3><a name="luaL_newlib"><code>luaL_newlib</code></a></h3><p> 6540 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 6541 1.3 lneto <pre>void luaL_newlib (lua_State *L, const luaL_Reg l[]);</pre> 6542 1.2 lneto 6543 1.2 lneto <p> 6544 1.2 lneto Creates a new table and registers there 6545 1.2 lneto the functions in list <code>l</code>. 6546 1.3 lneto 6547 1.3 lneto 6548 1.3 lneto <p> 6549 1.2 lneto It is implemented as the following macro: 6550 1.2 lneto 6551 1.2 lneto <pre> 6552 1.2 lneto (luaL_newlibtable(L,l), luaL_setfuncs(L,l,0)) 6553 1.3 lneto </pre><p> 6554 1.3 lneto The array <code>l</code> must be the actual array, 6555 1.3 lneto not a pointer to it. 6556 1.3 lneto 6557 1.2 lneto 6558 1.2 lneto 6559 1.2 lneto 6560 1.2 lneto 6561 1.2 lneto <hr><h3><a name="luaL_newlibtable"><code>luaL_newlibtable</code></a></h3><p> 6562 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 6563 1.2 lneto <pre>void luaL_newlibtable (lua_State *L, const luaL_Reg l[]);</pre> 6564 1.2 lneto 6565 1.2 lneto <p> 6566 1.2 lneto Creates a new table with a size optimized 6567 1.2 lneto to store all entries in the array <code>l</code> 6568 1.2 lneto (but does not actually store them). 6569 1.2 lneto It is intended to be used in conjunction with <a href="#luaL_setfuncs"><code>luaL_setfuncs</code></a> 6570 1.2 lneto (see <a href="#luaL_newlib"><code>luaL_newlib</code></a>). 6571 1.2 lneto 6572 1.2 lneto 6573 1.2 lneto <p> 6574 1.2 lneto It is implemented as a macro. 6575 1.2 lneto The array <code>l</code> must be the actual array, 6576 1.2 lneto not a pointer to it. 6577 1.2 lneto 6578 1.2 lneto 6579 1.2 lneto 6580 1.2 lneto 6581 1.2 lneto 6582 1.1 mbalmer <hr><h3><a name="luaL_newmetatable"><code>luaL_newmetatable</code></a></h3><p> 6583 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 6584 1.1 mbalmer <pre>int luaL_newmetatable (lua_State *L, const char *tname);</pre> 6585 1.1 mbalmer 6586 1.1 mbalmer <p> 6587 1.1 mbalmer If the registry already has the key <code>tname</code>, 6588 1.1 mbalmer returns 0. 6589 1.1 mbalmer Otherwise, 6590 1.1 mbalmer creates a new table to be used as a metatable for userdata, 6591 1.2 lneto adds to this new table the pair <code>__name = tname</code>, 6592 1.2 lneto adds to the registry the pair <code>[tname] = new table</code>, 6593 1.1 mbalmer and returns 1. 6594 1.3 lneto (The entry <code>__name</code> is used by some error-reporting functions.) 6595 1.1 mbalmer 6596 1.1 mbalmer 6597 1.1 mbalmer <p> 6598 1.1 mbalmer In both cases pushes onto the stack the final value associated 6599 1.1 mbalmer with <code>tname</code> in the registry. 6600 1.1 mbalmer 6601 1.1 mbalmer 6602 1.1 mbalmer 6603 1.1 mbalmer 6604 1.1 mbalmer 6605 1.1 mbalmer <hr><h3><a name="luaL_newstate"><code>luaL_newstate</code></a></h3><p> 6606 1.2 lneto <span class="apii">[-0, +0, –]</span> 6607 1.1 mbalmer <pre>lua_State *luaL_newstate (void);</pre> 6608 1.1 mbalmer 6609 1.1 mbalmer <p> 6610 1.1 mbalmer Creates a new Lua state. 6611 1.1 mbalmer It calls <a href="#lua_newstate"><code>lua_newstate</code></a> with an 6612 1.1 mbalmer allocator based on the standard C <code>realloc</code> function 6613 1.2 lneto and then sets a panic function (see <a href="#4.6">§4.6</a>) that prints 6614 1.1 mbalmer an error message to the standard error output in case of fatal 6615 1.1 mbalmer errors. 6616 1.1 mbalmer 6617 1.1 mbalmer 6618 1.1 mbalmer <p> 6619 1.1 mbalmer Returns the new state, 6620 1.1 mbalmer or <code>NULL</code> if there is a memory allocation error. 6621 1.1 mbalmer 6622 1.1 mbalmer 6623 1.1 mbalmer 6624 1.1 mbalmer 6625 1.1 mbalmer 6626 1.1 mbalmer <hr><h3><a name="luaL_openlibs"><code>luaL_openlibs</code></a></h3><p> 6627 1.2 lneto <span class="apii">[-0, +0, <em>e</em>]</span> 6628 1.1 mbalmer <pre>void luaL_openlibs (lua_State *L);</pre> 6629 1.1 mbalmer 6630 1.1 mbalmer <p> 6631 1.1 mbalmer Opens all standard Lua libraries into the given state. 6632 1.1 mbalmer 6633 1.1 mbalmer 6634 1.1 mbalmer 6635 1.1 mbalmer 6636 1.1 mbalmer 6637 1.1 mbalmer <hr><h3><a name="luaL_optinteger"><code>luaL_optinteger</code></a></h3><p> 6638 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6639 1.1 mbalmer <pre>lua_Integer luaL_optinteger (lua_State *L, 6640 1.2 lneto int arg, 6641 1.1 mbalmer lua_Integer d);</pre> 6642 1.1 mbalmer 6643 1.1 mbalmer <p> 6644 1.2 lneto If the function argument <code>arg</code> is an integer 6645 1.2 lneto (or convertible to an integer), 6646 1.2 lneto returns this integer. 6647 1.1 mbalmer If this argument is absent or is <b>nil</b>, 6648 1.1 mbalmer returns <code>d</code>. 6649 1.1 mbalmer Otherwise, raises an error. 6650 1.1 mbalmer 6651 1.1 mbalmer 6652 1.1 mbalmer 6653 1.1 mbalmer 6654 1.1 mbalmer 6655 1.1 mbalmer <hr><h3><a name="luaL_optlstring"><code>luaL_optlstring</code></a></h3><p> 6656 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6657 1.1 mbalmer <pre>const char *luaL_optlstring (lua_State *L, 6658 1.2 lneto int arg, 6659 1.1 mbalmer const char *d, 6660 1.1 mbalmer size_t *l);</pre> 6661 1.1 mbalmer 6662 1.1 mbalmer <p> 6663 1.2 lneto If the function argument <code>arg</code> is a string, 6664 1.1 mbalmer returns this string. 6665 1.1 mbalmer If this argument is absent or is <b>nil</b>, 6666 1.1 mbalmer returns <code>d</code>. 6667 1.1 mbalmer Otherwise, raises an error. 6668 1.1 mbalmer 6669 1.1 mbalmer 6670 1.1 mbalmer <p> 6671 1.1 mbalmer If <code>l</code> is not <code>NULL</code>, 6672 1.2 lneto fills the position <code>*l</code> with the result's length. 6673 1.5 lneto If the result is <code>NULL</code> 6674 1.5 lneto (only possible when returning <code>d</code> and <code>d == NULL</code>), 6675 1.5 lneto its length is considered zero. 6676 1.1 mbalmer 6677 1.1 mbalmer 6678 1.1 mbalmer 6679 1.1 mbalmer 6680 1.1 mbalmer 6681 1.1 mbalmer <hr><h3><a name="luaL_optnumber"><code>luaL_optnumber</code></a></h3><p> 6682 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6683 1.2 lneto <pre>lua_Number luaL_optnumber (lua_State *L, int arg, lua_Number d);</pre> 6684 1.1 mbalmer 6685 1.1 mbalmer <p> 6686 1.2 lneto If the function argument <code>arg</code> is a number, 6687 1.1 mbalmer returns this number. 6688 1.1 mbalmer If this argument is absent or is <b>nil</b>, 6689 1.1 mbalmer returns <code>d</code>. 6690 1.1 mbalmer Otherwise, raises an error. 6691 1.1 mbalmer 6692 1.1 mbalmer 6693 1.1 mbalmer 6694 1.1 mbalmer 6695 1.1 mbalmer 6696 1.1 mbalmer <hr><h3><a name="luaL_optstring"><code>luaL_optstring</code></a></h3><p> 6697 1.1 mbalmer <span class="apii">[-0, +0, <em>v</em>]</span> 6698 1.1 mbalmer <pre>const char *luaL_optstring (lua_State *L, 6699 1.2 lneto int arg, 6700 1.1 mbalmer const char *d);</pre> 6701 1.1 mbalmer 6702 1.1 mbalmer <p> 6703 1.2 lneto If the function argument <code>arg</code> is a string, 6704 1.1 mbalmer returns this string. 6705 1.1 mbalmer If this argument is absent or is <b>nil</b>, 6706 1.1 mbalmer returns <code>d</code>. 6707 1.1 mbalmer Otherwise, raises an error. 6708 1.1 mbalmer 6709 1.1 mbalmer 6710 1.1 mbalmer 6711 1.1 mbalmer 6712 1.1 mbalmer 6713 1.1 mbalmer <hr><h3><a name="luaL_prepbuffer"><code>luaL_prepbuffer</code></a></h3><p> 6714 1.5 lneto <span class="apii">[-?, +?, <em>m</em>]</span> 6715 1.1 mbalmer <pre>char *luaL_prepbuffer (luaL_Buffer *B);</pre> 6716 1.1 mbalmer 6717 1.1 mbalmer <p> 6718 1.2 lneto Equivalent to <a href="#luaL_prepbuffsize"><code>luaL_prepbuffsize</code></a> 6719 1.2 lneto with the predefined size <a name="pdf-LUAL_BUFFERSIZE"><code>LUAL_BUFFERSIZE</code></a>. 6720 1.2 lneto 6721 1.2 lneto 6722 1.2 lneto 6723 1.2 lneto 6724 1.2 lneto 6725 1.2 lneto <hr><h3><a name="luaL_prepbuffsize"><code>luaL_prepbuffsize</code></a></h3><p> 6726 1.5 lneto <span class="apii">[-?, +?, <em>m</em>]</span> 6727 1.2 lneto <pre>char *luaL_prepbuffsize (luaL_Buffer *B, size_t sz);</pre> 6728 1.2 lneto 6729 1.2 lneto <p> 6730 1.2 lneto Returns an address to a space of size <code>sz</code> 6731 1.1 mbalmer where you can copy a string to be added to buffer <code>B</code> 6732 1.1 mbalmer (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>). 6733 1.1 mbalmer After copying the string into this space you must call 6734 1.2 lneto <a href="#luaL_addsize"><code>luaL_addsize</code></a> with the size of the string to actually add 6735 1.1 mbalmer it to the buffer. 6736 1.1 mbalmer 6737 1.1 mbalmer 6738 1.1 mbalmer 6739 1.1 mbalmer 6740 1.1 mbalmer 6741 1.1 mbalmer <hr><h3><a name="luaL_pushresult"><code>luaL_pushresult</code></a></h3><p> 6742 1.5 lneto <span class="apii">[-?, +1, <em>m</em>]</span> 6743 1.1 mbalmer <pre>void luaL_pushresult (luaL_Buffer *B);</pre> 6744 1.1 mbalmer 6745 1.1 mbalmer <p> 6746 1.1 mbalmer Finishes the use of buffer <code>B</code> leaving the final string on 6747 1.1 mbalmer the top of the stack. 6748 1.1 mbalmer 6749 1.1 mbalmer 6750 1.1 mbalmer 6751 1.1 mbalmer 6752 1.1 mbalmer 6753 1.2 lneto <hr><h3><a name="luaL_pushresultsize"><code>luaL_pushresultsize</code></a></h3><p> 6754 1.5 lneto <span class="apii">[-?, +1, <em>m</em>]</span> 6755 1.2 lneto <pre>void luaL_pushresultsize (luaL_Buffer *B, size_t sz);</pre> 6756 1.2 lneto 6757 1.2 lneto <p> 6758 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>. 6759 1.2 lneto 6760 1.2 lneto 6761 1.2 lneto 6762 1.2 lneto 6763 1.2 lneto 6764 1.1 mbalmer <hr><h3><a name="luaL_ref"><code>luaL_ref</code></a></h3><p> 6765 1.5 lneto <span class="apii">[-1, +0, <em>m</em>]</span> 6766 1.1 mbalmer <pre>int luaL_ref (lua_State *L, int t);</pre> 6767 1.1 mbalmer 6768 1.1 mbalmer <p> 6769 1.1 mbalmer Creates and returns a <em>reference</em>, 6770 1.1 mbalmer in the table at index <code>t</code>, 6771 1.1 mbalmer for the object at the top of the stack (and pops the object). 6772 1.1 mbalmer 6773 1.1 mbalmer 6774 1.1 mbalmer <p> 6775 1.1 mbalmer A reference is a unique integer key. 6776 1.1 mbalmer As long as you do not manually add integer keys into table <code>t</code>, 6777 1.1 mbalmer <a href="#luaL_ref"><code>luaL_ref</code></a> ensures the uniqueness of the key it returns. 6778 1.1 mbalmer You can retrieve an object referred by reference <code>r</code> 6779 1.1 mbalmer by calling <code>lua_rawgeti(L, t, r)</code>. 6780 1.1 mbalmer Function <a href="#luaL_unref"><code>luaL_unref</code></a> frees a reference and its associated object. 6781 1.1 mbalmer 6782 1.1 mbalmer 6783 1.1 mbalmer <p> 6784 1.1 mbalmer If the object at the top of the stack is <b>nil</b>, 6785 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>. 6786 1.1 mbalmer The constant <a name="pdf-LUA_NOREF"><code>LUA_NOREF</code></a> is guaranteed to be different 6787 1.1 mbalmer from any reference returned by <a href="#luaL_ref"><code>luaL_ref</code></a>. 6788 1.1 mbalmer 6789 1.1 mbalmer 6790 1.1 mbalmer 6791 1.1 mbalmer 6792 1.1 mbalmer 6793 1.1 mbalmer <hr><h3><a name="luaL_Reg"><code>luaL_Reg</code></a></h3> 6794 1.1 mbalmer <pre>typedef struct luaL_Reg { 6795 1.1 mbalmer const char *name; 6796 1.1 mbalmer lua_CFunction func; 6797 1.1 mbalmer } luaL_Reg;</pre> 6798 1.1 mbalmer 6799 1.1 mbalmer <p> 6800 1.1 mbalmer Type for arrays of functions to be registered by 6801 1.2 lneto <a href="#luaL_setfuncs"><code>luaL_setfuncs</code></a>. 6802 1.1 mbalmer <code>name</code> is the function name and <code>func</code> is a pointer to 6803 1.1 mbalmer the function. 6804 1.3 lneto Any array of <a href="#luaL_Reg"><code>luaL_Reg</code></a> must end with a sentinel entry 6805 1.1 mbalmer in which both <code>name</code> and <code>func</code> are <code>NULL</code>. 6806 1.1 mbalmer 6807 1.1 mbalmer 6808 1.1 mbalmer 6809 1.1 mbalmer 6810 1.1 mbalmer 6811 1.2 lneto <hr><h3><a name="luaL_requiref"><code>luaL_requiref</code></a></h3><p> 6812 1.2 lneto <span class="apii">[-0, +1, <em>e</em>]</span> 6813 1.2 lneto <pre>void luaL_requiref (lua_State *L, const char *modname, 6814 1.2 lneto lua_CFunction openf, int glb);</pre> 6815 1.2 lneto 6816 1.2 lneto <p> 6817 1.3 lneto If <code>modname</code> is not already present in <a href="#pdf-package.loaded"><code>package.loaded</code></a>, 6818 1.3 lneto calls function <code>openf</code> with string <code>modname</code> as an argument 6819 1.2 lneto and sets the call result in <code>package.loaded[modname]</code>, 6820 1.2 lneto as if that function has been called through <a href="#pdf-require"><code>require</code></a>. 6821 1.2 lneto 6822 1.2 lneto 6823 1.2 lneto <p> 6824 1.2 lneto If <code>glb</code> is true, 6825 1.3 lneto also stores the module into global <code>modname</code>. 6826 1.2 lneto 6827 1.2 lneto 6828 1.2 lneto <p> 6829 1.3 lneto Leaves a copy of the module on the stack. 6830 1.2 lneto 6831 1.2 lneto 6832 1.2 lneto 6833 1.2 lneto 6834 1.2 lneto 6835 1.2 lneto <hr><h3><a name="luaL_setfuncs"><code>luaL_setfuncs</code></a></h3><p> 6836 1.5 lneto <span class="apii">[-nup, +0, <em>m</em>]</span> 6837 1.2 lneto <pre>void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup);</pre> 6838 1.2 lneto 6839 1.2 lneto <p> 6840 1.2 lneto Registers all functions in the array <code>l</code> 6841 1.2 lneto (see <a href="#luaL_Reg"><code>luaL_Reg</code></a>) into the table on the top of the stack 6842 1.2 lneto (below optional upvalues, see next). 6843 1.2 lneto 6844 1.1 mbalmer 6845 1.1 mbalmer <p> 6846 1.2 lneto When <code>nup</code> is not zero, 6847 1.2 lneto all functions are created sharing <code>nup</code> upvalues, 6848 1.2 lneto which must be previously pushed on the stack 6849 1.2 lneto on top of the library table. 6850 1.2 lneto These values are popped from the stack after the registration. 6851 1.1 mbalmer 6852 1.1 mbalmer 6853 1.2 lneto 6854 1.2 lneto 6855 1.2 lneto 6856 1.2 lneto <hr><h3><a name="luaL_setmetatable"><code>luaL_setmetatable</code></a></h3><p> 6857 1.2 lneto <span class="apii">[-0, +0, –]</span> 6858 1.2 lneto <pre>void luaL_setmetatable (lua_State *L, const char *tname);</pre> 6859 1.2 lneto 6860 1.2 lneto <p> 6861 1.2 lneto Sets the metatable of the object at the top of the stack 6862 1.2 lneto as the metatable associated with name <code>tname</code> 6863 1.2 lneto in the registry (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>). 6864 1.2 lneto 6865 1.2 lneto 6866 1.2 lneto 6867 1.2 lneto 6868 1.2 lneto 6869 1.2 lneto <hr><h3><a name="luaL_Stream"><code>luaL_Stream</code></a></h3> 6870 1.2 lneto <pre>typedef struct luaL_Stream { 6871 1.2 lneto FILE *f; 6872 1.2 lneto lua_CFunction closef; 6873 1.2 lneto } luaL_Stream;</pre> 6874 1.2 lneto 6875 1.1 mbalmer <p> 6876 1.2 lneto The standard representation for file handles, 6877 1.2 lneto which is used by the standard I/O library. 6878 1.1 mbalmer 6879 1.1 mbalmer 6880 1.1 mbalmer <p> 6881 1.2 lneto A file handle is implemented as a full userdata, 6882 1.3 lneto with a metatable called <code>LUA_FILEHANDLE</code> 6883 1.3 lneto (where <code>LUA_FILEHANDLE</code> is a macro with the actual metatable's name). 6884 1.2 lneto The metatable is created by the I/O library 6885 1.2 lneto (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>). 6886 1.2 lneto 6887 1.2 lneto 6888 1.2 lneto <p> 6889 1.2 lneto This userdata must start with the structure <code>luaL_Stream</code>; 6890 1.2 lneto it can contain other data after this initial structure. 6891 1.2 lneto Field <code>f</code> points to the corresponding C stream 6892 1.2 lneto (or it can be <code>NULL</code> to indicate an incompletely created handle). 6893 1.2 lneto Field <code>closef</code> points to a Lua function 6894 1.2 lneto that will be called to close the stream 6895 1.2 lneto when the handle is closed or collected; 6896 1.2 lneto this function receives the file handle as its sole argument and 6897 1.2 lneto must return either <b>true</b> (in case of success) 6898 1.2 lneto or <b>nil</b> plus an error message (in case of error). 6899 1.2 lneto Once Lua calls this field, 6900 1.5 lneto it changes the field value to <code>NULL</code> 6901 1.3 lneto to signal that the handle is closed. 6902 1.2 lneto 6903 1.1 mbalmer 6904 1.1 mbalmer 6905 1.2 lneto 6906 1.2 lneto 6907 1.2 lneto <hr><h3><a name="luaL_testudata"><code>luaL_testudata</code></a></h3><p> 6908 1.5 lneto <span class="apii">[-0, +0, <em>m</em>]</span> 6909 1.2 lneto <pre>void *luaL_testudata (lua_State *L, int arg, const char *tname);</pre> 6910 1.2 lneto 6911 1.1 mbalmer <p> 6912 1.2 lneto This function works like <a href="#luaL_checkudata"><code>luaL_checkudata</code></a>, 6913 1.2 lneto except that, when the test fails, 6914 1.2 lneto it returns <code>NULL</code> instead of raising an error. 6915 1.1 mbalmer 6916 1.1 mbalmer 6917 1.1 mbalmer 6918 1.1 mbalmer 6919 1.1 mbalmer 6920 1.2 lneto <hr><h3><a name="luaL_tolstring"><code>luaL_tolstring</code></a></h3><p> 6921 1.2 lneto <span class="apii">[-0, +1, <em>e</em>]</span> 6922 1.2 lneto <pre>const char *luaL_tolstring (lua_State *L, int idx, size_t *len);</pre> 6923 1.2 lneto 6924 1.2 lneto <p> 6925 1.2 lneto Converts any Lua value at the given index to a C string 6926 1.2 lneto in a reasonable format. 6927 1.2 lneto The resulting string is pushed onto the stack and also 6928 1.2 lneto returned by the function. 6929 1.2 lneto If <code>len</code> is not <code>NULL</code>, 6930 1.2 lneto the function also sets <code>*len</code> with the string length. 6931 1.2 lneto 6932 1.1 mbalmer 6933 1.1 mbalmer <p> 6934 1.2 lneto If the value has a metatable with a <code>"__tostring"</code> field, 6935 1.2 lneto then <code>luaL_tolstring</code> calls the corresponding metamethod 6936 1.2 lneto with the value as argument, 6937 1.2 lneto and uses the result of the call as its result. 6938 1.1 mbalmer 6939 1.1 mbalmer 6940 1.1 mbalmer 6941 1.1 mbalmer 6942 1.1 mbalmer 6943 1.2 lneto <hr><h3><a name="luaL_traceback"><code>luaL_traceback</code></a></h3><p> 6944 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 6945 1.2 lneto <pre>void luaL_traceback (lua_State *L, lua_State *L1, const char *msg, 6946 1.2 lneto int level);</pre> 6947 1.1 mbalmer 6948 1.1 mbalmer <p> 6949 1.2 lneto Creates and pushes a traceback of the stack <code>L1</code>. 6950 1.2 lneto If <code>msg</code> is not <code>NULL</code> it is appended 6951 1.2 lneto at the beginning of the traceback. 6952 1.2 lneto The <code>level</code> parameter tells at which level 6953 1.2 lneto to start the traceback. 6954 1.1 mbalmer 6955 1.2 lneto 6956 1.2 lneto 6957 1.2 lneto 6958 1.2 lneto 6959 1.2 lneto <hr><h3><a name="luaL_typename"><code>luaL_typename</code></a></h3><p> 6960 1.2 lneto <span class="apii">[-0, +0, –]</span> 6961 1.2 lneto <pre>const char *luaL_typename (lua_State *L, int index);</pre> 6962 1.2 lneto 6963 1.2 lneto <p> 6964 1.2 lneto Returns the name of the type of the value at the given index. 6965 1.1 mbalmer 6966 1.1 mbalmer 6967 1.1 mbalmer 6968 1.1 mbalmer 6969 1.1 mbalmer 6970 1.1 mbalmer <hr><h3><a name="luaL_unref"><code>luaL_unref</code></a></h3><p> 6971 1.2 lneto <span class="apii">[-0, +0, –]</span> 6972 1.1 mbalmer <pre>void luaL_unref (lua_State *L, int t, int ref);</pre> 6973 1.1 mbalmer 6974 1.1 mbalmer <p> 6975 1.1 mbalmer Releases reference <code>ref</code> from the table at index <code>t</code> 6976 1.1 mbalmer (see <a href="#luaL_ref"><code>luaL_ref</code></a>). 6977 1.1 mbalmer The entry is removed from the table, 6978 1.1 mbalmer so that the referred object can be collected. 6979 1.1 mbalmer The reference <code>ref</code> is also freed to be used again. 6980 1.1 mbalmer 6981 1.1 mbalmer 6982 1.1 mbalmer <p> 6983 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>, 6984 1.1 mbalmer <a href="#luaL_unref"><code>luaL_unref</code></a> does nothing. 6985 1.1 mbalmer 6986 1.1 mbalmer 6987 1.1 mbalmer 6988 1.1 mbalmer 6989 1.1 mbalmer 6990 1.1 mbalmer <hr><h3><a name="luaL_where"><code>luaL_where</code></a></h3><p> 6991 1.5 lneto <span class="apii">[-0, +1, <em>m</em>]</span> 6992 1.1 mbalmer <pre>void luaL_where (lua_State *L, int lvl);</pre> 6993 1.1 mbalmer 6994 1.1 mbalmer <p> 6995 1.1 mbalmer Pushes onto the stack a string identifying the current position 6996 1.1 mbalmer of the control at level <code>lvl</code> in the call stack. 6997 1.1 mbalmer Typically this string has the following format: 6998 1.1 mbalmer 6999 1.1 mbalmer <pre> 7000 1.1 mbalmer <em>chunkname</em>:<em>currentline</em>: 7001 1.1 mbalmer </pre><p> 7002 1.1 mbalmer Level 0 is the running function, 7003 1.1 mbalmer level 1 is the function that called the running function, 7004 1.1 mbalmer etc. 7005 1.1 mbalmer 7006 1.1 mbalmer 7007 1.1 mbalmer <p> 7008 1.1 mbalmer This function is used to build a prefix for error messages. 7009 1.1 mbalmer 7010 1.1 mbalmer 7011 1.1 mbalmer 7012 1.1 mbalmer 7013 1.1 mbalmer 7014 1.1 mbalmer 7015 1.1 mbalmer 7016 1.2 lneto <h1>6 – <a name="6">Standard Libraries</a></h1> 7017 1.1 mbalmer 7018 1.1 mbalmer <p> 7019 1.1 mbalmer The standard Lua libraries provide useful functions 7020 1.1 mbalmer that are implemented directly through the C API. 7021 1.1 mbalmer Some of these functions provide essential services to the language 7022 1.1 mbalmer (e.g., <a href="#pdf-type"><code>type</code></a> and <a href="#pdf-getmetatable"><code>getmetatable</code></a>); 7023 1.1 mbalmer others provide access to "outside" services (e.g., I/O); 7024 1.1 mbalmer and others could be implemented in Lua itself, 7025 1.1 mbalmer but are quite useful or have critical performance requirements that 7026 1.1 mbalmer deserve an implementation in C (e.g., <a href="#pdf-table.sort"><code>table.sort</code></a>). 7027 1.1 mbalmer 7028 1.1 mbalmer 7029 1.1 mbalmer <p> 7030 1.1 mbalmer All libraries are implemented through the official C API 7031 1.1 mbalmer and are provided as separate C modules. 7032 1.1 mbalmer Currently, Lua has the following standard libraries: 7033 1.1 mbalmer 7034 1.1 mbalmer <ul> 7035 1.1 mbalmer 7036 1.2 lneto <li>basic library (<a href="#6.1">§6.1</a>);</li> 7037 1.1 mbalmer 7038 1.2 lneto <li>coroutine library (<a href="#6.2">§6.2</a>);</li> 7039 1.1 mbalmer 7040 1.2 lneto <li>package library (<a href="#6.3">§6.3</a>);</li> 7041 1.1 mbalmer 7042 1.2 lneto <li>string manipulation (<a href="#6.4">§6.4</a>);</li> 7043 1.1 mbalmer 7044 1.2 lneto <li>basic UTF-8 support (<a href="#6.5">§6.5</a>);</li> 7045 1.1 mbalmer 7046 1.2 lneto <li>table manipulation (<a href="#6.6">§6.6</a>);</li> 7047 1.1 mbalmer 7048 1.2 lneto <li>mathematical functions (<a href="#6.7">§6.7</a>) (sin, log, etc.);</li> 7049 1.1 mbalmer 7050 1.2 lneto <li>input and output (<a href="#6.8">§6.8</a>);</li> 7051 1.2 lneto 7052 1.2 lneto <li>operating system facilities (<a href="#6.9">§6.9</a>);</li> 7053 1.2 lneto 7054 1.2 lneto <li>debug facilities (<a href="#6.10">§6.10</a>).</li> 7055 1.1 mbalmer 7056 1.1 mbalmer </ul><p> 7057 1.2 lneto Except for the basic and the package libraries, 7058 1.1 mbalmer each library provides all its functions as fields of a global table 7059 1.1 mbalmer or as methods of its objects. 7060 1.1 mbalmer 7061 1.1 mbalmer 7062 1.1 mbalmer <p> 7063 1.1 mbalmer To have access to these libraries, 7064 1.1 mbalmer the C host program should call the <a href="#luaL_openlibs"><code>luaL_openlibs</code></a> function, 7065 1.1 mbalmer which opens all standard libraries. 7066 1.1 mbalmer Alternatively, 7067 1.2 lneto the host program can open them individually by using 7068 1.2 lneto <a href="#luaL_requiref"><code>luaL_requiref</code></a> to call 7069 1.1 mbalmer <a name="pdf-luaopen_base"><code>luaopen_base</code></a> (for the basic library), 7070 1.1 mbalmer <a name="pdf-luaopen_package"><code>luaopen_package</code></a> (for the package library), 7071 1.2 lneto <a name="pdf-luaopen_coroutine"><code>luaopen_coroutine</code></a> (for the coroutine library), 7072 1.1 mbalmer <a name="pdf-luaopen_string"><code>luaopen_string</code></a> (for the string library), 7073 1.3 lneto <a name="pdf-luaopen_utf8"><code>luaopen_utf8</code></a> (for the UTF8 library), 7074 1.1 mbalmer <a name="pdf-luaopen_table"><code>luaopen_table</code></a> (for the table library), 7075 1.1 mbalmer <a name="pdf-luaopen_math"><code>luaopen_math</code></a> (for the mathematical library), 7076 1.1 mbalmer <a name="pdf-luaopen_io"><code>luaopen_io</code></a> (for the I/O library), 7077 1.3 lneto <a name="pdf-luaopen_os"><code>luaopen_os</code></a> (for the operating system library), 7078 1.1 mbalmer and <a name="pdf-luaopen_debug"><code>luaopen_debug</code></a> (for the debug library). 7079 1.2 lneto These functions are declared in <a name="pdf-lualib.h"><code>lualib.h</code></a>. 7080 1.1 mbalmer 7081 1.1 mbalmer 7082 1.1 mbalmer 7083 1.2 lneto <h2>6.1 – <a name="6.1">Basic Functions</a></h2> 7084 1.1 mbalmer 7085 1.1 mbalmer <p> 7086 1.2 lneto The basic library provides core functions to Lua. 7087 1.1 mbalmer If you do not include this library in your application, 7088 1.2 lneto you should check carefully whether you need to provide 7089 1.1 mbalmer implementations for some of its facilities. 7090 1.1 mbalmer 7091 1.1 mbalmer 7092 1.1 mbalmer <p> 7093 1.1 mbalmer <hr><h3><a name="pdf-assert"><code>assert (v [, message])</code></a></h3> 7094 1.2 lneto 7095 1.2 lneto 7096 1.2 lneto <p> 7097 1.2 lneto Calls <a href="#pdf-error"><code>error</code></a> if 7098 1.1 mbalmer the value of its argument <code>v</code> is false (i.e., <b>nil</b> or <b>false</b>); 7099 1.1 mbalmer otherwise, returns all its arguments. 7100 1.2 lneto In case of error, 7101 1.2 lneto <code>message</code> is the error object; 7102 1.2 lneto when absent, it defaults to "<code>assertion failed!</code>" 7103 1.1 mbalmer 7104 1.1 mbalmer 7105 1.1 mbalmer 7106 1.1 mbalmer 7107 1.1 mbalmer <p> 7108 1.2 lneto <hr><h3><a name="pdf-collectgarbage"><code>collectgarbage ([opt [, arg]])</code></a></h3> 7109 1.1 mbalmer 7110 1.1 mbalmer 7111 1.1 mbalmer <p> 7112 1.1 mbalmer This function is a generic interface to the garbage collector. 7113 1.1 mbalmer It performs different functions according to its first argument, <code>opt</code>: 7114 1.1 mbalmer 7115 1.1 mbalmer <ul> 7116 1.1 mbalmer 7117 1.2 lneto <li><b>"<code>collect</code>": </b> 7118 1.2 lneto performs a full garbage-collection cycle. 7119 1.2 lneto This is the default option. 7120 1.1 mbalmer </li> 7121 1.1 mbalmer 7122 1.2 lneto <li><b>"<code>stop</code>": </b> 7123 1.2 lneto stops automatic execution of the garbage collector. 7124 1.2 lneto The collector will run only when explicitly invoked, 7125 1.2 lneto until a call to restart it. 7126 1.1 mbalmer </li> 7127 1.1 mbalmer 7128 1.2 lneto <li><b>"<code>restart</code>": </b> 7129 1.2 lneto restarts automatic execution of the garbage collector. 7130 1.1 mbalmer </li> 7131 1.1 mbalmer 7132 1.2 lneto <li><b>"<code>count</code>": </b> 7133 1.2 lneto returns the total memory in use by Lua in Kbytes. 7134 1.2 lneto The value has a fractional part, 7135 1.2 lneto so that it multiplied by 1024 7136 1.2 lneto gives the exact number of bytes in use by Lua 7137 1.2 lneto (except for overflows). 7138 1.1 mbalmer </li> 7139 1.1 mbalmer 7140 1.2 lneto <li><b>"<code>step</code>": </b> 7141 1.1 mbalmer performs a garbage-collection step. 7142 1.2 lneto The step "size" is controlled by <code>arg</code>. 7143 1.2 lneto With a zero value, 7144 1.2 lneto the collector will perform one basic (indivisible) step. 7145 1.2 lneto For non-zero values, 7146 1.2 lneto the collector will perform as if that amount of memory 7147 1.2 lneto (in KBytes) had been allocated by Lua. 7148 1.1 mbalmer Returns <b>true</b> if the step finished a collection cycle. 7149 1.1 mbalmer </li> 7150 1.1 mbalmer 7151 1.2 lneto <li><b>"<code>setpause</code>": </b> 7152 1.1 mbalmer sets <code>arg</code> as the new value for the <em>pause</em> of 7153 1.2 lneto the collector (see <a href="#2.5">§2.5</a>). 7154 1.1 mbalmer Returns the previous value for <em>pause</em>. 7155 1.1 mbalmer </li> 7156 1.1 mbalmer 7157 1.2 lneto <li><b>"<code>setstepmul</code>": </b> 7158 1.1 mbalmer sets <code>arg</code> as the new value for the <em>step multiplier</em> of 7159 1.2 lneto the collector (see <a href="#2.5">§2.5</a>). 7160 1.1 mbalmer Returns the previous value for <em>step</em>. 7161 1.1 mbalmer </li> 7162 1.1 mbalmer 7163 1.2 lneto <li><b>"<code>isrunning</code>": </b> 7164 1.2 lneto returns a boolean that tells whether the collector is running 7165 1.2 lneto (i.e., not stopped). 7166 1.2 lneto </li> 7167 1.2 lneto 7168 1.1 mbalmer </ul> 7169 1.1 mbalmer 7170 1.1 mbalmer 7171 1.1 mbalmer 7172 1.1 mbalmer <p> 7173 1.2 lneto <hr><h3><a name="pdf-dofile"><code>dofile ([filename])</code></a></h3> 7174 1.1 mbalmer Opens the named file and executes its contents as a Lua chunk. 7175 1.1 mbalmer When called without arguments, 7176 1.1 mbalmer <code>dofile</code> executes the contents of the standard input (<code>stdin</code>). 7177 1.1 mbalmer Returns all values returned by the chunk. 7178 1.1 mbalmer In case of errors, <code>dofile</code> propagates the error 7179 1.1 mbalmer to its caller (that is, <code>dofile</code> does not run in protected mode). 7180 1.1 mbalmer 7181 1.1 mbalmer 7182 1.1 mbalmer 7183 1.1 mbalmer 7184 1.1 mbalmer <p> 7185 1.1 mbalmer <hr><h3><a name="pdf-error"><code>error (message [, level])</code></a></h3> 7186 1.1 mbalmer Terminates the last protected function called 7187 1.2 lneto and returns <code>message</code> as the error object. 7188 1.1 mbalmer Function <code>error</code> never returns. 7189 1.1 mbalmer 7190 1.1 mbalmer 7191 1.1 mbalmer <p> 7192 1.1 mbalmer Usually, <code>error</code> adds some information about the error position 7193 1.2 lneto at the beginning of the message, if the message is a string. 7194 1.1 mbalmer The <code>level</code> argument specifies how to get the error position. 7195 1.1 mbalmer With level 1 (the default), the error position is where the 7196 1.1 mbalmer <code>error</code> function was called. 7197 1.1 mbalmer Level 2 points the error to where the function 7198 1.1 mbalmer that called <code>error</code> was called; and so on. 7199 1.1 mbalmer Passing a level 0 avoids the addition of error position information 7200 1.1 mbalmer to the message. 7201 1.1 mbalmer 7202 1.1 mbalmer 7203 1.1 mbalmer 7204 1.1 mbalmer 7205 1.1 mbalmer <p> 7206 1.1 mbalmer <hr><h3><a name="pdf-_G"><code>_G</code></a></h3> 7207 1.1 mbalmer A global variable (not a function) that 7208 1.2 lneto holds the global environment (see <a href="#2.2">§2.2</a>). 7209 1.1 mbalmer Lua itself does not use this variable; 7210 1.1 mbalmer changing its value does not affect any environment, 7211 1.2 lneto nor vice versa. 7212 1.1 mbalmer 7213 1.1 mbalmer 7214 1.1 mbalmer 7215 1.1 mbalmer 7216 1.1 mbalmer <p> 7217 1.1 mbalmer <hr><h3><a name="pdf-getmetatable"><code>getmetatable (object)</code></a></h3> 7218 1.1 mbalmer 7219 1.1 mbalmer 7220 1.1 mbalmer <p> 7221 1.1 mbalmer If <code>object</code> does not have a metatable, returns <b>nil</b>. 7222 1.1 mbalmer Otherwise, 7223 1.1 mbalmer if the object's metatable has a <code>"__metatable"</code> field, 7224 1.1 mbalmer returns the associated value. 7225 1.1 mbalmer Otherwise, returns the metatable of the given object. 7226 1.1 mbalmer 7227 1.1 mbalmer 7228 1.1 mbalmer 7229 1.1 mbalmer 7230 1.1 mbalmer <p> 7231 1.1 mbalmer <hr><h3><a name="pdf-ipairs"><code>ipairs (t)</code></a></h3> 7232 1.1 mbalmer 7233 1.1 mbalmer 7234 1.1 mbalmer <p> 7235 1.3 lneto Returns three values (an iterator function, the table <code>t</code>, and 0) 7236 1.1 mbalmer so that the construction 7237 1.1 mbalmer 7238 1.1 mbalmer <pre> 7239 1.1 mbalmer for i,v in ipairs(t) do <em>body</em> end 7240 1.1 mbalmer </pre><p> 7241 1.3 lneto will iterate over the key–value pairs 7242 1.3 lneto (<code>1,t[1]</code>), (<code>2,t[2]</code>), ..., 7243 1.3 lneto up to the first nil value. 7244 1.1 mbalmer 7245 1.1 mbalmer 7246 1.1 mbalmer 7247 1.1 mbalmer 7248 1.1 mbalmer <p> 7249 1.3 lneto <hr><h3><a name="pdf-load"><code>load (chunk [, chunkname [, mode [, env]]])</code></a></h3> 7250 1.1 mbalmer 7251 1.1 mbalmer 7252 1.1 mbalmer <p> 7253 1.2 lneto Loads a chunk. 7254 1.2 lneto 7255 1.2 lneto 7256 1.2 lneto <p> 7257 1.3 lneto If <code>chunk</code> is a string, the chunk is this string. 7258 1.3 lneto If <code>chunk</code> is a function, 7259 1.2 lneto <code>load</code> calls it repeatedly to get the chunk pieces. 7260 1.3 lneto Each call to <code>chunk</code> must return a string that concatenates 7261 1.1 mbalmer with previous results. 7262 1.1 mbalmer A return of an empty string, <b>nil</b>, or no value signals the end of the chunk. 7263 1.1 mbalmer 7264 1.1 mbalmer 7265 1.1 mbalmer <p> 7266 1.2 lneto If there are no syntactic errors, 7267 1.1 mbalmer returns the compiled chunk as a function; 7268 1.1 mbalmer otherwise, returns <b>nil</b> plus the error message. 7269 1.1 mbalmer 7270 1.1 mbalmer 7271 1.1 mbalmer <p> 7272 1.2 lneto If the resulting function has upvalues, 7273 1.2 lneto the first upvalue is set to the value of <code>env</code>, 7274 1.2 lneto if that parameter is given, 7275 1.2 lneto or to the value of the global environment. 7276 1.3 lneto Other upvalues are initialized with <b>nil</b>. 7277 1.2 lneto (When you load a main chunk, 7278 1.2 lneto the resulting function will always have exactly one upvalue, 7279 1.2 lneto the <code>_ENV</code> variable (see <a href="#2.2">§2.2</a>). 7280 1.3 lneto However, 7281 1.3 lneto when you load a binary chunk created from a function (see <a href="#pdf-string.dump"><code>string.dump</code></a>), 7282 1.3 lneto the resulting function can have an arbitrary number of upvalues.) 7283 1.3 lneto All upvalues are fresh, that is, 7284 1.3 lneto they are not shared with any other function. 7285 1.1 mbalmer 7286 1.1 mbalmer 7287 1.2 lneto <p> 7288 1.3 lneto <code>chunkname</code> is used as the name of the chunk for error messages 7289 1.2 lneto and debug information (see <a href="#4.9">§4.9</a>). 7290 1.2 lneto When absent, 7291 1.3 lneto it defaults to <code>chunk</code>, if <code>chunk</code> is a string, 7292 1.2 lneto or to "<code>=(load)</code>" otherwise. 7293 1.1 mbalmer 7294 1.1 mbalmer 7295 1.1 mbalmer <p> 7296 1.2 lneto The string <code>mode</code> controls whether the chunk can be text or binary 7297 1.2 lneto (that is, a precompiled chunk). 7298 1.2 lneto It may be the string "<code>b</code>" (only binary chunks), 7299 1.2 lneto "<code>t</code>" (only text chunks), 7300 1.2 lneto or "<code>bt</code>" (both binary and text). 7301 1.2 lneto The default is "<code>bt</code>". 7302 1.1 mbalmer 7303 1.1 mbalmer 7304 1.1 mbalmer <p> 7305 1.2 lneto Lua does not check the consistency of binary chunks. 7306 1.2 lneto Maliciously crafted binary chunks can crash 7307 1.2 lneto the interpreter. 7308 1.1 mbalmer 7309 1.1 mbalmer 7310 1.1 mbalmer 7311 1.1 mbalmer 7312 1.1 mbalmer <p> 7313 1.2 lneto <hr><h3><a name="pdf-loadfile"><code>loadfile ([filename [, mode [, env]]])</code></a></h3> 7314 1.1 mbalmer 7315 1.1 mbalmer 7316 1.1 mbalmer <p> 7317 1.1 mbalmer Similar to <a href="#pdf-load"><code>load</code></a>, 7318 1.2 lneto but gets the chunk from file <code>filename</code> 7319 1.2 lneto or from the standard input, 7320 1.2 lneto if no file name is given. 7321 1.1 mbalmer 7322 1.1 mbalmer 7323 1.1 mbalmer 7324 1.1 mbalmer 7325 1.1 mbalmer <p> 7326 1.1 mbalmer <hr><h3><a name="pdf-next"><code>next (table [, index])</code></a></h3> 7327 1.1 mbalmer 7328 1.1 mbalmer 7329 1.1 mbalmer <p> 7330 1.1 mbalmer Allows a program to traverse all fields of a table. 7331 1.1 mbalmer Its first argument is a table and its second argument 7332 1.1 mbalmer is an index in this table. 7333 1.1 mbalmer <code>next</code> returns the next index of the table 7334 1.1 mbalmer and its associated value. 7335 1.1 mbalmer When called with <b>nil</b> as its second argument, 7336 1.1 mbalmer <code>next</code> returns an initial index 7337 1.1 mbalmer and its associated value. 7338 1.1 mbalmer When called with the last index, 7339 1.1 mbalmer or with <b>nil</b> in an empty table, 7340 1.1 mbalmer <code>next</code> returns <b>nil</b>. 7341 1.1 mbalmer If the second argument is absent, then it is interpreted as <b>nil</b>. 7342 1.1 mbalmer In particular, 7343 1.1 mbalmer you can use <code>next(t)</code> to check whether a table is empty. 7344 1.1 mbalmer 7345 1.1 mbalmer 7346 1.1 mbalmer <p> 7347 1.1 mbalmer The order in which the indices are enumerated is not specified, 7348 1.1 mbalmer <em>even for numeric indices</em>. 7349 1.4 mbalmer (To traverse a table in numerical order, 7350 1.2 lneto use a numerical <b>for</b>.) 7351 1.1 mbalmer 7352 1.1 mbalmer 7353 1.1 mbalmer <p> 7354 1.2 lneto The behavior of <code>next</code> is undefined if, 7355 1.1 mbalmer during the traversal, 7356 1.1 mbalmer you assign any value to a non-existent field in the table. 7357 1.1 mbalmer You may however modify existing fields. 7358 1.1 mbalmer In particular, you may clear existing fields. 7359 1.1 mbalmer 7360 1.1 mbalmer 7361 1.1 mbalmer 7362 1.1 mbalmer 7363 1.1 mbalmer <p> 7364 1.1 mbalmer <hr><h3><a name="pdf-pairs"><code>pairs (t)</code></a></h3> 7365 1.1 mbalmer 7366 1.1 mbalmer 7367 1.1 mbalmer <p> 7368 1.2 lneto If <code>t</code> has a metamethod <code>__pairs</code>, 7369 1.2 lneto calls it with <code>t</code> as argument and returns the first three 7370 1.2 lneto results from the call. 7371 1.2 lneto 7372 1.2 lneto 7373 1.2 lneto <p> 7374 1.2 lneto Otherwise, 7375 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>, 7376 1.1 mbalmer so that the construction 7377 1.1 mbalmer 7378 1.1 mbalmer <pre> 7379 1.1 mbalmer for k,v in pairs(t) do <em>body</em> end 7380 1.1 mbalmer </pre><p> 7381 1.1 mbalmer will iterate over all key–value pairs of table <code>t</code>. 7382 1.1 mbalmer 7383 1.1 mbalmer 7384 1.1 mbalmer <p> 7385 1.1 mbalmer See function <a href="#pdf-next"><code>next</code></a> for the caveats of modifying 7386 1.1 mbalmer the table during its traversal. 7387 1.1 mbalmer 7388 1.1 mbalmer 7389 1.1 mbalmer 7390 1.1 mbalmer 7391 1.1 mbalmer <p> 7392 1.2 lneto <hr><h3><a name="pdf-pcall"><code>pcall (f [, arg1, ···])</code></a></h3> 7393 1.1 mbalmer 7394 1.1 mbalmer 7395 1.1 mbalmer <p> 7396 1.1 mbalmer Calls function <code>f</code> with 7397 1.1 mbalmer the given arguments in <em>protected mode</em>. 7398 1.1 mbalmer This means that any error inside <code>f</code> is not propagated; 7399 1.1 mbalmer instead, <code>pcall</code> catches the error 7400 1.1 mbalmer and returns a status code. 7401 1.1 mbalmer Its first result is the status code (a boolean), 7402 1.1 mbalmer which is true if the call succeeds without errors. 7403 1.1 mbalmer In such case, <code>pcall</code> also returns all results from the call, 7404 1.1 mbalmer after this first result. 7405 1.1 mbalmer In case of any error, <code>pcall</code> returns <b>false</b> plus the error message. 7406 1.1 mbalmer 7407 1.1 mbalmer 7408 1.1 mbalmer 7409 1.1 mbalmer 7410 1.1 mbalmer <p> 7411 1.1 mbalmer <hr><h3><a name="pdf-print"><code>print (···)</code></a></h3> 7412 1.2 lneto Receives any number of arguments 7413 1.1 mbalmer and prints their values to <code>stdout</code>, 7414 1.2 lneto using the <a href="#pdf-tostring"><code>tostring</code></a> function to convert each argument to a string. 7415 1.1 mbalmer <code>print</code> is not intended for formatted output, 7416 1.1 mbalmer but only as a quick way to show a value, 7417 1.2 lneto for instance for debugging. 7418 1.2 lneto For complete control over the output, 7419 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>. 7420 1.1 mbalmer 7421 1.1 mbalmer 7422 1.1 mbalmer 7423 1.1 mbalmer 7424 1.1 mbalmer <p> 7425 1.1 mbalmer <hr><h3><a name="pdf-rawequal"><code>rawequal (v1, v2)</code></a></h3> 7426 1.1 mbalmer Checks whether <code>v1</code> is equal to <code>v2</code>, 7427 1.1 mbalmer without invoking any metamethod. 7428 1.1 mbalmer Returns a boolean. 7429 1.1 mbalmer 7430 1.1 mbalmer 7431 1.1 mbalmer 7432 1.1 mbalmer 7433 1.1 mbalmer <p> 7434 1.1 mbalmer <hr><h3><a name="pdf-rawget"><code>rawget (table, index)</code></a></h3> 7435 1.1 mbalmer Gets the real value of <code>table[index]</code>, 7436 1.1 mbalmer without invoking any metamethod. 7437 1.1 mbalmer <code>table</code> must be a table; 7438 1.1 mbalmer <code>index</code> may be any value. 7439 1.1 mbalmer 7440 1.1 mbalmer 7441 1.1 mbalmer 7442 1.1 mbalmer 7443 1.1 mbalmer <p> 7444 1.2 lneto <hr><h3><a name="pdf-rawlen"><code>rawlen (v)</code></a></h3> 7445 1.2 lneto Returns the length of the object <code>v</code>, 7446 1.2 lneto which must be a table or a string, 7447 1.2 lneto without invoking any metamethod. 7448 1.2 lneto Returns an integer. 7449 1.2 lneto 7450 1.2 lneto 7451 1.2 lneto 7452 1.2 lneto 7453 1.2 lneto <p> 7454 1.1 mbalmer <hr><h3><a name="pdf-rawset"><code>rawset (table, index, value)</code></a></h3> 7455 1.1 mbalmer Sets the real value of <code>table[index]</code> to <code>value</code>, 7456 1.1 mbalmer without invoking any metamethod. 7457 1.1 mbalmer <code>table</code> must be a table, 7458 1.2 lneto <code>index</code> any value different from <b>nil</b> and NaN, 7459 1.1 mbalmer and <code>value</code> any Lua value. 7460 1.1 mbalmer 7461 1.1 mbalmer 7462 1.1 mbalmer <p> 7463 1.1 mbalmer This function returns <code>table</code>. 7464 1.1 mbalmer 7465 1.1 mbalmer 7466 1.1 mbalmer 7467 1.1 mbalmer 7468 1.1 mbalmer <p> 7469 1.1 mbalmer <hr><h3><a name="pdf-select"><code>select (index, ···)</code></a></h3> 7470 1.1 mbalmer 7471 1.1 mbalmer 7472 1.1 mbalmer <p> 7473 1.1 mbalmer If <code>index</code> is a number, 7474 1.2 lneto returns all arguments after argument number <code>index</code>; 7475 1.2 lneto a negative number indexes from the end (-1 is the last argument). 7476 1.1 mbalmer Otherwise, <code>index</code> must be the string <code>"#"</code>, 7477 1.1 mbalmer and <code>select</code> returns the total number of extra arguments it received. 7478 1.1 mbalmer 7479 1.1 mbalmer 7480 1.1 mbalmer 7481 1.1 mbalmer 7482 1.1 mbalmer <p> 7483 1.1 mbalmer <hr><h3><a name="pdf-setmetatable"><code>setmetatable (table, metatable)</code></a></h3> 7484 1.1 mbalmer 7485 1.1 mbalmer 7486 1.1 mbalmer <p> 7487 1.1 mbalmer Sets the metatable for the given table. 7488 1.5 lneto (To change the metatable of other types from Lua code, 7489 1.5 lneto you must use the debug library (<a href="#6.10">§6.10</a>).) 7490 1.1 mbalmer If <code>metatable</code> is <b>nil</b>, 7491 1.1 mbalmer removes the metatable of the given table. 7492 1.1 mbalmer If the original metatable has a <code>"__metatable"</code> field, 7493 1.1 mbalmer raises an error. 7494 1.1 mbalmer 7495 1.1 mbalmer 7496 1.1 mbalmer <p> 7497 1.1 mbalmer This function returns <code>table</code>. 7498 1.1 mbalmer 7499 1.1 mbalmer 7500 1.1 mbalmer 7501 1.1 mbalmer 7502 1.1 mbalmer <p> 7503 1.1 mbalmer <hr><h3><a name="pdf-tonumber"><code>tonumber (e [, base])</code></a></h3> 7504 1.2 lneto 7505 1.2 lneto 7506 1.2 lneto <p> 7507 1.2 lneto When called with no <code>base</code>, 7508 1.2 lneto <code>tonumber</code> tries to convert its argument to a number. 7509 1.2 lneto If the argument is already a number or 7510 1.2 lneto a string convertible to a number, 7511 1.2 lneto then <code>tonumber</code> returns this number; 7512 1.1 mbalmer otherwise, it returns <b>nil</b>. 7513 1.1 mbalmer 7514 1.1 mbalmer 7515 1.1 mbalmer <p> 7516 1.2 lneto The conversion of strings can result in integers or floats, 7517 1.2 lneto according to the lexical conventions of Lua (see <a href="#3.1">§3.1</a>). 7518 1.2 lneto (The string may have leading and trailing spaces and a sign.) 7519 1.2 lneto 7520 1.2 lneto 7521 1.2 lneto <p> 7522 1.2 lneto When called with <code>base</code>, 7523 1.2 lneto then <code>e</code> must be a string to be interpreted as 7524 1.2 lneto an integer numeral in that base. 7525 1.1 mbalmer The base may be any integer between 2 and 36, inclusive. 7526 1.1 mbalmer In bases above 10, the letter '<code>A</code>' (in either upper or lower case) 7527 1.1 mbalmer represents 10, '<code>B</code>' represents 11, and so forth, 7528 1.1 mbalmer with '<code>Z</code>' representing 35. 7529 1.2 lneto If the string <code>e</code> is not a valid numeral in the given base, 7530 1.2 lneto the function returns <b>nil</b>. 7531 1.1 mbalmer 7532 1.1 mbalmer 7533 1.1 mbalmer 7534 1.1 mbalmer 7535 1.1 mbalmer <p> 7536 1.2 lneto <hr><h3><a name="pdf-tostring"><code>tostring (v)</code></a></h3> 7537 1.2 lneto Receives a value of any type and 7538 1.2 lneto converts it to a string in a human-readable format. 7539 1.2 lneto (For complete control of how numbers are converted, 7540 1.2 lneto use <a href="#pdf-string.format"><code>string.format</code></a>.) 7541 1.1 mbalmer 7542 1.1 mbalmer 7543 1.1 mbalmer <p> 7544 1.2 lneto If the metatable of <code>v</code> has a <code>"__tostring"</code> field, 7545 1.1 mbalmer then <code>tostring</code> calls the corresponding value 7546 1.2 lneto with <code>v</code> as argument, 7547 1.1 mbalmer and uses the result of the call as its result. 7548 1.1 mbalmer 7549 1.1 mbalmer 7550 1.1 mbalmer 7551 1.1 mbalmer 7552 1.1 mbalmer <p> 7553 1.1 mbalmer <hr><h3><a name="pdf-type"><code>type (v)</code></a></h3> 7554 1.1 mbalmer Returns the type of its only argument, coded as a string. 7555 1.1 mbalmer The possible results of this function are 7556 1.1 mbalmer "<code>nil</code>" (a string, not the value <b>nil</b>), 7557 1.1 mbalmer "<code>number</code>", 7558 1.1 mbalmer "<code>string</code>", 7559 1.1 mbalmer "<code>boolean</code>", 7560 1.1 mbalmer "<code>table</code>", 7561 1.1 mbalmer "<code>function</code>", 7562 1.1 mbalmer "<code>thread</code>", 7563 1.1 mbalmer and "<code>userdata</code>". 7564 1.1 mbalmer 7565 1.1 mbalmer 7566 1.1 mbalmer 7567 1.1 mbalmer 7568 1.1 mbalmer <p> 7569 1.1 mbalmer <hr><h3><a name="pdf-_VERSION"><code>_VERSION</code></a></h3> 7570 1.5 lneto 7571 1.5 lneto 7572 1.5 lneto <p> 7573 1.1 mbalmer A global variable (not a function) that 7574 1.5 lneto holds a string containing the running Lua version. 7575 1.2 lneto The current value of this variable is "<code>Lua 5.3</code>". 7576 1.1 mbalmer 7577 1.1 mbalmer 7578 1.1 mbalmer 7579 1.1 mbalmer 7580 1.1 mbalmer <p> 7581 1.2 lneto <hr><h3><a name="pdf-xpcall"><code>xpcall (f, msgh [, arg1, ···])</code></a></h3> 7582 1.1 mbalmer 7583 1.1 mbalmer 7584 1.1 mbalmer <p> 7585 1.1 mbalmer This function is similar to <a href="#pdf-pcall"><code>pcall</code></a>, 7586 1.2 lneto except that it sets a new message handler <code>msgh</code>. 7587 1.1 mbalmer 7588 1.1 mbalmer 7589 1.1 mbalmer 7590 1.1 mbalmer 7591 1.1 mbalmer 7592 1.1 mbalmer 7593 1.1 mbalmer 7594 1.2 lneto <h2>6.2 – <a name="6.2">Coroutine Manipulation</a></h2> 7595 1.1 mbalmer 7596 1.1 mbalmer <p> 7597 1.4 mbalmer This library comprises the operations to manipulate coroutines, 7598 1.4 mbalmer which come inside the table <a name="pdf-coroutine"><code>coroutine</code></a>. 7599 1.2 lneto See <a href="#2.6">§2.6</a> for a general description of coroutines. 7600 1.1 mbalmer 7601 1.1 mbalmer 7602 1.1 mbalmer <p> 7603 1.1 mbalmer <hr><h3><a name="pdf-coroutine.create"><code>coroutine.create (f)</code></a></h3> 7604 1.1 mbalmer 7605 1.1 mbalmer 7606 1.1 mbalmer <p> 7607 1.1 mbalmer Creates a new coroutine, with body <code>f</code>. 7608 1.4 mbalmer <code>f</code> must be a function. 7609 1.2 lneto Returns this new coroutine, 7610 1.2 lneto an object with type <code>"thread"</code>. 7611 1.2 lneto 7612 1.2 lneto 7613 1.2 lneto 7614 1.2 lneto 7615 1.2 lneto <p> 7616 1.2 lneto <hr><h3><a name="pdf-coroutine.isyieldable"><code>coroutine.isyieldable ()</code></a></h3> 7617 1.2 lneto 7618 1.2 lneto 7619 1.2 lneto <p> 7620 1.2 lneto Returns true when the running coroutine can yield. 7621 1.2 lneto 7622 1.2 lneto 7623 1.2 lneto <p> 7624 1.2 lneto A running coroutine is yieldable if it is not the main thread and 7625 1.2 lneto it is not inside a non-yieldable C function. 7626 1.1 mbalmer 7627 1.1 mbalmer 7628 1.1 mbalmer 7629 1.1 mbalmer 7630 1.1 mbalmer <p> 7631 1.1 mbalmer <hr><h3><a name="pdf-coroutine.resume"><code>coroutine.resume (co [, val1, ···])</code></a></h3> 7632 1.1 mbalmer 7633 1.1 mbalmer 7634 1.1 mbalmer <p> 7635 1.1 mbalmer Starts or continues the execution of coroutine <code>co</code>. 7636 1.1 mbalmer The first time you resume a coroutine, 7637 1.1 mbalmer it starts running its body. 7638 1.2 lneto The values <code>val1</code>, ... are passed 7639 1.1 mbalmer as the arguments to the body function. 7640 1.1 mbalmer If the coroutine has yielded, 7641 1.1 mbalmer <code>resume</code> restarts it; 7642 1.2 lneto the values <code>val1</code>, ... are passed 7643 1.1 mbalmer as the results from the yield. 7644 1.1 mbalmer 7645 1.1 mbalmer 7646 1.1 mbalmer <p> 7647 1.1 mbalmer If the coroutine runs without any errors, 7648 1.1 mbalmer <code>resume</code> returns <b>true</b> plus any values passed to <code>yield</code> 7649 1.2 lneto (when the coroutine yields) or any values returned by the body function 7650 1.2 lneto (when the coroutine terminates). 7651 1.1 mbalmer If there is any error, 7652 1.1 mbalmer <code>resume</code> returns <b>false</b> plus the error message. 7653 1.1 mbalmer 7654 1.1 mbalmer 7655 1.1 mbalmer 7656 1.1 mbalmer 7657 1.1 mbalmer <p> 7658 1.1 mbalmer <hr><h3><a name="pdf-coroutine.running"><code>coroutine.running ()</code></a></h3> 7659 1.1 mbalmer 7660 1.1 mbalmer 7661 1.1 mbalmer <p> 7662 1.2 lneto Returns the running coroutine plus a boolean, 7663 1.2 lneto true when the running coroutine is the main one. 7664 1.1 mbalmer 7665 1.1 mbalmer 7666 1.1 mbalmer 7667 1.1 mbalmer 7668 1.1 mbalmer <p> 7669 1.1 mbalmer <hr><h3><a name="pdf-coroutine.status"><code>coroutine.status (co)</code></a></h3> 7670 1.1 mbalmer 7671 1.1 mbalmer 7672 1.1 mbalmer <p> 7673 1.1 mbalmer Returns the status of coroutine <code>co</code>, as a string: 7674 1.1 mbalmer <code>"running"</code>, 7675 1.1 mbalmer if the coroutine is running (that is, it called <code>status</code>); 7676 1.1 mbalmer <code>"suspended"</code>, if the coroutine is suspended in a call to <code>yield</code>, 7677 1.1 mbalmer or if it has not started running yet; 7678 1.1 mbalmer <code>"normal"</code> if the coroutine is active but not running 7679 1.1 mbalmer (that is, it has resumed another coroutine); 7680 1.1 mbalmer and <code>"dead"</code> if the coroutine has finished its body function, 7681 1.1 mbalmer or if it has stopped with an error. 7682 1.1 mbalmer 7683 1.1 mbalmer 7684 1.1 mbalmer 7685 1.1 mbalmer 7686 1.1 mbalmer <p> 7687 1.1 mbalmer <hr><h3><a name="pdf-coroutine.wrap"><code>coroutine.wrap (f)</code></a></h3> 7688 1.1 mbalmer 7689 1.1 mbalmer 7690 1.1 mbalmer <p> 7691 1.1 mbalmer Creates a new coroutine, with body <code>f</code>. 7692 1.4 mbalmer <code>f</code> must be a function. 7693 1.1 mbalmer Returns a function that resumes the coroutine each time it is called. 7694 1.1 mbalmer Any arguments passed to the function behave as the 7695 1.1 mbalmer extra arguments to <code>resume</code>. 7696 1.1 mbalmer Returns the same values returned by <code>resume</code>, 7697 1.1 mbalmer except the first boolean. 7698 1.1 mbalmer In case of error, propagates the error. 7699 1.1 mbalmer 7700 1.1 mbalmer 7701 1.1 mbalmer 7702 1.1 mbalmer 7703 1.1 mbalmer <p> 7704 1.1 mbalmer <hr><h3><a name="pdf-coroutine.yield"><code>coroutine.yield (···)</code></a></h3> 7705 1.1 mbalmer 7706 1.1 mbalmer 7707 1.1 mbalmer <p> 7708 1.1 mbalmer Suspends the execution of the calling coroutine. 7709 1.1 mbalmer Any arguments to <code>yield</code> are passed as extra results to <code>resume</code>. 7710 1.1 mbalmer 7711 1.1 mbalmer 7712 1.1 mbalmer 7713 1.1 mbalmer 7714 1.1 mbalmer 7715 1.1 mbalmer 7716 1.1 mbalmer 7717 1.2 lneto <h2>6.3 – <a name="6.3">Modules</a></h2> 7718 1.1 mbalmer 7719 1.1 mbalmer <p> 7720 1.1 mbalmer The package library provides basic 7721 1.2 lneto facilities for loading modules in Lua. 7722 1.2 lneto It exports one function directly in the global environment: 7723 1.2 lneto <a href="#pdf-require"><code>require</code></a>. 7724 1.1 mbalmer Everything else is exported in a table <a name="pdf-package"><code>package</code></a>. 7725 1.1 mbalmer 7726 1.1 mbalmer 7727 1.1 mbalmer <p> 7728 1.1 mbalmer <hr><h3><a name="pdf-require"><code>require (modname)</code></a></h3> 7729 1.1 mbalmer 7730 1.1 mbalmer 7731 1.1 mbalmer <p> 7732 1.1 mbalmer Loads the given module. 7733 1.1 mbalmer The function starts by looking into the <a href="#pdf-package.loaded"><code>package.loaded</code></a> table 7734 1.1 mbalmer to determine whether <code>modname</code> is already loaded. 7735 1.1 mbalmer If it is, then <code>require</code> returns the value stored 7736 1.1 mbalmer at <code>package.loaded[modname]</code>. 7737 1.1 mbalmer Otherwise, it tries to find a <em>loader</em> for the module. 7738 1.1 mbalmer 7739 1.1 mbalmer 7740 1.1 mbalmer <p> 7741 1.1 mbalmer To find a loader, 7742 1.2 lneto <code>require</code> is guided by the <a href="#pdf-package.searchers"><code>package.searchers</code></a> sequence. 7743 1.2 lneto By changing this sequence, 7744 1.1 mbalmer we can change how <code>require</code> looks for a module. 7745 1.1 mbalmer The following explanation is based on the default configuration 7746 1.2 lneto for <a href="#pdf-package.searchers"><code>package.searchers</code></a>. 7747 1.1 mbalmer 7748 1.1 mbalmer 7749 1.1 mbalmer <p> 7750 1.1 mbalmer First <code>require</code> queries <code>package.preload[modname]</code>. 7751 1.1 mbalmer If it has a value, 7752 1.2 lneto this value (which must be a function) is the loader. 7753 1.1 mbalmer Otherwise <code>require</code> searches for a Lua loader using the 7754 1.1 mbalmer path stored in <a href="#pdf-package.path"><code>package.path</code></a>. 7755 1.1 mbalmer If that also fails, it searches for a C loader using the 7756 1.1 mbalmer path stored in <a href="#pdf-package.cpath"><code>package.cpath</code></a>. 7757 1.1 mbalmer If that also fails, 7758 1.2 lneto it tries an <em>all-in-one</em> loader (see <a href="#pdf-package.searchers"><code>package.searchers</code></a>). 7759 1.1 mbalmer 7760 1.1 mbalmer 7761 1.1 mbalmer <p> 7762 1.1 mbalmer Once a loader is found, 7763 1.2 lneto <code>require</code> calls the loader with two arguments: 7764 1.2 lneto <code>modname</code> and an extra value dependent on how it got the loader. 7765 1.2 lneto (If the loader came from a file, 7766 1.2 lneto this extra value is the file name.) 7767 1.2 lneto If the loader returns any non-nil value, 7768 1.1 mbalmer <code>require</code> assigns the returned value to <code>package.loaded[modname]</code>. 7769 1.2 lneto If the loader does not return a non-nil value and 7770 1.1 mbalmer has not assigned any value to <code>package.loaded[modname]</code>, 7771 1.1 mbalmer then <code>require</code> assigns <b>true</b> to this entry. 7772 1.1 mbalmer In any case, <code>require</code> returns the 7773 1.1 mbalmer final value of <code>package.loaded[modname]</code>. 7774 1.1 mbalmer 7775 1.1 mbalmer 7776 1.1 mbalmer <p> 7777 1.1 mbalmer If there is any error loading or running the module, 7778 1.1 mbalmer or if it cannot find any loader for the module, 7779 1.2 lneto then <code>require</code> raises an error. 7780 1.2 lneto 7781 1.2 lneto 7782 1.2 lneto 7783 1.2 lneto 7784 1.2 lneto <p> 7785 1.2 lneto <hr><h3><a name="pdf-package.config"><code>package.config</code></a></h3> 7786 1.2 lneto 7787 1.2 lneto 7788 1.2 lneto <p> 7789 1.2 lneto A string describing some compile-time configurations for packages. 7790 1.2 lneto This string is a sequence of lines: 7791 1.2 lneto 7792 1.2 lneto <ul> 7793 1.2 lneto 7794 1.2 lneto <li>The first line is the directory separator string. 7795 1.2 lneto Default is '<code>\</code>' for Windows and '<code>/</code>' for all other systems.</li> 7796 1.1 mbalmer 7797 1.2 lneto <li>The second line is the character that separates templates in a path. 7798 1.2 lneto Default is '<code>;</code>'.</li> 7799 1.2 lneto 7800 1.2 lneto <li>The third line is the string that marks the 7801 1.2 lneto substitution points in a template. 7802 1.2 lneto Default is '<code>?</code>'.</li> 7803 1.2 lneto 7804 1.2 lneto <li>The fourth line is a string that, in a path in Windows, 7805 1.2 lneto is replaced by the executable's directory. 7806 1.2 lneto Default is '<code>!</code>'.</li> 7807 1.2 lneto 7808 1.3 lneto <li>The fifth line is a mark to ignore all text after it 7809 1.2 lneto when building the <code>luaopen_</code> function name. 7810 1.2 lneto Default is '<code>-</code>'.</li> 7811 1.2 lneto 7812 1.2 lneto </ul> 7813 1.1 mbalmer 7814 1.1 mbalmer 7815 1.1 mbalmer 7816 1.1 mbalmer <p> 7817 1.1 mbalmer <hr><h3><a name="pdf-package.cpath"><code>package.cpath</code></a></h3> 7818 1.1 mbalmer 7819 1.1 mbalmer 7820 1.1 mbalmer <p> 7821 1.1 mbalmer The path used by <a href="#pdf-require"><code>require</code></a> to search for a C loader. 7822 1.1 mbalmer 7823 1.1 mbalmer 7824 1.1 mbalmer <p> 7825 1.1 mbalmer Lua initializes the C path <a href="#pdf-package.cpath"><code>package.cpath</code></a> in the same way 7826 1.1 mbalmer it initializes the Lua path <a href="#pdf-package.path"><code>package.path</code></a>, 7827 1.2 lneto using the environment variable <a name="pdf-LUA_CPATH_5_3"><code>LUA_CPATH_5_3</code></a> 7828 1.2 lneto or the environment variable <a name="pdf-LUA_CPATH"><code>LUA_CPATH</code></a> 7829 1.1 mbalmer or a default path defined in <code>luaconf.h</code>. 7830 1.1 mbalmer 7831 1.1 mbalmer 7832 1.1 mbalmer 7833 1.1 mbalmer 7834 1.1 mbalmer <p> 7835 1.1 mbalmer <hr><h3><a name="pdf-package.loaded"><code>package.loaded</code></a></h3> 7836 1.1 mbalmer 7837 1.1 mbalmer 7838 1.1 mbalmer <p> 7839 1.1 mbalmer A table used by <a href="#pdf-require"><code>require</code></a> to control which 7840 1.1 mbalmer modules are already loaded. 7841 1.1 mbalmer When you require a module <code>modname</code> and 7842 1.1 mbalmer <code>package.loaded[modname]</code> is not false, 7843 1.1 mbalmer <a href="#pdf-require"><code>require</code></a> simply returns the value stored there. 7844 1.1 mbalmer 7845 1.1 mbalmer 7846 1.2 lneto <p> 7847 1.2 lneto This variable is only a reference to the real table; 7848 1.2 lneto assignments to this variable do not change the 7849 1.2 lneto table used by <a href="#pdf-require"><code>require</code></a>. 7850 1.2 lneto 7851 1.2 lneto 7852 1.2 lneto 7853 1.2 lneto 7854 1.2 lneto <p> 7855 1.2 lneto <hr><h3><a name="pdf-package.loadlib"><code>package.loadlib (libname, funcname)</code></a></h3> 7856 1.2 lneto 7857 1.2 lneto 7858 1.2 lneto <p> 7859 1.2 lneto Dynamically links the host program with the C library <code>libname</code>. 7860 1.2 lneto 7861 1.2 lneto 7862 1.2 lneto <p> 7863 1.2 lneto If <code>funcname</code> is "<code>*</code>", 7864 1.2 lneto then it only links with the library, 7865 1.2 lneto making the symbols exported by the library 7866 1.2 lneto available to other dynamically linked libraries. 7867 1.2 lneto Otherwise, 7868 1.2 lneto it looks for a function <code>funcname</code> inside the library 7869 1.2 lneto and returns this function as a C function. 7870 1.2 lneto So, <code>funcname</code> must follow the <a href="#lua_CFunction"><code>lua_CFunction</code></a> prototype 7871 1.2 lneto (see <a href="#lua_CFunction"><code>lua_CFunction</code></a>). 7872 1.2 lneto 7873 1.2 lneto 7874 1.2 lneto <p> 7875 1.2 lneto This is a low-level function. 7876 1.2 lneto It completely bypasses the package and module system. 7877 1.2 lneto Unlike <a href="#pdf-require"><code>require</code></a>, 7878 1.2 lneto it does not perform any path searching and 7879 1.2 lneto does not automatically adds extensions. 7880 1.2 lneto <code>libname</code> must be the complete file name of the C library, 7881 1.2 lneto including if necessary a path and an extension. 7882 1.2 lneto <code>funcname</code> must be the exact name exported by the C library 7883 1.2 lneto (which may depend on the C compiler and linker used). 7884 1.2 lneto 7885 1.2 lneto 7886 1.2 lneto <p> 7887 1.2 lneto This function is not supported by Standard C. 7888 1.2 lneto As such, it is only available on some platforms 7889 1.2 lneto (Windows, Linux, Mac OS X, Solaris, BSD, 7890 1.2 lneto plus other Unix systems that support the <code>dlfcn</code> standard). 7891 1.2 lneto 7892 1.2 lneto 7893 1.2 lneto 7894 1.2 lneto 7895 1.2 lneto <p> 7896 1.2 lneto <hr><h3><a name="pdf-package.path"><code>package.path</code></a></h3> 7897 1.2 lneto 7898 1.2 lneto 7899 1.2 lneto <p> 7900 1.2 lneto The path used by <a href="#pdf-require"><code>require</code></a> to search for a Lua loader. 7901 1.2 lneto 7902 1.2 lneto 7903 1.2 lneto <p> 7904 1.2 lneto At start-up, Lua initializes this variable with 7905 1.2 lneto the value of the environment variable <a name="pdf-LUA_PATH_5_3"><code>LUA_PATH_5_3</code></a> or 7906 1.2 lneto the environment variable <a name="pdf-LUA_PATH"><code>LUA_PATH</code></a> or 7907 1.2 lneto with a default path defined in <code>luaconf.h</code>, 7908 1.2 lneto if those environment variables are not defined. 7909 1.2 lneto Any "<code>;;</code>" in the value of the environment variable 7910 1.2 lneto is replaced by the default path. 7911 1.2 lneto 7912 1.2 lneto 7913 1.2 lneto 7914 1.2 lneto 7915 1.2 lneto <p> 7916 1.2 lneto <hr><h3><a name="pdf-package.preload"><code>package.preload</code></a></h3> 7917 1.2 lneto 7918 1.2 lneto 7919 1.2 lneto <p> 7920 1.2 lneto A table to store loaders for specific modules 7921 1.2 lneto (see <a href="#pdf-require"><code>require</code></a>). 7922 1.2 lneto 7923 1.2 lneto 7924 1.2 lneto <p> 7925 1.2 lneto This variable is only a reference to the real table; 7926 1.2 lneto assignments to this variable do not change the 7927 1.2 lneto table used by <a href="#pdf-require"><code>require</code></a>. 7928 1.2 lneto 7929 1.2 lneto 7930 1.1 mbalmer 7931 1.1 mbalmer 7932 1.1 mbalmer <p> 7933 1.2 lneto <hr><h3><a name="pdf-package.searchers"><code>package.searchers</code></a></h3> 7934 1.1 mbalmer 7935 1.1 mbalmer 7936 1.1 mbalmer <p> 7937 1.1 mbalmer A table used by <a href="#pdf-require"><code>require</code></a> to control how to load modules. 7938 1.1 mbalmer 7939 1.1 mbalmer 7940 1.1 mbalmer <p> 7941 1.1 mbalmer Each entry in this table is a <em>searcher function</em>. 7942 1.1 mbalmer When looking for a module, 7943 1.1 mbalmer <a href="#pdf-require"><code>require</code></a> calls each of these searchers in ascending order, 7944 1.1 mbalmer with the module name (the argument given to <a href="#pdf-require"><code>require</code></a>) as its 7945 1.1 mbalmer sole parameter. 7946 1.1 mbalmer The function can return another function (the module <em>loader</em>) 7947 1.2 lneto plus an extra value that will be passed to that loader, 7948 1.1 mbalmer or a string explaining why it did not find that module 7949 1.1 mbalmer (or <b>nil</b> if it has nothing to say). 7950 1.2 lneto 7951 1.2 lneto 7952 1.2 lneto <p> 7953 1.2 lneto Lua initializes this table with four searcher functions. 7954 1.1 mbalmer 7955 1.1 mbalmer 7956 1.1 mbalmer <p> 7957 1.1 mbalmer The first searcher simply looks for a loader in the 7958 1.1 mbalmer <a href="#pdf-package.preload"><code>package.preload</code></a> table. 7959 1.1 mbalmer 7960 1.1 mbalmer 7961 1.1 mbalmer <p> 7962 1.1 mbalmer The second searcher looks for a loader as a Lua library, 7963 1.1 mbalmer using the path stored at <a href="#pdf-package.path"><code>package.path</code></a>. 7964 1.2 lneto The search is done as described in function <a href="#pdf-package.searchpath"><code>package.searchpath</code></a>. 7965 1.1 mbalmer 7966 1.1 mbalmer 7967 1.1 mbalmer <p> 7968 1.1 mbalmer The third searcher looks for a loader as a C library, 7969 1.1 mbalmer using the path given by the variable <a href="#pdf-package.cpath"><code>package.cpath</code></a>. 7970 1.2 lneto Again, 7971 1.2 lneto the search is done as described in function <a href="#pdf-package.searchpath"><code>package.searchpath</code></a>. 7972 1.1 mbalmer For instance, 7973 1.1 mbalmer if the C path is the string 7974 1.1 mbalmer 7975 1.1 mbalmer <pre> 7976 1.1 mbalmer "./?.so;./?.dll;/usr/local/?/init.so" 7977 1.1 mbalmer </pre><p> 7978 1.1 mbalmer the searcher for module <code>foo</code> 7979 1.1 mbalmer will try to open the files <code>./foo.so</code>, <code>./foo.dll</code>, 7980 1.1 mbalmer and <code>/usr/local/foo/init.so</code>, in that order. 7981 1.1 mbalmer Once it finds a C library, 7982 1.1 mbalmer this searcher first uses a dynamic link facility to link the 7983 1.1 mbalmer application with the library. 7984 1.1 mbalmer Then it tries to find a C function inside the library to 7985 1.1 mbalmer be used as the loader. 7986 1.1 mbalmer The name of this C function is the string "<code>luaopen_</code>" 7987 1.1 mbalmer concatenated with a copy of the module name where each dot 7988 1.1 mbalmer is replaced by an underscore. 7989 1.1 mbalmer Moreover, if the module name has a hyphen, 7990 1.3 lneto its suffix after (and including) the first hyphen is removed. 7991 1.3 lneto For instance, if the module name is <code>a.b.c-v2.1</code>, 7992 1.3 lneto the function name will be <code>luaopen_a_b_c</code>. 7993 1.1 mbalmer 7994 1.1 mbalmer 7995 1.1 mbalmer <p> 7996 1.1 mbalmer The fourth searcher tries an <em>all-in-one loader</em>. 7997 1.1 mbalmer It searches the C path for a library for 7998 1.1 mbalmer the root name of the given module. 7999 1.1 mbalmer For instance, when requiring <code>a.b.c</code>, 8000 1.1 mbalmer it will search for a C library for <code>a</code>. 8001 1.1 mbalmer If found, it looks into it for an open function for 8002 1.1 mbalmer the submodule; 8003 1.1 mbalmer in our example, that would be <code>luaopen_a_b_c</code>. 8004 1.1 mbalmer With this facility, a package can pack several C submodules 8005 1.1 mbalmer into one single library, 8006 1.1 mbalmer with each submodule keeping its original open function. 8007 1.1 mbalmer 8008 1.1 mbalmer 8009 1.1 mbalmer <p> 8010 1.2 lneto All searchers except the first one (preload) return as the extra value 8011 1.2 lneto the file name where the module was found, 8012 1.2 lneto as returned by <a href="#pdf-package.searchpath"><code>package.searchpath</code></a>. 8013 1.2 lneto The first searcher returns no extra value. 8014 1.1 mbalmer 8015 1.1 mbalmer 8016 1.1 mbalmer 8017 1.1 mbalmer 8018 1.1 mbalmer <p> 8019 1.2 lneto <hr><h3><a name="pdf-package.searchpath"><code>package.searchpath (name, path [, sep [, rep]])</code></a></h3> 8020 1.1 mbalmer 8021 1.1 mbalmer 8022 1.1 mbalmer <p> 8023 1.2 lneto Searches for the given <code>name</code> in the given <code>path</code>. 8024 1.1 mbalmer 8025 1.1 mbalmer 8026 1.1 mbalmer <p> 8027 1.2 lneto A path is a string containing a sequence of 8028 1.2 lneto <em>templates</em> separated by semicolons. 8029 1.2 lneto For each template, 8030 1.2 lneto the function replaces each interrogation mark (if any) 8031 1.2 lneto in the template with a copy of <code>name</code> 8032 1.2 lneto wherein all occurrences of <code>sep</code> 8033 1.2 lneto (a dot, by default) 8034 1.2 lneto were replaced by <code>rep</code> 8035 1.2 lneto (the system's directory separator, by default), 8036 1.2 lneto and then tries to open the resulting file name. 8037 1.1 mbalmer 8038 1.1 mbalmer 8039 1.1 mbalmer <p> 8040 1.2 lneto For instance, if the path is the string 8041 1.1 mbalmer 8042 1.2 lneto <pre> 8043 1.2 lneto "./?.lua;./?.lc;/usr/local/?/init.lua" 8044 1.2 lneto </pre><p> 8045 1.2 lneto the search for the name <code>foo.a</code> 8046 1.2 lneto will try to open the files 8047 1.2 lneto <code>./foo/a.lua</code>, <code>./foo/a.lc</code>, and 8048 1.2 lneto <code>/usr/local/foo/a/init.lua</code>, in that order. 8049 1.1 mbalmer 8050 1.1 mbalmer 8051 1.1 mbalmer <p> 8052 1.2 lneto Returns the resulting name of the first file that it can 8053 1.2 lneto open in read mode (after closing the file), 8054 1.2 lneto or <b>nil</b> plus an error message if none succeeds. 8055 1.2 lneto (This error message lists all file names it tried to open.) 8056 1.1 mbalmer 8057 1.1 mbalmer 8058 1.1 mbalmer 8059 1.1 mbalmer 8060 1.1 mbalmer 8061 1.1 mbalmer 8062 1.1 mbalmer 8063 1.2 lneto <h2>6.4 – <a name="6.4">String Manipulation</a></h2> 8064 1.1 mbalmer 8065 1.1 mbalmer <p> 8066 1.1 mbalmer This library provides generic functions for string manipulation, 8067 1.1 mbalmer such as finding and extracting substrings, and pattern matching. 8068 1.1 mbalmer When indexing a string in Lua, the first character is at position 1 8069 1.1 mbalmer (not at 0, as in C). 8070 1.1 mbalmer Indices are allowed to be negative and are interpreted as indexing backwards, 8071 1.1 mbalmer from the end of the string. 8072 1.1 mbalmer Thus, the last character is at position -1, and so on. 8073 1.1 mbalmer 8074 1.1 mbalmer 8075 1.1 mbalmer <p> 8076 1.1 mbalmer The string library provides all its functions inside the table 8077 1.1 mbalmer <a name="pdf-string"><code>string</code></a>. 8078 1.1 mbalmer It also sets a metatable for strings 8079 1.1 mbalmer where the <code>__index</code> field points to the <code>string</code> table. 8080 1.1 mbalmer Therefore, you can use the string functions in object-oriented style. 8081 1.2 lneto For instance, <code>string.byte(s,i)</code> 8082 1.1 mbalmer can be written as <code>s:byte(i)</code>. 8083 1.1 mbalmer 8084 1.1 mbalmer 8085 1.1 mbalmer <p> 8086 1.1 mbalmer The string library assumes one-byte character encodings. 8087 1.1 mbalmer 8088 1.1 mbalmer 8089 1.1 mbalmer <p> 8090 1.1 mbalmer <hr><h3><a name="pdf-string.byte"><code>string.byte (s [, i [, j]])</code></a></h3> 8091 1.4 mbalmer Returns the internal numeric codes of the characters <code>s[i]</code>, 8092 1.2 lneto <code>s[i+1]</code>, ..., <code>s[j]</code>. 8093 1.1 mbalmer The default value for <code>i</code> is 1; 8094 1.1 mbalmer the default value for <code>j</code> is <code>i</code>. 8095 1.2 lneto These indices are corrected 8096 1.2 lneto following the same rules of function <a href="#pdf-string.sub"><code>string.sub</code></a>. 8097 1.1 mbalmer 8098 1.1 mbalmer 8099 1.1 mbalmer <p> 8100 1.4 mbalmer Numeric codes are not necessarily portable across platforms. 8101 1.1 mbalmer 8102 1.1 mbalmer 8103 1.1 mbalmer 8104 1.1 mbalmer 8105 1.1 mbalmer <p> 8106 1.1 mbalmer <hr><h3><a name="pdf-string.char"><code>string.char (···)</code></a></h3> 8107 1.1 mbalmer Receives zero or more integers. 8108 1.1 mbalmer Returns a string with length equal to the number of arguments, 8109 1.4 mbalmer in which each character has the internal numeric code equal 8110 1.1 mbalmer to its corresponding argument. 8111 1.1 mbalmer 8112 1.1 mbalmer 8113 1.1 mbalmer <p> 8114 1.4 mbalmer Numeric codes are not necessarily portable across platforms. 8115 1.2 lneto 8116 1.2 lneto 8117 1.2 lneto 8118 1.2 lneto 8119 1.2 lneto <p> 8120 1.2 lneto <hr><h3><a name="pdf-string.dump"><code>string.dump (function [, strip])</code></a></h3> 8121 1.1 mbalmer 8122 1.1 mbalmer 8123 1.2 lneto <p> 8124 1.2 lneto Returns a string containing a binary representation 8125 1.2 lneto (a <em>binary chunk</em>) 8126 1.2 lneto of the given function, 8127 1.2 lneto so that a later <a href="#pdf-load"><code>load</code></a> on this string returns 8128 1.2 lneto a copy of the function (but with new upvalues). 8129 1.2 lneto If <code>strip</code> is a true value, 8130 1.4 mbalmer the binary representation may not include all debug information 8131 1.4 mbalmer about the function, 8132 1.4 mbalmer to save space. 8133 1.2 lneto 8134 1.2 lneto 8135 1.2 lneto <p> 8136 1.3 lneto Functions with upvalues have only their number of upvalues saved. 8137 1.3 lneto When (re)loaded, 8138 1.3 lneto those upvalues receive fresh instances containing <b>nil</b>. 8139 1.3 lneto (You can use the debug library to serialize 8140 1.3 lneto and reload the upvalues of a function 8141 1.3 lneto in a way adequate to your needs.) 8142 1.1 mbalmer 8143 1.1 mbalmer 8144 1.1 mbalmer 8145 1.1 mbalmer 8146 1.1 mbalmer <p> 8147 1.1 mbalmer <hr><h3><a name="pdf-string.find"><code>string.find (s, pattern [, init [, plain]])</code></a></h3> 8148 1.2 lneto 8149 1.2 lneto 8150 1.2 lneto <p> 8151 1.1 mbalmer Looks for the first match of 8152 1.3 lneto <code>pattern</code> (see <a href="#6.4.1">§6.4.1</a>) in the string <code>s</code>. 8153 1.1 mbalmer If it finds a match, then <code>find</code> returns the indices of <code>s</code> 8154 1.1 mbalmer where this occurrence starts and ends; 8155 1.1 mbalmer otherwise, it returns <b>nil</b>. 8156 1.4 mbalmer A third, optional numeric argument <code>init</code> specifies 8157 1.1 mbalmer where to start the search; 8158 1.1 mbalmer its default value is 1 and can be negative. 8159 1.1 mbalmer A value of <b>true</b> as a fourth, optional argument <code>plain</code> 8160 1.1 mbalmer turns off the pattern matching facilities, 8161 1.1 mbalmer so the function does a plain "find substring" operation, 8162 1.2 lneto with no characters in <code>pattern</code> being considered magic. 8163 1.1 mbalmer Note that if <code>plain</code> is given, then <code>init</code> must be given as well. 8164 1.1 mbalmer 8165 1.1 mbalmer 8166 1.1 mbalmer <p> 8167 1.1 mbalmer If the pattern has captures, 8168 1.1 mbalmer then in a successful match 8169 1.1 mbalmer the captured values are also returned, 8170 1.1 mbalmer after the two indices. 8171 1.1 mbalmer 8172 1.1 mbalmer 8173 1.1 mbalmer 8174 1.1 mbalmer 8175 1.1 mbalmer <p> 8176 1.1 mbalmer <hr><h3><a name="pdf-string.format"><code>string.format (formatstring, ···)</code></a></h3> 8177 1.2 lneto 8178 1.2 lneto 8179 1.2 lneto <p> 8180 1.1 mbalmer Returns a formatted version of its variable number of arguments 8181 1.1 mbalmer following the description given in its first argument (which must be a string). 8182 1.3 lneto The format string follows the same rules as the ISO C function <code>sprintf</code>. 8183 1.1 mbalmer The only differences are that the options/modifiers 8184 1.2 lneto <code>*</code>, <code>h</code>, <code>L</code>, <code>l</code>, <code>n</code>, 8185 1.2 lneto and <code>p</code> are not supported 8186 1.1 mbalmer and that there is an extra option, <code>q</code>. 8187 1.2 lneto The <code>q</code> option formats a string between double quotes, 8188 1.2 lneto using escape sequences when necessary to ensure that 8189 1.2 lneto it can safely be read back by the Lua interpreter. 8190 1.1 mbalmer For instance, the call 8191 1.1 mbalmer 8192 1.1 mbalmer <pre> 8193 1.1 mbalmer string.format('%q', 'a string with "quotes" and \n new line') 8194 1.1 mbalmer </pre><p> 8195 1.2 lneto may produce the string: 8196 1.1 mbalmer 8197 1.1 mbalmer <pre> 8198 1.1 mbalmer "a string with \"quotes\" and \ 8199 1.1 mbalmer new line" 8200 1.1 mbalmer </pre> 8201 1.1 mbalmer 8202 1.1 mbalmer <p> 8203 1.2 lneto Options 8204 1.4 mbalmer <code>A</code>, <code>a</code>, <code>E</code>, <code>e</code>, <code>f</code>, 8205 1.2 lneto <code>G</code>, and <code>g</code> all expect a number as argument. 8206 1.2 lneto Options <code>c</code>, <code>d</code>, 8207 1.2 lneto <code>i</code>, <code>o</code>, <code>u</code>, <code>X</code>, and <code>x</code> 8208 1.2 lneto expect an integer. 8209 1.4 mbalmer Option <code>q</code> expects a string. 8210 1.5 lneto Option <code>s</code> expects a string; 8211 1.4 mbalmer if its argument is not a string, 8212 1.2 lneto it is converted to one following the same rules of <a href="#pdf-tostring"><code>tostring</code></a>. 8213 1.5 lneto If the option has any modifier (flags, width, length), 8214 1.5 lneto the string argument should not contain embedded zeros. 8215 1.1 mbalmer 8216 1.1 mbalmer 8217 1.4 mbalmer <p> 8218 1.4 mbalmer When Lua is compiled with a non-C99 compiler, 8219 1.4 mbalmer options <code>A</code> and <code>a</code> (hexadecimal floats) 8220 1.4 mbalmer do not support any modifier (flags, width, length). 8221 1.4 mbalmer 8222 1.4 mbalmer 8223 1.1 mbalmer 8224 1.1 mbalmer 8225 1.1 mbalmer <p> 8226 1.1 mbalmer <hr><h3><a name="pdf-string.gmatch"><code>string.gmatch (s, pattern)</code></a></h3> 8227 1.1 mbalmer Returns an iterator function that, 8228 1.1 mbalmer each time it is called, 8229 1.3 lneto returns the next captures from <code>pattern</code> (see <a href="#6.4.1">§6.4.1</a>) 8230 1.3 lneto over the string <code>s</code>. 8231 1.1 mbalmer If <code>pattern</code> specifies no captures, 8232 1.1 mbalmer then the whole match is produced in each call. 8233 1.1 mbalmer 8234 1.1 mbalmer 8235 1.1 mbalmer <p> 8236 1.1 mbalmer As an example, the following loop 8237 1.2 lneto will iterate over all the words from string <code>s</code>, 8238 1.2 lneto printing one per line: 8239 1.1 mbalmer 8240 1.1 mbalmer <pre> 8241 1.1 mbalmer s = "hello world from Lua" 8242 1.1 mbalmer for w in string.gmatch(s, "%a+") do 8243 1.1 mbalmer print(w) 8244 1.1 mbalmer end 8245 1.1 mbalmer </pre><p> 8246 1.1 mbalmer The next example collects all pairs <code>key=value</code> from the 8247 1.1 mbalmer given string into a table: 8248 1.1 mbalmer 8249 1.1 mbalmer <pre> 8250 1.1 mbalmer t = {} 8251 1.1 mbalmer s = "from=world, to=Lua" 8252 1.1 mbalmer for k, v in string.gmatch(s, "(%w+)=(%w+)") do 8253 1.1 mbalmer t[k] = v 8254 1.1 mbalmer end 8255 1.1 mbalmer </pre> 8256 1.1 mbalmer 8257 1.1 mbalmer <p> 8258 1.2 lneto For this function, a caret '<code>^</code>' at the start of a pattern does not 8259 1.1 mbalmer work as an anchor, as this would prevent the iteration. 8260 1.1 mbalmer 8261 1.1 mbalmer 8262 1.1 mbalmer 8263 1.1 mbalmer 8264 1.1 mbalmer <p> 8265 1.1 mbalmer <hr><h3><a name="pdf-string.gsub"><code>string.gsub (s, pattern, repl [, n])</code></a></h3> 8266 1.1 mbalmer Returns a copy of <code>s</code> 8267 1.1 mbalmer in which all (or the first <code>n</code>, if given) 8268 1.3 lneto occurrences of the <code>pattern</code> (see <a href="#6.4.1">§6.4.1</a>) have been 8269 1.1 mbalmer replaced by a replacement string specified by <code>repl</code>, 8270 1.1 mbalmer which can be a string, a table, or a function. 8271 1.1 mbalmer <code>gsub</code> also returns, as its second value, 8272 1.1 mbalmer the total number of matches that occurred. 8273 1.2 lneto The name <code>gsub</code> comes from <em>Global SUBstitution</em>. 8274 1.1 mbalmer 8275 1.1 mbalmer 8276 1.1 mbalmer <p> 8277 1.1 mbalmer If <code>repl</code> is a string, then its value is used for replacement. 8278 1.1 mbalmer The character <code>%</code> works as an escape character: 8279 1.2 lneto any sequence in <code>repl</code> of the form <code>%<em>d</em></code>, 8280 1.2 lneto with <em>d</em> between 1 and 9, 8281 1.2 lneto stands for the value of the <em>d</em>-th captured substring. 8282 1.1 mbalmer The sequence <code>%0</code> stands for the whole match. 8283 1.1 mbalmer The sequence <code>%%</code> stands for a single <code>%</code>. 8284 1.1 mbalmer 8285 1.1 mbalmer 8286 1.1 mbalmer <p> 8287 1.1 mbalmer If <code>repl</code> is a table, then the table is queried for every match, 8288 1.2 lneto using the first capture as the key. 8289 1.1 mbalmer 8290 1.1 mbalmer 8291 1.1 mbalmer <p> 8292 1.1 mbalmer If <code>repl</code> is a function, then this function is called every time a 8293 1.1 mbalmer match occurs, with all captured substrings passed as arguments, 8294 1.2 lneto in order. 8295 1.2 lneto 8296 1.2 lneto 8297 1.2 lneto <p> 8298 1.2 lneto In any case, 8299 1.1 mbalmer if the pattern specifies no captures, 8300 1.2 lneto then it behaves as if the whole pattern was inside a capture. 8301 1.1 mbalmer 8302 1.1 mbalmer 8303 1.1 mbalmer <p> 8304 1.1 mbalmer If the value returned by the table query or by the function call 8305 1.1 mbalmer is a string or a number, 8306 1.1 mbalmer then it is used as the replacement string; 8307 1.1 mbalmer otherwise, if it is <b>false</b> or <b>nil</b>, 8308 1.1 mbalmer then there is no replacement 8309 1.1 mbalmer (that is, the original match is kept in the string). 8310 1.1 mbalmer 8311 1.1 mbalmer 8312 1.1 mbalmer <p> 8313 1.1 mbalmer Here are some examples: 8314 1.1 mbalmer 8315 1.1 mbalmer <pre> 8316 1.1 mbalmer x = string.gsub("hello world", "(%w+)", "%1 %1") 8317 1.1 mbalmer --> x="hello hello world world" 8318 1.1 mbalmer 8319 1.1 mbalmer x = string.gsub("hello world", "%w+", "%0 %0", 1) 8320 1.1 mbalmer --> x="hello hello world" 8321 1.1 mbalmer 8322 1.1 mbalmer x = string.gsub("hello world from Lua", "(%w+)%s*(%w+)", "%2 %1") 8323 1.1 mbalmer --> x="world hello Lua from" 8324 1.1 mbalmer 8325 1.1 mbalmer x = string.gsub("home = $HOME, user = $USER", "%$(%w+)", os.getenv) 8326 1.1 mbalmer --> x="home = /home/roberto, user = roberto" 8327 1.1 mbalmer 8328 1.1 mbalmer x = string.gsub("4+5 = $return 4+5$", "%$(.-)%$", function (s) 8329 1.2 lneto return load(s)() 8330 1.1 mbalmer end) 8331 1.1 mbalmer --> x="4+5 = 9" 8332 1.1 mbalmer 8333 1.2 lneto local t = {name="lua", version="5.3"} 8334 1.1 mbalmer x = string.gsub("$name-$version.tar.gz", "%$(%w+)", t) 8335 1.2 lneto --> x="lua-5.3.tar.gz" 8336 1.1 mbalmer </pre> 8337 1.1 mbalmer 8338 1.1 mbalmer 8339 1.1 mbalmer 8340 1.1 mbalmer <p> 8341 1.1 mbalmer <hr><h3><a name="pdf-string.len"><code>string.len (s)</code></a></h3> 8342 1.1 mbalmer Receives a string and returns its length. 8343 1.1 mbalmer The empty string <code>""</code> has length 0. 8344 1.1 mbalmer Embedded zeros are counted, 8345 1.1 mbalmer so <code>"a\000bc\000"</code> has length 5. 8346 1.1 mbalmer 8347 1.1 mbalmer 8348 1.1 mbalmer 8349 1.1 mbalmer 8350 1.1 mbalmer <p> 8351 1.1 mbalmer <hr><h3><a name="pdf-string.lower"><code>string.lower (s)</code></a></h3> 8352 1.1 mbalmer Receives a string and returns a copy of this string with all 8353 1.1 mbalmer uppercase letters changed to lowercase. 8354 1.1 mbalmer All other characters are left unchanged. 8355 1.1 mbalmer The definition of what an uppercase letter is depends on the current locale. 8356 1.1 mbalmer 8357 1.1 mbalmer 8358 1.1 mbalmer 8359 1.1 mbalmer 8360 1.1 mbalmer <p> 8361 1.1 mbalmer <hr><h3><a name="pdf-string.match"><code>string.match (s, pattern [, init])</code></a></h3> 8362 1.1 mbalmer Looks for the first <em>match</em> of 8363 1.3 lneto <code>pattern</code> (see <a href="#6.4.1">§6.4.1</a>) in the string <code>s</code>. 8364 1.1 mbalmer If it finds one, then <code>match</code> returns 8365 1.1 mbalmer the captures from the pattern; 8366 1.1 mbalmer otherwise it returns <b>nil</b>. 8367 1.1 mbalmer If <code>pattern</code> specifies no captures, 8368 1.1 mbalmer then the whole match is returned. 8369 1.4 mbalmer A third, optional numeric argument <code>init</code> specifies 8370 1.1 mbalmer where to start the search; 8371 1.1 mbalmer its default value is 1 and can be negative. 8372 1.1 mbalmer 8373 1.1 mbalmer 8374 1.1 mbalmer 8375 1.1 mbalmer 8376 1.1 mbalmer <p> 8377 1.3 lneto <hr><h3><a name="pdf-string.pack"><code>string.pack (fmt, v1, v2, ···)</code></a></h3> 8378 1.3 lneto 8379 1.3 lneto 8380 1.3 lneto <p> 8381 1.3 lneto Returns a binary string containing the values <code>v1</code>, <code>v2</code>, etc. 8382 1.3 lneto packed (that is, serialized in binary form) 8383 1.3 lneto according to the format string <code>fmt</code> (see <a href="#6.4.2">§6.4.2</a>). 8384 1.3 lneto 8385 1.3 lneto 8386 1.3 lneto 8387 1.3 lneto 8388 1.3 lneto <p> 8389 1.3 lneto <hr><h3><a name="pdf-string.packsize"><code>string.packsize (fmt)</code></a></h3> 8390 1.3 lneto 8391 1.3 lneto 8392 1.3 lneto <p> 8393 1.3 lneto Returns the size of a string resulting from <a href="#pdf-string.pack"><code>string.pack</code></a> 8394 1.3 lneto with the given format. 8395 1.3 lneto The format string cannot have the variable-length options 8396 1.3 lneto '<code>s</code>' or '<code>z</code>' (see <a href="#6.4.2">§6.4.2</a>). 8397 1.3 lneto 8398 1.3 lneto 8399 1.3 lneto 8400 1.3 lneto 8401 1.3 lneto <p> 8402 1.2 lneto <hr><h3><a name="pdf-string.rep"><code>string.rep (s, n [, sep])</code></a></h3> 8403 1.1 mbalmer Returns a string that is the concatenation of <code>n</code> copies of 8404 1.2 lneto the string <code>s</code> separated by the string <code>sep</code>. 8405 1.2 lneto The default value for <code>sep</code> is the empty string 8406 1.2 lneto (that is, no separator). 8407 1.3 lneto Returns the empty string if <code>n</code> is not positive. 8408 1.1 mbalmer 8409 1.1 mbalmer 8410 1.5 lneto <p> 8411 1.5 lneto (Note that it is very easy to exhaust the memory of your machine 8412 1.5 lneto with a single call to this function.) 8413 1.5 lneto 8414 1.5 lneto 8415 1.1 mbalmer 8416 1.1 mbalmer 8417 1.1 mbalmer <p> 8418 1.1 mbalmer <hr><h3><a name="pdf-string.reverse"><code>string.reverse (s)</code></a></h3> 8419 1.1 mbalmer Returns a string that is the string <code>s</code> reversed. 8420 1.1 mbalmer 8421 1.1 mbalmer 8422 1.1 mbalmer 8423 1.1 mbalmer 8424 1.1 mbalmer <p> 8425 1.1 mbalmer <hr><h3><a name="pdf-string.sub"><code>string.sub (s, i [, j])</code></a></h3> 8426 1.1 mbalmer Returns the substring of <code>s</code> that 8427 1.1 mbalmer starts at <code>i</code> and continues until <code>j</code>; 8428 1.1 mbalmer <code>i</code> and <code>j</code> can be negative. 8429 1.1 mbalmer If <code>j</code> is absent, then it is assumed to be equal to -1 8430 1.1 mbalmer (which is the same as the string length). 8431 1.1 mbalmer In particular, 8432 1.1 mbalmer the call <code>string.sub(s,1,j)</code> returns a prefix of <code>s</code> 8433 1.1 mbalmer with length <code>j</code>, 8434 1.1 mbalmer and <code>string.sub(s, -i)</code> returns a suffix of <code>s</code> 8435 1.1 mbalmer with length <code>i</code>. 8436 1.1 mbalmer 8437 1.1 mbalmer 8438 1.2 lneto <p> 8439 1.2 lneto If, after the translation of negative indices, 8440 1.2 lneto <code>i</code> is less than 1, 8441 1.2 lneto it is corrected to 1. 8442 1.2 lneto If <code>j</code> is greater than the string length, 8443 1.2 lneto it is corrected to that length. 8444 1.2 lneto If, after these corrections, 8445 1.2 lneto <code>i</code> is greater than <code>j</code>, 8446 1.2 lneto the function returns the empty string. 8447 1.2 lneto 8448 1.2 lneto 8449 1.2 lneto 8450 1.2 lneto 8451 1.2 lneto <p> 8452 1.3 lneto <hr><h3><a name="pdf-string.unpack"><code>string.unpack (fmt, s [, pos])</code></a></h3> 8453 1.2 lneto 8454 1.2 lneto 8455 1.2 lneto <p> 8456 1.3 lneto Returns the values packed in string <code>s</code> (see <a href="#pdf-string.pack"><code>string.pack</code></a>) 8457 1.3 lneto according to the format string <code>fmt</code> (see <a href="#6.4.2">§6.4.2</a>). 8458 1.3 lneto An optional <code>pos</code> marks where 8459 1.3 lneto to start reading in <code>s</code> (default is 1). 8460 1.3 lneto After the read values, 8461 1.3 lneto this function also returns the index of the first unread byte in <code>s</code>. 8462 1.2 lneto 8463 1.2 lneto 8464 1.1 mbalmer 8465 1.1 mbalmer 8466 1.1 mbalmer <p> 8467 1.1 mbalmer <hr><h3><a name="pdf-string.upper"><code>string.upper (s)</code></a></h3> 8468 1.1 mbalmer Receives a string and returns a copy of this string with all 8469 1.1 mbalmer lowercase letters changed to uppercase. 8470 1.1 mbalmer All other characters are left unchanged. 8471 1.1 mbalmer The definition of what a lowercase letter is depends on the current locale. 8472 1.1 mbalmer 8473 1.1 mbalmer 8474 1.1 mbalmer 8475 1.3 lneto 8476 1.3 lneto 8477 1.2 lneto <h3>6.4.1 – <a name="6.4.1">Patterns</a></h3> 8478 1.1 mbalmer 8479 1.3 lneto <p> 8480 1.3 lneto Patterns in Lua are described by regular strings, 8481 1.3 lneto which are interpreted as patterns by the pattern-matching functions 8482 1.3 lneto <a href="#pdf-string.find"><code>string.find</code></a>, 8483 1.3 lneto <a href="#pdf-string.gmatch"><code>string.gmatch</code></a>, 8484 1.3 lneto <a href="#pdf-string.gsub"><code>string.gsub</code></a>, 8485 1.3 lneto and <a href="#pdf-string.match"><code>string.match</code></a>. 8486 1.3 lneto This section describes the syntax and the meaning 8487 1.3 lneto (that is, what they match) of these strings. 8488 1.3 lneto 8489 1.3 lneto 8490 1.1 mbalmer 8491 1.1 mbalmer <h4>Character Class:</h4><p> 8492 1.1 mbalmer A <em>character class</em> is used to represent a set of characters. 8493 1.1 mbalmer The following combinations are allowed in describing a character class: 8494 1.1 mbalmer 8495 1.1 mbalmer <ul> 8496 1.1 mbalmer 8497 1.2 lneto <li><b><em>x</em>: </b> 8498 1.1 mbalmer (where <em>x</em> is not one of the <em>magic characters</em> 8499 1.1 mbalmer <code>^$()%.[]*+-?</code>) 8500 1.1 mbalmer represents the character <em>x</em> itself. 8501 1.1 mbalmer </li> 8502 1.1 mbalmer 8503 1.2 lneto <li><b><code>.</code>: </b> (a dot) represents all characters.</li> 8504 1.1 mbalmer 8505 1.2 lneto <li><b><code>%a</code>: </b> represents all letters.</li> 8506 1.1 mbalmer 8507 1.2 lneto <li><b><code>%c</code>: </b> represents all control characters.</li> 8508 1.1 mbalmer 8509 1.2 lneto <li><b><code>%d</code>: </b> represents all digits.</li> 8510 1.1 mbalmer 8511 1.2 lneto <li><b><code>%g</code>: </b> represents all printable characters except space.</li> 8512 1.1 mbalmer 8513 1.2 lneto <li><b><code>%l</code>: </b> represents all lowercase letters.</li> 8514 1.1 mbalmer 8515 1.2 lneto <li><b><code>%p</code>: </b> represents all punctuation characters.</li> 8516 1.1 mbalmer 8517 1.2 lneto <li><b><code>%s</code>: </b> represents all space characters.</li> 8518 1.1 mbalmer 8519 1.2 lneto <li><b><code>%u</code>: </b> represents all uppercase letters.</li> 8520 1.1 mbalmer 8521 1.2 lneto <li><b><code>%w</code>: </b> represents all alphanumeric characters.</li> 8522 1.1 mbalmer 8523 1.2 lneto <li><b><code>%x</code>: </b> represents all hexadecimal digits.</li> 8524 1.1 mbalmer 8525 1.2 lneto <li><b><code>%<em>x</em></code>: </b> (where <em>x</em> is any non-alphanumeric character) 8526 1.1 mbalmer represents the character <em>x</em>. 8527 1.1 mbalmer This is the standard way to escape the magic characters. 8528 1.3 lneto Any non-alphanumeric character 8529 1.4 mbalmer (including all punctuation characters, even the non-magical) 8530 1.1 mbalmer can be preceded by a '<code>%</code>' 8531 1.1 mbalmer when used to represent itself in a pattern. 8532 1.1 mbalmer </li> 8533 1.1 mbalmer 8534 1.2 lneto <li><b><code>[<em>set</em>]</code>: </b> 8535 1.1 mbalmer represents the class which is the union of all 8536 1.1 mbalmer characters in <em>set</em>. 8537 1.1 mbalmer A range of characters can be specified by 8538 1.2 lneto separating the end characters of the range, 8539 1.2 lneto in ascending order, with a '<code>-</code>'. 8540 1.1 mbalmer All classes <code>%</code><em>x</em> described above can also be used as 8541 1.1 mbalmer components in <em>set</em>. 8542 1.1 mbalmer All other characters in <em>set</em> represent themselves. 8543 1.1 mbalmer For example, <code>[%w_]</code> (or <code>[_%w]</code>) 8544 1.1 mbalmer represents all alphanumeric characters plus the underscore, 8545 1.1 mbalmer <code>[0-7]</code> represents the octal digits, 8546 1.1 mbalmer and <code>[0-7%l%-]</code> represents the octal digits plus 8547 1.1 mbalmer the lowercase letters plus the '<code>-</code>' character. 8548 1.1 mbalmer 8549 1.1 mbalmer 8550 1.1 mbalmer <p> 8551 1.1 mbalmer The interaction between ranges and classes is not defined. 8552 1.1 mbalmer Therefore, patterns like <code>[%a-z]</code> or <code>[a-%%]</code> 8553 1.1 mbalmer have no meaning. 8554 1.1 mbalmer </li> 8555 1.1 mbalmer 8556 1.2 lneto <li><b><code>[^<em>set</em>]</code>: </b> 8557 1.1 mbalmer represents the complement of <em>set</em>, 8558 1.1 mbalmer where <em>set</em> is interpreted as above. 8559 1.1 mbalmer </li> 8560 1.1 mbalmer 8561 1.1 mbalmer </ul><p> 8562 1.1 mbalmer For all classes represented by single letters (<code>%a</code>, <code>%c</code>, etc.), 8563 1.1 mbalmer the corresponding uppercase letter represents the complement of the class. 8564 1.1 mbalmer For instance, <code>%S</code> represents all non-space characters. 8565 1.1 mbalmer 8566 1.1 mbalmer 8567 1.1 mbalmer <p> 8568 1.1 mbalmer The definitions of letter, space, and other character groups 8569 1.1 mbalmer depend on the current locale. 8570 1.1 mbalmer In particular, the class <code>[a-z]</code> may not be equivalent to <code>%l</code>. 8571 1.1 mbalmer 8572 1.1 mbalmer 8573 1.1 mbalmer 8574 1.1 mbalmer 8575 1.1 mbalmer 8576 1.1 mbalmer <h4>Pattern Item:</h4><p> 8577 1.1 mbalmer A <em>pattern item</em> can be 8578 1.1 mbalmer 8579 1.1 mbalmer <ul> 8580 1.1 mbalmer 8581 1.1 mbalmer <li> 8582 1.1 mbalmer a single character class, 8583 1.1 mbalmer which matches any single character in the class; 8584 1.1 mbalmer </li> 8585 1.1 mbalmer 8586 1.1 mbalmer <li> 8587 1.1 mbalmer a single character class followed by '<code>*</code>', 8588 1.3 lneto which matches zero or more repetitions of characters in the class. 8589 1.1 mbalmer These repetition items will always match the longest possible sequence; 8590 1.1 mbalmer </li> 8591 1.1 mbalmer 8592 1.1 mbalmer <li> 8593 1.1 mbalmer a single character class followed by '<code>+</code>', 8594 1.3 lneto which matches one or more repetitions of characters in the class. 8595 1.1 mbalmer These repetition items will always match the longest possible sequence; 8596 1.1 mbalmer </li> 8597 1.1 mbalmer 8598 1.1 mbalmer <li> 8599 1.1 mbalmer a single character class followed by '<code>-</code>', 8600 1.3 lneto which also matches zero or more repetitions of characters in the class. 8601 1.1 mbalmer Unlike '<code>*</code>', 8602 1.2 lneto these repetition items will always match the shortest possible sequence; 8603 1.1 mbalmer </li> 8604 1.1 mbalmer 8605 1.1 mbalmer <li> 8606 1.1 mbalmer a single character class followed by '<code>?</code>', 8607 1.3 lneto which matches zero or one occurrence of a character in the class. 8608 1.3 lneto It always matches one occurrence if possible; 8609 1.1 mbalmer </li> 8610 1.1 mbalmer 8611 1.1 mbalmer <li> 8612 1.1 mbalmer <code>%<em>n</em></code>, for <em>n</em> between 1 and 9; 8613 1.1 mbalmer such item matches a substring equal to the <em>n</em>-th captured string 8614 1.1 mbalmer (see below); 8615 1.1 mbalmer </li> 8616 1.1 mbalmer 8617 1.1 mbalmer <li> 8618 1.1 mbalmer <code>%b<em>xy</em></code>, where <em>x</em> and <em>y</em> are two distinct characters; 8619 1.1 mbalmer such item matches strings that start with <em>x</em>, end with <em>y</em>, 8620 1.1 mbalmer and where the <em>x</em> and <em>y</em> are <em>balanced</em>. 8621 1.1 mbalmer This means that, if one reads the string from left to right, 8622 1.1 mbalmer counting <em>+1</em> for an <em>x</em> and <em>-1</em> for a <em>y</em>, 8623 1.1 mbalmer the ending <em>y</em> is the first <em>y</em> where the count reaches 0. 8624 1.1 mbalmer For instance, the item <code>%b()</code> matches expressions with 8625 1.1 mbalmer balanced parentheses. 8626 1.1 mbalmer </li> 8627 1.1 mbalmer 8628 1.2 lneto <li> 8629 1.2 lneto <code>%f[<em>set</em>]</code>, a <em>frontier pattern</em>; 8630 1.2 lneto such item matches an empty string at any position such that 8631 1.2 lneto the next character belongs to <em>set</em> 8632 1.2 lneto and the previous character does not belong to <em>set</em>. 8633 1.2 lneto The set <em>set</em> is interpreted as previously described. 8634 1.2 lneto The beginning and the end of the subject are handled as if 8635 1.2 lneto they were the character '<code>\0</code>'. 8636 1.2 lneto </li> 8637 1.2 lneto 8638 1.1 mbalmer </ul> 8639 1.1 mbalmer 8640 1.1 mbalmer 8641 1.1 mbalmer 8642 1.1 mbalmer 8643 1.1 mbalmer <h4>Pattern:</h4><p> 8644 1.1 mbalmer A <em>pattern</em> is a sequence of pattern items. 8645 1.2 lneto A caret '<code>^</code>' at the beginning of a pattern anchors the match at the 8646 1.1 mbalmer beginning of the subject string. 8647 1.1 mbalmer A '<code>$</code>' at the end of a pattern anchors the match at the 8648 1.1 mbalmer end of the subject string. 8649 1.1 mbalmer At other positions, 8650 1.1 mbalmer '<code>^</code>' and '<code>$</code>' have no special meaning and represent themselves. 8651 1.1 mbalmer 8652 1.1 mbalmer 8653 1.1 mbalmer 8654 1.1 mbalmer 8655 1.1 mbalmer 8656 1.1 mbalmer <h4>Captures:</h4><p> 8657 1.1 mbalmer A pattern can contain sub-patterns enclosed in parentheses; 8658 1.1 mbalmer they describe <em>captures</em>. 8659 1.1 mbalmer When a match succeeds, the substrings of the subject string 8660 1.1 mbalmer that match captures are stored (<em>captured</em>) for future use. 8661 1.1 mbalmer Captures are numbered according to their left parentheses. 8662 1.1 mbalmer For instance, in the pattern <code>"(a*(.)%w(%s*))"</code>, 8663 1.1 mbalmer the part of the string matching <code>"a*(.)%w(%s*)"</code> is 8664 1.1 mbalmer stored as the first capture (and therefore has number 1); 8665 1.1 mbalmer the character matching "<code>.</code>" is captured with number 2, 8666 1.1 mbalmer and the part matching "<code>%s*</code>" has number 3. 8667 1.1 mbalmer 8668 1.1 mbalmer 8669 1.1 mbalmer <p> 8670 1.1 mbalmer As a special case, the empty capture <code>()</code> captures 8671 1.1 mbalmer the current string position (a number). 8672 1.1 mbalmer For instance, if we apply the pattern <code>"()aa()"</code> on the 8673 1.1 mbalmer string <code>"flaaap"</code>, there will be two captures: 3 and 5. 8674 1.1 mbalmer 8675 1.1 mbalmer 8676 1.2 lneto 8677 1.2 lneto 8678 1.2 lneto 8679 1.2 lneto 8680 1.2 lneto 8681 1.3 lneto <h3>6.4.2 – <a name="6.4.2">Format Strings for Pack and Unpack</a></h3> 8682 1.3 lneto 8683 1.3 lneto <p> 8684 1.3 lneto The first argument to <a href="#pdf-string.pack"><code>string.pack</code></a>, 8685 1.3 lneto <a href="#pdf-string.packsize"><code>string.packsize</code></a>, and <a href="#pdf-string.unpack"><code>string.unpack</code></a> 8686 1.3 lneto is a format string, 8687 1.3 lneto which describes the layout of the structure being created or read. 8688 1.3 lneto 8689 1.3 lneto 8690 1.3 lneto <p> 8691 1.3 lneto A format string is a sequence of conversion options. 8692 1.3 lneto The conversion options are as follows: 8693 1.3 lneto 8694 1.3 lneto <ul> 8695 1.3 lneto <li><b><code><</code>: </b>sets little endian</li> 8696 1.3 lneto <li><b><code>></code>: </b>sets big endian</li> 8697 1.3 lneto <li><b><code>=</code>: </b>sets native endian</li> 8698 1.3 lneto <li><b><code>![<em>n</em>]</code>: </b>sets maximum alignment to <code>n</code> 8699 1.3 lneto (default is native alignment)</li> 8700 1.3 lneto <li><b><code>b</code>: </b>a signed byte (<code>char</code>)</li> 8701 1.3 lneto <li><b><code>B</code>: </b>an unsigned byte (<code>char</code>)</li> 8702 1.3 lneto <li><b><code>h</code>: </b>a signed <code>short</code> (native size)</li> 8703 1.3 lneto <li><b><code>H</code>: </b>an unsigned <code>short</code> (native size)</li> 8704 1.3 lneto <li><b><code>l</code>: </b>a signed <code>long</code> (native size)</li> 8705 1.3 lneto <li><b><code>L</code>: </b>an unsigned <code>long</code> (native size)</li> 8706 1.3 lneto <li><b><code>j</code>: </b>a <code>lua_Integer</code></li> 8707 1.3 lneto <li><b><code>J</code>: </b>a <code>lua_Unsigned</code></li> 8708 1.3 lneto <li><b><code>T</code>: </b>a <code>size_t</code> (native size)</li> 8709 1.3 lneto <li><b><code>i[<em>n</em>]</code>: </b>a signed <code>int</code> with <code>n</code> bytes 8710 1.3 lneto (default is native size)</li> 8711 1.3 lneto <li><b><code>I[<em>n</em>]</code>: </b>an unsigned <code>int</code> with <code>n</code> bytes 8712 1.3 lneto (default is native size)</li> 8713 1.3 lneto <li><b><code>f</code>: </b>a <code>float</code> (native size)</li> 8714 1.3 lneto <li><b><code>d</code>: </b>a <code>double</code> (native size)</li> 8715 1.3 lneto <li><b><code>n</code>: </b>a <code>lua_Number</code></li> 8716 1.3 lneto <li><b><code>c<em>n</em></code>: </b>a fixed-sized string with <code>n</code> bytes</li> 8717 1.3 lneto <li><b><code>z</code>: </b>a zero-terminated string</li> 8718 1.3 lneto <li><b><code>s[<em>n</em>]</code>: </b>a string preceded by its length 8719 1.3 lneto coded as an unsigned integer with <code>n</code> bytes 8720 1.3 lneto (default is a <code>size_t</code>)</li> 8721 1.3 lneto <li><b><code>x</code>: </b>one byte of padding</li> 8722 1.3 lneto <li><b><code>X<em>op</em></code>: </b>an empty item that aligns 8723 1.3 lneto according to option <code>op</code> 8724 1.3 lneto (which is otherwise ignored)</li> 8725 1.3 lneto <li><b>'<code> </code>': </b>(empty space) ignored</li> 8726 1.3 lneto </ul><p> 8727 1.3 lneto (A "<code>[<em>n</em>]</code>" means an optional integral numeral.) 8728 1.3 lneto Except for padding, spaces, and configurations 8729 1.3 lneto (options "<code>xX <=>!</code>"), 8730 1.3 lneto each option corresponds to an argument (in <a href="#pdf-string.pack"><code>string.pack</code></a>) 8731 1.3 lneto or a result (in <a href="#pdf-string.unpack"><code>string.unpack</code></a>). 8732 1.3 lneto 8733 1.3 lneto 8734 1.3 lneto <p> 8735 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>", 8736 1.3 lneto <code>n</code> can be any integer between 1 and 16. 8737 1.3 lneto All integral options check overflows; 8738 1.3 lneto <a href="#pdf-string.pack"><code>string.pack</code></a> checks whether the given value fits in the given size; 8739 1.3 lneto <a href="#pdf-string.unpack"><code>string.unpack</code></a> checks whether the read value fits in a Lua integer. 8740 1.3 lneto 8741 1.3 lneto 8742 1.3 lneto <p> 8743 1.3 lneto Any format string starts as if prefixed by "<code>!1=</code>", 8744 1.3 lneto that is, 8745 1.3 lneto with maximum alignment of 1 (no alignment) 8746 1.3 lneto and native endianness. 8747 1.3 lneto 8748 1.3 lneto 8749 1.3 lneto <p> 8750 1.3 lneto Alignment works as follows: 8751 1.3 lneto For each option, 8752 1.3 lneto the format gets extra padding until the data starts 8753 1.3 lneto at an offset that is a multiple of the minimum between the 8754 1.3 lneto option size and the maximum alignment; 8755 1.3 lneto this minimum must be a power of 2. 8756 1.3 lneto Options "<code>c</code>" and "<code>z</code>" are not aligned; 8757 1.3 lneto option "<code>s</code>" follows the alignment of its starting integer. 8758 1.3 lneto 8759 1.3 lneto 8760 1.3 lneto <p> 8761 1.3 lneto All padding is filled with zeros by <a href="#pdf-string.pack"><code>string.pack</code></a> 8762 1.3 lneto (and ignored by <a href="#pdf-string.unpack"><code>string.unpack</code></a>). 8763 1.3 lneto 8764 1.3 lneto 8765 1.3 lneto 8766 1.2 lneto 8767 1.2 lneto 8768 1.2 lneto 8769 1.2 lneto 8770 1.2 lneto <h2>6.5 – <a name="6.5">UTF-8 Support</a></h2> 8771 1.2 lneto 8772 1.2 lneto <p> 8773 1.2 lneto This library provides basic support for UTF-8 encoding. 8774 1.2 lneto It provides all its functions inside the table <a name="pdf-utf8"><code>utf8</code></a>. 8775 1.2 lneto This library does not provide any support for Unicode other 8776 1.2 lneto than the handling of the encoding. 8777 1.2 lneto Any operation that needs the meaning of a character, 8778 1.2 lneto such as character classification, is outside its scope. 8779 1.2 lneto 8780 1.2 lneto 8781 1.2 lneto <p> 8782 1.2 lneto Unless stated otherwise, 8783 1.2 lneto all functions that expect a byte position as a parameter 8784 1.2 lneto assume that the given position is either the start of a byte sequence 8785 1.2 lneto or one plus the length of the subject string. 8786 1.2 lneto As in the string library, 8787 1.2 lneto negative indices count from the end of the string. 8788 1.2 lneto 8789 1.2 lneto 8790 1.2 lneto <p> 8791 1.2 lneto <hr><h3><a name="pdf-utf8.char"><code>utf8.char (···)</code></a></h3> 8792 1.2 lneto Receives zero or more integers, 8793 1.2 lneto converts each one to its corresponding UTF-8 byte sequence 8794 1.2 lneto and returns a string with the concatenation of all these sequences. 8795 1.2 lneto 8796 1.2 lneto 8797 1.2 lneto 8798 1.2 lneto 8799 1.2 lneto <p> 8800 1.3 lneto <hr><h3><a name="pdf-utf8.charpattern"><code>utf8.charpattern</code></a></h3> 8801 1.2 lneto The pattern (a string, not a function) "<code>[\0-\x7F\xC2-\xF4][\x80-\xBF]*</code>" 8802 1.2 lneto (see <a href="#6.4.1">§6.4.1</a>), 8803 1.2 lneto which matches exactly one UTF-8 byte sequence, 8804 1.2 lneto assuming that the subject is a valid UTF-8 string. 8805 1.2 lneto 8806 1.2 lneto 8807 1.2 lneto 8808 1.2 lneto 8809 1.2 lneto <p> 8810 1.2 lneto <hr><h3><a name="pdf-utf8.codes"><code>utf8.codes (s)</code></a></h3> 8811 1.2 lneto 8812 1.2 lneto 8813 1.2 lneto <p> 8814 1.2 lneto Returns values so that the construction 8815 1.2 lneto 8816 1.2 lneto <pre> 8817 1.2 lneto for p, c in utf8.codes(s) do <em>body</em> end 8818 1.2 lneto </pre><p> 8819 1.2 lneto will iterate over all characters in string <code>s</code>, 8820 1.2 lneto with <code>p</code> being the position (in bytes) and <code>c</code> the code point 8821 1.2 lneto of each character. 8822 1.2 lneto It raises an error if it meets any invalid byte sequence. 8823 1.2 lneto 8824 1.2 lneto 8825 1.2 lneto 8826 1.2 lneto 8827 1.2 lneto <p> 8828 1.2 lneto <hr><h3><a name="pdf-utf8.codepoint"><code>utf8.codepoint (s [, i [, j]])</code></a></h3> 8829 1.2 lneto Returns the codepoints (as integers) from all characters in <code>s</code> 8830 1.2 lneto that start between byte position <code>i</code> and <code>j</code> (both included). 8831 1.2 lneto The default for <code>i</code> is 1 and for <code>j</code> is <code>i</code>. 8832 1.2 lneto It raises an error if it meets any invalid byte sequence. 8833 1.2 lneto 8834 1.2 lneto 8835 1.2 lneto 8836 1.2 lneto 8837 1.2 lneto <p> 8838 1.2 lneto <hr><h3><a name="pdf-utf8.len"><code>utf8.len (s [, i [, j]])</code></a></h3> 8839 1.2 lneto Returns the number of UTF-8 characters in string <code>s</code> 8840 1.3 lneto that start between positions <code>i</code> and <code>j</code> (both inclusive). 8841 1.2 lneto The default for <code>i</code> is 1 and for <code>j</code> is -1. 8842 1.2 lneto If it finds any invalid byte sequence, 8843 1.3 lneto returns a false value plus the position of the first invalid byte. 8844 1.2 lneto 8845 1.2 lneto 8846 1.2 lneto 8847 1.2 lneto 8848 1.2 lneto <p> 8849 1.2 lneto <hr><h3><a name="pdf-utf8.offset"><code>utf8.offset (s, n [, i])</code></a></h3> 8850 1.2 lneto Returns the position (in bytes) where the encoding of the 8851 1.2 lneto <code>n</code>-th character of <code>s</code> 8852 1.2 lneto (counting from position <code>i</code>) starts. 8853 1.2 lneto A negative <code>n</code> gets characters before position <code>i</code>. 8854 1.2 lneto The default for <code>i</code> is 1 when <code>n</code> is non-negative 8855 1.2 lneto and <code>#s + 1</code> otherwise, 8856 1.2 lneto so that <code>utf8.offset(s, -n)</code> gets the offset of the 8857 1.2 lneto <code>n</code>-th character from the end of the string. 8858 1.3 lneto If the specified character is neither in the subject 8859 1.3 lneto nor right after its end, 8860 1.2 lneto the function returns <b>nil</b>. 8861 1.2 lneto 8862 1.2 lneto 8863 1.2 lneto <p> 8864 1.2 lneto As a special case, 8865 1.2 lneto when <code>n</code> is 0 the function returns the start of the encoding 8866 1.2 lneto of the character that contains the <code>i</code>-th byte of <code>s</code>. 8867 1.2 lneto 8868 1.2 lneto 8869 1.1 mbalmer <p> 8870 1.2 lneto This function assumes that <code>s</code> is a valid UTF-8 string. 8871 1.1 mbalmer 8872 1.1 mbalmer 8873 1.1 mbalmer 8874 1.1 mbalmer 8875 1.1 mbalmer 8876 1.1 mbalmer 8877 1.1 mbalmer 8878 1.2 lneto <h2>6.6 – <a name="6.6">Table Manipulation</a></h2> 8879 1.2 lneto 8880 1.2 lneto <p> 8881 1.2 lneto This library provides generic functions for table manipulation. 8882 1.2 lneto It provides all its functions inside the table <a name="pdf-table"><code>table</code></a>. 8883 1.1 mbalmer 8884 1.1 mbalmer 8885 1.2 lneto <p> 8886 1.2 lneto Remember that, whenever an operation needs the length of a table, 8887 1.2 lneto the table must be a proper sequence 8888 1.2 lneto or have a <code>__len</code> metamethod (see <a href="#3.4.7">§3.4.7</a>). 8889 1.2 lneto All functions ignore non-numeric keys 8890 1.3 lneto in the tables given as arguments. 8891 1.1 mbalmer 8892 1.1 mbalmer 8893 1.1 mbalmer <p> 8894 1.2 lneto <hr><h3><a name="pdf-table.concat"><code>table.concat (list [, sep [, i [, j]]])</code></a></h3> 8895 1.1 mbalmer 8896 1.1 mbalmer 8897 1.1 mbalmer <p> 8898 1.2 lneto Given a list where all elements are strings or numbers, 8899 1.2 lneto returns the string <code>list[i]..sep..list[i+1] ··· sep..list[j]</code>. 8900 1.1 mbalmer The default value for <code>sep</code> is the empty string, 8901 1.1 mbalmer the default for <code>i</code> is 1, 8902 1.2 lneto and the default for <code>j</code> is <code>#list</code>. 8903 1.1 mbalmer If <code>i</code> is greater than <code>j</code>, returns the empty string. 8904 1.1 mbalmer 8905 1.1 mbalmer 8906 1.1 mbalmer 8907 1.1 mbalmer 8908 1.1 mbalmer <p> 8909 1.2 lneto <hr><h3><a name="pdf-table.insert"><code>table.insert (list, [pos,] value)</code></a></h3> 8910 1.1 mbalmer 8911 1.1 mbalmer 8912 1.1 mbalmer <p> 8913 1.2 lneto Inserts element <code>value</code> at position <code>pos</code> in <code>list</code>, 8914 1.2 lneto shifting up the elements 8915 1.2 lneto <code>list[pos], list[pos+1], ···, list[#list]</code>. 8916 1.2 lneto The default value for <code>pos</code> is <code>#list+1</code>, 8917 1.1 mbalmer so that a call <code>table.insert(t,x)</code> inserts <code>x</code> at the end 8918 1.2 lneto of list <code>t</code>. 8919 1.1 mbalmer 8920 1.1 mbalmer 8921 1.1 mbalmer 8922 1.1 mbalmer 8923 1.1 mbalmer <p> 8924 1.3 lneto <hr><h3><a name="pdf-table.move"><code>table.move (a1, f, e, t [,a2])</code></a></h3> 8925 1.3 lneto 8926 1.3 lneto 8927 1.3 lneto <p> 8928 1.3 lneto Moves elements from table <code>a1</code> to table <code>a2</code>. 8929 1.3 lneto This function performs the equivalent to the following 8930 1.3 lneto multiple assignment: 8931 1.3 lneto <code>a2[t],··· = a1[f],···,a1[e]</code>. 8932 1.3 lneto The default for <code>a2</code> is <code>a1</code>. 8933 1.3 lneto The destination range can overlap with the source range. 8934 1.4 mbalmer The number of elements to be moved must fit in a Lua integer. 8935 1.3 lneto 8936 1.3 lneto 8937 1.3 lneto 8938 1.3 lneto 8939 1.3 lneto <p> 8940 1.2 lneto <hr><h3><a name="pdf-table.pack"><code>table.pack (···)</code></a></h3> 8941 1.1 mbalmer 8942 1.1 mbalmer 8943 1.1 mbalmer <p> 8944 1.2 lneto Returns a new table with all parameters stored into keys 1, 2, etc. 8945 1.2 lneto and with a field "<code>n</code>" with the total number of parameters. 8946 1.2 lneto Note that the resulting table may not be a sequence. 8947 1.1 mbalmer 8948 1.1 mbalmer 8949 1.1 mbalmer 8950 1.1 mbalmer 8951 1.1 mbalmer <p> 8952 1.2 lneto <hr><h3><a name="pdf-table.remove"><code>table.remove (list [, pos])</code></a></h3> 8953 1.1 mbalmer 8954 1.1 mbalmer 8955 1.1 mbalmer <p> 8956 1.2 lneto Removes from <code>list</code> the element at position <code>pos</code>, 8957 1.2 lneto returning the value of the removed element. 8958 1.2 lneto When <code>pos</code> is an integer between 1 and <code>#list</code>, 8959 1.2 lneto it shifts down the elements 8960 1.2 lneto <code>list[pos+1], list[pos+2], ···, list[#list]</code> 8961 1.2 lneto and erases element <code>list[#list]</code>; 8962 1.2 lneto The index <code>pos</code> can also be 0 when <code>#list</code> is 0, 8963 1.2 lneto or <code>#list + 1</code>; 8964 1.2 lneto in those cases, the function erases the element <code>list[pos]</code>. 8965 1.2 lneto 8966 1.2 lneto 8967 1.2 lneto <p> 8968 1.2 lneto The default value for <code>pos</code> is <code>#list</code>, 8969 1.2 lneto so that a call <code>table.remove(l)</code> removes the last element 8970 1.2 lneto of list <code>l</code>. 8971 1.2 lneto 8972 1.1 mbalmer 8973 1.1 mbalmer 8974 1.1 mbalmer 8975 1.2 lneto <p> 8976 1.2 lneto <hr><h3><a name="pdf-table.sort"><code>table.sort (list [, comp])</code></a></h3> 8977 1.2 lneto 8978 1.1 mbalmer 8979 1.1 mbalmer <p> 8980 1.2 lneto Sorts list elements in a given order, <em>in-place</em>, 8981 1.2 lneto from <code>list[1]</code> to <code>list[#list]</code>. 8982 1.1 mbalmer If <code>comp</code> is given, 8983 1.2 lneto then it must be a function that receives two list elements 8984 1.2 lneto and returns true when the first element must come 8985 1.2 lneto before the second in the final order 8986 1.5 lneto (so that, after the sort, 8987 1.5 lneto <code>i < j</code> implies <code>not comp(list[j],list[i])</code>). 8988 1.1 mbalmer If <code>comp</code> is not given, 8989 1.1 mbalmer then the standard Lua operator <code><</code> is used instead. 8990 1.1 mbalmer 8991 1.1 mbalmer 8992 1.1 mbalmer <p> 8993 1.5 lneto Note that the <code>comp</code> function must define 8994 1.5 lneto a strict partial order over the elements in the list; 8995 1.5 lneto that is, it must be asymmetric and transitive. 8996 1.5 lneto Otherwise, no valid sort may be possible. 8997 1.5 lneto 8998 1.5 lneto 8999 1.5 lneto <p> 9000 1.1 mbalmer The sort algorithm is not stable; 9001 1.5 lneto that is, elements not comparable by the given order 9002 1.5 lneto (e.g., equal elements) 9003 1.1 mbalmer may have their relative positions changed by the sort. 9004 1.1 mbalmer 9005 1.1 mbalmer 9006 1.1 mbalmer 9007 1.1 mbalmer 9008 1.2 lneto <p> 9009 1.2 lneto <hr><h3><a name="pdf-table.unpack"><code>table.unpack (list [, i [, j]])</code></a></h3> 9010 1.2 lneto 9011 1.2 lneto 9012 1.2 lneto <p> 9013 1.2 lneto Returns the elements from the given list. 9014 1.2 lneto This function is equivalent to 9015 1.2 lneto 9016 1.2 lneto <pre> 9017 1.2 lneto return list[i], list[i+1], ···, list[j] 9018 1.2 lneto </pre><p> 9019 1.2 lneto By default, <code>i</code> is 1 and <code>j</code> is <code>#list</code>. 9020 1.2 lneto 9021 1.2 lneto 9022 1.2 lneto 9023 1.1 mbalmer 9024 1.1 mbalmer 9025 1.1 mbalmer 9026 1.2 lneto 9027 1.2 lneto <h2>6.7 – <a name="6.7">Mathematical Functions</a></h2> 9028 1.1 mbalmer 9029 1.1 mbalmer <p> 9030 1.2 lneto This library provides basic mathematical functions. 9031 1.2 lneto It provides all its functions and constants inside the table <a name="pdf-math"><code>math</code></a>. 9032 1.2 lneto Functions with the annotation "<code>integer/float</code>" give 9033 1.2 lneto integer results for integer arguments 9034 1.2 lneto and float results for float (or mixed) arguments. 9035 1.2 lneto Rounding functions 9036 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>) 9037 1.2 lneto return an integer when the result fits in the range of an integer, 9038 1.3 lneto or a float otherwise. 9039 1.1 mbalmer 9040 1.1 mbalmer 9041 1.1 mbalmer <p> 9042 1.1 mbalmer <hr><h3><a name="pdf-math.abs"><code>math.abs (x)</code></a></h3> 9043 1.1 mbalmer 9044 1.1 mbalmer 9045 1.1 mbalmer <p> 9046 1.2 lneto Returns the absolute value of <code>x</code>. (integer/float) 9047 1.1 mbalmer 9048 1.1 mbalmer 9049 1.1 mbalmer 9050 1.1 mbalmer 9051 1.1 mbalmer <p> 9052 1.1 mbalmer <hr><h3><a name="pdf-math.acos"><code>math.acos (x)</code></a></h3> 9053 1.1 mbalmer 9054 1.1 mbalmer 9055 1.1 mbalmer <p> 9056 1.1 mbalmer Returns the arc cosine of <code>x</code> (in radians). 9057 1.1 mbalmer 9058 1.1 mbalmer 9059 1.1 mbalmer 9060 1.1 mbalmer 9061 1.1 mbalmer <p> 9062 1.1 mbalmer <hr><h3><a name="pdf-math.asin"><code>math.asin (x)</code></a></h3> 9063 1.1 mbalmer 9064 1.1 mbalmer 9065 1.1 mbalmer <p> 9066 1.1 mbalmer Returns the arc sine of <code>x</code> (in radians). 9067 1.1 mbalmer 9068 1.1 mbalmer 9069 1.1 mbalmer 9070 1.1 mbalmer 9071 1.1 mbalmer <p> 9072 1.2 lneto <hr><h3><a name="pdf-math.atan"><code>math.atan (y [, x])</code></a></h3> 9073 1.1 mbalmer 9074 1.1 mbalmer 9075 1.1 mbalmer <p> 9076 1.1 mbalmer 9077 1.1 mbalmer Returns the arc tangent of <code>y/x</code> (in radians), 9078 1.1 mbalmer but uses the signs of both parameters to find the 9079 1.1 mbalmer quadrant of the result. 9080 1.1 mbalmer (It also handles correctly the case of <code>x</code> being zero.) 9081 1.1 mbalmer 9082 1.1 mbalmer 9083 1.2 lneto <p> 9084 1.2 lneto The default value for <code>x</code> is 1, 9085 1.2 lneto so that the call <code>math.atan(y)</code> 9086 1.2 lneto returns the arc tangent of <code>y</code>. 9087 1.2 lneto 9088 1.2 lneto 9089 1.1 mbalmer 9090 1.1 mbalmer 9091 1.1 mbalmer <p> 9092 1.1 mbalmer <hr><h3><a name="pdf-math.ceil"><code>math.ceil (x)</code></a></h3> 9093 1.1 mbalmer 9094 1.1 mbalmer 9095 1.1 mbalmer <p> 9096 1.3 lneto Returns the smallest integral value larger than or equal to <code>x</code>. 9097 1.1 mbalmer 9098 1.1 mbalmer 9099 1.1 mbalmer 9100 1.1 mbalmer 9101 1.1 mbalmer <p> 9102 1.1 mbalmer <hr><h3><a name="pdf-math.cos"><code>math.cos (x)</code></a></h3> 9103 1.1 mbalmer 9104 1.1 mbalmer 9105 1.1 mbalmer <p> 9106 1.1 mbalmer Returns the cosine of <code>x</code> (assumed to be in radians). 9107 1.1 mbalmer 9108 1.1 mbalmer 9109 1.1 mbalmer 9110 1.1 mbalmer 9111 1.1 mbalmer <p> 9112 1.1 mbalmer <hr><h3><a name="pdf-math.deg"><code>math.deg (x)</code></a></h3> 9113 1.1 mbalmer 9114 1.1 mbalmer 9115 1.1 mbalmer <p> 9116 1.2 lneto Converts the angle <code>x</code> from radians to degrees. 9117 1.1 mbalmer 9118 1.1 mbalmer 9119 1.1 mbalmer 9120 1.1 mbalmer 9121 1.1 mbalmer <p> 9122 1.3 lneto <hr><h3><a name="pdf-math.exp"><code>math.exp (x)</code></a></h3> 9123 1.3 lneto 9124 1.3 lneto 9125 1.3 lneto <p> 9126 1.3 lneto Returns the value <em>e<sup>x</sup></em> 9127 1.3 lneto (where <code>e</code> is the base of natural logarithms). 9128 1.3 lneto 9129 1.3 lneto 9130 1.3 lneto 9131 1.3 lneto 9132 1.3 lneto <p> 9133 1.1 mbalmer <hr><h3><a name="pdf-math.floor"><code>math.floor (x)</code></a></h3> 9134 1.1 mbalmer 9135 1.1 mbalmer 9136 1.1 mbalmer <p> 9137 1.2 lneto Returns the largest integral value smaller than or equal to <code>x</code>. 9138 1.1 mbalmer 9139 1.1 mbalmer 9140 1.1 mbalmer 9141 1.1 mbalmer 9142 1.1 mbalmer <p> 9143 1.1 mbalmer <hr><h3><a name="pdf-math.fmod"><code>math.fmod (x, y)</code></a></h3> 9144 1.1 mbalmer 9145 1.1 mbalmer 9146 1.1 mbalmer <p> 9147 1.1 mbalmer Returns the remainder of the division of <code>x</code> by <code>y</code> 9148 1.2 lneto that rounds the quotient towards zero. (integer/float) 9149 1.1 mbalmer 9150 1.1 mbalmer 9151 1.1 mbalmer 9152 1.1 mbalmer 9153 1.1 mbalmer <p> 9154 1.2 lneto <hr><h3><a name="pdf-math.huge"><code>math.huge</code></a></h3> 9155 1.1 mbalmer 9156 1.1 mbalmer 9157 1.1 mbalmer <p> 9158 1.2 lneto The float value <code>HUGE_VAL</code>, 9159 1.4 mbalmer a value larger than any other numeric value. 9160 1.1 mbalmer 9161 1.1 mbalmer 9162 1.1 mbalmer 9163 1.1 mbalmer 9164 1.1 mbalmer <p> 9165 1.2 lneto <hr><h3><a name="pdf-math.log"><code>math.log (x [, base])</code></a></h3> 9166 1.1 mbalmer 9167 1.1 mbalmer 9168 1.1 mbalmer <p> 9169 1.2 lneto Returns the logarithm of <code>x</code> in the given base. 9170 1.2 lneto The default for <code>base</code> is <em>e</em> 9171 1.2 lneto (so that the function returns the natural logarithm of <code>x</code>). 9172 1.1 mbalmer 9173 1.1 mbalmer 9174 1.1 mbalmer 9175 1.1 mbalmer 9176 1.1 mbalmer <p> 9177 1.2 lneto <hr><h3><a name="pdf-math.max"><code>math.max (x, ···)</code></a></h3> 9178 1.1 mbalmer 9179 1.1 mbalmer 9180 1.1 mbalmer <p> 9181 1.2 lneto Returns the argument with the maximum value, 9182 1.2 lneto according to the Lua operator <code><</code>. (integer/float) 9183 1.1 mbalmer 9184 1.1 mbalmer 9185 1.1 mbalmer 9186 1.1 mbalmer 9187 1.1 mbalmer <p> 9188 1.2 lneto <hr><h3><a name="pdf-math.maxinteger"><code>math.maxinteger</code></a></h3> 9189 1.2 lneto An integer with the maximum value for an integer. 9190 1.1 mbalmer 9191 1.1 mbalmer 9192 1.1 mbalmer 9193 1.1 mbalmer 9194 1.1 mbalmer <p> 9195 1.2 lneto <hr><h3><a name="pdf-math.min"><code>math.min (x, ···)</code></a></h3> 9196 1.1 mbalmer 9197 1.1 mbalmer 9198 1.1 mbalmer <p> 9199 1.2 lneto Returns the argument with the minimum value, 9200 1.2 lneto according to the Lua operator <code><</code>. (integer/float) 9201 1.1 mbalmer 9202 1.1 mbalmer 9203 1.1 mbalmer 9204 1.1 mbalmer 9205 1.1 mbalmer <p> 9206 1.2 lneto <hr><h3><a name="pdf-math.mininteger"><code>math.mininteger</code></a></h3> 9207 1.2 lneto An integer with the minimum value for an integer. 9208 1.1 mbalmer 9209 1.1 mbalmer 9210 1.1 mbalmer 9211 1.1 mbalmer 9212 1.1 mbalmer <p> 9213 1.1 mbalmer <hr><h3><a name="pdf-math.modf"><code>math.modf (x)</code></a></h3> 9214 1.1 mbalmer 9215 1.1 mbalmer 9216 1.1 mbalmer <p> 9217 1.2 lneto Returns the integral part of <code>x</code> and the fractional part of <code>x</code>. 9218 1.2 lneto Its second result is always a float. 9219 1.1 mbalmer 9220 1.1 mbalmer 9221 1.1 mbalmer 9222 1.1 mbalmer 9223 1.1 mbalmer <p> 9224 1.1 mbalmer <hr><h3><a name="pdf-math.pi"><code>math.pi</code></a></h3> 9225 1.1 mbalmer 9226 1.1 mbalmer 9227 1.1 mbalmer <p> 9228 1.2 lneto The value of <em>π</em>. 9229 1.1 mbalmer 9230 1.1 mbalmer 9231 1.1 mbalmer 9232 1.1 mbalmer 9233 1.1 mbalmer <p> 9234 1.1 mbalmer <hr><h3><a name="pdf-math.rad"><code>math.rad (x)</code></a></h3> 9235 1.1 mbalmer 9236 1.1 mbalmer 9237 1.1 mbalmer <p> 9238 1.2 lneto Converts the angle <code>x</code> from degrees to radians. 9239 1.1 mbalmer 9240 1.1 mbalmer 9241 1.1 mbalmer 9242 1.1 mbalmer 9243 1.1 mbalmer <p> 9244 1.1 mbalmer <hr><h3><a name="pdf-math.random"><code>math.random ([m [, n]])</code></a></h3> 9245 1.1 mbalmer 9246 1.1 mbalmer 9247 1.1 mbalmer <p> 9248 1.2 lneto When called without arguments, 9249 1.2 lneto returns a pseudo-random float with uniform distribution 9250 1.2 lneto in the range <em>[0,1)</em>. 9251 1.2 lneto When called with two integers <code>m</code> and <code>n</code>, 9252 1.2 lneto <code>math.random</code> returns a pseudo-random integer 9253 1.2 lneto with uniform distribution in the range <em>[m, n]</em>. 9254 1.5 lneto (The value <em>n-m</em> cannot be negative and must fit in a Lua integer.) 9255 1.2 lneto The call <code>math.random(n)</code> is equivalent to <code>math.random(1,n)</code>. 9256 1.1 mbalmer 9257 1.1 mbalmer 9258 1.1 mbalmer <p> 9259 1.2 lneto This function is an interface to the underling 9260 1.2 lneto pseudo-random generator function provided by C. 9261 1.1 mbalmer 9262 1.1 mbalmer 9263 1.1 mbalmer 9264 1.1 mbalmer 9265 1.1 mbalmer <p> 9266 1.1 mbalmer <hr><h3><a name="pdf-math.randomseed"><code>math.randomseed (x)</code></a></h3> 9267 1.1 mbalmer 9268 1.1 mbalmer 9269 1.1 mbalmer <p> 9270 1.1 mbalmer Sets <code>x</code> as the "seed" 9271 1.1 mbalmer for the pseudo-random generator: 9272 1.1 mbalmer equal seeds produce equal sequences of numbers. 9273 1.1 mbalmer 9274 1.1 mbalmer 9275 1.1 mbalmer 9276 1.1 mbalmer 9277 1.1 mbalmer <p> 9278 1.1 mbalmer <hr><h3><a name="pdf-math.sin"><code>math.sin (x)</code></a></h3> 9279 1.1 mbalmer 9280 1.1 mbalmer 9281 1.1 mbalmer <p> 9282 1.1 mbalmer Returns the sine of <code>x</code> (assumed to be in radians). 9283 1.1 mbalmer 9284 1.1 mbalmer 9285 1.1 mbalmer 9286 1.1 mbalmer 9287 1.1 mbalmer <p> 9288 1.1 mbalmer <hr><h3><a name="pdf-math.sqrt"><code>math.sqrt (x)</code></a></h3> 9289 1.1 mbalmer 9290 1.1 mbalmer 9291 1.1 mbalmer <p> 9292 1.1 mbalmer Returns the square root of <code>x</code>. 9293 1.1 mbalmer (You can also use the expression <code>x^0.5</code> to compute this value.) 9294 1.1 mbalmer 9295 1.1 mbalmer 9296 1.1 mbalmer 9297 1.1 mbalmer 9298 1.1 mbalmer <p> 9299 1.1 mbalmer <hr><h3><a name="pdf-math.tan"><code>math.tan (x)</code></a></h3> 9300 1.1 mbalmer 9301 1.1 mbalmer 9302 1.1 mbalmer <p> 9303 1.1 mbalmer Returns the tangent of <code>x</code> (assumed to be in radians). 9304 1.1 mbalmer 9305 1.1 mbalmer 9306 1.1 mbalmer 9307 1.1 mbalmer 9308 1.1 mbalmer <p> 9309 1.3 lneto <hr><h3><a name="pdf-math.tointeger"><code>math.tointeger (x)</code></a></h3> 9310 1.3 lneto 9311 1.3 lneto 9312 1.3 lneto <p> 9313 1.3 lneto If the value <code>x</code> is convertible to an integer, 9314 1.3 lneto returns that integer. 9315 1.3 lneto Otherwise, returns <b>nil</b>. 9316 1.3 lneto 9317 1.3 lneto 9318 1.3 lneto 9319 1.3 lneto 9320 1.3 lneto <p> 9321 1.2 lneto <hr><h3><a name="pdf-math.type"><code>math.type (x)</code></a></h3> 9322 1.1 mbalmer 9323 1.1 mbalmer 9324 1.1 mbalmer <p> 9325 1.2 lneto Returns "<code>integer</code>" if <code>x</code> is an integer, 9326 1.2 lneto "<code>float</code>" if it is a float, 9327 1.2 lneto or <b>nil</b> if <code>x</code> is not a number. 9328 1.1 mbalmer 9329 1.1 mbalmer 9330 1.1 mbalmer 9331 1.1 mbalmer 9332 1.3 lneto <p> 9333 1.3 lneto <hr><h3><a name="pdf-math.ult"><code>math.ult (m, n)</code></a></h3> 9334 1.3 lneto 9335 1.3 lneto 9336 1.3 lneto <p> 9337 1.3 lneto Returns a boolean, 9338 1.3 lneto true if integer <code>m</code> is below integer <code>n</code> when 9339 1.3 lneto they are compared as unsigned integers. 9340 1.3 lneto 9341 1.3 lneto 9342 1.3 lneto 9343 1.3 lneto 9344 1.1 mbalmer 9345 1.1 mbalmer 9346 1.1 mbalmer 9347 1.2 lneto <h2>6.8 – <a name="6.8">Input and Output Facilities</a></h2> 9348 1.1 mbalmer 9349 1.1 mbalmer <p> 9350 1.1 mbalmer The I/O library provides two different styles for file manipulation. 9351 1.2 lneto The first one uses implicit file handles; 9352 1.1 mbalmer that is, there are operations to set a default input file and a 9353 1.1 mbalmer default output file, 9354 1.1 mbalmer and all input/output operations are over these default files. 9355 1.2 lneto The second style uses explicit file handles. 9356 1.1 mbalmer 9357 1.1 mbalmer 9358 1.1 mbalmer <p> 9359 1.2 lneto When using implicit file handles, 9360 1.1 mbalmer all operations are supplied by table <a name="pdf-io"><code>io</code></a>. 9361 1.2 lneto When using explicit file handles, 9362 1.2 lneto the operation <a href="#pdf-io.open"><code>io.open</code></a> returns a file handle 9363 1.2 lneto and then all operations are supplied as methods of the file handle. 9364 1.1 mbalmer 9365 1.1 mbalmer 9366 1.1 mbalmer <p> 9367 1.1 mbalmer The table <code>io</code> also provides 9368 1.2 lneto three predefined file handles with their usual meanings from C: 9369 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>. 9370 1.1 mbalmer The I/O library never closes these files. 9371 1.1 mbalmer 9372 1.1 mbalmer 9373 1.1 mbalmer <p> 9374 1.1 mbalmer Unless otherwise stated, 9375 1.1 mbalmer all I/O functions return <b>nil</b> on failure 9376 1.1 mbalmer (plus an error message as a second result and 9377 1.1 mbalmer a system-dependent error code as a third result) 9378 1.1 mbalmer and some value different from <b>nil</b> on success. 9379 1.2 lneto On non-POSIX systems, 9380 1.2 lneto the computation of the error message and error code 9381 1.2 lneto in case of errors 9382 1.2 lneto may be not thread safe, 9383 1.2 lneto because they rely on the global C variable <code>errno</code>. 9384 1.1 mbalmer 9385 1.1 mbalmer 9386 1.1 mbalmer <p> 9387 1.1 mbalmer <hr><h3><a name="pdf-io.close"><code>io.close ([file])</code></a></h3> 9388 1.1 mbalmer 9389 1.1 mbalmer 9390 1.1 mbalmer <p> 9391 1.1 mbalmer Equivalent to <code>file:close()</code>. 9392 1.1 mbalmer Without a <code>file</code>, closes the default output file. 9393 1.1 mbalmer 9394 1.1 mbalmer 9395 1.1 mbalmer 9396 1.1 mbalmer 9397 1.1 mbalmer <p> 9398 1.1 mbalmer <hr><h3><a name="pdf-io.flush"><code>io.flush ()</code></a></h3> 9399 1.1 mbalmer 9400 1.1 mbalmer 9401 1.1 mbalmer <p> 9402 1.2 lneto Equivalent to <code>io.output():flush()</code>. 9403 1.1 mbalmer 9404 1.1 mbalmer 9405 1.1 mbalmer 9406 1.1 mbalmer 9407 1.1 mbalmer <p> 9408 1.1 mbalmer <hr><h3><a name="pdf-io.input"><code>io.input ([file])</code></a></h3> 9409 1.1 mbalmer 9410 1.1 mbalmer 9411 1.1 mbalmer <p> 9412 1.1 mbalmer When called with a file name, it opens the named file (in text mode), 9413 1.1 mbalmer and sets its handle as the default input file. 9414 1.1 mbalmer When called with a file handle, 9415 1.1 mbalmer it simply sets this file handle as the default input file. 9416 1.1 mbalmer When called without parameters, 9417 1.1 mbalmer it returns the current default input file. 9418 1.1 mbalmer 9419 1.1 mbalmer 9420 1.1 mbalmer <p> 9421 1.1 mbalmer In case of errors this function raises the error, 9422 1.1 mbalmer instead of returning an error code. 9423 1.1 mbalmer 9424 1.1 mbalmer 9425 1.1 mbalmer 9426 1.1 mbalmer 9427 1.1 mbalmer <p> 9428 1.5 lneto <hr><h3><a name="pdf-io.lines"><code>io.lines ([filename, ···])</code></a></h3> 9429 1.1 mbalmer 9430 1.1 mbalmer 9431 1.1 mbalmer <p> 9432 1.1 mbalmer Opens the given file name in read mode 9433 1.2 lneto and returns an iterator function that 9434 1.2 lneto works like <code>file:lines(···)</code> over the opened file. 9435 1.1 mbalmer When the iterator function detects the end of file, 9436 1.2 lneto it returns no values (to finish the loop) and automatically closes the file. 9437 1.1 mbalmer 9438 1.1 mbalmer 9439 1.1 mbalmer <p> 9440 1.1 mbalmer The call <code>io.lines()</code> (with no file name) is equivalent 9441 1.2 lneto to <code>io.input():lines("*l")</code>; 9442 1.1 mbalmer that is, it iterates over the lines of the default input file. 9443 1.1 mbalmer In this case it does not close the file when the loop ends. 9444 1.1 mbalmer 9445 1.1 mbalmer 9446 1.2 lneto <p> 9447 1.2 lneto In case of errors this function raises the error, 9448 1.2 lneto instead of returning an error code. 9449 1.2 lneto 9450 1.2 lneto 9451 1.1 mbalmer 9452 1.1 mbalmer 9453 1.1 mbalmer <p> 9454 1.1 mbalmer <hr><h3><a name="pdf-io.open"><code>io.open (filename [, mode])</code></a></h3> 9455 1.1 mbalmer 9456 1.1 mbalmer 9457 1.1 mbalmer <p> 9458 1.1 mbalmer This function opens a file, 9459 1.1 mbalmer in the mode specified in the string <code>mode</code>. 9460 1.1 mbalmer It returns a new file handle, 9461 1.1 mbalmer or, in case of errors, <b>nil</b> plus an error message. 9462 1.1 mbalmer 9463 1.1 mbalmer 9464 1.1 mbalmer <p> 9465 1.1 mbalmer The <code>mode</code> string can be any of the following: 9466 1.1 mbalmer 9467 1.1 mbalmer <ul> 9468 1.2 lneto <li><b>"<code>r</code>": </b> read mode (the default);</li> 9469 1.2 lneto <li><b>"<code>w</code>": </b> write mode;</li> 9470 1.2 lneto <li><b>"<code>a</code>": </b> append mode;</li> 9471 1.2 lneto <li><b>"<code>r+</code>": </b> update mode, all previous data is preserved;</li> 9472 1.2 lneto <li><b>"<code>w+</code>": </b> update mode, all previous data is erased;</li> 9473 1.2 lneto <li><b>"<code>a+</code>": </b> append update mode, previous data is preserved, 9474 1.1 mbalmer writing is only allowed at the end of file.</li> 9475 1.1 mbalmer </ul><p> 9476 1.1 mbalmer The <code>mode</code> string can also have a '<code>b</code>' at the end, 9477 1.1 mbalmer which is needed in some systems to open the file in binary mode. 9478 1.1 mbalmer 9479 1.1 mbalmer 9480 1.1 mbalmer 9481 1.1 mbalmer 9482 1.1 mbalmer <p> 9483 1.1 mbalmer <hr><h3><a name="pdf-io.output"><code>io.output ([file])</code></a></h3> 9484 1.1 mbalmer 9485 1.1 mbalmer 9486 1.1 mbalmer <p> 9487 1.1 mbalmer Similar to <a href="#pdf-io.input"><code>io.input</code></a>, but operates over the default output file. 9488 1.1 mbalmer 9489 1.1 mbalmer 9490 1.1 mbalmer 9491 1.1 mbalmer 9492 1.1 mbalmer <p> 9493 1.1 mbalmer <hr><h3><a name="pdf-io.popen"><code>io.popen (prog [, mode])</code></a></h3> 9494 1.1 mbalmer 9495 1.1 mbalmer 9496 1.1 mbalmer <p> 9497 1.2 lneto This function is system dependent and is not available 9498 1.2 lneto on all platforms. 9499 1.2 lneto 9500 1.2 lneto 9501 1.2 lneto <p> 9502 1.1 mbalmer Starts program <code>prog</code> in a separated process and returns 9503 1.1 mbalmer a file handle that you can use to read data from this program 9504 1.1 mbalmer (if <code>mode</code> is <code>"r"</code>, the default) 9505 1.1 mbalmer or to write data to this program 9506 1.1 mbalmer (if <code>mode</code> is <code>"w"</code>). 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.read"><code>io.read (···)</code></a></h3> 9513 1.1 mbalmer 9514 1.1 mbalmer 9515 1.1 mbalmer <p> 9516 1.2 lneto Equivalent to <code>io.input():read(···)</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-io.tmpfile"><code>io.tmpfile ()</code></a></h3> 9523 1.1 mbalmer 9524 1.1 mbalmer 9525 1.1 mbalmer <p> 9526 1.1 mbalmer Returns a handle for a temporary file. 9527 1.1 mbalmer This file is opened in update mode 9528 1.1 mbalmer and it is automatically removed when the program ends. 9529 1.1 mbalmer 9530 1.1 mbalmer 9531 1.1 mbalmer 9532 1.1 mbalmer 9533 1.1 mbalmer <p> 9534 1.1 mbalmer <hr><h3><a name="pdf-io.type"><code>io.type (obj)</code></a></h3> 9535 1.1 mbalmer 9536 1.1 mbalmer 9537 1.1 mbalmer <p> 9538 1.1 mbalmer Checks whether <code>obj</code> is a valid file handle. 9539 1.1 mbalmer Returns the string <code>"file"</code> if <code>obj</code> is an open file handle, 9540 1.1 mbalmer <code>"closed file"</code> if <code>obj</code> is a closed file handle, 9541 1.1 mbalmer or <b>nil</b> if <code>obj</code> is not a file handle. 9542 1.1 mbalmer 9543 1.1 mbalmer 9544 1.1 mbalmer 9545 1.1 mbalmer 9546 1.1 mbalmer <p> 9547 1.1 mbalmer <hr><h3><a name="pdf-io.write"><code>io.write (···)</code></a></h3> 9548 1.1 mbalmer 9549 1.1 mbalmer 9550 1.1 mbalmer <p> 9551 1.2 lneto Equivalent to <code>io.output():write(···)</code>. 9552 1.1 mbalmer 9553 1.1 mbalmer 9554 1.1 mbalmer 9555 1.1 mbalmer 9556 1.1 mbalmer <p> 9557 1.1 mbalmer <hr><h3><a name="pdf-file:close"><code>file:close ()</code></a></h3> 9558 1.1 mbalmer 9559 1.1 mbalmer 9560 1.1 mbalmer <p> 9561 1.1 mbalmer Closes <code>file</code>. 9562 1.1 mbalmer Note that files are automatically closed when 9563 1.1 mbalmer their handles are garbage collected, 9564 1.1 mbalmer but that takes an unpredictable amount of time to happen. 9565 1.1 mbalmer 9566 1.1 mbalmer 9567 1.2 lneto <p> 9568 1.2 lneto When closing a file handle created with <a href="#pdf-io.popen"><code>io.popen</code></a>, 9569 1.2 lneto <a href="#pdf-file:close"><code>file:close</code></a> returns the same values 9570 1.2 lneto returned by <a href="#pdf-os.execute"><code>os.execute</code></a>. 9571 1.2 lneto 9572 1.2 lneto 9573 1.1 mbalmer 9574 1.1 mbalmer 9575 1.1 mbalmer <p> 9576 1.1 mbalmer <hr><h3><a name="pdf-file:flush"><code>file:flush ()</code></a></h3> 9577 1.1 mbalmer 9578 1.1 mbalmer 9579 1.1 mbalmer <p> 9580 1.1 mbalmer Saves any written data to <code>file</code>. 9581 1.1 mbalmer 9582 1.1 mbalmer 9583 1.1 mbalmer 9584 1.1 mbalmer 9585 1.1 mbalmer <p> 9586 1.2 lneto <hr><h3><a name="pdf-file:lines"><code>file:lines (···)</code></a></h3> 9587 1.1 mbalmer 9588 1.1 mbalmer 9589 1.1 mbalmer <p> 9590 1.1 mbalmer Returns an iterator function that, 9591 1.1 mbalmer each time it is called, 9592 1.2 lneto reads the file according to the given formats. 9593 1.2 lneto When no format is given, 9594 1.2 lneto uses "<code>l</code>" as a default. 9595 1.2 lneto As an example, the construction 9596 1.1 mbalmer 9597 1.1 mbalmer <pre> 9598 1.2 lneto for c in file:lines(1) do <em>body</em> end 9599 1.2 lneto </pre><p> 9600 1.2 lneto will iterate over all characters of the file, 9601 1.2 lneto starting at the current position. 9602 1.2 lneto Unlike <a href="#pdf-io.lines"><code>io.lines</code></a>, this function does not close the file 9603 1.2 lneto when the loop ends. 9604 1.2 lneto 9605 1.2 lneto 9606 1.2 lneto <p> 9607 1.2 lneto In case of errors this function raises the error, 9608 1.2 lneto instead of returning an error code. 9609 1.1 mbalmer 9610 1.1 mbalmer 9611 1.1 mbalmer 9612 1.1 mbalmer 9613 1.1 mbalmer <p> 9614 1.1 mbalmer <hr><h3><a name="pdf-file:read"><code>file:read (···)</code></a></h3> 9615 1.1 mbalmer 9616 1.1 mbalmer 9617 1.1 mbalmer <p> 9618 1.1 mbalmer Reads the file <code>file</code>, 9619 1.1 mbalmer according to the given formats, which specify what to read. 9620 1.1 mbalmer For each format, 9621 1.2 lneto the function returns a string or a number with the characters read, 9622 1.1 mbalmer or <b>nil</b> if it cannot read data with the specified format. 9623 1.3 lneto (In this latter case, 9624 1.3 lneto the function does not read subsequent formats.) 9625 1.1 mbalmer When called without formats, 9626 1.2 lneto it uses a default format that reads the next line 9627 1.1 mbalmer (see below). 9628 1.1 mbalmer 9629 1.1 mbalmer 9630 1.1 mbalmer <p> 9631 1.1 mbalmer The available formats are 9632 1.1 mbalmer 9633 1.1 mbalmer <ul> 9634 1.1 mbalmer 9635 1.2 lneto <li><b>"<code>n</code>": </b> 9636 1.2 lneto reads a numeral and returns it as a float or an integer, 9637 1.2 lneto following the lexical conventions of Lua. 9638 1.2 lneto (The numeral may have leading spaces and a sign.) 9639 1.2 lneto This format always reads the longest input sequence that 9640 1.4 mbalmer is a valid prefix for a numeral; 9641 1.4 mbalmer if that prefix does not form a valid numeral 9642 1.2 lneto (e.g., an empty string, "<code>0x</code>", or "<code>3.4e-</code>"), 9643 1.2 lneto it is discarded and the function returns <b>nil</b>. 9644 1.2 lneto </li> 9645 1.2 lneto 9646 1.2 lneto <li><b>"<code>a</code>": </b> 9647 1.1 mbalmer reads the whole file, starting at the current position. 9648 1.1 mbalmer On end of file, it returns the empty string. 9649 1.1 mbalmer </li> 9650 1.1 mbalmer 9651 1.2 lneto <li><b>"<code>l</code>": </b> 9652 1.2 lneto reads the next line skipping the end of line, 9653 1.1 mbalmer returning <b>nil</b> on end of file. 9654 1.1 mbalmer This is the default format. 9655 1.1 mbalmer </li> 9656 1.1 mbalmer 9657 1.2 lneto <li><b>"<code>L</code>": </b> 9658 1.2 lneto reads the next line keeping the end-of-line character (if present), 9659 1.2 lneto returning <b>nil</b> on end of file. 9660 1.2 lneto </li> 9661 1.2 lneto 9662 1.2 lneto <li><b><em>number</em>: </b> 9663 1.2 lneto reads a string with up to this number of bytes, 9664 1.1 mbalmer returning <b>nil</b> on end of file. 9665 1.2 lneto If <code>number</code> is zero, 9666 1.1 mbalmer it reads nothing and returns an empty string, 9667 1.1 mbalmer or <b>nil</b> on end of file. 9668 1.1 mbalmer </li> 9669 1.1 mbalmer 9670 1.2 lneto </ul><p> 9671 1.2 lneto The formats "<code>l</code>" and "<code>L</code>" should be used only for text files. 9672 1.2 lneto 9673 1.1 mbalmer 9674 1.1 mbalmer 9675 1.1 mbalmer 9676 1.1 mbalmer <p> 9677 1.2 lneto <hr><h3><a name="pdf-file:seek"><code>file:seek ([whence [, offset]])</code></a></h3> 9678 1.1 mbalmer 9679 1.1 mbalmer 9680 1.1 mbalmer <p> 9681 1.1 mbalmer Sets and gets the file position, 9682 1.1 mbalmer measured from the beginning of the file, 9683 1.1 mbalmer to the position given by <code>offset</code> plus a base 9684 1.1 mbalmer specified by the string <code>whence</code>, as follows: 9685 1.1 mbalmer 9686 1.1 mbalmer <ul> 9687 1.2 lneto <li><b>"<code>set</code>": </b> base is position 0 (beginning of the file);</li> 9688 1.2 lneto <li><b>"<code>cur</code>": </b> base is current position;</li> 9689 1.2 lneto <li><b>"<code>end</code>": </b> base is end of file;</li> 9690 1.1 mbalmer </ul><p> 9691 1.2 lneto In case of success, <code>seek</code> returns the final file position, 9692 1.1 mbalmer measured in bytes from the beginning of the file. 9693 1.2 lneto If <code>seek</code> fails, it returns <b>nil</b>, 9694 1.1 mbalmer plus a string describing the error. 9695 1.1 mbalmer 9696 1.1 mbalmer 9697 1.1 mbalmer <p> 9698 1.1 mbalmer The default value for <code>whence</code> is <code>"cur"</code>, 9699 1.1 mbalmer and for <code>offset</code> is 0. 9700 1.1 mbalmer Therefore, the call <code>file:seek()</code> returns the current 9701 1.1 mbalmer file position, without changing it; 9702 1.1 mbalmer the call <code>file:seek("set")</code> sets the position to the 9703 1.1 mbalmer beginning of the file (and returns 0); 9704 1.1 mbalmer and the call <code>file:seek("end")</code> sets the position to the 9705 1.1 mbalmer end of the file, and returns its size. 9706 1.1 mbalmer 9707 1.1 mbalmer 9708 1.1 mbalmer 9709 1.1 mbalmer 9710 1.1 mbalmer <p> 9711 1.1 mbalmer <hr><h3><a name="pdf-file:setvbuf"><code>file:setvbuf (mode [, size])</code></a></h3> 9712 1.1 mbalmer 9713 1.1 mbalmer 9714 1.1 mbalmer <p> 9715 1.1 mbalmer Sets the buffering mode for an output file. 9716 1.1 mbalmer There are three available modes: 9717 1.1 mbalmer 9718 1.1 mbalmer <ul> 9719 1.1 mbalmer 9720 1.2 lneto <li><b>"<code>no</code>": </b> 9721 1.1 mbalmer no buffering; the result of any output operation appears immediately. 9722 1.1 mbalmer </li> 9723 1.1 mbalmer 9724 1.2 lneto <li><b>"<code>full</code>": </b> 9725 1.1 mbalmer full buffering; output operation is performed only 9726 1.2 lneto when the buffer is full or when 9727 1.2 lneto you explicitly <code>flush</code> the file (see <a href="#pdf-io.flush"><code>io.flush</code></a>). 9728 1.1 mbalmer </li> 9729 1.1 mbalmer 9730 1.2 lneto <li><b>"<code>line</code>": </b> 9731 1.1 mbalmer line buffering; output is buffered until a newline is output 9732 1.1 mbalmer or there is any input from some special files 9733 1.1 mbalmer (such as a terminal device). 9734 1.1 mbalmer </li> 9735 1.1 mbalmer 9736 1.1 mbalmer </ul><p> 9737 1.1 mbalmer For the last two cases, <code>size</code> 9738 1.1 mbalmer specifies the size of the buffer, in bytes. 9739 1.1 mbalmer The default is an appropriate size. 9740 1.1 mbalmer 9741 1.1 mbalmer 9742 1.1 mbalmer 9743 1.1 mbalmer 9744 1.1 mbalmer <p> 9745 1.1 mbalmer <hr><h3><a name="pdf-file:write"><code>file:write (···)</code></a></h3> 9746 1.1 mbalmer 9747 1.1 mbalmer 9748 1.1 mbalmer <p> 9749 1.2 lneto Writes the value of each of its arguments to <code>file</code>. 9750 1.1 mbalmer The arguments must be strings or numbers. 9751 1.2 lneto 9752 1.2 lneto 9753 1.2 lneto <p> 9754 1.2 lneto In case of success, this function returns <code>file</code>. 9755 1.2 lneto Otherwise it returns <b>nil</b> plus a string describing the error. 9756 1.1 mbalmer 9757 1.1 mbalmer 9758 1.1 mbalmer 9759 1.1 mbalmer 9760 1.1 mbalmer 9761 1.1 mbalmer 9762 1.1 mbalmer 9763 1.2 lneto <h2>6.9 – <a name="6.9">Operating System Facilities</a></h2> 9764 1.1 mbalmer 9765 1.1 mbalmer <p> 9766 1.1 mbalmer This library is implemented through table <a name="pdf-os"><code>os</code></a>. 9767 1.1 mbalmer 9768 1.1 mbalmer 9769 1.1 mbalmer <p> 9770 1.1 mbalmer <hr><h3><a name="pdf-os.clock"><code>os.clock ()</code></a></h3> 9771 1.1 mbalmer 9772 1.1 mbalmer 9773 1.1 mbalmer <p> 9774 1.1 mbalmer Returns an approximation of the amount in seconds of CPU time 9775 1.1 mbalmer used by the program. 9776 1.1 mbalmer 9777 1.1 mbalmer 9778 1.1 mbalmer 9779 1.1 mbalmer 9780 1.1 mbalmer <p> 9781 1.1 mbalmer <hr><h3><a name="pdf-os.date"><code>os.date ([format [, time]])</code></a></h3> 9782 1.1 mbalmer 9783 1.1 mbalmer 9784 1.1 mbalmer <p> 9785 1.1 mbalmer Returns a string or a table containing date and time, 9786 1.1 mbalmer formatted according to the given string <code>format</code>. 9787 1.1 mbalmer 9788 1.1 mbalmer 9789 1.1 mbalmer <p> 9790 1.1 mbalmer If the <code>time</code> argument is present, 9791 1.1 mbalmer this is the time to be formatted 9792 1.1 mbalmer (see the <a href="#pdf-os.time"><code>os.time</code></a> function for a description of this value). 9793 1.1 mbalmer Otherwise, <code>date</code> formats the current time. 9794 1.1 mbalmer 9795 1.1 mbalmer 9796 1.1 mbalmer <p> 9797 1.1 mbalmer If <code>format</code> starts with '<code>!</code>', 9798 1.1 mbalmer then the date is formatted in Coordinated Universal Time. 9799 1.1 mbalmer After this optional character, 9800 1.1 mbalmer if <code>format</code> is the string "<code>*t</code>", 9801 1.1 mbalmer then <code>date</code> returns a table with the following fields: 9802 1.5 lneto <code>year</code>, <code>month</code> (1–12), <code>day</code> (1–31), 9803 1.2 lneto <code>hour</code> (0–23), <code>min</code> (0–59), <code>sec</code> (0–61), 9804 1.1 mbalmer <code>wday</code> (weekday, Sunday is 1), 9805 1.1 mbalmer <code>yday</code> (day of the year), 9806 1.1 mbalmer and <code>isdst</code> (daylight saving flag, a boolean). 9807 1.2 lneto This last field may be absent 9808 1.2 lneto if the information is not available. 9809 1.1 mbalmer 9810 1.1 mbalmer 9811 1.1 mbalmer <p> 9812 1.1 mbalmer If <code>format</code> is not "<code>*t</code>", 9813 1.1 mbalmer then <code>date</code> returns the date as a string, 9814 1.3 lneto formatted according to the same rules as the ISO C function <code>strftime</code>. 9815 1.1 mbalmer 9816 1.1 mbalmer 9817 1.1 mbalmer <p> 9818 1.1 mbalmer When called without arguments, 9819 1.1 mbalmer <code>date</code> returns a reasonable date and time representation that depends on 9820 1.5 lneto the host system and on the current locale. 9821 1.5 lneto (More specifically, <code>os.date()</code> is equivalent to <code>os.date("%c")</code>.) 9822 1.1 mbalmer 9823 1.1 mbalmer 9824 1.2 lneto <p> 9825 1.2 lneto On non-POSIX systems, 9826 1.2 lneto this function may be not thread safe 9827 1.2 lneto because of its reliance on C function <code>gmtime</code> and C function <code>localtime</code>. 9828 1.2 lneto 9829 1.2 lneto 9830 1.1 mbalmer 9831 1.1 mbalmer 9832 1.1 mbalmer <p> 9833 1.1 mbalmer <hr><h3><a name="pdf-os.difftime"><code>os.difftime (t2, t1)</code></a></h3> 9834 1.1 mbalmer 9835 1.1 mbalmer 9836 1.1 mbalmer <p> 9837 1.3 lneto Returns the difference, in seconds, 9838 1.3 lneto from time <code>t1</code> to time <code>t2</code> 9839 1.3 lneto (where the times are values returned by <a href="#pdf-os.time"><code>os.time</code></a>). 9840 1.1 mbalmer In POSIX, Windows, and some other systems, 9841 1.1 mbalmer this value is exactly <code>t2</code><em>-</em><code>t1</code>. 9842 1.1 mbalmer 9843 1.1 mbalmer 9844 1.1 mbalmer 9845 1.1 mbalmer 9846 1.1 mbalmer <p> 9847 1.1 mbalmer <hr><h3><a name="pdf-os.execute"><code>os.execute ([command])</code></a></h3> 9848 1.1 mbalmer 9849 1.1 mbalmer 9850 1.1 mbalmer <p> 9851 1.3 lneto This function is equivalent to the ISO C function <code>system</code>. 9852 1.1 mbalmer It passes <code>command</code> to be executed by an operating system shell. 9853 1.2 lneto Its first result is <b>true</b> 9854 1.2 lneto if the command terminated successfully, 9855 1.2 lneto or <b>nil</b> otherwise. 9856 1.2 lneto After this first result 9857 1.2 lneto the function returns a string plus a number, 9858 1.2 lneto as follows: 9859 1.2 lneto 9860 1.2 lneto <ul> 9861 1.2 lneto 9862 1.2 lneto <li><b>"<code>exit</code>": </b> 9863 1.2 lneto the command terminated normally; 9864 1.2 lneto the following number is the exit status of the command. 9865 1.2 lneto </li> 9866 1.2 lneto 9867 1.2 lneto <li><b>"<code>signal</code>": </b> 9868 1.2 lneto the command was terminated by a signal; 9869 1.2 lneto the following number is the signal that terminated the command. 9870 1.2 lneto </li> 9871 1.2 lneto 9872 1.2 lneto </ul> 9873 1.2 lneto 9874 1.2 lneto <p> 9875 1.2 lneto When called without a <code>command</code>, 9876 1.2 lneto <code>os.execute</code> returns a boolean that is true if a shell is available. 9877 1.2 lneto 9878 1.1 mbalmer 9879 1.1 mbalmer 9880 1.1 mbalmer 9881 1.2 lneto <p> 9882 1.2 lneto <hr><h3><a name="pdf-os.exit"><code>os.exit ([code [, close]])</code></a></h3> 9883 1.2 lneto 9884 1.1 mbalmer 9885 1.1 mbalmer <p> 9886 1.3 lneto Calls the ISO C function <code>exit</code> to terminate the host program. 9887 1.2 lneto If <code>code</code> is <b>true</b>, 9888 1.2 lneto the returned status is <code>EXIT_SUCCESS</code>; 9889 1.2 lneto if <code>code</code> is <b>false</b>, 9890 1.2 lneto the returned status is <code>EXIT_FAILURE</code>; 9891 1.2 lneto if <code>code</code> is a number, 9892 1.2 lneto the returned status is this number. 9893 1.2 lneto The default value for <code>code</code> is <b>true</b>. 9894 1.1 mbalmer 9895 1.1 mbalmer 9896 1.1 mbalmer <p> 9897 1.2 lneto If the optional second argument <code>close</code> is true, 9898 1.2 lneto closes the Lua state before exiting. 9899 1.1 mbalmer 9900 1.1 mbalmer 9901 1.1 mbalmer 9902 1.1 mbalmer 9903 1.1 mbalmer <p> 9904 1.1 mbalmer <hr><h3><a name="pdf-os.getenv"><code>os.getenv (varname)</code></a></h3> 9905 1.1 mbalmer 9906 1.1 mbalmer 9907 1.1 mbalmer <p> 9908 1.1 mbalmer Returns the value of the process environment variable <code>varname</code>, 9909 1.1 mbalmer or <b>nil</b> if the variable is not defined. 9910 1.1 mbalmer 9911 1.1 mbalmer 9912 1.1 mbalmer 9913 1.1 mbalmer 9914 1.1 mbalmer <p> 9915 1.1 mbalmer <hr><h3><a name="pdf-os.remove"><code>os.remove (filename)</code></a></h3> 9916 1.1 mbalmer 9917 1.1 mbalmer 9918 1.1 mbalmer <p> 9919 1.2 lneto Deletes the file (or empty directory, on POSIX systems) 9920 1.2 lneto with the given name. 9921 1.1 mbalmer If this function fails, it returns <b>nil</b>, 9922 1.2 lneto plus a string describing the error and the error code. 9923 1.1 mbalmer 9924 1.1 mbalmer 9925 1.1 mbalmer 9926 1.1 mbalmer 9927 1.1 mbalmer <p> 9928 1.1 mbalmer <hr><h3><a name="pdf-os.rename"><code>os.rename (oldname, newname)</code></a></h3> 9929 1.1 mbalmer 9930 1.1 mbalmer 9931 1.1 mbalmer <p> 9932 1.1 mbalmer Renames file or directory named <code>oldname</code> to <code>newname</code>. 9933 1.1 mbalmer If this function fails, it returns <b>nil</b>, 9934 1.2 lneto plus a string describing the error and the error code. 9935 1.1 mbalmer 9936 1.1 mbalmer 9937 1.1 mbalmer 9938 1.1 mbalmer 9939 1.1 mbalmer <p> 9940 1.1 mbalmer <hr><h3><a name="pdf-os.setlocale"><code>os.setlocale (locale [, category])</code></a></h3> 9941 1.1 mbalmer 9942 1.1 mbalmer 9943 1.1 mbalmer <p> 9944 1.1 mbalmer Sets the current locale of the program. 9945 1.2 lneto <code>locale</code> is a system-dependent string specifying a locale; 9946 1.1 mbalmer <code>category</code> is an optional string describing which category to change: 9947 1.1 mbalmer <code>"all"</code>, <code>"collate"</code>, <code>"ctype"</code>, 9948 1.1 mbalmer <code>"monetary"</code>, <code>"numeric"</code>, or <code>"time"</code>; 9949 1.1 mbalmer the default category is <code>"all"</code>. 9950 1.1 mbalmer The function returns the name of the new locale, 9951 1.1 mbalmer or <b>nil</b> if the request cannot be honored. 9952 1.1 mbalmer 9953 1.1 mbalmer 9954 1.1 mbalmer <p> 9955 1.1 mbalmer If <code>locale</code> is the empty string, 9956 1.1 mbalmer the current locale is set to an implementation-defined native locale. 9957 1.1 mbalmer If <code>locale</code> is the string "<code>C</code>", 9958 1.1 mbalmer the current locale is set to the standard C locale. 9959 1.1 mbalmer 9960 1.1 mbalmer 9961 1.1 mbalmer <p> 9962 1.1 mbalmer When called with <b>nil</b> as the first argument, 9963 1.1 mbalmer this function only returns the name of the current locale 9964 1.1 mbalmer for the given category. 9965 1.1 mbalmer 9966 1.1 mbalmer 9967 1.2 lneto <p> 9968 1.2 lneto This function may be not thread safe 9969 1.2 lneto because of its reliance on C function <code>setlocale</code>. 9970 1.2 lneto 9971 1.2 lneto 9972 1.1 mbalmer 9973 1.1 mbalmer 9974 1.1 mbalmer <p> 9975 1.1 mbalmer <hr><h3><a name="pdf-os.time"><code>os.time ([table])</code></a></h3> 9976 1.1 mbalmer 9977 1.1 mbalmer 9978 1.1 mbalmer <p> 9979 1.1 mbalmer Returns the current time when called without arguments, 9980 1.4 mbalmer or a time representing the local date and time specified by the given table. 9981 1.1 mbalmer This table must have fields <code>year</code>, <code>month</code>, and <code>day</code>, 9982 1.2 lneto and may have fields 9983 1.2 lneto <code>hour</code> (default is 12), 9984 1.2 lneto <code>min</code> (default is 0), 9985 1.2 lneto <code>sec</code> (default is 0), 9986 1.2 lneto and <code>isdst</code> (default is <b>nil</b>). 9987 1.4 mbalmer Other fields are ignored. 9988 1.2 lneto For a description of these fields, see the <a href="#pdf-os.date"><code>os.date</code></a> function. 9989 1.1 mbalmer 9990 1.1 mbalmer 9991 1.1 mbalmer <p> 9992 1.4 mbalmer The values in these fields do not need to be inside their valid ranges. 9993 1.4 mbalmer For instance, if <code>sec</code> is -10, 9994 1.4 mbalmer it means -10 seconds from the time specified by the other fields; 9995 1.4 mbalmer if <code>hour</code> is 1000, 9996 1.4 mbalmer it means +1000 hours from the time specified by the other fields. 9997 1.4 mbalmer 9998 1.4 mbalmer 9999 1.4 mbalmer <p> 10000 1.1 mbalmer The returned value is a number, whose meaning depends on your system. 10001 1.2 lneto In POSIX, Windows, and some other systems, 10002 1.2 lneto this number counts the number 10003 1.1 mbalmer of seconds since some given start time (the "epoch"). 10004 1.1 mbalmer In other systems, the meaning is not specified, 10005 1.1 mbalmer and the number returned by <code>time</code> can be used only as an argument to 10006 1.2 lneto <a href="#pdf-os.date"><code>os.date</code></a> and <a href="#pdf-os.difftime"><code>os.difftime</code></a>. 10007 1.1 mbalmer 10008 1.1 mbalmer 10009 1.1 mbalmer 10010 1.1 mbalmer 10011 1.1 mbalmer <p> 10012 1.1 mbalmer <hr><h3><a name="pdf-os.tmpname"><code>os.tmpname ()</code></a></h3> 10013 1.1 mbalmer 10014 1.1 mbalmer 10015 1.1 mbalmer <p> 10016 1.1 mbalmer Returns a string with a file name that can 10017 1.1 mbalmer be used for a temporary file. 10018 1.1 mbalmer The file must be explicitly opened before its use 10019 1.1 mbalmer and explicitly removed when no longer needed. 10020 1.1 mbalmer 10021 1.1 mbalmer 10022 1.1 mbalmer <p> 10023 1.2 lneto On POSIX systems, 10024 1.1 mbalmer this function also creates a file with that name, 10025 1.1 mbalmer to avoid security risks. 10026 1.1 mbalmer (Someone else might create the file with wrong permissions 10027 1.1 mbalmer in the time between getting the name and creating the file.) 10028 1.1 mbalmer You still have to open the file to use it 10029 1.1 mbalmer and to remove it (even if you do not use it). 10030 1.1 mbalmer 10031 1.1 mbalmer 10032 1.1 mbalmer <p> 10033 1.1 mbalmer When possible, 10034 1.1 mbalmer you may prefer to use <a href="#pdf-io.tmpfile"><code>io.tmpfile</code></a>, 10035 1.1 mbalmer which automatically removes the file when the program ends. 10036 1.1 mbalmer 10037 1.1 mbalmer 10038 1.1 mbalmer 10039 1.1 mbalmer 10040 1.1 mbalmer 10041 1.1 mbalmer 10042 1.1 mbalmer 10043 1.2 lneto <h2>6.10 – <a name="6.10">The Debug Library</a></h2> 10044 1.1 mbalmer 10045 1.1 mbalmer <p> 10046 1.1 mbalmer This library provides 10047 1.2 lneto the functionality of the debug interface (<a href="#4.9">§4.9</a>) to Lua programs. 10048 1.1 mbalmer You should exert care when using this library. 10049 1.2 lneto Several of its functions 10050 1.2 lneto violate basic assumptions about Lua code 10051 1.1 mbalmer (e.g., that variables local to a function 10052 1.2 lneto cannot be accessed from outside; 10053 1.2 lneto that userdata metatables cannot be changed by Lua code; 10054 1.2 lneto that Lua programs do not crash) 10055 1.1 mbalmer and therefore can compromise otherwise secure code. 10056 1.2 lneto Moreover, some functions in this library may be slow. 10057 1.1 mbalmer 10058 1.1 mbalmer 10059 1.1 mbalmer <p> 10060 1.1 mbalmer All functions in this library are provided 10061 1.1 mbalmer inside the <a name="pdf-debug"><code>debug</code></a> table. 10062 1.1 mbalmer All functions that operate over a thread 10063 1.1 mbalmer have an optional first argument which is the 10064 1.1 mbalmer thread to operate over. 10065 1.1 mbalmer The default is always the current thread. 10066 1.1 mbalmer 10067 1.1 mbalmer 10068 1.1 mbalmer <p> 10069 1.1 mbalmer <hr><h3><a name="pdf-debug.debug"><code>debug.debug ()</code></a></h3> 10070 1.1 mbalmer 10071 1.1 mbalmer 10072 1.1 mbalmer <p> 10073 1.1 mbalmer Enters an interactive mode with the user, 10074 1.1 mbalmer running each string that the user enters. 10075 1.1 mbalmer Using simple commands and other debug facilities, 10076 1.1 mbalmer the user can inspect global and local variables, 10077 1.1 mbalmer change their values, evaluate expressions, and so on. 10078 1.1 mbalmer A line containing only the word <code>cont</code> finishes this function, 10079 1.1 mbalmer so that the caller continues its execution. 10080 1.1 mbalmer 10081 1.1 mbalmer 10082 1.1 mbalmer <p> 10083 1.1 mbalmer Note that commands for <code>debug.debug</code> are not lexically nested 10084 1.2 lneto within any function and so have no direct access to local variables. 10085 1.1 mbalmer 10086 1.1 mbalmer 10087 1.1 mbalmer 10088 1.1 mbalmer 10089 1.1 mbalmer <p> 10090 1.1 mbalmer <hr><h3><a name="pdf-debug.gethook"><code>debug.gethook ([thread])</code></a></h3> 10091 1.1 mbalmer 10092 1.1 mbalmer 10093 1.1 mbalmer <p> 10094 1.1 mbalmer Returns the current hook settings of the thread, as three values: 10095 1.1 mbalmer the current hook function, the current hook mask, 10096 1.1 mbalmer and the current hook count 10097 1.1 mbalmer (as set by the <a href="#pdf-debug.sethook"><code>debug.sethook</code></a> function). 10098 1.1 mbalmer 10099 1.1 mbalmer 10100 1.1 mbalmer 10101 1.1 mbalmer 10102 1.1 mbalmer <p> 10103 1.2 lneto <hr><h3><a name="pdf-debug.getinfo"><code>debug.getinfo ([thread,] f [, what])</code></a></h3> 10104 1.1 mbalmer 10105 1.1 mbalmer 10106 1.1 mbalmer <p> 10107 1.1 mbalmer Returns a table with information about a function. 10108 1.2 lneto You can give the function directly 10109 1.2 lneto or you can give a number as the value of <code>f</code>, 10110 1.2 lneto which means the function running at level <code>f</code> of the call stack 10111 1.1 mbalmer of the given thread: 10112 1.1 mbalmer level 0 is the current function (<code>getinfo</code> itself); 10113 1.2 lneto level 1 is the function that called <code>getinfo</code> 10114 1.2 lneto (except for tail calls, which do not count on the stack); 10115 1.1 mbalmer and so on. 10116 1.2 lneto If <code>f</code> is a number larger than the number of active functions, 10117 1.1 mbalmer then <code>getinfo</code> returns <b>nil</b>. 10118 1.1 mbalmer 10119 1.1 mbalmer 10120 1.1 mbalmer <p> 10121 1.1 mbalmer The returned table can contain all the fields returned by <a href="#lua_getinfo"><code>lua_getinfo</code></a>, 10122 1.1 mbalmer with the string <code>what</code> describing which fields to fill in. 10123 1.1 mbalmer The default for <code>what</code> is to get all information available, 10124 1.1 mbalmer except the table of valid lines. 10125 1.1 mbalmer If present, 10126 1.1 mbalmer the option '<code>f</code>' 10127 1.1 mbalmer adds a field named <code>func</code> with the function itself. 10128 1.1 mbalmer If present, 10129 1.1 mbalmer the option '<code>L</code>' 10130 1.1 mbalmer adds a field named <code>activelines</code> with the table of 10131 1.1 mbalmer valid lines. 10132 1.1 mbalmer 10133 1.1 mbalmer 10134 1.1 mbalmer <p> 10135 1.1 mbalmer For instance, the expression <code>debug.getinfo(1,"n").name</code> returns 10136 1.4 mbalmer a name for the current function, 10137 1.1 mbalmer if a reasonable name can be found, 10138 1.1 mbalmer and the expression <code>debug.getinfo(print)</code> 10139 1.1 mbalmer returns a table with all available information 10140 1.1 mbalmer about the <a href="#pdf-print"><code>print</code></a> function. 10141 1.1 mbalmer 10142 1.1 mbalmer 10143 1.1 mbalmer 10144 1.1 mbalmer 10145 1.1 mbalmer <p> 10146 1.2 lneto <hr><h3><a name="pdf-debug.getlocal"><code>debug.getlocal ([thread,] f, local)</code></a></h3> 10147 1.1 mbalmer 10148 1.1 mbalmer 10149 1.1 mbalmer <p> 10150 1.1 mbalmer This function returns the name and the value of the local variable 10151 1.2 lneto with index <code>local</code> of the function at level <code>f</code> of the stack. 10152 1.2 lneto This function accesses not only explicit local variables, 10153 1.2 lneto but also parameters, temporaries, etc. 10154 1.2 lneto 10155 1.2 lneto 10156 1.2 lneto <p> 10157 1.2 lneto The first parameter or local variable has index 1, and so on, 10158 1.3 lneto following the order that they are declared in the code, 10159 1.3 lneto counting only the variables that are active 10160 1.3 lneto in the current scope of the function. 10161 1.2 lneto Negative indices refer to vararg parameters; 10162 1.2 lneto -1 is the first vararg parameter. 10163 1.2 lneto The function returns <b>nil</b> if there is no variable with the given index, 10164 1.2 lneto and raises an error when called with a level out of range. 10165 1.1 mbalmer (You can call <a href="#pdf-debug.getinfo"><code>debug.getinfo</code></a> to check whether the level is valid.) 10166 1.1 mbalmer 10167 1.1 mbalmer 10168 1.1 mbalmer <p> 10169 1.2 lneto Variable names starting with '<code>(</code>' (open parenthesis) 10170 1.2 lneto represent variables with no known names 10171 1.3 lneto (internal variables such as loop control variables, 10172 1.2 lneto and variables from chunks saved without debug information). 10173 1.2 lneto 10174 1.2 lneto 10175 1.2 lneto <p> 10176 1.2 lneto The parameter <code>f</code> may also be a function. 10177 1.2 lneto In that case, <code>getlocal</code> returns only the name of function parameters. 10178 1.1 mbalmer 10179 1.1 mbalmer 10180 1.1 mbalmer 10181 1.1 mbalmer 10182 1.1 mbalmer <p> 10183 1.2 lneto <hr><h3><a name="pdf-debug.getmetatable"><code>debug.getmetatable (value)</code></a></h3> 10184 1.1 mbalmer 10185 1.1 mbalmer 10186 1.1 mbalmer <p> 10187 1.2 lneto Returns the metatable of the given <code>value</code> 10188 1.1 mbalmer or <b>nil</b> if it does not have a metatable. 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.getregistry"><code>debug.getregistry ()</code></a></h3> 10195 1.1 mbalmer 10196 1.1 mbalmer 10197 1.1 mbalmer <p> 10198 1.2 lneto Returns the registry table (see <a href="#4.5">§4.5</a>). 10199 1.1 mbalmer 10200 1.1 mbalmer 10201 1.1 mbalmer 10202 1.1 mbalmer 10203 1.1 mbalmer <p> 10204 1.2 lneto <hr><h3><a name="pdf-debug.getupvalue"><code>debug.getupvalue (f, up)</code></a></h3> 10205 1.1 mbalmer 10206 1.1 mbalmer 10207 1.1 mbalmer <p> 10208 1.1 mbalmer This function returns the name and the value of the upvalue 10209 1.2 lneto with index <code>up</code> of the function <code>f</code>. 10210 1.1 mbalmer The function returns <b>nil</b> if there is no upvalue with the given index. 10211 1.1 mbalmer 10212 1.1 mbalmer 10213 1.2 lneto <p> 10214 1.2 lneto Variable names starting with '<code>(</code>' (open parenthesis) 10215 1.2 lneto represent variables with no known names 10216 1.2 lneto (variables from chunks saved without debug information). 10217 1.2 lneto 10218 1.2 lneto 10219 1.1 mbalmer 10220 1.1 mbalmer 10221 1.1 mbalmer <p> 10222 1.2 lneto <hr><h3><a name="pdf-debug.getuservalue"><code>debug.getuservalue (u)</code></a></h3> 10223 1.1 mbalmer 10224 1.1 mbalmer 10225 1.1 mbalmer <p> 10226 1.2 lneto Returns the Lua value associated to <code>u</code>. 10227 1.2 lneto If <code>u</code> is not a userdata, 10228 1.2 lneto returns <b>nil</b>. 10229 1.1 mbalmer 10230 1.1 mbalmer 10231 1.1 mbalmer 10232 1.1 mbalmer 10233 1.1 mbalmer <p> 10234 1.1 mbalmer <hr><h3><a name="pdf-debug.sethook"><code>debug.sethook ([thread,] hook, mask [, count])</code></a></h3> 10235 1.1 mbalmer 10236 1.1 mbalmer 10237 1.1 mbalmer <p> 10238 1.1 mbalmer Sets the given function as a hook. 10239 1.1 mbalmer The string <code>mask</code> and the number <code>count</code> describe 10240 1.1 mbalmer when the hook will be called. 10241 1.2 lneto The string mask may have any combination of the following characters, 10242 1.1 mbalmer with the given meaning: 10243 1.1 mbalmer 10244 1.1 mbalmer <ul> 10245 1.2 lneto <li><b>'<code>c</code>': </b> the hook is called every time Lua calls a function;</li> 10246 1.2 lneto <li><b>'<code>r</code>': </b> the hook is called every time Lua returns from a function;</li> 10247 1.2 lneto <li><b>'<code>l</code>': </b> the hook is called every time Lua enters a new line of code.</li> 10248 1.1 mbalmer </ul><p> 10249 1.2 lneto Moreover, 10250 1.2 lneto with a <code>count</code> different from zero, 10251 1.2 lneto the hook is called also after every <code>count</code> instructions. 10252 1.1 mbalmer 10253 1.1 mbalmer 10254 1.1 mbalmer <p> 10255 1.1 mbalmer When called without arguments, 10256 1.1 mbalmer <a href="#pdf-debug.sethook"><code>debug.sethook</code></a> turns off the hook. 10257 1.1 mbalmer 10258 1.1 mbalmer 10259 1.1 mbalmer <p> 10260 1.1 mbalmer When the hook is called, its first parameter is a string 10261 1.1 mbalmer describing the event that has triggered its call: 10262 1.2 lneto <code>"call"</code> (or <code>"tail call"</code>), 10263 1.2 lneto <code>"return"</code>, 10264 1.1 mbalmer <code>"line"</code>, and <code>"count"</code>. 10265 1.1 mbalmer For line events, 10266 1.1 mbalmer the hook also gets the new line number as its second parameter. 10267 1.1 mbalmer Inside a hook, 10268 1.1 mbalmer you can call <code>getinfo</code> with level 2 to get more information about 10269 1.1 mbalmer the running function 10270 1.1 mbalmer (level 0 is the <code>getinfo</code> function, 10271 1.2 lneto and level 1 is the hook function). 10272 1.1 mbalmer 10273 1.1 mbalmer 10274 1.1 mbalmer 10275 1.1 mbalmer 10276 1.1 mbalmer <p> 10277 1.1 mbalmer <hr><h3><a name="pdf-debug.setlocal"><code>debug.setlocal ([thread,] level, local, value)</code></a></h3> 10278 1.1 mbalmer 10279 1.1 mbalmer 10280 1.1 mbalmer <p> 10281 1.1 mbalmer This function assigns the value <code>value</code> to the local variable 10282 1.1 mbalmer with index <code>local</code> of the function at level <code>level</code> of the stack. 10283 1.1 mbalmer The function returns <b>nil</b> if there is no local 10284 1.1 mbalmer variable with the given index, 10285 1.1 mbalmer and raises an error when called with a <code>level</code> out of range. 10286 1.1 mbalmer (You can call <code>getinfo</code> to check whether the level is valid.) 10287 1.1 mbalmer Otherwise, it returns the name of the local variable. 10288 1.1 mbalmer 10289 1.1 mbalmer 10290 1.2 lneto <p> 10291 1.2 lneto See <a href="#pdf-debug.getlocal"><code>debug.getlocal</code></a> for more information about 10292 1.2 lneto variable indices and names. 10293 1.2 lneto 10294 1.2 lneto 10295 1.1 mbalmer 10296 1.1 mbalmer 10297 1.1 mbalmer <p> 10298 1.2 lneto <hr><h3><a name="pdf-debug.setmetatable"><code>debug.setmetatable (value, table)</code></a></h3> 10299 1.1 mbalmer 10300 1.1 mbalmer 10301 1.1 mbalmer <p> 10302 1.2 lneto Sets the metatable for the given <code>value</code> to the given <code>table</code> 10303 1.1 mbalmer (which can be <b>nil</b>). 10304 1.2 lneto Returns <code>value</code>. 10305 1.1 mbalmer 10306 1.1 mbalmer 10307 1.1 mbalmer 10308 1.1 mbalmer 10309 1.1 mbalmer <p> 10310 1.2 lneto <hr><h3><a name="pdf-debug.setupvalue"><code>debug.setupvalue (f, up, value)</code></a></h3> 10311 1.1 mbalmer 10312 1.1 mbalmer 10313 1.1 mbalmer <p> 10314 1.1 mbalmer This function assigns the value <code>value</code> to the upvalue 10315 1.2 lneto with index <code>up</code> of the function <code>f</code>. 10316 1.1 mbalmer The function returns <b>nil</b> if there is no upvalue 10317 1.1 mbalmer with the given index. 10318 1.1 mbalmer Otherwise, it returns the name of the upvalue. 10319 1.1 mbalmer 10320 1.1 mbalmer 10321 1.1 mbalmer 10322 1.1 mbalmer 10323 1.1 mbalmer <p> 10324 1.2 lneto <hr><h3><a name="pdf-debug.setuservalue"><code>debug.setuservalue (udata, value)</code></a></h3> 10325 1.2 lneto 10326 1.2 lneto 10327 1.2 lneto <p> 10328 1.2 lneto Sets the given <code>value</code> as 10329 1.2 lneto the Lua value associated to the given <code>udata</code>. 10330 1.2 lneto <code>udata</code> must be a full userdata. 10331 1.2 lneto 10332 1.2 lneto 10333 1.2 lneto <p> 10334 1.2 lneto Returns <code>udata</code>. 10335 1.2 lneto 10336 1.2 lneto 10337 1.2 lneto 10338 1.2 lneto 10339 1.2 lneto <p> 10340 1.2 lneto <hr><h3><a name="pdf-debug.traceback"><code>debug.traceback ([thread,] [message [, level]])</code></a></h3> 10341 1.1 mbalmer 10342 1.1 mbalmer 10343 1.1 mbalmer <p> 10344 1.2 lneto If <code>message</code> is present but is neither a string nor <b>nil</b>, 10345 1.2 lneto this function returns <code>message</code> without further processing. 10346 1.2 lneto Otherwise, 10347 1.2 lneto it returns a string with a traceback of the call stack. 10348 1.3 lneto The optional <code>message</code> string is appended 10349 1.1 mbalmer at the beginning of the traceback. 10350 1.1 mbalmer An optional <code>level</code> number tells at which level 10351 1.1 mbalmer to start the traceback 10352 1.1 mbalmer (default is 1, the function calling <code>traceback</code>). 10353 1.1 mbalmer 10354 1.1 mbalmer 10355 1.1 mbalmer 10356 1.1 mbalmer 10357 1.2 lneto <p> 10358 1.2 lneto <hr><h3><a name="pdf-debug.upvalueid"><code>debug.upvalueid (f, n)</code></a></h3> 10359 1.2 lneto 10360 1.2 lneto 10361 1.2 lneto <p> 10362 1.3 lneto Returns a unique identifier (as a light userdata) 10363 1.2 lneto for the upvalue numbered <code>n</code> 10364 1.2 lneto from the given function. 10365 1.2 lneto 10366 1.2 lneto 10367 1.2 lneto <p> 10368 1.2 lneto These unique identifiers allow a program to check whether different 10369 1.2 lneto closures share upvalues. 10370 1.2 lneto Lua closures that share an upvalue 10371 1.2 lneto (that is, that access a same external local variable) 10372 1.2 lneto will return identical ids for those upvalue indices. 10373 1.2 lneto 10374 1.2 lneto 10375 1.2 lneto 10376 1.2 lneto 10377 1.2 lneto <p> 10378 1.2 lneto <hr><h3><a name="pdf-debug.upvaluejoin"><code>debug.upvaluejoin (f1, n1, f2, n2)</code></a></h3> 10379 1.2 lneto 10380 1.2 lneto 10381 1.2 lneto <p> 10382 1.2 lneto Make the <code>n1</code>-th upvalue of the Lua closure <code>f1</code> 10383 1.2 lneto refer to the <code>n2</code>-th upvalue of the Lua closure <code>f2</code>. 10384 1.2 lneto 10385 1.2 lneto 10386 1.2 lneto 10387 1.2 lneto 10388 1.1 mbalmer 10389 1.1 mbalmer 10390 1.1 mbalmer 10391 1.2 lneto <h1>7 – <a name="7">Lua Standalone</a></h1> 10392 1.1 mbalmer 10393 1.1 mbalmer <p> 10394 1.1 mbalmer Although Lua has been designed as an extension language, 10395 1.1 mbalmer to be embedded in a host C program, 10396 1.2 lneto it is also frequently used as a standalone language. 10397 1.2 lneto An interpreter for Lua as a standalone language, 10398 1.1 mbalmer called simply <code>lua</code>, 10399 1.1 mbalmer is provided with the standard distribution. 10400 1.2 lneto The standalone interpreter includes 10401 1.1 mbalmer all standard libraries, including the debug library. 10402 1.1 mbalmer Its usage is: 10403 1.1 mbalmer 10404 1.1 mbalmer <pre> 10405 1.1 mbalmer lua [options] [script [args]] 10406 1.1 mbalmer </pre><p> 10407 1.1 mbalmer The options are: 10408 1.1 mbalmer 10409 1.1 mbalmer <ul> 10410 1.2 lneto <li><b><code>-e <em>stat</em></code>: </b> executes string <em>stat</em>;</li> 10411 1.2 lneto <li><b><code>-l <em>mod</em></code>: </b> "requires" <em>mod</em>;</li> 10412 1.2 lneto <li><b><code>-i</code>: </b> enters interactive mode after running <em>script</em>;</li> 10413 1.2 lneto <li><b><code>-v</code>: </b> prints version information;</li> 10414 1.2 lneto <li><b><code>-E</code>: </b> ignores environment variables;</li> 10415 1.2 lneto <li><b><code>--</code>: </b> stops handling options;</li> 10416 1.2 lneto <li><b><code>-</code>: </b> executes <code>stdin</code> as a file and stops handling options.</li> 10417 1.1 mbalmer </ul><p> 10418 1.3 lneto After handling its options, <code>lua</code> runs the given <em>script</em>. 10419 1.1 mbalmer When called without arguments, 10420 1.1 mbalmer <code>lua</code> behaves as <code>lua -v -i</code> 10421 1.1 mbalmer when the standard input (<code>stdin</code>) is a terminal, 10422 1.1 mbalmer and as <code>lua -</code> otherwise. 10423 1.1 mbalmer 10424 1.1 mbalmer 10425 1.1 mbalmer <p> 10426 1.2 lneto When called without option <code>-E</code>, 10427 1.2 lneto the interpreter checks for an environment variable <a name="pdf-LUA_INIT_5_3"><code>LUA_INIT_5_3</code></a> 10428 1.3 lneto (or <a name="pdf-LUA_INIT"><code>LUA_INIT</code></a> if the versioned name is not defined) 10429 1.2 lneto before running any argument. 10430 1.2 lneto If the variable content has the format <code>@<em>filename</em></code>, 10431 1.1 mbalmer then <code>lua</code> executes the file. 10432 1.1 mbalmer Otherwise, <code>lua</code> executes the string itself. 10433 1.1 mbalmer 10434 1.1 mbalmer 10435 1.1 mbalmer <p> 10436 1.2 lneto When called with option <code>-E</code>, 10437 1.2 lneto besides ignoring <code>LUA_INIT</code>, 10438 1.2 lneto Lua also ignores 10439 1.2 lneto the values of <code>LUA_PATH</code> and <code>LUA_CPATH</code>, 10440 1.2 lneto setting the values of 10441 1.2 lneto <a href="#pdf-package.path"><code>package.path</code></a> and <a href="#pdf-package.cpath"><code>package.cpath</code></a> 10442 1.2 lneto with the default paths defined in <code>luaconf.h</code>. 10443 1.2 lneto 10444 1.2 lneto 10445 1.2 lneto <p> 10446 1.2 lneto All options are handled in order, except <code>-i</code> and <code>-E</code>. 10447 1.1 mbalmer For instance, an invocation like 10448 1.1 mbalmer 10449 1.1 mbalmer <pre> 10450 1.1 mbalmer $ lua -e'a=1' -e 'print(a)' script.lua 10451 1.1 mbalmer </pre><p> 10452 1.2 lneto will first set <code>a</code> to 1, then print the value of <code>a</code>, 10453 1.1 mbalmer and finally run the file <code>script.lua</code> with no arguments. 10454 1.1 mbalmer (Here <code>$</code> is the shell prompt. Your prompt may be different.) 10455 1.1 mbalmer 10456 1.1 mbalmer 10457 1.1 mbalmer <p> 10458 1.2 lneto Before running any code, 10459 1.2 lneto <code>lua</code> collects all command-line arguments 10460 1.1 mbalmer in a global table called <code>arg</code>. 10461 1.2 lneto The script name goes to index 0, 10462 1.1 mbalmer the first argument after the script name goes to index 1, 10463 1.1 mbalmer and so on. 10464 1.1 mbalmer Any arguments before the script name 10465 1.2 lneto (that is, the interpreter name plus its options) 10466 1.1 mbalmer go to negative indices. 10467 1.1 mbalmer For instance, in the call 10468 1.1 mbalmer 10469 1.1 mbalmer <pre> 10470 1.1 mbalmer $ lua -la b.lua t1 t2 10471 1.1 mbalmer </pre><p> 10472 1.2 lneto the table is like this: 10473 1.1 mbalmer 10474 1.1 mbalmer <pre> 10475 1.1 mbalmer arg = { [-2] = "lua", [-1] = "-la", 10476 1.1 mbalmer [0] = "b.lua", 10477 1.1 mbalmer [1] = "t1", [2] = "t2" } 10478 1.1 mbalmer </pre><p> 10479 1.2 lneto If there is no script in the call, 10480 1.2 lneto the interpreter name goes to index 0, 10481 1.2 lneto followed by the other arguments. 10482 1.2 lneto For instance, the call 10483 1.2 lneto 10484 1.2 lneto <pre> 10485 1.2 lneto $ lua -e "print(arg[1])" 10486 1.2 lneto </pre><p> 10487 1.2 lneto will print "<code>-e</code>". 10488 1.3 lneto If there is a script, 10489 1.3 lneto the script is called with parameters 10490 1.3 lneto <code>arg[1]</code>, ···, <code>arg[#arg]</code>. 10491 1.3 lneto (Like all chunks in Lua, 10492 1.3 lneto the script is compiled as a vararg function.) 10493 1.1 mbalmer 10494 1.1 mbalmer 10495 1.1 mbalmer <p> 10496 1.1 mbalmer In interactive mode, 10497 1.2 lneto Lua repeatedly prompts and waits for a line. 10498 1.2 lneto After reading a line, 10499 1.2 lneto Lua first try to interpret the line as an expression. 10500 1.2 lneto If it succeeds, it prints its value. 10501 1.2 lneto Otherwise, it interprets the line as a statement. 10502 1.2 lneto If you write an incomplete statement, 10503 1.1 mbalmer the interpreter waits for its completion 10504 1.1 mbalmer by issuing a different prompt. 10505 1.1 mbalmer 10506 1.1 mbalmer 10507 1.1 mbalmer <p> 10508 1.2 lneto In case of unprotected errors in the script, 10509 1.2 lneto the interpreter reports the error to the standard error stream. 10510 1.3 lneto If the error object is not a string but 10511 1.3 lneto has a metamethod <code>__tostring</code>, 10512 1.2 lneto the interpreter calls this metamethod to produce the final message. 10513 1.3 lneto Otherwise, the interpreter converts the error object to a string 10514 1.3 lneto and adds a stack traceback to it. 10515 1.2 lneto 10516 1.2 lneto 10517 1.2 lneto <p> 10518 1.2 lneto When finishing normally, 10519 1.2 lneto the interpreter closes its main Lua state 10520 1.2 lneto (see <a href="#lua_close"><code>lua_close</code></a>). 10521 1.2 lneto The script can avoid this step by 10522 1.2 lneto calling <a href="#pdf-os.exit"><code>os.exit</code></a> to terminate. 10523 1.1 mbalmer 10524 1.1 mbalmer 10525 1.1 mbalmer <p> 10526 1.1 mbalmer To allow the use of Lua as a 10527 1.1 mbalmer script interpreter in Unix systems, 10528 1.2 lneto the standalone interpreter skips 10529 1.1 mbalmer the first line of a chunk if it starts with <code>#</code>. 10530 1.1 mbalmer Therefore, Lua scripts can be made into executable programs 10531 1.1 mbalmer by using <code>chmod +x</code> and the <code>#!</code> form, 10532 1.1 mbalmer as in 10533 1.1 mbalmer 10534 1.1 mbalmer <pre> 10535 1.1 mbalmer #!/usr/local/bin/lua 10536 1.1 mbalmer </pre><p> 10537 1.1 mbalmer (Of course, 10538 1.1 mbalmer the location of the Lua interpreter may be different in your machine. 10539 1.1 mbalmer If <code>lua</code> is in your <code>PATH</code>, 10540 1.2 lneto then 10541 1.1 mbalmer 10542 1.1 mbalmer <pre> 10543 1.1 mbalmer #!/usr/bin/env lua 10544 1.1 mbalmer </pre><p> 10545 1.2 lneto is a more portable solution.) 10546 1.1 mbalmer 10547 1.1 mbalmer 10548 1.1 mbalmer 10549 1.2 lneto <h1>8 – <a name="8">Incompatibilities with the Previous Version</a></h1> 10550 1.1 mbalmer 10551 1.1 mbalmer <p> 10552 1.1 mbalmer Here we list the incompatibilities that you may find when moving a program 10553 1.2 lneto from Lua 5.2 to Lua 5.3. 10554 1.2 lneto You can avoid some incompatibilities by compiling Lua with 10555 1.1 mbalmer appropriate options (see file <code>luaconf.h</code>). 10556 1.1 mbalmer However, 10557 1.2 lneto all these compatibility options will be removed in the future. 10558 1.1 mbalmer 10559 1.1 mbalmer 10560 1.2 lneto <p> 10561 1.2 lneto Lua versions can always change the C API in ways that 10562 1.2 lneto do not imply source-code changes in a program, 10563 1.2 lneto such as the numeric values for constants 10564 1.2 lneto or the implementation of functions as macros. 10565 1.2 lneto Therefore, 10566 1.3 lneto you should not assume that binaries are compatible between 10567 1.2 lneto different Lua versions. 10568 1.2 lneto Always recompile clients of the Lua API when 10569 1.2 lneto using a new version. 10570 1.1 mbalmer 10571 1.1 mbalmer 10572 1.2 lneto <p> 10573 1.2 lneto Similarly, Lua versions can always change the internal representation 10574 1.2 lneto of precompiled chunks; 10575 1.3 lneto precompiled chunks are not compatible between different Lua versions. 10576 1.1 mbalmer 10577 1.1 mbalmer 10578 1.2 lneto <p> 10579 1.2 lneto The standard paths in the official distribution may 10580 1.2 lneto change between versions. 10581 1.1 mbalmer 10582 1.1 mbalmer 10583 1.1 mbalmer 10584 1.2 lneto <h2>8.1 – <a name="8.1">Changes in the Language</a></h2> 10585 1.1 mbalmer <ul> 10586 1.1 mbalmer 10587 1.1 mbalmer <li> 10588 1.2 lneto The main difference between Lua 5.2 and Lua 5.3 is the 10589 1.2 lneto introduction of an integer subtype for numbers. 10590 1.2 lneto Although this change should not affect "normal" computations, 10591 1.2 lneto some computations 10592 1.2 lneto (mainly those that involve some kind of overflow) 10593 1.2 lneto can give different results. 10594 1.2 lneto 10595 1.1 mbalmer 10596 1.2 lneto <p> 10597 1.2 lneto You can fix these differences by forcing a number to be a float 10598 1.2 lneto (in Lua 5.2 all numbers were float), 10599 1.2 lneto in particular writing constants with an ending <code>.0</code> 10600 1.2 lneto or using <code>x = x + 0.0</code> to convert a variable. 10601 1.2 lneto (This recommendation is only for a quick fix 10602 1.2 lneto for an occasional incompatibility; 10603 1.2 lneto it is not a general guideline for good programming. 10604 1.2 lneto For good programming, 10605 1.2 lneto use floats where you need floats 10606 1.2 lneto and integers where you need integers.) 10607 1.1 mbalmer </li> 10608 1.1 mbalmer 10609 1.1 mbalmer <li> 10610 1.2 lneto The conversion of a float to a string now adds a <code>.0</code> suffix 10611 1.2 lneto to the result if it looks like an integer. 10612 1.2 lneto (For instance, the float 2.0 will be printed as <code>2.0</code>, 10613 1.2 lneto not as <code>2</code>.) 10614 1.2 lneto You should always use an explicit format 10615 1.2 lneto when you need a specific format for numbers. 10616 1.1 mbalmer 10617 1.1 mbalmer 10618 1.2 lneto <p> 10619 1.2 lneto (Formally this is not an incompatibility, 10620 1.2 lneto because Lua does not specify how numbers are formatted as strings, 10621 1.2 lneto but some programs assumed a specific format.) 10622 1.1 mbalmer </li> 10623 1.1 mbalmer 10624 1.1 mbalmer <li> 10625 1.2 lneto The generational mode for the garbage collector was removed. 10626 1.2 lneto (It was an experimental feature in Lua 5.2.) 10627 1.1 mbalmer </li> 10628 1.1 mbalmer 10629 1.1 mbalmer </ul> 10630 1.1 mbalmer 10631 1.1 mbalmer 10632 1.1 mbalmer 10633 1.1 mbalmer 10634 1.2 lneto <h2>8.2 – <a name="8.2">Changes in the Libraries</a></h2> 10635 1.1 mbalmer <ul> 10636 1.1 mbalmer 10637 1.1 mbalmer <li> 10638 1.2 lneto The <code>bit32</code> library has been deprecated. 10639 1.2 lneto It is easy to require a compatible external library or, 10640 1.2 lneto better yet, to replace its functions with appropriate bitwise operations. 10641 1.2 lneto (Keep in mind that <code>bit32</code> operates on 32-bit integers, 10642 1.4 mbalmer while the bitwise operators in Lua 5.3 operate on Lua integers, 10643 1.4 mbalmer which by default have 64 bits.) 10644 1.3 lneto </li> 10645 1.3 lneto 10646 1.3 lneto <li> 10647 1.3 lneto The Table library now respects metamethods 10648 1.3 lneto for setting and getting elements. 10649 1.3 lneto </li> 10650 1.3 lneto 10651 1.3 lneto <li> 10652 1.3 lneto The <a href="#pdf-ipairs"><code>ipairs</code></a> iterator now respects metamethods and 10653 1.3 lneto its <code>__ipairs</code> metamethod has been deprecated. 10654 1.1 mbalmer </li> 10655 1.1 mbalmer 10656 1.1 mbalmer <li> 10657 1.2 lneto Option names in <a href="#pdf-io.read"><code>io.read</code></a> do not have a starting '<code>*</code>' anymore. 10658 1.4 mbalmer For compatibility, Lua will continue to accept (and ignore) this character. 10659 1.1 mbalmer </li> 10660 1.1 mbalmer 10661 1.1 mbalmer <li> 10662 1.2 lneto The following functions were deprecated in the mathematical library: 10663 1.2 lneto <code>atan2</code>, <code>cosh</code>, <code>sinh</code>, <code>tanh</code>, <code>pow</code>, 10664 1.2 lneto <code>frexp</code>, and <code>ldexp</code>. 10665 1.2 lneto You can replace <code>math.pow(x,y)</code> with <code>x^y</code>; 10666 1.2 lneto you can replace <code>math.atan2</code> with <code>math.atan</code>, 10667 1.3 lneto which now accepts one or two parameters; 10668 1.2 lneto you can replace <code>math.ldexp(x,exp)</code> with <code>x * 2.0^exp</code>. 10669 1.2 lneto For the other operations, 10670 1.3 lneto you can either use an external library or 10671 1.3 lneto implement them in Lua. 10672 1.3 lneto </li> 10673 1.3 lneto 10674 1.3 lneto <li> 10675 1.3 lneto The searcher for C loaders used by <a href="#pdf-require"><code>require</code></a> 10676 1.3 lneto changed the way it handles versioned names. 10677 1.3 lneto Now, the version should come after the module name 10678 1.3 lneto (as is usual in most other tools). 10679 1.3 lneto For compatibility, that searcher still tries the old format 10680 1.3 lneto if it cannot find an open function according to the new style. 10681 1.3 lneto (Lua 5.2 already worked that way, 10682 1.3 lneto but it did not document the change.) 10683 1.1 mbalmer </li> 10684 1.1 mbalmer 10685 1.4 mbalmer <li> 10686 1.4 mbalmer The call <code>collectgarbage("count")</code> now returns only one result. 10687 1.4 mbalmer (You can compute that second result from the fractional part 10688 1.4 mbalmer of the first result.) 10689 1.4 mbalmer </li> 10690 1.4 mbalmer 10691 1.2 lneto </ul> 10692 1.2 lneto 10693 1.2 lneto 10694 1.2 lneto 10695 1.2 lneto 10696 1.2 lneto <h2>8.3 – <a name="8.3">Changes in the API</a></h2> 10697 1.2 lneto 10698 1.2 lneto 10699 1.2 lneto <ul> 10700 1.2 lneto 10701 1.1 mbalmer <li> 10702 1.2 lneto Continuation functions now receive as parameters what they needed 10703 1.2 lneto to get through <code>lua_getctx</code>, 10704 1.2 lneto so <code>lua_getctx</code> has been removed. 10705 1.2 lneto Adapt your code accordingly. 10706 1.1 mbalmer </li> 10707 1.1 mbalmer 10708 1.1 mbalmer <li> 10709 1.2 lneto Function <a href="#lua_dump"><code>lua_dump</code></a> has an extra parameter, <code>strip</code>. 10710 1.2 lneto Use 0 as the value of this parameter to get the old behavior. 10711 1.1 mbalmer </li> 10712 1.1 mbalmer 10713 1.3 lneto <li> 10714 1.3 lneto Functions to inject/project unsigned integers 10715 1.3 lneto (<code>lua_pushunsigned</code>, <code>lua_tounsigned</code>, <code>lua_tounsignedx</code>, 10716 1.3 lneto <code>luaL_checkunsigned</code>, <code>luaL_optunsigned</code>) 10717 1.3 lneto were deprecated. 10718 1.3 lneto Use their signed equivalents with a type cast. 10719 1.3 lneto </li> 10720 1.3 lneto 10721 1.3 lneto <li> 10722 1.3 lneto Macros to project non-default integer types 10723 1.3 lneto (<code>luaL_checkint</code>, <code>luaL_optint</code>, <code>luaL_checklong</code>, <code>luaL_optlong</code>) 10724 1.3 lneto were deprecated. 10725 1.3 lneto Use their equivalent over <a href="#lua_Integer"><code>lua_Integer</code></a> with a type cast 10726 1.3 lneto (or, when possible, use <a href="#lua_Integer"><code>lua_Integer</code></a> in your code). 10727 1.3 lneto </li> 10728 1.3 lneto 10729 1.1 mbalmer </ul> 10730 1.1 mbalmer 10731 1.1 mbalmer 10732 1.1 mbalmer 10733 1.1 mbalmer 10734 1.2 lneto <h1>9 – <a name="9">The Complete Syntax of Lua</a></h1> 10735 1.1 mbalmer 10736 1.1 mbalmer <p> 10737 1.1 mbalmer Here is the complete syntax of Lua in extended BNF. 10738 1.3 lneto As usual in extended BNF, 10739 1.3 lneto {A} means 0 or more As, 10740 1.3 lneto and [A] means an optional A. 10741 1.3 lneto (For operator precedences, see <a href="#3.4.8">§3.4.8</a>; 10742 1.3 lneto for a description of the terminals 10743 1.3 lneto Name, Numeral, 10744 1.3 lneto and LiteralString, see <a href="#3.1">§3.1</a>.) 10745 1.1 mbalmer 10746 1.1 mbalmer 10747 1.1 mbalmer 10748 1.1 mbalmer 10749 1.1 mbalmer <pre> 10750 1.1 mbalmer 10751 1.2 lneto chunk ::= block 10752 1.1 mbalmer 10753 1.2 lneto block ::= {stat} [retstat] 10754 1.1 mbalmer 10755 1.2 lneto stat ::= ‘<b>;</b>’ | 10756 1.2 lneto varlist ‘<b>=</b>’ explist | 10757 1.1 mbalmer functioncall | 10758 1.2 lneto label | 10759 1.2 lneto <b>break</b> | 10760 1.2 lneto <b>goto</b> Name | 10761 1.1 mbalmer <b>do</b> block <b>end</b> | 10762 1.1 mbalmer <b>while</b> exp <b>do</b> block <b>end</b> | 10763 1.1 mbalmer <b>repeat</b> block <b>until</b> exp | 10764 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> | 10765 1.2 lneto <b>for</b> Name ‘<b>=</b>’ exp ‘<b>,</b>’ exp [‘<b>,</b>’ exp] <b>do</b> block <b>end</b> | 10766 1.1 mbalmer <b>for</b> namelist <b>in</b> explist <b>do</b> block <b>end</b> | 10767 1.1 mbalmer <b>function</b> funcname funcbody | 10768 1.1 mbalmer <b>local</b> <b>function</b> Name funcbody | 10769 1.2 lneto <b>local</b> namelist [‘<b>=</b>’ explist] 10770 1.1 mbalmer 10771 1.2 lneto retstat ::= <b>return</b> [explist] [‘<b>;</b>’] 10772 1.1 mbalmer 10773 1.2 lneto label ::= ‘<b>::</b>’ Name ‘<b>::</b>’ 10774 1.1 mbalmer 10775 1.2 lneto funcname ::= Name {‘<b>.</b>’ Name} [‘<b>:</b>’ Name] 10776 1.1 mbalmer 10777 1.2 lneto varlist ::= var {‘<b>,</b>’ var} 10778 1.1 mbalmer 10779 1.2 lneto var ::= Name | prefixexp ‘<b>[</b>’ exp ‘<b>]</b>’ | prefixexp ‘<b>.</b>’ Name 10780 1.1 mbalmer 10781 1.2 lneto namelist ::= Name {‘<b>,</b>’ Name} 10782 1.1 mbalmer 10783 1.2 lneto explist ::= exp {‘<b>,</b>’ exp} 10784 1.2 lneto 10785 1.3 lneto exp ::= <b>nil</b> | <b>false</b> | <b>true</b> | Numeral | LiteralString | ‘<b>...</b>’ | functiondef | 10786 1.1 mbalmer prefixexp | tableconstructor | exp binop exp | unop exp 10787 1.1 mbalmer 10788 1.2 lneto prefixexp ::= var | functioncall | ‘<b>(</b>’ exp ‘<b>)</b>’ 10789 1.1 mbalmer 10790 1.2 lneto functioncall ::= prefixexp args | prefixexp ‘<b>:</b>’ Name args 10791 1.1 mbalmer 10792 1.3 lneto args ::= ‘<b>(</b>’ [explist] ‘<b>)</b>’ | tableconstructor | LiteralString 10793 1.1 mbalmer 10794 1.2 lneto functiondef ::= <b>function</b> funcbody 10795 1.1 mbalmer 10796 1.2 lneto funcbody ::= ‘<b>(</b>’ [parlist] ‘<b>)</b>’ block <b>end</b> 10797 1.1 mbalmer 10798 1.2 lneto parlist ::= namelist [‘<b>,</b>’ ‘<b>...</b>’] | ‘<b>...</b>’ 10799 1.1 mbalmer 10800 1.2 lneto tableconstructor ::= ‘<b>{</b>’ [fieldlist] ‘<b>}</b>’ 10801 1.1 mbalmer 10802 1.1 mbalmer fieldlist ::= field {fieldsep field} [fieldsep] 10803 1.1 mbalmer 10804 1.2 lneto field ::= ‘<b>[</b>’ exp ‘<b>]</b>’ ‘<b>=</b>’ exp | Name ‘<b>=</b>’ exp | exp 10805 1.1 mbalmer 10806 1.2 lneto fieldsep ::= ‘<b>,</b>’ | ‘<b>;</b>’ 10807 1.1 mbalmer 10808 1.2 lneto binop ::= ‘<b>+</b>’ | ‘<b>-</b>’ | ‘<b>*</b>’ | ‘<b>/</b>’ | ‘<b>//</b>’ | ‘<b>^</b>’ | ‘<b>%</b>’ | 10809 1.2 lneto ‘<b>&</b>’ | ‘<b>~</b>’ | ‘<b>|</b>’ | ‘<b>>></b>’ | ‘<b><<</b>’ | ‘<b>..</b>’ | 10810 1.2 lneto ‘<b><</b>’ | ‘<b><=</b>’ | ‘<b>></b>’ | ‘<b>>=</b>’ | ‘<b>==</b>’ | ‘<b>~=</b>’ | 10811 1.1 mbalmer <b>and</b> | <b>or</b> 10812 1.1 mbalmer 10813 1.2 lneto unop ::= ‘<b>-</b>’ | <b>not</b> | ‘<b>#</b>’ | ‘<b>~</b>’ 10814 1.1 mbalmer 10815 1.1 mbalmer </pre> 10816 1.1 mbalmer 10817 1.1 mbalmer <p> 10818 1.1 mbalmer 10819 1.1 mbalmer 10820 1.1 mbalmer 10821 1.1 mbalmer 10822 1.1 mbalmer 10823 1.1 mbalmer 10824 1.1 mbalmer 10825 1.2 lneto 10826 1.4 mbalmer <P CLASS="footer"> 10827 1.1 mbalmer Last update: 10828 1.5 lneto Wed Nov 25 15:19:10 BRST 2015 10829 1.4 mbalmer </P> 10830 1.1 mbalmer <!-- 10831 1.5 lneto Last change: revised for Lua 5.3.2 10832 1.1 mbalmer --> 10833 1.1 mbalmer 10834 1.1 mbalmer </body></html> 10835 1.1 mbalmer 10836
Indexes created Mon Apr 27 00:23:16 UTC 2026