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| 2 <html> |
| 3 |
| 4 <head> |
| 5 <title>Lua 5.2 Reference Manual</title> |
| 6 <link rel="stylesheet" type="text/css" href="lua.css"> |
| 7 <link rel="stylesheet" type="text/css" href="manual.css"> |
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| 10 |
| 11 <body> |
| 12 |
| 13 <hr> |
| 14 <h1> |
| 15 <a href="http://www.lua.org/"><img src="logo.gif" alt="" border="0"></a> |
| 16 Lua 5.2 Reference Manual |
| 17 </h1> |
| 18 |
| 19 by Roberto Ierusalimschy, Luiz Henrique de Figueiredo, Waldemar Celes |
| 20 <p> |
| 21 <small> |
| 22 Copyright © 2011–2013 Lua.org, PUC-Rio. |
| 23 Freely available under the terms of the |
| 24 <a href="http://www.lua.org/license.html">Lua license</a>. |
| 25 </small> |
| 26 <hr> |
| 27 <p> |
| 28 |
| 29 <a href="contents.html#contents">contents</A> |
| 30 · |
| 31 <a href="contents.html#index">index</A> |
| 32 |
| 33 <!-- ====================================================================== --> |
| 34 <p> |
| 35 |
| 36 <!-- $Id: manual.of,v 1.103 2013/03/14 18:51:56 roberto Exp $ --> |
| 37 |
| 38 |
| 39 |
| 40 |
| 41 <h1>1 – <a name="1">Introduction</a></h1> |
| 42 |
| 43 <p> |
| 44 Lua is an extension programming language designed to support |
| 45 general procedural programming with data description |
| 46 facilities. |
| 47 It also offers good support for object-oriented programming, |
| 48 functional programming, and data-driven programming. |
| 49 Lua is intended to be used as a powerful, lightweight, |
| 50 embeddable scripting language for any program that needs one. |
| 51 Lua is implemented as a library, written in <em>clean C</em>, |
| 52 the common subset of Standard C and C++. |
| 53 |
| 54 |
| 55 <p> |
| 56 Being an extension language, Lua has no notion of a "main" program: |
| 57 it only works <em>embedded</em> in a host client, |
| 58 called the <em>embedding program</em> or simply the <em>host</em>. |
| 59 The host program can invoke functions to execute a piece of Lua code, |
| 60 can write and read Lua variables, |
| 61 and can register C functions to be called by Lua code. |
| 62 Through the use of C functions, Lua can be augmented to cope with |
| 63 a wide range of different domains, |
| 64 thus creating customized programming languages sharing a syntactical framework. |
| 65 The Lua distribution includes a sample host program called <code>lua</code>, |
| 66 which uses the Lua library to offer a complete, standalone Lua interpreter, |
| 67 for interactive or batch use. |
| 68 |
| 69 |
| 70 <p> |
| 71 Lua is free software, |
| 72 and is provided as usual with no guarantees, |
| 73 as stated in its license. |
| 74 The implementation described in this manual is available |
| 75 at Lua's official web site, <code>www.lua.org</code>. |
| 76 |
| 77 |
| 78 <p> |
| 79 Like any other reference manual, |
| 80 this document is dry in places. |
| 81 For a discussion of the decisions behind the design of Lua, |
| 82 see the technical papers available at Lua's web site. |
| 83 For a detailed introduction to programming in Lua, |
| 84 see Roberto's book, <em>Programming in Lua</em>. |
| 85 |
| 86 |
| 87 |
| 88 <h1>2 – <a name="2">Basic Concepts</a></h1> |
| 89 |
| 90 <p> |
| 91 This section describes the basic concepts of the language. |
| 92 |
| 93 |
| 94 |
| 95 <h2>2.1 – <a name="2.1">Values and Types</a></h2> |
| 96 |
| 97 <p> |
| 98 Lua is a <em>dynamically typed language</em>. |
| 99 This means that |
| 100 variables do not have types; only values do. |
| 101 There are no type definitions in the language. |
| 102 All values carry their own type. |
| 103 |
| 104 |
| 105 <p> |
| 106 All values in Lua are <em>first-class values</em>. |
| 107 This means that all values can be stored in variables, |
| 108 passed as arguments to other functions, and returned as results. |
| 109 |
| 110 |
| 111 <p> |
| 112 There are eight basic types in Lua: |
| 113 <em>nil</em>, <em>boolean</em>, <em>number</em>, |
| 114 <em>string</em>, <em>function</em>, <em>userdata</em>, |
| 115 <em>thread</em>, and <em>table</em>. |
| 116 <em>Nil</em> is the type of the value <b>nil</b>, |
| 117 whose main property is to be different from any other value; |
| 118 it usually represents the absence of a useful value. |
| 119 <em>Boolean</em> is the type of the values <b>false</b> and <b>true</b>. |
| 120 Both <b>nil</b> and <b>false</b> make a condition false; |
| 121 any other value makes it true. |
| 122 <em>Number</em> represents real (double-precision floating-point) numbers. |
| 123 Operations on numbers follow the same rules of |
| 124 the underlying C implementation, |
| 125 which, in turn, usually follows the IEEE 754 standard. |
| 126 (It is easy to build Lua interpreters that use other |
| 127 internal representations for numbers, |
| 128 such as single-precision floats or long integers; |
| 129 see file <code>luaconf.h</code>.) |
| 130 <em>String</em> represents immutable sequences of bytes. |
| 131 |
| 132 Lua is 8-bit clean: |
| 133 strings can contain any 8-bit value, |
| 134 including embedded zeros ('<code>\0</code>'). |
| 135 |
| 136 |
| 137 <p> |
| 138 Lua can call (and manipulate) functions written in Lua and |
| 139 functions written in C |
| 140 (see <a href="#3.4.9">§3.4.9</a>). |
| 141 |
| 142 |
| 143 <p> |
| 144 The type <em>userdata</em> is provided to allow arbitrary C data to |
| 145 be stored in Lua variables. |
| 146 A userdata value is a pointer to a block of raw memory. |
| 147 There are two kinds of userdata: |
| 148 full userdata, where the block of memory is managed by Lua, |
| 149 and light userdata, where the block of memory is managed by the host. |
| 150 Userdata has no predefined operations in Lua, |
| 151 except assignment and identity test. |
| 152 By using <em>metatables</em>, |
| 153 the programmer can define operations for full userdata values |
| 154 (see <a href="#2.4">§2.4</a>). |
| 155 Userdata values cannot be created or modified in Lua, |
| 156 only through the C API. |
| 157 This guarantees the integrity of data owned by the host program. |
| 158 |
| 159 |
| 160 <p> |
| 161 The type <em>thread</em> represents independent threads of execution |
| 162 and it is used to implement coroutines (see <a href="#2.6">§2.6</a>). |
| 163 Do not confuse Lua threads with operating-system threads. |
| 164 Lua supports coroutines on all systems, |
| 165 even those that do not support threads. |
| 166 |
| 167 |
| 168 <p> |
| 169 The type <em>table</em> implements associative arrays, |
| 170 that is, arrays that can be indexed not only with numbers, |
| 171 but with any Lua value except <b>nil</b> and NaN |
| 172 (<em>Not a Number</em>, a special numeric value used to represent |
| 173 undefined or unrepresentable results, such as <code>0/0</code>). |
| 174 Tables can be <em>heterogeneous</em>; |
| 175 that is, they can contain values of all types (except <b>nil</b>). |
| 176 Any key with value <b>nil</b> is not considered part of the table. |
| 177 Conversely, any key that is not part of a table has |
| 178 an associated value <b>nil</b>. |
| 179 |
| 180 |
| 181 <p> |
| 182 Tables are the sole data structuring mechanism in Lua; |
| 183 they can be used to represent ordinary arrays, sequences, |
| 184 symbol tables, sets, records, graphs, trees, etc. |
| 185 To represent records, Lua uses the field name as an index. |
| 186 The language supports this representation by |
| 187 providing <code>a.name</code> as syntactic sugar for <code>a["name"]</code>. |
| 188 There are several convenient ways to create tables in Lua |
| 189 (see <a href="#3.4.8">§3.4.8</a>). |
| 190 |
| 191 |
| 192 <p> |
| 193 We use the term <em>sequence</em> to denote a table where |
| 194 the set of all positive numeric keys is equal to <em>{1..n}</em> |
| 195 for some integer <em>n</em>, |
| 196 which is called the length of the sequence (see <a href="#3.4.6">§3.4.6</a>
). |
| 197 |
| 198 |
| 199 <p> |
| 200 Like indices, |
| 201 the values of table fields can be of any type. |
| 202 In particular, |
| 203 because functions are first-class values, |
| 204 table fields can contain functions. |
| 205 Thus tables can also carry <em>methods</em> (see <a href="#3.4.10">§3.4.10<
/a>). |
| 206 |
| 207 |
| 208 <p> |
| 209 The indexing of tables follows |
| 210 the definition of raw equality in the language. |
| 211 The expressions <code>a[i]</code> and <code>a[j]</code> |
| 212 denote the same table element |
| 213 if and only if <code>i</code> and <code>j</code> are raw equal |
| 214 (that is, equal without metamethods). |
| 215 |
| 216 |
| 217 <p> |
| 218 Tables, functions, threads, and (full) userdata values are <em>objects</em>: |
| 219 variables do not actually <em>contain</em> these values, |
| 220 only <em>references</em> to them. |
| 221 Assignment, parameter passing, and function returns |
| 222 always manipulate references to such values; |
| 223 these operations do not imply any kind of copy. |
| 224 |
| 225 |
| 226 <p> |
| 227 The library function <a href="#pdf-type"><code>type</code></a> returns a string
describing the type |
| 228 of a given value (see <a href="#6.1">§6.1</a>). |
| 229 |
| 230 |
| 231 |
| 232 |
| 233 |
| 234 <h2>2.2 – <a name="2.2">Environments and the Global Environment</a></h2> |
| 235 |
| 236 <p> |
| 237 As will be discussed in <a href="#3.2">§3.2</a> and <a href="#3.3.3">§
3.3.3</a>, |
| 238 any reference to a global name <code>var</code> is syntactically translated |
| 239 to <code>_ENV.var</code>. |
| 240 Moreover, every chunk is compiled in the scope of |
| 241 an external local variable called <code>_ENV</code> (see <a href="#3.3.2">§
3.3.2</a>), |
| 242 so <code>_ENV</code> itself is never a global name in a chunk. |
| 243 |
| 244 |
| 245 <p> |
| 246 Despite the existence of this external <code>_ENV</code> variable and |
| 247 the translation of global names, |
| 248 <code>_ENV</code> is a completely regular name. |
| 249 In particular, |
| 250 you can define new variables and parameters with that name. |
| 251 Each reference to a global name uses the <code>_ENV</code> that is |
| 252 visible at that point in the program, |
| 253 following the usual visibility rules of Lua (see <a href="#3.5">§3.5</a>). |
| 254 |
| 255 |
| 256 <p> |
| 257 Any table used as the value of <code>_ENV</code> is called an <em>environment</e
m>. |
| 258 |
| 259 |
| 260 <p> |
| 261 Lua keeps a distinguished environment called the <em>global environment</em>. |
| 262 This value is kept at a special index in the C registry (see <a href="#4.5">&sec
t;4.5</a>). |
| 263 In Lua, the variable <a href="#pdf-_G"><code>_G</code></a> is initialized with t
his same value. |
| 264 |
| 265 |
| 266 <p> |
| 267 When Lua compiles a chunk, |
| 268 it initializes the value of its <code>_ENV</code> upvalue |
| 269 with the global environment (see <a href="#pdf-load"><code>load</code></a>). |
| 270 Therefore, by default, |
| 271 global variables in Lua code refer to entries in the global environment. |
| 272 Moreover, all standard libraries are loaded in the global environment |
| 273 and several functions there operate on that environment. |
| 274 You can use <a href="#pdf-load"><code>load</code></a> (or <a href="#pdf-loadfile
"><code>loadfile</code></a>) |
| 275 to load a chunk with a different environment. |
| 276 (In C, you have to load the chunk and then change the value |
| 277 of its first upvalue.) |
| 278 |
| 279 |
| 280 <p> |
| 281 If you change the global environment in the registry |
| 282 (through C code or the debug library), |
| 283 all chunks loaded after the change will get the new environment. |
| 284 Previously loaded chunks are not affected, however, |
| 285 as each has its own reference to the environment in its <code>_ENV</code> variab
le. |
| 286 Moreover, the variable <a href="#pdf-_G"><code>_G</code></a> |
| 287 (which is stored in the original global environment) |
| 288 is never updated by Lua. |
| 289 |
| 290 |
| 291 |
| 292 |
| 293 |
| 294 <h2>2.3 – <a name="2.3">Error Handling</a></h2> |
| 295 |
| 296 <p> |
| 297 Because Lua is an embedded extension language, |
| 298 all Lua actions start from C code in the host program |
| 299 calling a function from the Lua library (see <a href="#lua_pcall"><code>lua_pcal
l</code></a>). |
| 300 Whenever an error occurs during |
| 301 the compilation or execution of a Lua chunk, |
| 302 control returns to the host, |
| 303 which can take appropriate measures |
| 304 (such as printing an error message). |
| 305 |
| 306 |
| 307 <p> |
| 308 Lua code can explicitly generate an error by calling the |
| 309 <a href="#pdf-error"><code>error</code></a> function. |
| 310 If you need to catch errors in Lua, |
| 311 you can use <a href="#pdf-pcall"><code>pcall</code></a> or <a href="#pdf-xpcall"
><code>xpcall</code></a> |
| 312 to call a given function in <em>protected mode</em>. |
| 313 |
| 314 |
| 315 <p> |
| 316 Whenever there is an error, |
| 317 an <em>error object</em> (also called an <em>error message</em>) |
| 318 is propagated with information about the error. |
| 319 Lua itself only generates errors where the error object is a string, |
| 320 but programs may generate errors with |
| 321 any value for the error object. |
| 322 |
| 323 |
| 324 <p> |
| 325 When you use <a href="#pdf-xpcall"><code>xpcall</code></a> or <a href="#lua_pcal
l"><code>lua_pcall</code></a>, |
| 326 you may give a <em>message handler</em> |
| 327 to be called in case of errors. |
| 328 This function is called with the original error message |
| 329 and returns a new error message. |
| 330 It is called before the error unwinds the stack, |
| 331 so that it can gather more information about the error, |
| 332 for instance by inspecting the stack and creating a stack traceback. |
| 333 This message handler is still protected by the protected call; |
| 334 so, an error inside the message handler |
| 335 will call the message handler again. |
| 336 If this loop goes on, Lua breaks it and returns an appropriate message. |
| 337 |
| 338 |
| 339 |
| 340 |
| 341 |
| 342 <h2>2.4 – <a name="2.4">Metatables and Metamethods</a></h2> |
| 343 |
| 344 <p> |
| 345 Every value in Lua can have a <em>metatable</em>. |
| 346 This <em>metatable</em> is an ordinary Lua table |
| 347 that defines the behavior of the original value |
| 348 under certain special operations. |
| 349 You can change several aspects of the behavior |
| 350 of operations over a value by setting specific fields in its metatable. |
| 351 For instance, when a non-numeric value is the operand of an addition, |
| 352 Lua checks for a function in the field "<code>__add</code>" of the value's metat
able. |
| 353 If it finds one, |
| 354 Lua calls this function to perform the addition. |
| 355 |
| 356 |
| 357 <p> |
| 358 The keys in a metatable are derived from the <em>event</em> names; |
| 359 the corresponding values are called <em>metamethods</em>. |
| 360 In the previous example, the event is <code>"add"</code> |
| 361 and the metamethod is the function that performs the addition. |
| 362 |
| 363 |
| 364 <p> |
| 365 You can query the metatable of any value |
| 366 using the <a href="#pdf-getmetatable"><code>getmetatable</code></a> function. |
| 367 |
| 368 |
| 369 <p> |
| 370 You can replace the metatable of tables |
| 371 using the <a href="#pdf-setmetatable"><code>setmetatable</code></a> function. |
| 372 You cannot change the metatable of other types from Lua |
| 373 (except by using the debug library); |
| 374 you must use the C API for that. |
| 375 |
| 376 |
| 377 <p> |
| 378 Tables and full userdata have individual metatables |
| 379 (although multiple tables and userdata can share their metatables). |
| 380 Values of all other types share one single metatable per type; |
| 381 that is, there is one single metatable for all numbers, |
| 382 one for all strings, etc. |
| 383 By default, a value has no metatable, |
| 384 but the string library sets a metatable for the string type (see <a href="#6.4">
§6.4</a>). |
| 385 |
| 386 |
| 387 <p> |
| 388 A metatable controls how an object behaves in arithmetic operations, |
| 389 order comparisons, concatenation, length operation, and indexing. |
| 390 A metatable also can define a function to be called |
| 391 when a userdata or a table is garbage collected. |
| 392 When Lua performs one of these operations over a value, |
| 393 it checks whether this value has a metatable with the corresponding event. |
| 394 If so, the value associated with that key (the metamethod) |
| 395 controls how Lua will perform the operation. |
| 396 |
| 397 |
| 398 <p> |
| 399 Metatables control the operations listed next. |
| 400 Each operation is identified by its corresponding name. |
| 401 The key for each operation is a string with its name prefixed by |
| 402 two underscores, '<code>__</code>'; |
| 403 for instance, the key for operation "add" is the |
| 404 string "<code>__add</code>". |
| 405 |
| 406 |
| 407 <p> |
| 408 The semantics of these operations is better explained by a Lua function |
| 409 describing how the interpreter executes the operation. |
| 410 The code shown here in Lua is only illustrative; |
| 411 the real behavior is hard coded in the interpreter |
| 412 and it is much more efficient than this simulation. |
| 413 All functions used in these descriptions |
| 414 (<a href="#pdf-rawget"><code>rawget</code></a>, <a href="#pdf-tonumber"><code>to
number</code></a>, etc.) |
| 415 are described in <a href="#6.1">§6.1</a>. |
| 416 In particular, to retrieve the metamethod of a given object, |
| 417 we use the expression |
| 418 |
| 419 <pre> |
| 420 metatable(obj)[event] |
| 421 </pre><p> |
| 422 This should be read as |
| 423 |
| 424 <pre> |
| 425 rawget(getmetatable(obj) or {}, event) |
| 426 </pre><p> |
| 427 This means that the access to a metamethod does not invoke other metamethods, |
| 428 and access to objects with no metatables does not fail |
| 429 (it simply results in <b>nil</b>). |
| 430 |
| 431 |
| 432 <p> |
| 433 For the unary <code>-</code> and <code>#</code> operators, |
| 434 the metamethod is called with a dummy second argument. |
| 435 This extra argument is only to simplify Lua's internals; |
| 436 it may be removed in future versions and therefore it is not present |
| 437 in the following code. |
| 438 (For most uses this extra argument is irrelevant.) |
| 439 |
| 440 |
| 441 |
| 442 <ul> |
| 443 |
| 444 <li><b>"add": </b> |
| 445 the <code>+</code> operation. |
| 446 |
| 447 |
| 448 |
| 449 <p> |
| 450 The function <code>getbinhandler</code> below defines how Lua chooses a handler |
| 451 for a binary operation. |
| 452 First, Lua tries the first operand. |
| 453 If its type does not define a handler for the operation, |
| 454 then Lua tries the second operand. |
| 455 |
| 456 <pre> |
| 457 function getbinhandler (op1, op2, event) |
| 458 return metatable(op1)[event] or metatable(op2)[event] |
| 459 end |
| 460 </pre><p> |
| 461 By using this function, |
| 462 the behavior of the <code>op1 + op2</code> is |
| 463 |
| 464 <pre> |
| 465 function add_event (op1, op2) |
| 466 local o1, o2 = tonumber(op1), tonumber(op2) |
| 467 if o1 and o2 then -- both operands are numeric? |
| 468 return o1 + o2 -- '+' here is the primitive 'add' |
| 469 else -- at least one of the operands is not numeric |
| 470 local h = getbinhandler(op1, op2, "__add") |
| 471 if h then |
| 472 -- call the handler with both operands |
| 473 return (h(op1, op2)) |
| 474 else -- no handler available: default behavior |
| 475 error(···) |
| 476 end |
| 477 end |
| 478 end |
| 479 </pre><p> |
| 480 </li> |
| 481 |
| 482 <li><b>"sub": </b> |
| 483 the <code>-</code> operation. |
| 484 |
| 485 Behavior similar to the "add" operation. |
| 486 </li> |
| 487 |
| 488 <li><b>"mul": </b> |
| 489 the <code>*</code> operation. |
| 490 |
| 491 Behavior similar to the "add" operation. |
| 492 </li> |
| 493 |
| 494 <li><b>"div": </b> |
| 495 the <code>/</code> operation. |
| 496 |
| 497 Behavior similar to the "add" operation. |
| 498 </li> |
| 499 |
| 500 <li><b>"mod": </b> |
| 501 the <code>%</code> operation. |
| 502 |
| 503 Behavior similar to the "add" operation, |
| 504 with the operation |
| 505 <code>o1 - floor(o1/o2)*o2</code> as the primitive operation. |
| 506 </li> |
| 507 |
| 508 <li><b>"pow": </b> |
| 509 the <code>^</code> (exponentiation) operation. |
| 510 |
| 511 Behavior similar to the "add" operation, |
| 512 with the function <code>pow</code> (from the C math library) |
| 513 as the primitive operation. |
| 514 </li> |
| 515 |
| 516 <li><b>"unm": </b> |
| 517 the unary <code>-</code> operation. |
| 518 |
| 519 |
| 520 <pre> |
| 521 function unm_event (op) |
| 522 local o = tonumber(op) |
| 523 if o then -- operand is numeric? |
| 524 return -o -- '-' here is the primitive 'unm' |
| 525 else -- the operand is not numeric. |
| 526 -- Try to get a handler from the operand |
| 527 local h = metatable(op).__unm |
| 528 if h then |
| 529 -- call the handler with the operand |
| 530 return (h(op)) |
| 531 else -- no handler available: default behavior |
| 532 error(···) |
| 533 end |
| 534 end |
| 535 end |
| 536 </pre><p> |
| 537 </li> |
| 538 |
| 539 <li><b>"concat": </b> |
| 540 the <code>..</code> (concatenation) operation. |
| 541 |
| 542 |
| 543 <pre> |
| 544 function concat_event (op1, op2) |
| 545 if (type(op1) == "string" or type(op1) == "number") and |
| 546 (type(op2) == "string" or type(op2) == "number") then |
| 547 return op1 .. op2 -- primitive string concatenation |
| 548 else |
| 549 local h = getbinhandler(op1, op2, "__concat") |
| 550 if h then |
| 551 return (h(op1, op2)) |
| 552 else |
| 553 error(···) |
| 554 end |
| 555 end |
| 556 end |
| 557 </pre><p> |
| 558 </li> |
| 559 |
| 560 <li><b>"len": </b> |
| 561 the <code>#</code> operation. |
| 562 |
| 563 |
| 564 <pre> |
| 565 function len_event (op) |
| 566 if type(op) == "string" then |
| 567 return strlen(op) -- primitive string length |
| 568 else |
| 569 local h = metatable(op).__len |
| 570 if h then |
| 571 return (h(op)) -- call handler with the operand |
| 572 elseif type(op) == "table" then |
| 573 return #op -- primitive table length |
| 574 else -- no handler available: error |
| 575 error(···) |
| 576 end |
| 577 end |
| 578 end |
| 579 </pre><p> |
| 580 See <a href="#3.4.6">§3.4.6</a> for a description of the length of a table. |
| 581 </li> |
| 582 |
| 583 <li><b>"eq": </b> |
| 584 the <code>==</code> operation. |
| 585 |
| 586 The function <code>getequalhandler</code> defines how Lua chooses a metamethod |
| 587 for equality. |
| 588 A metamethod is selected only when both values |
| 589 being compared have the same type |
| 590 and the same metamethod for the selected operation, |
| 591 and the values are either tables or full userdata. |
| 592 |
| 593 <pre> |
| 594 function getequalhandler (op1, op2) |
| 595 if type(op1) ~= type(op2) or |
| 596 (type(op1) ~= "table" and type(op1) ~= "userdata") then |
| 597 return nil -- different values |
| 598 end |
| 599 local mm1 = metatable(op1).__eq |
| 600 local mm2 = metatable(op2).__eq |
| 601 if mm1 == mm2 then return mm1 else return nil end |
| 602 end |
| 603 </pre><p> |
| 604 The "eq" event is defined as follows: |
| 605 |
| 606 <pre> |
| 607 function eq_event (op1, op2) |
| 608 if op1 == op2 then -- primitive equal? |
| 609 return true -- values are equal |
| 610 end |
| 611 -- try metamethod |
| 612 local h = getequalhandler(op1, op2) |
| 613 if h then |
| 614 return not not h(op1, op2) |
| 615 else |
| 616 return false |
| 617 end |
| 618 end |
| 619 </pre><p> |
| 620 Note that the result is always a boolean. |
| 621 </li> |
| 622 |
| 623 <li><b>"lt": </b> |
| 624 the <code><</code> operation. |
| 625 |
| 626 |
| 627 <pre> |
| 628 function lt_event (op1, op2) |
| 629 if type(op1) == "number" and type(op2) == "number" then |
| 630 return op1 < op2 -- numeric comparison |
| 631 elseif type(op1) == "string" and type(op2) == "string" then |
| 632 return op1 < op2 -- lexicographic comparison |
| 633 else |
| 634 local h = getbinhandler(op1, op2, "__lt") |
| 635 if h then |
| 636 return not not h(op1, op2) |
| 637 else |
| 638 error(···) |
| 639 end |
| 640 end |
| 641 end |
| 642 </pre><p> |
| 643 Note that the result is always a boolean. |
| 644 </li> |
| 645 |
| 646 <li><b>"le": </b> |
| 647 the <code><=</code> operation. |
| 648 |
| 649 |
| 650 <pre> |
| 651 function le_event (op1, op2) |
| 652 if type(op1) == "number" and type(op2) == "number" then |
| 653 return op1 <= op2 -- numeric comparison |
| 654 elseif type(op1) == "string" and type(op2) == "string" then |
| 655 return op1 <= op2 -- lexicographic comparison |
| 656 else |
| 657 local h = getbinhandler(op1, op2, "__le") |
| 658 if h then |
| 659 return not not h(op1, op2) |
| 660 else |
| 661 h = getbinhandler(op1, op2, "__lt") |
| 662 if h then |
| 663 return not h(op2, op1) |
| 664 else |
| 665 error(···) |
| 666 end |
| 667 end |
| 668 end |
| 669 end |
| 670 </pre><p> |
| 671 Note that, in the absence of a "le" metamethod, |
| 672 Lua tries the "lt", assuming that <code>a <= b</code> is |
| 673 equivalent to <code>not (b < a)</code>. |
| 674 |
| 675 |
| 676 <p> |
| 677 As with the other comparison operators, |
| 678 the result is always a boolean. |
| 679 </li> |
| 680 |
| 681 <li><b>"index": </b> |
| 682 The indexing access <code>table[key]</code>. |
| 683 Note that the metamethod is tried only |
| 684 when <code>key</code> is not present in <code>table</code>. |
| 685 (When <code>table</code> is not a table, |
| 686 no key is ever present, |
| 687 so the metamethod is always tried.) |
| 688 |
| 689 |
| 690 <pre> |
| 691 function gettable_event (table, key) |
| 692 local h |
| 693 if type(table) == "table" then |
| 694 local v = rawget(table, key) |
| 695 -- if key is present, return raw value |
| 696 if v ~= nil then return v end |
| 697 h = metatable(table).__index |
| 698 if h == nil then return nil end |
| 699 else |
| 700 h = metatable(table).__index |
| 701 if h == nil then |
| 702 error(···) |
| 703 end |
| 704 end |
| 705 if type(h) == "function" then |
| 706 return (h(table, key)) -- call the handler |
| 707 else return h[key] -- or repeat operation on it |
| 708 end |
| 709 end |
| 710 </pre><p> |
| 711 </li> |
| 712 |
| 713 <li><b>"newindex": </b> |
| 714 The indexing assignment <code>table[key] = value</code>. |
| 715 Note that the metamethod is tried only |
| 716 when <code>key</code> is not present in <code>table</code>. |
| 717 |
| 718 |
| 719 <pre> |
| 720 function settable_event (table, key, value) |
| 721 local h |
| 722 if type(table) == "table" then |
| 723 local v = rawget(table, key) |
| 724 -- if key is present, do raw assignment |
| 725 if v ~= nil then rawset(table, key, value); return end |
| 726 h = metatable(table).__newindex |
| 727 if h == nil then rawset(table, key, value); return end |
| 728 else |
| 729 h = metatable(table).__newindex |
| 730 if h == nil then |
| 731 error(···) |
| 732 end |
| 733 end |
| 734 if type(h) == "function" then |
| 735 h(table, key,value) -- call the handler |
| 736 else h[key] = value -- or repeat operation on it |
| 737 end |
| 738 end |
| 739 </pre><p> |
| 740 </li> |
| 741 |
| 742 <li><b>"call": </b> |
| 743 called when Lua calls a value. |
| 744 |
| 745 |
| 746 <pre> |
| 747 function function_event (func, ...) |
| 748 if type(func) == "function" then |
| 749 return func(...) -- primitive call |
| 750 else |
| 751 local h = metatable(func).__call |
| 752 if h then |
| 753 return h(func, ...) |
| 754 else |
| 755 error(···) |
| 756 end |
| 757 end |
| 758 end |
| 759 </pre><p> |
| 760 </li> |
| 761 |
| 762 </ul> |
| 763 |
| 764 |
| 765 |
| 766 |
| 767 <h2>2.5 – <a name="2.5">Garbage Collection</a></h2> |
| 768 |
| 769 <p> |
| 770 Lua performs automatic memory management. |
| 771 This means that |
| 772 you have to worry neither about allocating memory for new objects |
| 773 nor about freeing it when the objects are no longer needed. |
| 774 Lua manages memory automatically by running |
| 775 a <em>garbage collector</em> to collect all <em>dead objects</em> |
| 776 (that is, objects that are no longer accessible from Lua). |
| 777 All memory used by Lua is subject to automatic management: |
| 778 strings, tables, userdata, functions, threads, internal structures, etc. |
| 779 |
| 780 |
| 781 <p> |
| 782 Lua implements an incremental mark-and-sweep collector. |
| 783 It uses two numbers to control its garbage-collection cycles: |
| 784 the <em>garbage-collector pause</em> and |
| 785 the <em>garbage-collector step multiplier</em>. |
| 786 Both use percentage points as units |
| 787 (e.g., a value of 100 means an internal value of 1). |
| 788 |
| 789 |
| 790 <p> |
| 791 The garbage-collector pause |
| 792 controls how long the collector waits before starting a new cycle. |
| 793 Larger values make the collector less aggressive. |
| 794 Values smaller than 100 mean the collector will not wait to |
| 795 start a new cycle. |
| 796 A value of 200 means that the collector waits for the total memory in use |
| 797 to double before starting a new cycle. |
| 798 |
| 799 |
| 800 <p> |
| 801 The garbage-collector step multiplier |
| 802 controls the relative speed of the collector relative to |
| 803 memory allocation. |
| 804 Larger values make the collector more aggressive but also increase |
| 805 the size of each incremental step. |
| 806 Values smaller than 100 make the collector too slow and |
| 807 can result in the collector never finishing a cycle. |
| 808 The default is 200, |
| 809 which means that the collector runs at "twice" |
| 810 the speed of memory allocation. |
| 811 |
| 812 |
| 813 <p> |
| 814 If you set the step multiplier to a very large number |
| 815 (larger than 10% of the maximum number of |
| 816 bytes that the program may use), |
| 817 the collector behaves like a stop-the-world collector. |
| 818 If you then set the pause to 200, |
| 819 the collector behaves as in old Lua versions, |
| 820 doing a complete collection every time Lua doubles its |
| 821 memory usage. |
| 822 |
| 823 |
| 824 <p> |
| 825 You can change these numbers by calling <a href="#lua_gc"><code>lua_gc</code></a
> in C |
| 826 or <a href="#pdf-collectgarbage"><code>collectgarbage</code></a> in Lua. |
| 827 You can also use these functions to control |
| 828 the collector directly (e.g., stop and restart it). |
| 829 |
| 830 |
| 831 <p> |
| 832 As an experimental feature in Lua 5.2, |
| 833 you can change the collector's operation mode |
| 834 from incremental to <em>generational</em>. |
| 835 A <em>generational collector</em> assumes that most objects die young, |
| 836 and therefore it traverses only young (recently created) objects. |
| 837 This behavior can reduce the time used by the collector, |
| 838 but also increases memory usage (as old dead objects may accumulate). |
| 839 To mitigate this second problem, |
| 840 from time to time the generational collector performs a full collection. |
| 841 Remember that this is an experimental feature; |
| 842 you are welcome to try it, |
| 843 but check your gains. |
| 844 |
| 845 |
| 846 |
| 847 <h3>2.5.1 – <a name="2.5.1">Garbage-Collection Metamethods</a></h3> |
| 848 |
| 849 <p> |
| 850 You can set garbage-collector metamethods for tables |
| 851 and, using the C API, |
| 852 for full userdata (see <a href="#2.4">§2.4</a>). |
| 853 These metamethods are also called <em>finalizers</em>. |
| 854 Finalizers allow you to coordinate Lua's garbage collection |
| 855 with external resource management |
| 856 (such as closing files, network or database connections, |
| 857 or freeing your own memory). |
| 858 |
| 859 |
| 860 <p> |
| 861 For an object (table or userdata) to be finalized when collected, |
| 862 you must <em>mark</em> it for finalization. |
| 863 |
| 864 You mark an object for finalization when you set its metatable |
| 865 and the metatable has a field indexed by the string "<code>__gc</code>". |
| 866 Note that if you set a metatable without a <code>__gc</code> field |
| 867 and later create that field in the metatable, |
| 868 the object will not be marked for finalization. |
| 869 However, after an object is marked, |
| 870 you can freely change the <code>__gc</code> field of its metatable. |
| 871 |
| 872 |
| 873 <p> |
| 874 When a marked object becomes garbage, |
| 875 it is not collected immediately by the garbage collector. |
| 876 Instead, Lua puts it in a list. |
| 877 After the collection, |
| 878 Lua does the equivalent of the following function |
| 879 for each object in that list: |
| 880 |
| 881 <pre> |
| 882 function gc_event (obj) |
| 883 local h = metatable(obj).__gc |
| 884 if type(h) == "function" then |
| 885 h(obj) |
| 886 end |
| 887 end |
| 888 </pre> |
| 889 |
| 890 <p> |
| 891 At the end of each garbage-collection cycle, |
| 892 the finalizers for objects are called in |
| 893 the reverse order that they were marked for collection, |
| 894 among those collected in that cycle; |
| 895 that is, the first finalizer to be called is the one associated |
| 896 with the object marked last in the program. |
| 897 The execution of each finalizer may occur at any point during |
| 898 the execution of the regular code. |
| 899 |
| 900 |
| 901 <p> |
| 902 Because the object being collected must still be used by the finalizer, |
| 903 it (and other objects accessible only through it) |
| 904 must be <em>resurrected</em> by Lua. |
| 905 Usually, this resurrection is transient, |
| 906 and the object memory is freed in the next garbage-collection cycle. |
| 907 However, if the finalizer stores the object in some global place |
| 908 (e.g., a global variable), |
| 909 then there is a permanent resurrection. |
| 910 In any case, |
| 911 the object memory is freed only when it becomes completely inaccessible; |
| 912 its finalizer will never be called twice. |
| 913 |
| 914 |
| 915 <p> |
| 916 When you close a state (see <a href="#lua_close"><code>lua_close</code></a>), |
| 917 Lua calls the finalizers of all objects marked for finalization, |
| 918 following the reverse order that they were marked. |
| 919 If any finalizer marks new objects for collection during that phase, |
| 920 these new objects will not be finalized. |
| 921 |
| 922 |
| 923 |
| 924 |
| 925 |
| 926 <h3>2.5.2 – <a name="2.5.2">Weak Tables</a></h3> |
| 927 |
| 928 <p> |
| 929 A <em>weak table</em> is a table whose elements are |
| 930 <em>weak references</em>. |
| 931 A weak reference is ignored by the garbage collector. |
| 932 In other words, |
| 933 if the only references to an object are weak references, |
| 934 then the garbage collector will collect that object. |
| 935 |
| 936 |
| 937 <p> |
| 938 A weak table can have weak keys, weak values, or both. |
| 939 A table with weak keys allows the collection of its keys, |
| 940 but prevents the collection of its values. |
| 941 A table with both weak keys and weak values allows the collection of |
| 942 both keys and values. |
| 943 In any case, if either the key or the value is collected, |
| 944 the whole pair is removed from the table. |
| 945 The weakness of a table is controlled by the |
| 946 <code>__mode</code> field of its metatable. |
| 947 If the <code>__mode</code> field is a string containing the character '<cod
e>k</code>', |
| 948 the keys in the table are weak. |
| 949 If <code>__mode</code> contains '<code>v</code>', |
| 950 the values in the table are weak. |
| 951 |
| 952 |
| 953 <p> |
| 954 A table with weak keys and strong values |
| 955 is also called an <em>ephemeron table</em>. |
| 956 In an ephemeron table, |
| 957 a value is considered reachable only if its key is reachable. |
| 958 In particular, |
| 959 if the only reference to a key comes through its value, |
| 960 the pair is removed. |
| 961 |
| 962 |
| 963 <p> |
| 964 Any change in the weakness of a table may take effect only |
| 965 at the next collect cycle. |
| 966 In particular, if you change the weakness to a stronger mode, |
| 967 Lua may still collect some items from that table |
| 968 before the change takes effect. |
| 969 |
| 970 |
| 971 <p> |
| 972 Only objects that have an explicit construction |
| 973 are removed from weak tables. |
| 974 Values, such as numbers and light C functions, |
| 975 are not subject to garbage collection, |
| 976 and therefore are not removed from weak tables |
| 977 (unless its associated value is collected). |
| 978 Although strings are subject to garbage collection, |
| 979 they do not have an explicit construction, |
| 980 and therefore are not removed from weak tables. |
| 981 |
| 982 |
| 983 <p> |
| 984 Resurrected objects |
| 985 (that is, objects being finalized |
| 986 and objects accessible only through objects being finalized) |
| 987 have a special behavior in weak tables. |
| 988 They are removed from weak values before running their finalizers, |
| 989 but are removed from weak keys only in the next collection |
| 990 after running their finalizers, when such objects are actually freed. |
| 991 This behavior allows the finalizer to access properties |
| 992 associated with the object through weak tables. |
| 993 |
| 994 |
| 995 <p> |
| 996 If a weak table is among the resurrected objects in a collection cycle, |
| 997 it may not be properly cleared until the next cycle. |
| 998 |
| 999 |
| 1000 |
| 1001 |
| 1002 |
| 1003 |
| 1004 |
| 1005 <h2>2.6 – <a name="2.6">Coroutines</a></h2> |
| 1006 |
| 1007 <p> |
| 1008 Lua supports coroutines, |
| 1009 also called <em>collaborative multithreading</em>. |
| 1010 A coroutine in Lua represents an independent thread of execution. |
| 1011 Unlike threads in multithread systems, however, |
| 1012 a coroutine only suspends its execution by explicitly calling |
| 1013 a yield function. |
| 1014 |
| 1015 |
| 1016 <p> |
| 1017 You create a coroutine by calling <a href="#pdf-coroutine.create"><code>coroutin
e.create</code></a>. |
| 1018 Its sole argument is a function |
| 1019 that is the main function of the coroutine. |
| 1020 The <code>create</code> function only creates a new coroutine and |
| 1021 returns a handle to it (an object of type <em>thread</em>); |
| 1022 it does not start the coroutine. |
| 1023 |
| 1024 |
| 1025 <p> |
| 1026 You execute a coroutine by calling <a href="#pdf-coroutine.resume"><code>corouti
ne.resume</code></a>. |
| 1027 When you first call <a href="#pdf-coroutine.resume"><code>coroutine.resume</code
></a>, |
| 1028 passing as its first argument |
| 1029 a thread returned by <a href="#pdf-coroutine.create"><code>coroutine.create</cod
e></a>, |
| 1030 the coroutine starts its execution, |
| 1031 at the first line of its main function. |
| 1032 Extra arguments passed to <a href="#pdf-coroutine.resume"><code>coroutine.resume
</code></a> are passed on |
| 1033 to the coroutine main function. |
| 1034 After the coroutine starts running, |
| 1035 it runs until it terminates or <em>yields</em>. |
| 1036 |
| 1037 |
| 1038 <p> |
| 1039 A coroutine can terminate its execution in two ways: |
| 1040 normally, when its main function returns |
| 1041 (explicitly or implicitly, after the last instruction); |
| 1042 and abnormally, if there is an unprotected error. |
| 1043 In the first case, <a href="#pdf-coroutine.resume"><code>coroutine.resume</code>
</a> returns <b>true</b>, |
| 1044 plus any values returned by the coroutine main function. |
| 1045 In case of errors, <a href="#pdf-coroutine.resume"><code>coroutine.resume</code>
</a> returns <b>false</b> |
| 1046 plus an error message. |
| 1047 |
| 1048 |
| 1049 <p> |
| 1050 A coroutine yields by calling <a href="#pdf-coroutine.yield"><code>coroutine.yie
ld</code></a>. |
| 1051 When a coroutine yields, |
| 1052 the corresponding <a href="#pdf-coroutine.resume"><code>coroutine.resume</code><
/a> returns immediately, |
| 1053 even if the yield happens inside nested function calls |
| 1054 (that is, not in the main function, |
| 1055 but in a function directly or indirectly called by the main function). |
| 1056 In the case of a yield, <a href="#pdf-coroutine.resume"><code>coroutine.resume</
code></a> also returns <b>true</b>, |
| 1057 plus any values passed to <a href="#pdf-coroutine.yield"><code>coroutine.yield</
code></a>. |
| 1058 The next time you resume the same coroutine, |
| 1059 it continues its execution from the point where it yielded, |
| 1060 with the call to <a href="#pdf-coroutine.yield"><code>coroutine.yield</code></a>
returning any extra |
| 1061 arguments passed to <a href="#pdf-coroutine.resume"><code>coroutine.resume</code
></a>. |
| 1062 |
| 1063 |
| 1064 <p> |
| 1065 Like <a href="#pdf-coroutine.create"><code>coroutine.create</code></a>, |
| 1066 the <a href="#pdf-coroutine.wrap"><code>coroutine.wrap</code></a> function also
creates a coroutine, |
| 1067 but instead of returning the coroutine itself, |
| 1068 it returns a function that, when called, resumes the coroutine. |
| 1069 Any arguments passed to this function |
| 1070 go as extra arguments to <a href="#pdf-coroutine.resume"><code>coroutine.resume<
/code></a>. |
| 1071 <a href="#pdf-coroutine.wrap"><code>coroutine.wrap</code></a> returns all the va
lues returned by <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></
a>, |
| 1072 except the first one (the boolean error code). |
| 1073 Unlike <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>, |
| 1074 <a href="#pdf-coroutine.wrap"><code>coroutine.wrap</code></a> does not catch err
ors; |
| 1075 any error is propagated to the caller. |
| 1076 |
| 1077 |
| 1078 <p> |
| 1079 As an example of how coroutines work, |
| 1080 consider the following code: |
| 1081 |
| 1082 <pre> |
| 1083 function foo (a) |
| 1084 print("foo", a) |
| 1085 return coroutine.yield(2*a) |
| 1086 end |
| 1087 |
| 1088 co = coroutine.create(function (a,b) |
| 1089 print("co-body", a, b) |
| 1090 local r = foo(a+1) |
| 1091 print("co-body", r) |
| 1092 local r, s = coroutine.yield(a+b, a-b) |
| 1093 print("co-body", r, s) |
| 1094 return b, "end" |
| 1095 end) |
| 1096 |
| 1097 print("main", coroutine.resume(co, 1, 10)) |
| 1098 print("main", coroutine.resume(co, "r")) |
| 1099 print("main", coroutine.resume(co, "x", "y")) |
| 1100 print("main", coroutine.resume(co, "x", "y")) |
| 1101 </pre><p> |
| 1102 When you run it, it produces the following output: |
| 1103 |
| 1104 <pre> |
| 1105 co-body 1 10 |
| 1106 foo 2 |
| 1107 main true 4 |
| 1108 co-body r |
| 1109 main true 11 -9 |
| 1110 co-body x y |
| 1111 main true 10 end |
| 1112 main false cannot resume dead coroutine |
| 1113 </pre> |
| 1114 |
| 1115 <p> |
| 1116 You can also create and manipulate coroutines through the C API: |
| 1117 see functions <a href="#lua_newthread"><code>lua_newthread</code></a>, <a href="
#lua_resume"><code>lua_resume</code></a>, |
| 1118 and <a href="#lua_yield"><code>lua_yield</code></a>. |
| 1119 |
| 1120 |
| 1121 |
| 1122 |
| 1123 |
| 1124 <h1>3 – <a name="3">The Language</a></h1> |
| 1125 |
| 1126 <p> |
| 1127 This section describes the lexis, the syntax, and the semantics of Lua. |
| 1128 In other words, |
| 1129 this section describes |
| 1130 which tokens are valid, |
| 1131 how they can be combined, |
| 1132 and what their combinations mean. |
| 1133 |
| 1134 |
| 1135 <p> |
| 1136 Language constructs will be explained using the usual extended BNF notation, |
| 1137 in which |
| 1138 {<em>a</em>} means 0 or more <em>a</em>'s, and |
| 1139 [<em>a</em>] means an optional <em>a</em>. |
| 1140 Non-terminals are shown like non-terminal, |
| 1141 keywords are shown like <b>kword</b>, |
| 1142 and other terminal symbols are shown like ‘<b>=</b>’. |
| 1143 The complete syntax of Lua can be found in <a href="#9">§9</a> |
| 1144 at the end of this manual. |
| 1145 |
| 1146 |
| 1147 |
| 1148 <h2>3.1 – <a name="3.1">Lexical Conventions</a></h2> |
| 1149 |
| 1150 <p> |
| 1151 Lua is a free-form language. |
| 1152 It ignores spaces (including new lines) and comments |
| 1153 between lexical elements (tokens), |
| 1154 except as delimiters between names and keywords. |
| 1155 |
| 1156 |
| 1157 <p> |
| 1158 <em>Names</em> |
| 1159 (also called <em>identifiers</em>) |
| 1160 in Lua can be any string of letters, |
| 1161 digits, and underscores, |
| 1162 not beginning with a digit. |
| 1163 Identifiers are used to name variables, table fields, and labels. |
| 1164 |
| 1165 |
| 1166 <p> |
| 1167 The following <em>keywords</em> are reserved |
| 1168 and cannot be used as names: |
| 1169 |
| 1170 |
| 1171 <pre> |
| 1172 and break do else elseif end |
| 1173 false for function goto if in |
| 1174 local nil not or repeat return |
| 1175 then true until while |
| 1176 </pre> |
| 1177 |
| 1178 <p> |
| 1179 Lua is a case-sensitive language: |
| 1180 <code>and</code> is a reserved word, but <code>And</code> and <code>AND</code> |
| 1181 are two different, valid names. |
| 1182 As a convention, names starting with an underscore followed by |
| 1183 uppercase letters (such as <a href="#pdf-_VERSION"><code>_VERSION</code></a>) |
| 1184 are reserved for variables used by Lua. |
| 1185 |
| 1186 |
| 1187 <p> |
| 1188 The following strings denote other tokens: |
| 1189 |
| 1190 <pre> |
| 1191 + - * / % ^ # |
| 1192 == ~= <= >= < > = |
| 1193 ( ) { } [ ] :: |
| 1194 ; : , . .. ... |
| 1195 </pre> |
| 1196 |
| 1197 <p> |
| 1198 <em>Literal strings</em> |
| 1199 can be delimited by matching single or double quotes, |
| 1200 and can contain the following C-like escape sequences: |
| 1201 '<code>\a</code>' (bell), |
| 1202 '<code>\b</code>' (backspace), |
| 1203 '<code>\f</code>' (form feed), |
| 1204 '<code>\n</code>' (newline), |
| 1205 '<code>\r</code>' (carriage return), |
| 1206 '<code>\t</code>' (horizontal tab), |
| 1207 '<code>\v</code>' (vertical tab), |
| 1208 '<code>\\</code>' (backslash), |
| 1209 '<code>\"</code>' (quotation mark [double quote]), |
| 1210 and '<code>\'</code>' (apostrophe [single quote]). |
| 1211 A backslash followed by a real newline |
| 1212 results in a newline in the string. |
| 1213 The escape sequence '<code>\z</code>' skips the following span |
| 1214 of white-space characters, |
| 1215 including line breaks; |
| 1216 it is particularly useful to break and indent a long literal string |
| 1217 into multiple lines without adding the newlines and spaces |
| 1218 into the string contents. |
| 1219 |
| 1220 |
| 1221 <p> |
| 1222 A byte in a literal string can also be specified by its numerical value. |
| 1223 This can be done with the escape sequence <code>\x<em>XX</em></code>, |
| 1224 where <em>XX</em> is a sequence of exactly two hexadecimal digits, |
| 1225 or with the escape sequence <code>\<em>ddd</em></code>, |
| 1226 where <em>ddd</em> is a sequence of up to three decimal digits. |
| 1227 (Note that if a decimal escape is to be followed by a digit, |
| 1228 it must be expressed using exactly three digits.) |
| 1229 Strings in Lua can contain any 8-bit value, including embedded zeros, |
| 1230 which can be specified as '<code>\0</code>'. |
| 1231 |
| 1232 |
| 1233 <p> |
| 1234 Literal strings can also be defined using a long format |
| 1235 enclosed by <em>long brackets</em>. |
| 1236 We define an <em>opening long bracket of level <em>n</em></em> as an opening |
| 1237 square bracket followed by <em>n</em> equal signs followed by another |
| 1238 opening square bracket. |
| 1239 So, an opening long bracket of level 0 is written as <code>[[</code>, |
| 1240 an opening long bracket of level 1 is written as <code>[=[</code>, |
| 1241 and so on. |
| 1242 A <em>closing long bracket</em> is defined similarly; |
| 1243 for instance, a closing long bracket of level 4 is written as <code>]====]<
/code>. |
| 1244 A <em>long literal</em> starts with an opening long bracket of any level and |
| 1245 ends at the first closing long bracket of the same level. |
| 1246 It can contain any text except a closing bracket of the proper level. |
| 1247 Literals in this bracketed form can run for several lines, |
| 1248 do not interpret any escape sequences, |
| 1249 and ignore long brackets of any other level. |
| 1250 Any kind of end-of-line sequence |
| 1251 (carriage return, newline, carriage return followed by newline, |
| 1252 or newline followed by carriage return) |
| 1253 is converted to a simple newline. |
| 1254 |
| 1255 |
| 1256 <p> |
| 1257 Any byte in a literal string not |
| 1258 explicitly affected by the previous rules represents itself. |
| 1259 However, Lua opens files for parsing in text mode, |
| 1260 and the system file functions may have problems with |
| 1261 some control characters. |
| 1262 So, it is safer to represent |
| 1263 non-text data as a quoted literal with |
| 1264 explicit escape sequences for non-text characters. |
| 1265 |
| 1266 |
| 1267 <p> |
| 1268 For convenience, |
| 1269 when the opening long bracket is immediately followed by a newline, |
| 1270 the newline is not included in the string. |
| 1271 As an example, in a system using ASCII |
| 1272 (in which '<code>a</code>' is coded as 97, |
| 1273 newline is coded as 10, and '<code>1</code>' is coded as 49), |
| 1274 the five literal strings below denote the same string: |
| 1275 |
| 1276 <pre> |
| 1277 a = 'alo\n123"' |
| 1278 a = "alo\n123\"" |
| 1279 a = '\97lo\10\04923"' |
| 1280 a = [[alo |
| 1281 123"]] |
| 1282 a = [==[ |
| 1283 alo |
| 1284 123"]==] |
| 1285 </pre> |
| 1286 |
| 1287 <p> |
| 1288 A <em>numerical constant</em> can be written with an optional fractional part |
| 1289 and an optional decimal exponent, |
| 1290 marked by a letter '<code>e</code>' or '<code>E</code>'. |
| 1291 Lua also accepts hexadecimal constants, |
| 1292 which start with <code>0x</code> or <code>0X</code>. |
| 1293 Hexadecimal constants also accept an optional fractional part |
| 1294 plus an optional binary exponent, |
| 1295 marked by a letter '<code>p</code>' or '<code>P</code>'. |
| 1296 Examples of valid numerical constants are |
| 1297 |
| 1298 <pre> |
| 1299 3 3.0 3.1416 314.16e-2 0.31416E1 |
| 1300 0xff 0x0.1E 0xA23p-4 0X1.921FB54442D18P+1 |
| 1301 </pre> |
| 1302 |
| 1303 <p> |
| 1304 A <em>comment</em> starts with a double hyphen (<code>--</code>) |
| 1305 anywhere outside a string. |
| 1306 If the text immediately after <code>--</code> is not an opening long bracket, |
| 1307 the comment is a <em>short comment</em>, |
| 1308 which runs until the end of the line. |
| 1309 Otherwise, it is a <em>long comment</em>, |
| 1310 which runs until the corresponding closing long bracket. |
| 1311 Long comments are frequently used to disable code temporarily. |
| 1312 |
| 1313 |
| 1314 |
| 1315 |
| 1316 |
| 1317 <h2>3.2 – <a name="3.2">Variables</a></h2> |
| 1318 |
| 1319 <p> |
| 1320 Variables are places that store values. |
| 1321 There are three kinds of variables in Lua: |
| 1322 global variables, local variables, and table fields. |
| 1323 |
| 1324 |
| 1325 <p> |
| 1326 A single name can denote a global variable or a local variable |
| 1327 (or a function's formal parameter, |
| 1328 which is a particular kind of local variable): |
| 1329 |
| 1330 <pre> |
| 1331 var ::= Name |
| 1332 </pre><p> |
| 1333 Name denotes identifiers, as defined in <a href="#3.1">§3.1</a>. |
| 1334 |
| 1335 |
| 1336 <p> |
| 1337 Any variable name is assumed to be global unless explicitly declared |
| 1338 as a local (see <a href="#3.3.7">§3.3.7</a>). |
| 1339 Local variables are <em>lexically scoped</em>: |
| 1340 local variables can be freely accessed by functions |
| 1341 defined inside their scope (see <a href="#3.5">§3.5</a>). |
| 1342 |
| 1343 |
| 1344 <p> |
| 1345 Before the first assignment to a variable, its value is <b>nil</b>. |
| 1346 |
| 1347 |
| 1348 <p> |
| 1349 Square brackets are used to index a table: |
| 1350 |
| 1351 <pre> |
| 1352 var ::= prefixexp ‘<b>[</b>’ exp ‘<b>]</b>’ |
| 1353 </pre><p> |
| 1354 The meaning of accesses to table fields can be changed via metatables. |
| 1355 An access to an indexed variable <code>t[i]</code> is equivalent to |
| 1356 a call <code>gettable_event(t,i)</code>. |
| 1357 (See <a href="#2.4">§2.4</a> for a complete description of the |
| 1358 <code>gettable_event</code> function. |
| 1359 This function is not defined or callable in Lua. |
| 1360 We use it here only for explanatory purposes.) |
| 1361 |
| 1362 |
| 1363 <p> |
| 1364 The syntax <code>var.Name</code> is just syntactic sugar for |
| 1365 <code>var["Name"]</code>: |
| 1366 |
| 1367 <pre> |
| 1368 var ::= prefixexp ‘<b>.</b>’ Name |
| 1369 </pre> |
| 1370 |
| 1371 <p> |
| 1372 An access to a global variable <code>x</code> |
| 1373 is equivalent to <code>_ENV.x</code>. |
| 1374 Due to the way that chunks are compiled, |
| 1375 <code>_ENV</code> is never a global name (see <a href="#2.2">§2.2</a>). |
| 1376 |
| 1377 |
| 1378 |
| 1379 |
| 1380 |
| 1381 <h2>3.3 – <a name="3.3">Statements</a></h2> |
| 1382 |
| 1383 <p> |
| 1384 Lua supports an almost conventional set of statements, |
| 1385 similar to those in Pascal or C. |
| 1386 This set includes |
| 1387 assignments, control structures, function calls, |
| 1388 and variable declarations. |
| 1389 |
| 1390 |
| 1391 |
| 1392 <h3>3.3.1 – <a name="3.3.1">Blocks</a></h3> |
| 1393 |
| 1394 <p> |
| 1395 A block is a list of statements, |
| 1396 which are executed sequentially: |
| 1397 |
| 1398 <pre> |
| 1399 block ::= {stat} |
| 1400 </pre><p> |
| 1401 Lua has <em>empty statements</em> |
| 1402 that allow you to separate statements with semicolons, |
| 1403 start a block with a semicolon |
| 1404 or write two semicolons in sequence: |
| 1405 |
| 1406 <pre> |
| 1407 stat ::= ‘<b>;</b>’ |
| 1408 </pre> |
| 1409 |
| 1410 <p> |
| 1411 Function calls and assignments |
| 1412 can start with an open parenthesis. |
| 1413 This possibility leads to an ambiguity in Lua's grammar. |
| 1414 Consider the following fragment: |
| 1415 |
| 1416 <pre> |
| 1417 a = b + c |
| 1418 (print or io.write)('done') |
| 1419 </pre><p> |
| 1420 The grammar could see it in two ways: |
| 1421 |
| 1422 <pre> |
| 1423 a = b + c(print or io.write)('done') |
| 1424 |
| 1425 a = b + c; (print or io.write)('done') |
| 1426 </pre><p> |
| 1427 The current parser always sees such constructions |
| 1428 in the first way, |
| 1429 interpreting the open parenthesis |
| 1430 as the start of the arguments to a call. |
| 1431 To avoid this ambiguity, |
| 1432 it is a good practice to always precede with a semicolon |
| 1433 statements that start with a parenthesis: |
| 1434 |
| 1435 <pre> |
| 1436 ;(print or io.write)('done') |
| 1437 </pre> |
| 1438 |
| 1439 <p> |
| 1440 A block can be explicitly delimited to produce a single statement: |
| 1441 |
| 1442 <pre> |
| 1443 stat ::= <b>do</b> block <b>end</b> |
| 1444 </pre><p> |
| 1445 Explicit blocks are useful |
| 1446 to control the scope of variable declarations. |
| 1447 Explicit blocks are also sometimes used to |
| 1448 add a <b>return</b> statement in the middle |
| 1449 of another block (see <a href="#3.3.4">§3.3.4</a>). |
| 1450 |
| 1451 |
| 1452 |
| 1453 |
| 1454 |
| 1455 <h3>3.3.2 – <a name="3.3.2">Chunks</a></h3> |
| 1456 |
| 1457 <p> |
| 1458 The unit of compilation of Lua is called a <em>chunk</em>. |
| 1459 Syntactically, |
| 1460 a chunk is simply a block: |
| 1461 |
| 1462 <pre> |
| 1463 chunk ::= block |
| 1464 </pre> |
| 1465 |
| 1466 <p> |
| 1467 Lua handles a chunk as the body of an anonymous function |
| 1468 with a variable number of arguments |
| 1469 (see <a href="#3.4.10">§3.4.10</a>). |
| 1470 As such, chunks can define local variables, |
| 1471 receive arguments, and return values. |
| 1472 Moreover, such anonymous function is compiled as in the |
| 1473 scope of an external local variable called <code>_ENV</code> (see <a href="#2.2"
>§2.2</a>). |
| 1474 The resulting function always has <code>_ENV</code> as its only upvalue, |
| 1475 even if it does not use that variable. |
| 1476 |
| 1477 |
| 1478 <p> |
| 1479 A chunk can be stored in a file or in a string inside the host program. |
| 1480 To execute a chunk, |
| 1481 Lua first precompiles the chunk into instructions for a virtual machine, |
| 1482 and then it executes the compiled code |
| 1483 with an interpreter for the virtual machine. |
| 1484 |
| 1485 |
| 1486 <p> |
| 1487 Chunks can also be precompiled into binary form; |
| 1488 see program <code>luac</code> for details. |
| 1489 Programs in source and compiled forms are interchangeable; |
| 1490 Lua automatically detects the file type and acts accordingly. |
| 1491 |
| 1492 |
| 1493 |
| 1494 |
| 1495 |
| 1496 |
| 1497 <h3>3.3.3 – <a name="3.3.3">Assignment</a></h3> |
| 1498 |
| 1499 <p> |
| 1500 Lua allows multiple assignments. |
| 1501 Therefore, the syntax for assignment |
| 1502 defines a list of variables on the left side |
| 1503 and a list of expressions on the right side. |
| 1504 The elements in both lists are separated by commas: |
| 1505 |
| 1506 <pre> |
| 1507 stat ::= varlist ‘<b>=</b>’ explist |
| 1508 varlist ::= var {‘<b>,</b>’ var} |
| 1509 explist ::= exp {‘<b>,</b>’ exp} |
| 1510 </pre><p> |
| 1511 Expressions are discussed in <a href="#3.4">§3.4</a>. |
| 1512 |
| 1513 |
| 1514 <p> |
| 1515 Before the assignment, |
| 1516 the list of values is <em>adjusted</em> to the length of |
| 1517 the list of variables. |
| 1518 If there are more values than needed, |
| 1519 the excess values are thrown away. |
| 1520 If there are fewer values than needed, |
| 1521 the list is extended with as many <b>nil</b>'s as needed. |
| 1522 If the list of expressions ends with a function call, |
| 1523 then all values returned by that call enter the list of values, |
| 1524 before the adjustment |
| 1525 (except when the call is enclosed in parentheses; see <a href="#3.4">§3.4</
a>). |
| 1526 |
| 1527 |
| 1528 <p> |
| 1529 The assignment statement first evaluates all its expressions |
| 1530 and only then are the assignments performed. |
| 1531 Thus the code |
| 1532 |
| 1533 <pre> |
| 1534 i = 3 |
| 1535 i, a[i] = i+1, 20 |
| 1536 </pre><p> |
| 1537 sets <code>a[3]</code> to 20, without affecting <code>a[4]</code> |
| 1538 because the <code>i</code> in <code>a[i]</code> is evaluated (to 3) |
| 1539 before it is assigned 4. |
| 1540 Similarly, the line |
| 1541 |
| 1542 <pre> |
| 1543 x, y = y, x |
| 1544 </pre><p> |
| 1545 exchanges the values of <code>x</code> and <code>y</code>, |
| 1546 and |
| 1547 |
| 1548 <pre> |
| 1549 x, y, z = y, z, x |
| 1550 </pre><p> |
| 1551 cyclically permutes the values of <code>x</code>, <code>y</code>, and <code>z</c
ode>. |
| 1552 |
| 1553 |
| 1554 <p> |
| 1555 The meaning of assignments to global variables |
| 1556 and table fields can be changed via metatables. |
| 1557 An assignment to an indexed variable <code>t[i] = val</code> is equivalent to |
| 1558 <code>settable_event(t,i,val)</code>. |
| 1559 (See <a href="#2.4">§2.4</a> for a complete description of the |
| 1560 <code>settable_event</code> function. |
| 1561 This function is not defined or callable in Lua. |
| 1562 We use it here only for explanatory purposes.) |
| 1563 |
| 1564 |
| 1565 <p> |
| 1566 An assignment to a global variable <code>x = val</code> |
| 1567 is equivalent to the assignment |
| 1568 <code>_ENV.x = val</code> (see <a href="#2.2">§2.2</a>). |
| 1569 |
| 1570 |
| 1571 |
| 1572 |
| 1573 |
| 1574 <h3>3.3.4 – <a name="3.3.4">Control Structures</a></h3><p> |
| 1575 The control structures |
| 1576 <b>if</b>, <b>while</b>, and <b>repeat</b> have the usual meaning and |
| 1577 familiar syntax: |
| 1578 |
| 1579 |
| 1580 |
| 1581 |
| 1582 <pre> |
| 1583 stat ::= <b>while</b> exp <b>do</b> block <b>end</b> |
| 1584 stat ::= <b>repeat</b> block <b>until</b> exp |
| 1585 stat ::= <b>if</b> exp <b>then</b> block {<b>elseif</b> exp <b>then</b>
block} [<b>else</b> block] <b>end</b> |
| 1586 </pre><p> |
| 1587 Lua also has a <b>for</b> statement, in two flavors (see <a href="#3.3.5">§
3.3.5</a>). |
| 1588 |
| 1589 |
| 1590 <p> |
| 1591 The condition expression of a |
| 1592 control structure can return any value. |
| 1593 Both <b>false</b> and <b>nil</b> are considered false. |
| 1594 All values different from <b>nil</b> and <b>false</b> are considered true |
| 1595 (in particular, the number 0 and the empty string are also true). |
| 1596 |
| 1597 |
| 1598 <p> |
| 1599 In the <b>repeat</b>–<b>until</b> loop, |
| 1600 the inner block does not end at the <b>until</b> keyword, |
| 1601 but only after the condition. |
| 1602 So, the condition can refer to local variables |
| 1603 declared inside the loop block. |
| 1604 |
| 1605 |
| 1606 <p> |
| 1607 The <b>goto</b> statement transfers the program control to a label. |
| 1608 For syntactical reasons, |
| 1609 labels in Lua are considered statements too: |
| 1610 |
| 1611 |
| 1612 |
| 1613 <pre> |
| 1614 stat ::= <b>goto</b> Name |
| 1615 stat ::= label |
| 1616 label ::= ‘<b>::</b>’ Name ‘<b>::</b>’ |
| 1617 </pre> |
| 1618 |
| 1619 <p> |
| 1620 A label is visible in the entire block where it is defined, |
| 1621 except |
| 1622 inside nested blocks where a label with the same name is defined and |
| 1623 inside nested functions. |
| 1624 A goto may jump to any visible label as long as it does not |
| 1625 enter into the scope of a local variable. |
| 1626 |
| 1627 |
| 1628 <p> |
| 1629 Labels and empty statements are called <em>void statements</em>, |
| 1630 as they perform no actions. |
| 1631 |
| 1632 |
| 1633 <p> |
| 1634 The <b>break</b> statement terminates the execution of a |
| 1635 <b>while</b>, <b>repeat</b>, or <b>for</b> loop, |
| 1636 skipping to the next statement after the loop: |
| 1637 |
| 1638 |
| 1639 <pre> |
| 1640 stat ::= <b>break</b> |
| 1641 </pre><p> |
| 1642 A <b>break</b> ends the innermost enclosing loop. |
| 1643 |
| 1644 |
| 1645 <p> |
| 1646 The <b>return</b> statement is used to return values |
| 1647 from a function or a chunk (which is a function in disguise). |
| 1648 |
| 1649 Functions can return more than one value, |
| 1650 so the syntax for the <b>return</b> statement is |
| 1651 |
| 1652 <pre> |
| 1653 stat ::= <b>return</b> [explist] [‘<b>;</b>’] |
| 1654 </pre> |
| 1655 |
| 1656 <p> |
| 1657 The <b>return</b> statement can only be written |
| 1658 as the last statement of a block. |
| 1659 If it is really necessary to <b>return</b> in the middle of a block, |
| 1660 then an explicit inner block can be used, |
| 1661 as in the idiom <code>do return end</code>, |
| 1662 because now <b>return</b> is the last statement in its (inner) block. |
| 1663 |
| 1664 |
| 1665 |
| 1666 |
| 1667 |
| 1668 <h3>3.3.5 – <a name="3.3.5">For Statement</a></h3> |
| 1669 |
| 1670 <p> |
| 1671 |
| 1672 The <b>for</b> statement has two forms: |
| 1673 one numeric and one generic. |
| 1674 |
| 1675 |
| 1676 <p> |
| 1677 The numeric <b>for</b> loop repeats a block of code while a |
| 1678 control variable runs through an arithmetic progression. |
| 1679 It has the following syntax: |
| 1680 |
| 1681 <pre> |
| 1682 stat ::= <b>for</b> Name ‘<b>=</b>’ exp ‘<b>,</b>&rsqu
o; exp [‘<b>,</b>’ exp] <b>do</b> block <b>end</b> |
| 1683 </pre><p> |
| 1684 The <em>block</em> is repeated for <em>name</em> starting at the value of |
| 1685 the first <em>exp</em>, until it passes the second <em>exp</em> by steps of the |
| 1686 third <em>exp</em>. |
| 1687 More precisely, a <b>for</b> statement like |
| 1688 |
| 1689 <pre> |
| 1690 for v = <em>e1</em>, <em>e2</em>, <em>e3</em> do <em>block</em> end |
| 1691 </pre><p> |
| 1692 is equivalent to the code: |
| 1693 |
| 1694 <pre> |
| 1695 do |
| 1696 local <em>var</em>, <em>limit</em>, <em>step</em> = tonumber(<em>e1</em>)
, tonumber(<em>e2</em>), tonumber(<em>e3</em>) |
| 1697 if not (<em>var</em> and <em>limit</em> and <em>step</em>) then error() e
nd |
| 1698 while (<em>step</em> > 0 and <em>var</em> <= <em>limit</em>) or (<e
m>step</em> <= 0 and <em>var</em> >= <em>limit</em>) do |
| 1699 local v = <em>var</em> |
| 1700 <em>block</em> |
| 1701 <em>var</em> = <em>var</em> + <em>step</em> |
| 1702 end |
| 1703 end |
| 1704 </pre><p> |
| 1705 Note the following: |
| 1706 |
| 1707 <ul> |
| 1708 |
| 1709 <li> |
| 1710 All three control expressions are evaluated only once, |
| 1711 before the loop starts. |
| 1712 They must all result in numbers. |
| 1713 </li> |
| 1714 |
| 1715 <li> |
| 1716 <code><em>var</em></code>, <code><em>limit</em></code>, and <code><em>step</em><
/code> are invisible variables. |
| 1717 The names shown here are for explanatory purposes only. |
| 1718 </li> |
| 1719 |
| 1720 <li> |
| 1721 If the third expression (the step) is absent, |
| 1722 then a step of 1 is used. |
| 1723 </li> |
| 1724 |
| 1725 <li> |
| 1726 You can use <b>break</b> to exit a <b>for</b> loop. |
| 1727 </li> |
| 1728 |
| 1729 <li> |
| 1730 The loop variable <code>v</code> is local to the loop; |
| 1731 you cannot use its value after the <b>for</b> ends or is broken. |
| 1732 If you need this value, |
| 1733 assign it to another variable before breaking or exiting the loop. |
| 1734 </li> |
| 1735 |
| 1736 </ul> |
| 1737 |
| 1738 <p> |
| 1739 The generic <b>for</b> statement works over functions, |
| 1740 called <em>iterators</em>. |
| 1741 On each iteration, the iterator function is called to produce a new value, |
| 1742 stopping when this new value is <b>nil</b>. |
| 1743 The generic <b>for</b> loop has the following syntax: |
| 1744 |
| 1745 <pre> |
| 1746 stat ::= <b>for</b> namelist <b>in</b> explist <b>do</b> block <b>end</b
> |
| 1747 namelist ::= Name {‘<b>,</b>’ Name} |
| 1748 </pre><p> |
| 1749 A <b>for</b> statement like |
| 1750 |
| 1751 <pre> |
| 1752 for <em>var_1</em>, ···, <em>var_n</em> in <em>explist
</em> do <em>block</em> end |
| 1753 </pre><p> |
| 1754 is equivalent to the code: |
| 1755 |
| 1756 <pre> |
| 1757 do |
| 1758 local <em>f</em>, <em>s</em>, <em>var</em> = <em>explist</em> |
| 1759 while true do |
| 1760 local <em>var_1</em>, ···, <em>var_n</em> = <em>f<
/em>(<em>s</em>, <em>var</em>) |
| 1761 if <em>var_1</em> == nil then break end |
| 1762 <em>var</em> = <em>var_1</em> |
| 1763 <em>block</em> |
| 1764 end |
| 1765 end |
| 1766 </pre><p> |
| 1767 Note the following: |
| 1768 |
| 1769 <ul> |
| 1770 |
| 1771 <li> |
| 1772 <code><em>explist</em></code> is evaluated only once. |
| 1773 Its results are an <em>iterator</em> function, |
| 1774 a <em>state</em>, |
| 1775 and an initial value for the first <em>iterator variable</em>. |
| 1776 </li> |
| 1777 |
| 1778 <li> |
| 1779 <code><em>f</em></code>, <code><em>s</em></code>, and <code><em>var</em></code>
are invisible variables. |
| 1780 The names are here for explanatory purposes only. |
| 1781 </li> |
| 1782 |
| 1783 <li> |
| 1784 You can use <b>break</b> to exit a <b>for</b> loop. |
| 1785 </li> |
| 1786 |
| 1787 <li> |
| 1788 The loop variables <code><em>var_i</em></code> are local to the loop; |
| 1789 you cannot use their values after the <b>for</b> ends. |
| 1790 If you need these values, |
| 1791 then assign them to other variables before breaking or exiting the loop. |
| 1792 </li> |
| 1793 |
| 1794 </ul> |
| 1795 |
| 1796 |
| 1797 |
| 1798 |
| 1799 <h3>3.3.6 – <a name="3.3.6">Function Calls as Statements</a></h3><p> |
| 1800 To allow possible side-effects, |
| 1801 function calls can be executed as statements: |
| 1802 |
| 1803 <pre> |
| 1804 stat ::= functioncall |
| 1805 </pre><p> |
| 1806 In this case, all returned values are thrown away. |
| 1807 Function calls are explained in <a href="#3.4.9">§3.4.9</a>. |
| 1808 |
| 1809 |
| 1810 |
| 1811 |
| 1812 |
| 1813 <h3>3.3.7 – <a name="3.3.7">Local Declarations</a></h3><p> |
| 1814 Local variables can be declared anywhere inside a block. |
| 1815 The declaration can include an initial assignment: |
| 1816 |
| 1817 <pre> |
| 1818 stat ::= <b>local</b> namelist [‘<b>=</b>’ explist] |
| 1819 </pre><p> |
| 1820 If present, an initial assignment has the same semantics |
| 1821 of a multiple assignment (see <a href="#3.3.3">§3.3.3</a>). |
| 1822 Otherwise, all variables are initialized with <b>nil</b>. |
| 1823 |
| 1824 |
| 1825 <p> |
| 1826 A chunk is also a block (see <a href="#3.3.2">§3.3.2</a>), |
| 1827 and so local variables can be declared in a chunk outside any explicit block. |
| 1828 |
| 1829 |
| 1830 <p> |
| 1831 The visibility rules for local variables are explained in <a href="#3.5">§3
.5</a>. |
| 1832 |
| 1833 |
| 1834 |
| 1835 |
| 1836 |
| 1837 |
| 1838 |
| 1839 <h2>3.4 – <a name="3.4">Expressions</a></h2> |
| 1840 |
| 1841 <p> |
| 1842 The basic expressions in Lua are the following: |
| 1843 |
| 1844 <pre> |
| 1845 exp ::= prefixexp |
| 1846 exp ::= <b>nil</b> | <b>false</b> | <b>true</b> |
| 1847 exp ::= Number |
| 1848 exp ::= String |
| 1849 exp ::= functiondef |
| 1850 exp ::= tableconstructor |
| 1851 exp ::= ‘<b>...</b>’ |
| 1852 exp ::= exp binop exp |
| 1853 exp ::= unop exp |
| 1854 prefixexp ::= var | functioncall | ‘<b>(</b>’ exp ‘<b>
)</b>’ |
| 1855 </pre> |
| 1856 |
| 1857 <p> |
| 1858 Numbers and literal strings are explained in <a href="#3.1">§3.1</a>; |
| 1859 variables are explained in <a href="#3.2">§3.2</a>; |
| 1860 function definitions are explained in <a href="#3.4.10">§3.4.10</a>; |
| 1861 function calls are explained in <a href="#3.4.9">§3.4.9</a>; |
| 1862 table constructors are explained in <a href="#3.4.8">§3.4.8</a>. |
| 1863 Vararg expressions, |
| 1864 denoted by three dots ('<code>...</code>'), can only be used when |
| 1865 directly inside a vararg function; |
| 1866 they are explained in <a href="#3.4.10">§3.4.10</a>. |
| 1867 |
| 1868 |
| 1869 <p> |
| 1870 Binary operators comprise arithmetic operators (see <a href="#3.4.1">§3.4.1
</a>), |
| 1871 relational operators (see <a href="#3.4.3">§3.4.3</a>), logical operators (
see <a href="#3.4.4">§3.4.4</a>), |
| 1872 and the concatenation operator (see <a href="#3.4.5">§3.4.5</a>). |
| 1873 Unary operators comprise the unary minus (see <a href="#3.4.1">§3.4.1</a>), |
| 1874 the unary <b>not</b> (see <a href="#3.4.4">§3.4.4</a>), |
| 1875 and the unary <em>length operator</em> (see <a href="#3.4.6">§3.4.6</a>). |
| 1876 |
| 1877 |
| 1878 <p> |
| 1879 Both function calls and vararg expressions can result in multiple values. |
| 1880 If a function call is used as a statement (see <a href="#3.3.6">§3.3.6</a>)
, |
| 1881 then its return list is adjusted to zero elements, |
| 1882 thus discarding all returned values. |
| 1883 If an expression is used as the last (or the only) element |
| 1884 of a list of expressions, |
| 1885 then no adjustment is made |
| 1886 (unless the expression is enclosed in parentheses). |
| 1887 In all other contexts, |
| 1888 Lua adjusts the result list to one element, |
| 1889 either discarding all values except the first one |
| 1890 or adding a single <b>nil</b> if there are no values. |
| 1891 |
| 1892 |
| 1893 <p> |
| 1894 Here are some examples: |
| 1895 |
| 1896 <pre> |
| 1897 f() -- adjusted to 0 results |
| 1898 g(f(), x) -- f() is adjusted to 1 result |
| 1899 g(x, f()) -- g gets x plus all results from f() |
| 1900 a,b,c = f(), x -- f() is adjusted to 1 result (c gets nil) |
| 1901 a,b = ... -- a gets the first vararg parameter, b gets |
| 1902 -- the second (both a and b can get nil if there |
| 1903 -- is no corresponding vararg parameter) |
| 1904 |
| 1905 a,b,c = x, f() -- f() is adjusted to 2 results |
| 1906 a,b,c = f() -- f() is adjusted to 3 results |
| 1907 return f() -- returns all results from f() |
| 1908 return ... -- returns all received vararg parameters |
| 1909 return x,y,f() -- returns x, y, and all results from f() |
| 1910 {f()} -- creates a list with all results from f() |
| 1911 {...} -- creates a list with all vararg parameters |
| 1912 {f(), nil} -- f() is adjusted to 1 result |
| 1913 </pre> |
| 1914 |
| 1915 <p> |
| 1916 Any expression enclosed in parentheses always results in only one value. |
| 1917 Thus, |
| 1918 <code>(f(x,y,z))</code> is always a single value, |
| 1919 even if <code>f</code> returns several values. |
| 1920 (The value of <code>(f(x,y,z))</code> is the first value returned by <code>f</co
de> |
| 1921 or <b>nil</b> if <code>f</code> does not return any values.) |
| 1922 |
| 1923 |
| 1924 |
| 1925 <h3>3.4.1 – <a name="3.4.1">Arithmetic Operators</a></h3><p> |
| 1926 Lua supports the usual arithmetic operators: |
| 1927 the binary <code>+</code> (addition), |
| 1928 <code>-</code> (subtraction), <code>*</code> (multiplication), |
| 1929 <code>/</code> (division), <code>%</code> (modulo), and <code>^</code> (exponent
iation); |
| 1930 and unary <code>-</code> (mathematical negation). |
| 1931 If the operands are numbers, or strings that can be converted to |
| 1932 numbers (see <a href="#3.4.2">§3.4.2</a>), |
| 1933 then all operations have the usual meaning. |
| 1934 Exponentiation works for any exponent. |
| 1935 For instance, <code>x^(-0.5)</code> computes the inverse of the square root of <
code>x</code>. |
| 1936 Modulo is defined as |
| 1937 |
| 1938 <pre> |
| 1939 a % b == a - math.floor(a/b)*b |
| 1940 </pre><p> |
| 1941 That is, it is the remainder of a division that rounds |
| 1942 the quotient towards minus infinity. |
| 1943 |
| 1944 |
| 1945 |
| 1946 |
| 1947 |
| 1948 <h3>3.4.2 – <a name="3.4.2">Coercion</a></h3> |
| 1949 |
| 1950 <p> |
| 1951 Lua provides automatic conversion between |
| 1952 string and number values at run time. |
| 1953 Any arithmetic operation applied to a string tries to convert |
| 1954 this string to a number, following the rules of the Lua lexer. |
| 1955 (The string may have leading and trailing spaces and a sign.) |
| 1956 Conversely, whenever a number is used where a string is expected, |
| 1957 the number is converted to a string, in a reasonable format. |
| 1958 For complete control over how numbers are converted to strings, |
| 1959 use the <code>format</code> function from the string library |
| 1960 (see <a href="#pdf-string.format"><code>string.format</code></a>). |
| 1961 |
| 1962 |
| 1963 |
| 1964 |
| 1965 |
| 1966 <h3>3.4.3 – <a name="3.4.3">Relational Operators</a></h3><p> |
| 1967 The relational operators in Lua are |
| 1968 |
| 1969 <pre> |
| 1970 == ~= < > <= >= |
| 1971 </pre><p> |
| 1972 These operators always result in <b>false</b> or <b>true</b>. |
| 1973 |
| 1974 |
| 1975 <p> |
| 1976 Equality (<code>==</code>) first compares the type of its operands. |
| 1977 If the types are different, then the result is <b>false</b>. |
| 1978 Otherwise, the values of the operands are compared. |
| 1979 Numbers and strings are compared in the usual way. |
| 1980 Tables, userdata, and threads |
| 1981 are compared by reference: |
| 1982 two objects are considered equal only if they are the same object. |
| 1983 Every time you create a new object |
| 1984 (a table, userdata, or thread), |
| 1985 this new object is different from any previously existing object. |
| 1986 Closures with the same reference are always equal. |
| 1987 Closures with any detectable difference |
| 1988 (different behavior, different definition) are always different. |
| 1989 |
| 1990 |
| 1991 <p> |
| 1992 You can change the way that Lua compares tables and userdata |
| 1993 by using the "eq" metamethod (see <a href="#2.4">§2.4</a>). |
| 1994 |
| 1995 |
| 1996 <p> |
| 1997 The conversion rules of <a href="#3.4.2">§3.4.2</a> |
| 1998 do not apply to equality comparisons. |
| 1999 Thus, <code>"0"==0</code> evaluates to <b>false</b>, |
| 2000 and <code>t[0]</code> and <code>t["0"]</code> denote different |
| 2001 entries in a table. |
| 2002 |
| 2003 |
| 2004 <p> |
| 2005 The operator <code>~=</code> is exactly the negation of equality (<code>==</code
>). |
| 2006 |
| 2007 |
| 2008 <p> |
| 2009 The order operators work as follows. |
| 2010 If both arguments are numbers, then they are compared as such. |
| 2011 Otherwise, if both arguments are strings, |
| 2012 then their values are compared according to the current locale. |
| 2013 Otherwise, Lua tries to call the "lt" or the "le" |
| 2014 metamethod (see <a href="#2.4">§2.4</a>). |
| 2015 A comparison <code>a > b</code> is translated to <code>b < a</code> |
| 2016 and <code>a >= b</code> is translated to <code>b <= a</code>. |
| 2017 |
| 2018 |
| 2019 |
| 2020 |
| 2021 |
| 2022 <h3>3.4.4 – <a name="3.4.4">Logical Operators</a></h3><p> |
| 2023 The logical operators in Lua are |
| 2024 <b>and</b>, <b>or</b>, and <b>not</b>. |
| 2025 Like the control structures (see <a href="#3.3.4">§3.3.4</a>), |
| 2026 all logical operators consider both <b>false</b> and <b>nil</b> as false |
| 2027 and anything else as true. |
| 2028 |
| 2029 |
| 2030 <p> |
| 2031 The negation operator <b>not</b> always returns <b>false</b> or <b>true</b>. |
| 2032 The conjunction operator <b>and</b> returns its first argument |
| 2033 if this value is <b>false</b> or <b>nil</b>; |
| 2034 otherwise, <b>and</b> returns its second argument. |
| 2035 The disjunction operator <b>or</b> returns its first argument |
| 2036 if this value is different from <b>nil</b> and <b>false</b>; |
| 2037 otherwise, <b>or</b> returns its second argument. |
| 2038 Both <b>and</b> and <b>or</b> use short-cut evaluation; |
| 2039 that is, |
| 2040 the second operand is evaluated only if necessary. |
| 2041 Here are some examples: |
| 2042 |
| 2043 <pre> |
| 2044 10 or 20 --> 10 |
| 2045 10 or error() --> 10 |
| 2046 nil or "a" --> "a" |
| 2047 nil and 10 --> nil |
| 2048 false and error() --> false |
| 2049 false and nil --> false |
| 2050 false or nil --> nil |
| 2051 10 and 20 --> 20 |
| 2052 </pre><p> |
| 2053 (In this manual, |
| 2054 <code>--></code> indicates the result of the preceding expression.) |
| 2055 |
| 2056 |
| 2057 |
| 2058 |
| 2059 |
| 2060 <h3>3.4.5 – <a name="3.4.5">Concatenation</a></h3><p> |
| 2061 The string concatenation operator in Lua is |
| 2062 denoted by two dots ('<code>..</code>'). |
| 2063 If both operands are strings or numbers, then they are converted to |
| 2064 strings according to the rules mentioned in <a href="#3.4.2">§3.4.2</a>. |
| 2065 Otherwise, the <code>__concat</code> metamethod is called (see <a href="#2.4">&s
ect;2.4</a>). |
| 2066 |
| 2067 |
| 2068 |
| 2069 |
| 2070 |
| 2071 <h3>3.4.6 – <a name="3.4.6">The Length Operator</a></h3> |
| 2072 |
| 2073 <p> |
| 2074 The length operator is denoted by the unary prefix operator <code>#</code>. |
| 2075 The length of a string is its number of bytes |
| 2076 (that is, the usual meaning of string length when each |
| 2077 character is one byte). |
| 2078 |
| 2079 |
| 2080 <p> |
| 2081 A program can modify the behavior of the length operator for |
| 2082 any value but strings through the <code>__len</code> metamethod (see <a href="#2
.4">§2.4</a>). |
| 2083 |
| 2084 |
| 2085 <p> |
| 2086 Unless a <code>__len</code> metamethod is given, |
| 2087 the length of a table <code>t</code> is only defined if the |
| 2088 table is a <em>sequence</em>, |
| 2089 that is, |
| 2090 the set of its positive numeric keys is equal to <em>{1..n}</em> |
| 2091 for some integer <em>n</em>. |
| 2092 In that case, <em>n</em> is its length. |
| 2093 Note that a table like |
| 2094 |
| 2095 <pre> |
| 2096 {10, 20, nil, 40} |
| 2097 </pre><p> |
| 2098 is not a sequence, because it has the key <code>4</code> |
| 2099 but does not have the key <code>3</code>. |
| 2100 (So, there is no <em>n</em> such that the set <em>{1..n}</em> is equal |
| 2101 to the set of positive numeric keys of that table.) |
| 2102 Note, however, that non-numeric keys do not interfere |
| 2103 with whether a table is a sequence. |
| 2104 |
| 2105 |
| 2106 |
| 2107 |
| 2108 |
| 2109 <h3>3.4.7 – <a name="3.4.7">Precedence</a></h3><p> |
| 2110 Operator precedence in Lua follows the table below, |
| 2111 from lower to higher priority: |
| 2112 |
| 2113 <pre> |
| 2114 or |
| 2115 and |
| 2116 < > <= >= ~= == |
| 2117 .. |
| 2118 + - |
| 2119 * / % |
| 2120 not # - (unary) |
| 2121 ^ |
| 2122 </pre><p> |
| 2123 As usual, |
| 2124 you can use parentheses to change the precedences of an expression. |
| 2125 The concatenation ('<code>..</code>') and exponentiation ('<code>^</code>') |
| 2126 operators are right associative. |
| 2127 All other binary operators are left associative. |
| 2128 |
| 2129 |
| 2130 |
| 2131 |
| 2132 |
| 2133 <h3>3.4.8 – <a name="3.4.8">Table Constructors</a></h3><p> |
| 2134 Table constructors are expressions that create tables. |
| 2135 Every time a constructor is evaluated, a new table is created. |
| 2136 A constructor can be used to create an empty table |
| 2137 or to create a table and initialize some of its fields. |
| 2138 The general syntax for constructors is |
| 2139 |
| 2140 <pre> |
| 2141 tableconstructor ::= ‘<b>{</b>’ [fieldlist] ‘<b>}</b>&
rsquo; |
| 2142 fieldlist ::= field {fieldsep field} [fieldsep] |
| 2143 field ::= ‘<b>[</b>’ exp ‘<b>]</b>’ ‘<b>=<
/b>’ exp | Name ‘<b>=</b>’ exp | exp |
| 2144 fieldsep ::= ‘<b>,</b>’ | ‘<b>;</b>’ |
| 2145 </pre> |
| 2146 |
| 2147 <p> |
| 2148 Each field of the form <code>[exp1] = exp2</code> adds to the new table an entry |
| 2149 with key <code>exp1</code> and value <code>exp2</code>. |
| 2150 A field of the form <code>name = exp</code> is equivalent to |
| 2151 <code>["name"] = exp</code>. |
| 2152 Finally, fields of the form <code>exp</code> are equivalent to |
| 2153 <code>[i] = exp</code>, where <code>i</code> are consecutive numerical integers, |
| 2154 starting with 1. |
| 2155 Fields in the other formats do not affect this counting. |
| 2156 For example, |
| 2157 |
| 2158 <pre> |
| 2159 a = { [f(1)] = g; "x", "y"; x = 1, f(x), [30] = 23; 45 } |
| 2160 </pre><p> |
| 2161 is equivalent to |
| 2162 |
| 2163 <pre> |
| 2164 do |
| 2165 local t = {} |
| 2166 t[f(1)] = g |
| 2167 t[1] = "x" -- 1st exp |
| 2168 t[2] = "y" -- 2nd exp |
| 2169 t.x = 1 -- t["x"] = 1 |
| 2170 t[3] = f(x) -- 3rd exp |
| 2171 t[30] = 23 |
| 2172 t[4] = 45 -- 4th exp |
| 2173 a = t |
| 2174 end |
| 2175 </pre> |
| 2176 |
| 2177 <p> |
| 2178 If the last field in the list has the form <code>exp</code> |
| 2179 and the expression is a function call or a vararg expression, |
| 2180 then all values returned by this expression enter the list consecutively |
| 2181 (see <a href="#3.4.9">§3.4.9</a>). |
| 2182 |
| 2183 |
| 2184 <p> |
| 2185 The field list can have an optional trailing separator, |
| 2186 as a convenience for machine-generated code. |
| 2187 |
| 2188 |
| 2189 |
| 2190 |
| 2191 |
| 2192 <h3>3.4.9 – <a name="3.4.9">Function Calls</a></h3><p> |
| 2193 A function call in Lua has the following syntax: |
| 2194 |
| 2195 <pre> |
| 2196 functioncall ::= prefixexp args |
| 2197 </pre><p> |
| 2198 In a function call, |
| 2199 first prefixexp and args are evaluated. |
| 2200 If the value of prefixexp has type <em>function</em>, |
| 2201 then this function is called |
| 2202 with the given arguments. |
| 2203 Otherwise, the prefixexp "call" metamethod is called, |
| 2204 having as first parameter the value of prefixexp, |
| 2205 followed by the original call arguments |
| 2206 (see <a href="#2.4">§2.4</a>). |
| 2207 |
| 2208 |
| 2209 <p> |
| 2210 The form |
| 2211 |
| 2212 <pre> |
| 2213 functioncall ::= prefixexp ‘<b>:</b>’ Name args |
| 2214 </pre><p> |
| 2215 can be used to call "methods". |
| 2216 A call <code>v:name(<em>args</em>)</code> |
| 2217 is syntactic sugar for <code>v.name(v,<em>args</em>)</code>, |
| 2218 except that <code>v</code> is evaluated only once. |
| 2219 |
| 2220 |
| 2221 <p> |
| 2222 Arguments have the following syntax: |
| 2223 |
| 2224 <pre> |
| 2225 args ::= ‘<b>(</b>’ [explist] ‘<b>)</b>’ |
| 2226 args ::= tableconstructor |
| 2227 args ::= String |
| 2228 </pre><p> |
| 2229 All argument expressions are evaluated before the call. |
| 2230 A call of the form <code>f{<em>fields</em>}</code> is |
| 2231 syntactic sugar for <code>f({<em>fields</em>})</code>; |
| 2232 that is, the argument list is a single new table. |
| 2233 A call of the form <code>f'<em>string</em>'</code> |
| 2234 (or <code>f"<em>string</em>"</code> or <code>f[[<em>string</em>]]</code>) |
| 2235 is syntactic sugar for <code>f('<em>string</em>')</code>; |
| 2236 that is, the argument list is a single literal string. |
| 2237 |
| 2238 |
| 2239 <p> |
| 2240 A call of the form <code>return <em>functioncall</em></code> is called |
| 2241 a <em>tail call</em>. |
| 2242 Lua implements <em>proper tail calls</em> |
| 2243 (or <em>proper tail recursion</em>): |
| 2244 in a tail call, |
| 2245 the called function reuses the stack entry of the calling function. |
| 2246 Therefore, there is no limit on the number of nested tail calls that |
| 2247 a program can execute. |
| 2248 However, a tail call erases any debug information about the |
| 2249 calling function. |
| 2250 Note that a tail call only happens with a particular syntax, |
| 2251 where the <b>return</b> has one single function call as argument; |
| 2252 this syntax makes the calling function return exactly |
| 2253 the returns of the called function. |
| 2254 So, none of the following examples are tail calls: |
| 2255 |
| 2256 <pre> |
| 2257 return (f(x)) -- results adjusted to 1 |
| 2258 return 2 * f(x) |
| 2259 return x, f(x) -- additional results |
| 2260 f(x); return -- results discarded |
| 2261 return x or f(x) -- results adjusted to 1 |
| 2262 </pre> |
| 2263 |
| 2264 |
| 2265 |
| 2266 |
| 2267 <h3>3.4.10 – <a name="3.4.10">Function Definitions</a></h3> |
| 2268 |
| 2269 <p> |
| 2270 The syntax for function definition is |
| 2271 |
| 2272 <pre> |
| 2273 functiondef ::= <b>function</b> funcbody |
| 2274 funcbody ::= ‘<b>(</b>’ [parlist] ‘<b>)</b>’ blo
ck <b>end</b> |
| 2275 </pre> |
| 2276 |
| 2277 <p> |
| 2278 The following syntactic sugar simplifies function definitions: |
| 2279 |
| 2280 <pre> |
| 2281 stat ::= <b>function</b> funcname funcbody |
| 2282 stat ::= <b>local</b> <b>function</b> Name funcbody |
| 2283 funcname ::= Name {‘<b>.</b>’ Name} [‘<b>:</b>’
Name] |
| 2284 </pre><p> |
| 2285 The statement |
| 2286 |
| 2287 <pre> |
| 2288 function f () <em>body</em> end |
| 2289 </pre><p> |
| 2290 translates to |
| 2291 |
| 2292 <pre> |
| 2293 f = function () <em>body</em> end |
| 2294 </pre><p> |
| 2295 The statement |
| 2296 |
| 2297 <pre> |
| 2298 function t.a.b.c.f () <em>body</em> end |
| 2299 </pre><p> |
| 2300 translates to |
| 2301 |
| 2302 <pre> |
| 2303 t.a.b.c.f = function () <em>body</em> end |
| 2304 </pre><p> |
| 2305 The statement |
| 2306 |
| 2307 <pre> |
| 2308 local function f () <em>body</em> end |
| 2309 </pre><p> |
| 2310 translates to |
| 2311 |
| 2312 <pre> |
| 2313 local f; f = function () <em>body</em> end |
| 2314 </pre><p> |
| 2315 not to |
| 2316 |
| 2317 <pre> |
| 2318 local f = function () <em>body</em> end |
| 2319 </pre><p> |
| 2320 (This only makes a difference when the body of the function |
| 2321 contains references to <code>f</code>.) |
| 2322 |
| 2323 |
| 2324 <p> |
| 2325 A function definition is an executable expression, |
| 2326 whose value has type <em>function</em>. |
| 2327 When Lua precompiles a chunk, |
| 2328 all its function bodies are precompiled too. |
| 2329 Then, whenever Lua executes the function definition, |
| 2330 the function is <em>instantiated</em> (or <em>closed</em>). |
| 2331 This function instance (or <em>closure</em>) |
| 2332 is the final value of the expression. |
| 2333 |
| 2334 |
| 2335 <p> |
| 2336 Parameters act as local variables that are |
| 2337 initialized with the argument values: |
| 2338 |
| 2339 <pre> |
| 2340 parlist ::= namelist [‘<b>,</b>’ ‘<b>...</b>’] |
‘<b>...</b>’ |
| 2341 </pre><p> |
| 2342 When a function is called, |
| 2343 the list of arguments is adjusted to |
| 2344 the length of the list of parameters, |
| 2345 unless the function is a <em>vararg function</em>, |
| 2346 which is indicated by three dots ('<code>...</code>') |
| 2347 at the end of its parameter list. |
| 2348 A vararg function does not adjust its argument list; |
| 2349 instead, it collects all extra arguments and supplies them |
| 2350 to the function through a <em>vararg expression</em>, |
| 2351 which is also written as three dots. |
| 2352 The value of this expression is a list of all actual extra arguments, |
| 2353 similar to a function with multiple results. |
| 2354 If a vararg expression is used inside another expression |
| 2355 or in the middle of a list of expressions, |
| 2356 then its return list is adjusted to one element. |
| 2357 If the expression is used as the last element of a list of expressions, |
| 2358 then no adjustment is made |
| 2359 (unless that last expression is enclosed in parentheses). |
| 2360 |
| 2361 |
| 2362 <p> |
| 2363 As an example, consider the following definitions: |
| 2364 |
| 2365 <pre> |
| 2366 function f(a, b) end |
| 2367 function g(a, b, ...) end |
| 2368 function r() return 1,2,3 end |
| 2369 </pre><p> |
| 2370 Then, we have the following mapping from arguments to parameters and |
| 2371 to the vararg expression: |
| 2372 |
| 2373 <pre> |
| 2374 CALL PARAMETERS |
| 2375 |
| 2376 f(3) a=3, b=nil |
| 2377 f(3, 4) a=3, b=4 |
| 2378 f(3, 4, 5) a=3, b=4 |
| 2379 f(r(), 10) a=1, b=10 |
| 2380 f(r()) a=1, b=2 |
| 2381 |
| 2382 g(3) a=3, b=nil, ... --> (nothing) |
| 2383 g(3, 4) a=3, b=4, ... --> (nothing) |
| 2384 g(3, 4, 5, 8) a=3, b=4, ... --> 5 8 |
| 2385 g(5, r()) a=5, b=1, ... --> 2 3 |
| 2386 </pre> |
| 2387 |
| 2388 <p> |
| 2389 Results are returned using the <b>return</b> statement (see <a href="#3.3.4">&se
ct;3.3.4</a>). |
| 2390 If control reaches the end of a function |
| 2391 without encountering a <b>return</b> statement, |
| 2392 then the function returns with no results. |
| 2393 |
| 2394 |
| 2395 <p> |
| 2396 |
| 2397 There is a system-dependent limit on the number of values |
| 2398 that a function may return. |
| 2399 This limit is guaranteed to be larger than 1000. |
| 2400 |
| 2401 |
| 2402 <p> |
| 2403 The <em>colon</em> syntax |
| 2404 is used for defining <em>methods</em>, |
| 2405 that is, functions that have an implicit extra parameter <code>self</code>. |
| 2406 Thus, the statement |
| 2407 |
| 2408 <pre> |
| 2409 function t.a.b.c:f (<em>params</em>) <em>body</em> end |
| 2410 </pre><p> |
| 2411 is syntactic sugar for |
| 2412 |
| 2413 <pre> |
| 2414 t.a.b.c.f = function (self, <em>params</em>) <em>body</em> end |
| 2415 </pre> |
| 2416 |
| 2417 |
| 2418 |
| 2419 |
| 2420 |
| 2421 |
| 2422 <h2>3.5 – <a name="3.5">Visibility Rules</a></h2> |
| 2423 |
| 2424 <p> |
| 2425 |
| 2426 Lua is a lexically scoped language. |
| 2427 The scope of a local variable begins at the first statement after |
| 2428 its declaration and lasts until the last non-void statement |
| 2429 of the innermost block that includes the declaration. |
| 2430 Consider the following example: |
| 2431 |
| 2432 <pre> |
| 2433 x = 10 -- global variable |
| 2434 do -- new block |
| 2435 local x = x -- new 'x', with value 10 |
| 2436 print(x) --> 10 |
| 2437 x = x+1 |
| 2438 do -- another block |
| 2439 local x = x+1 -- another 'x' |
| 2440 print(x) --> 12 |
| 2441 end |
| 2442 print(x) --> 11 |
| 2443 end |
| 2444 print(x) --> 10 (the global one) |
| 2445 </pre> |
| 2446 |
| 2447 <p> |
| 2448 Notice that, in a declaration like <code>local x = x</code>, |
| 2449 the new <code>x</code> being declared is not in scope yet, |
| 2450 and so the second <code>x</code> refers to the outside variable. |
| 2451 |
| 2452 |
| 2453 <p> |
| 2454 Because of the lexical scoping rules, |
| 2455 local variables can be freely accessed by functions |
| 2456 defined inside their scope. |
| 2457 A local variable used by an inner function is called |
| 2458 an <em>upvalue</em>, or <em>external local variable</em>, |
| 2459 inside the inner function. |
| 2460 |
| 2461 |
| 2462 <p> |
| 2463 Notice that each execution of a <b>local</b> statement |
| 2464 defines new local variables. |
| 2465 Consider the following example: |
| 2466 |
| 2467 <pre> |
| 2468 a = {} |
| 2469 local x = 20 |
| 2470 for i=1,10 do |
| 2471 local y = 0 |
| 2472 a[i] = function () y=y+1; return x+y end |
| 2473 end |
| 2474 </pre><p> |
| 2475 The loop creates ten closures |
| 2476 (that is, ten instances of the anonymous function). |
| 2477 Each of these closures uses a different <code>y</code> variable, |
| 2478 while all of them share the same <code>x</code>. |
| 2479 |
| 2480 |
| 2481 |
| 2482 |
| 2483 |
| 2484 <h1>4 – <a name="4">The Application Program Interface</a></h1> |
| 2485 |
| 2486 <p> |
| 2487 |
| 2488 This section describes the C API for Lua, that is, |
| 2489 the set of C functions available to the host program to communicate |
| 2490 with Lua. |
| 2491 All API functions and related types and constants |
| 2492 are declared in the header file <a name="pdf-lua.h"><code>lua.h</code></a>. |
| 2493 |
| 2494 |
| 2495 <p> |
| 2496 Even when we use the term "function", |
| 2497 any facility in the API may be provided as a macro instead. |
| 2498 Except where stated otherwise, |
| 2499 all such macros use each of their arguments exactly once |
| 2500 (except for the first argument, which is always a Lua state), |
| 2501 and so do not generate any hidden side-effects. |
| 2502 |
| 2503 |
| 2504 <p> |
| 2505 As in most C libraries, |
| 2506 the Lua API functions do not check their arguments for validity or consistency. |
| 2507 However, you can change this behavior by compiling Lua |
| 2508 with the macro <a name="pdf-LUA_USE_APICHECK"><code>LUA_USE_APICHECK</code></a>
defined. |
| 2509 |
| 2510 |
| 2511 |
| 2512 <h2>4.1 – <a name="4.1">The Stack</a></h2> |
| 2513 |
| 2514 <p> |
| 2515 Lua uses a <em>virtual stack</em> to pass values to and from C. |
| 2516 Each element in this stack represents a Lua value |
| 2517 (<b>nil</b>, number, string, etc.). |
| 2518 |
| 2519 |
| 2520 <p> |
| 2521 Whenever Lua calls C, the called function gets a new stack, |
| 2522 which is independent of previous stacks and of stacks of |
| 2523 C functions that are still active. |
| 2524 This stack initially contains any arguments to the C function |
| 2525 and it is where the C function pushes its results |
| 2526 to be returned to the caller (see <a href="#lua_CFunction"><code>lua_CFunction</
code></a>). |
| 2527 |
| 2528 |
| 2529 <p> |
| 2530 For convenience, |
| 2531 most query operations in the API do not follow a strict stack discipline. |
| 2532 Instead, they can refer to any element in the stack |
| 2533 by using an <em>index</em>: |
| 2534 A positive index represents an absolute stack position |
| 2535 (starting at 1); |
| 2536 a negative index represents an offset relative to the top of the stack. |
| 2537 More specifically, if the stack has <em>n</em> elements, |
| 2538 then index 1 represents the first element |
| 2539 (that is, the element that was pushed onto the stack first) |
| 2540 and |
| 2541 index <em>n</em> represents the last element; |
| 2542 index -1 also represents the last element |
| 2543 (that is, the element at the top) |
| 2544 and index <em>-n</em> represents the first element. |
| 2545 |
| 2546 |
| 2547 |
| 2548 |
| 2549 |
| 2550 <h2>4.2 – <a name="4.2">Stack Size</a></h2> |
| 2551 |
| 2552 <p> |
| 2553 When you interact with the Lua API, |
| 2554 you are responsible for ensuring consistency. |
| 2555 In particular, |
| 2556 <em>you are responsible for controlling stack overflow</em>. |
| 2557 You can use the function <a href="#lua_checkstack"><code>lua_checkstack</code></
a> |
| 2558 to ensure that the stack has extra slots when pushing new elements. |
| 2559 |
| 2560 |
| 2561 <p> |
| 2562 Whenever Lua calls C, |
| 2563 it ensures that the stack has at least <a name="pdf-LUA_MINSTACK"><code>LUA_MINS
TACK</code></a> extra slots. |
| 2564 <code>LUA_MINSTACK</code> is defined as 20, |
| 2565 so that usually you do not have to worry about stack space |
| 2566 unless your code has loops pushing elements onto the stack. |
| 2567 |
| 2568 |
| 2569 <p> |
| 2570 When you call a Lua function |
| 2571 without a fixed number of results (see <a href="#lua_call"><code>lua_call</code>
</a>), |
| 2572 Lua ensures that the stack has enough size for all results, |
| 2573 but it does not ensure any extra space. |
| 2574 So, before pushing anything in the stack after such a call |
| 2575 you should use <a href="#lua_checkstack"><code>lua_checkstack</code></a>. |
| 2576 |
| 2577 |
| 2578 |
| 2579 |
| 2580 |
| 2581 <h2>4.3 – <a name="4.3">Valid and Acceptable Indices</a></h2> |
| 2582 |
| 2583 <p> |
| 2584 Any function in the API that receives stack indices |
| 2585 works only with <em>valid indices</em> or <em>acceptable indices</em>. |
| 2586 |
| 2587 |
| 2588 <p> |
| 2589 A <em>valid index</em> is an index that refers to a |
| 2590 real position within the stack, that is, |
| 2591 its position lies between 1 and the stack top |
| 2592 (<code>1 ≤ abs(index) ≤ top</code>). |
| 2593 |
| 2594 Usually, functions that can modify the value at an index |
| 2595 require valid indices. |
| 2596 |
| 2597 |
| 2598 <p> |
| 2599 Unless otherwise noted, |
| 2600 any function that accepts valid indices also accepts <em>pseudo-indices</em>, |
| 2601 which represent some Lua values that are accessible to C code |
| 2602 but which are not in the stack. |
| 2603 Pseudo-indices are used to access the registry |
| 2604 and the upvalues of a C function (see <a href="#4.4">§4.4</a>). |
| 2605 |
| 2606 |
| 2607 <p> |
| 2608 Functions that do not need a specific stack position, |
| 2609 but only a value in the stack (e.g., query functions), |
| 2610 can be called with acceptable indices. |
| 2611 An <em>acceptable index</em> can be any valid index, |
| 2612 including the pseudo-indices, |
| 2613 but it also can be any positive index after the stack top |
| 2614 within the space allocated for the stack, |
| 2615 that is, indices up to the stack size. |
| 2616 (Note that 0 is never an acceptable index.) |
| 2617 Except when noted otherwise, |
| 2618 functions in the API work with acceptable indices. |
| 2619 |
| 2620 |
| 2621 <p> |
| 2622 Acceptable indices serve to avoid extra tests |
| 2623 against the stack top when querying the stack. |
| 2624 For instance, a C function can query its third argument |
| 2625 without the need to first check whether there is a third argument, |
| 2626 that is, without the need to check whether 3 is a valid index. |
| 2627 |
| 2628 |
| 2629 <p> |
| 2630 For functions that can be called with acceptable indices, |
| 2631 any non-valid index is treated as if it |
| 2632 contains a value of a virtual type <a name="pdf-LUA_TNONE"><code>LUA_TNONE</code
></a>, |
| 2633 which behaves like a nil value. |
| 2634 |
| 2635 |
| 2636 |
| 2637 |
| 2638 |
| 2639 <h2>4.4 – <a name="4.4">C Closures</a></h2> |
| 2640 |
| 2641 <p> |
| 2642 When a C function is created, |
| 2643 it is possible to associate some values with it, |
| 2644 thus creating a <em>C closure</em> |
| 2645 (see <a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a>); |
| 2646 these values are called <em>upvalues</em> and are |
| 2647 accessible to the function whenever it is called. |
| 2648 |
| 2649 |
| 2650 <p> |
| 2651 Whenever a C function is called, |
| 2652 its upvalues are located at specific pseudo-indices. |
| 2653 These pseudo-indices are produced by the macro |
| 2654 <a href="#lua_upvalueindex"><code>lua_upvalueindex</code></a>. |
| 2655 The first value associated with a function is at position |
| 2656 <code>lua_upvalueindex(1)</code>, and so on. |
| 2657 Any access to <code>lua_upvalueindex(<em>n</em>)</code>, |
| 2658 where <em>n</em> is greater than the number of upvalues of the |
| 2659 current function (but not greater than 256), |
| 2660 produces an acceptable but invalid index. |
| 2661 |
| 2662 |
| 2663 |
| 2664 |
| 2665 |
| 2666 <h2>4.5 – <a name="4.5">Registry</a></h2> |
| 2667 |
| 2668 <p> |
| 2669 Lua provides a <em>registry</em>, |
| 2670 a predefined table that can be used by any C code to |
| 2671 store whatever Lua values it needs to store. |
| 2672 The registry table is always located at pseudo-index |
| 2673 <a name="pdf-LUA_REGISTRYINDEX"><code>LUA_REGISTRYINDEX</code></a>, |
| 2674 which is a valid index. |
| 2675 Any C library can store data into this table, |
| 2676 but it should take care to choose keys |
| 2677 that are different from those used |
| 2678 by other libraries, to avoid collisions. |
| 2679 Typically, you should use as key a string containing your library name, |
| 2680 or a light userdata with the address of a C object in your code, |
| 2681 or any Lua object created by your code. |
| 2682 As with global names, |
| 2683 string keys starting with an underscore followed by |
| 2684 uppercase letters are reserved for Lua. |
| 2685 |
| 2686 |
| 2687 <p> |
| 2688 The integer keys in the registry are used by the reference mechanism, |
| 2689 implemented by the auxiliary library, |
| 2690 and by some predefined values. |
| 2691 Therefore, integer keys should not be used for other purposes. |
| 2692 |
| 2693 |
| 2694 <p> |
| 2695 When you create a new Lua state, |
| 2696 its registry comes with some predefined values. |
| 2697 These predefined values are indexed with integer keys |
| 2698 defined as constants in <code>lua.h</code>. |
| 2699 The following constants are defined: |
| 2700 |
| 2701 <ul> |
| 2702 <li><b><a name="pdf-LUA_RIDX_MAINTHREAD"><code>LUA_RIDX_MAINTHREAD</code></a>: <
/b> At this index the registry has |
| 2703 the main thread of the state. |
| 2704 (The main thread is the one created together with the state.) |
| 2705 </li> |
| 2706 |
| 2707 <li><b><a name="pdf-LUA_RIDX_GLOBALS"><code>LUA_RIDX_GLOBALS</code></a>: </b> At
this index the registry has |
| 2708 the global environment. |
| 2709 </li> |
| 2710 </ul> |
| 2711 |
| 2712 |
| 2713 |
| 2714 |
| 2715 <h2>4.6 – <a name="4.6">Error Handling in C</a></h2> |
| 2716 |
| 2717 <p> |
| 2718 Internally, Lua uses the C <code>longjmp</code> facility to handle errors. |
| 2719 (You can also choose to use exceptions if you compile Lua as C++; |
| 2720 search for <code>LUAI_THROW</code> in the source code.) |
| 2721 When Lua faces any error |
| 2722 (such as a memory allocation error, type errors, syntax errors, |
| 2723 and runtime errors) |
| 2724 it <em>raises</em> an error; |
| 2725 that is, it does a long jump. |
| 2726 A <em>protected environment</em> uses <code>setjmp</code> |
| 2727 to set a recovery point; |
| 2728 any error jumps to the most recent active recovery point. |
| 2729 |
| 2730 |
| 2731 <p> |
| 2732 If an error happens outside any protected environment, |
| 2733 Lua calls a <em>panic function</em> (see <a href="#lua_atpanic"><code>lua_atpani
c</code></a>) |
| 2734 and then calls <code>abort</code>, |
| 2735 thus exiting the host application. |
| 2736 Your panic function can avoid this exit by |
| 2737 never returning |
| 2738 (e.g., doing a long jump to your own recovery point outside Lua). |
| 2739 |
| 2740 |
| 2741 <p> |
| 2742 The panic function runs as if it were a message handler (see <a href="#2.3">&sec
t;2.3</a>); |
| 2743 in particular, the error message is at the top of the stack. |
| 2744 However, there is no guarantees about stack space. |
| 2745 To push anything on the stack, |
| 2746 the panic function should first check the available space (see <a href="#4.2">&s
ect;4.2</a>). |
| 2747 |
| 2748 |
| 2749 <p> |
| 2750 Most functions in the API can throw an error, |
| 2751 for instance due to a memory allocation error. |
| 2752 The documentation for each function indicates whether |
| 2753 it can throw errors. |
| 2754 |
| 2755 |
| 2756 <p> |
| 2757 Inside a C function you can throw an error by calling <a href="#lua_error">
<code>lua_error</code></a>. |
| 2758 |
| 2759 |
| 2760 |
| 2761 |
| 2762 |
| 2763 <h2>4.7 – <a name="4.7">Handling Yields in C</a></h2> |
| 2764 |
| 2765 <p> |
| 2766 Internally, Lua uses the C <code>longjmp</code> facility to yield a coroutine. |
| 2767 Therefore, if a function <code>foo</code> calls an API function |
| 2768 and this API function yields |
| 2769 (directly or indirectly by calling another function that yields), |
| 2770 Lua cannot return to <code>foo</code> any more, |
| 2771 because the <code>longjmp</code> removes its frame from the C stack. |
| 2772 |
| 2773 |
| 2774 <p> |
| 2775 To avoid this kind of problem, |
| 2776 Lua raises an error whenever it tries to yield across an API call, |
| 2777 except for three functions: |
| 2778 <a href="#lua_yieldk"><code>lua_yieldk</code></a>, <a href="#lua_callk"><code>lu
a_callk</code></a>, and <a href="#lua_pcallk"><code>lua_pcallk</code></a>. |
| 2779 All those functions receive a <em>continuation function</em> |
| 2780 (as a parameter called <code>k</code>) to continue execution after a yield. |
| 2781 |
| 2782 |
| 2783 <p> |
| 2784 We need to set some terminology to explain continuations. |
| 2785 We have a C function called from Lua which we will call |
| 2786 the <em>original function</em>. |
| 2787 This original function then calls one of those three functions in the C API, |
| 2788 which we will call the <em>callee function</em>, |
| 2789 that then yields the current thread. |
| 2790 (This can happen when the callee function is <a href="#lua_yieldk"><code>lua_yie
ldk</code></a>, |
| 2791 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> |
| 2792 and the function called by them yields.) |
| 2793 |
| 2794 |
| 2795 <p> |
| 2796 Suppose the running thread yields while executing the callee function. |
| 2797 After the thread resumes, |
| 2798 it eventually will finish running the callee function. |
| 2799 However, |
| 2800 the callee function cannot return to the original function, |
| 2801 because its frame in the C stack was destroyed by the yield. |
| 2802 Instead, Lua calls a <em>continuation function</em>, |
| 2803 which was given as an argument to the callee function. |
| 2804 As the name implies, |
| 2805 the continuation function should continue the task |
| 2806 of the original function. |
| 2807 |
| 2808 |
| 2809 <p> |
| 2810 Lua treats the continuation function as if it were the original function. |
| 2811 The continuation function receives the same Lua stack |
| 2812 from the original function, |
| 2813 in the same state it would be if the callee function had returned. |
| 2814 (For instance, |
| 2815 after a <a href="#lua_callk"><code>lua_callk</code></a> the function and its arg
uments are |
| 2816 removed from the stack and replaced by the results from the call.) |
| 2817 It also has the same upvalues. |
| 2818 Whatever it returns is handled by Lua as if it were the return |
| 2819 of the original function. |
| 2820 |
| 2821 |
| 2822 <p> |
| 2823 The only difference in the Lua state between the original function |
| 2824 and its continuation is the result of a call to <a href="#lua_getctx"><code>lua_
getctx</code></a>. |
| 2825 |
| 2826 |
| 2827 |
| 2828 |
| 2829 |
| 2830 <h2>4.8 – <a name="4.8">Functions and Types</a></h2> |
| 2831 |
| 2832 <p> |
| 2833 Here we list all functions and types from the C API in |
| 2834 alphabetical order. |
| 2835 Each function has an indicator like this: |
| 2836 <span class="apii">[-o, +p, <em>x</em>]</span> |
| 2837 |
| 2838 |
| 2839 <p> |
| 2840 The first field, <code>o</code>, |
| 2841 is how many elements the function pops from the stack. |
| 2842 The second field, <code>p</code>, |
| 2843 is how many elements the function pushes onto the stack. |
| 2844 (Any function always pushes its results after popping its arguments.) |
| 2845 A field in the form <code>x|y</code> means the function can push (or pop) |
| 2846 <code>x</code> or <code>y</code> elements, |
| 2847 depending on the situation; |
| 2848 an interrogation mark '<code>?</code>' means that |
| 2849 we cannot know how many elements the function pops/pushes |
| 2850 by looking only at its arguments |
| 2851 (e.g., they may depend on what is on the stack). |
| 2852 The third field, <code>x</code>, |
| 2853 tells whether the function may throw errors: |
| 2854 '<code>-</code>' means the function never throws any error; |
| 2855 '<code>e</code>' means the function may throw errors; |
| 2856 '<code>v</code>' means the function may throw an error on purpose. |
| 2857 |
| 2858 |
| 2859 |
| 2860 <hr><h3><a name="lua_absindex"><code>lua_absindex</code></a></h3><p> |
| 2861 <span class="apii">[-0, +0, –]</span> |
| 2862 <pre>int lua_absindex (lua_State *L, int idx);</pre> |
| 2863 |
| 2864 <p> |
| 2865 Converts the acceptable index <code>idx</code> into an absolute index |
| 2866 (that is, one that does not depend on the stack top). |
| 2867 |
| 2868 |
| 2869 |
| 2870 |
| 2871 |
| 2872 <hr><h3><a name="lua_Alloc"><code>lua_Alloc</code></a></h3> |
| 2873 <pre>typedef void * (*lua_Alloc) (void *ud, |
| 2874 void *ptr, |
| 2875 size_t osize, |
| 2876 size_t nsize);</pre> |
| 2877 |
| 2878 <p> |
| 2879 The type of the memory-allocation function used by Lua states. |
| 2880 The allocator function must provide a |
| 2881 functionality similar to <code>realloc</code>, |
| 2882 but not exactly the same. |
| 2883 Its arguments are |
| 2884 <code>ud</code>, an opaque pointer passed to <a href="#lua_newstate"><code>lua_n
ewstate</code></a>; |
| 2885 <code>ptr</code>, a pointer to the block being allocated/reallocated/freed; |
| 2886 <code>osize</code>, the original size of the block or some code about what |
| 2887 is being allocated; |
| 2888 <code>nsize</code>, the new size of the block. |
| 2889 |
| 2890 |
| 2891 <p> |
| 2892 When <code>ptr</code> is not <code>NULL</code>, |
| 2893 <code>osize</code> is the size of the block pointed by <code>ptr</code>, |
| 2894 that is, the size given when it was allocated or reallocated. |
| 2895 |
| 2896 |
| 2897 <p> |
| 2898 When <code>ptr</code> is <code>NULL</code>, |
| 2899 <code>osize</code> encodes the kind of object that Lua is allocating. |
| 2900 <code>osize</code> is any of |
| 2901 <a href="#pdf-LUA_TSTRING"><code>LUA_TSTRING</code></a>, <a href="#pdf-LUA_TTABL
E"><code>LUA_TTABLE</code></a>, <a href="#pdf-LUA_TFUNCTION"><code>LUA_TFUNCTION
</code></a>, |
| 2902 <a href="#pdf-LUA_TUSERDATA"><code>LUA_TUSERDATA</code></a>, or <a href="#pdf-LU
A_TTHREAD"><code>LUA_TTHREAD</code></a> when (and only when) |
| 2903 Lua is creating a new object of that type. |
| 2904 When <code>osize</code> is some other value, |
| 2905 Lua is allocating memory for something else. |
| 2906 |
| 2907 |
| 2908 <p> |
| 2909 Lua assumes the following behavior from the allocator function: |
| 2910 |
| 2911 |
| 2912 <p> |
| 2913 When <code>nsize</code> is zero, |
| 2914 the allocator should behave like <code>free</code> |
| 2915 and return <code>NULL</code>. |
| 2916 |
| 2917 |
| 2918 <p> |
| 2919 When <code>nsize</code> is not zero, |
| 2920 the allocator should behave like <code>realloc</code>. |
| 2921 The allocator returns <code>NULL</code> |
| 2922 if and only if it cannot fulfill the request. |
| 2923 Lua assumes that the allocator never fails when |
| 2924 <code>osize >= nsize</code>. |
| 2925 |
| 2926 |
| 2927 <p> |
| 2928 Here is a simple implementation for the allocator function. |
| 2929 It is used in the auxiliary library by <a href="#luaL_newstate"><code>luaL_newst
ate</code></a>. |
| 2930 |
| 2931 <pre> |
| 2932 static void *l_alloc (void *ud, void *ptr, size_t osize, |
| 2933 size_t nsize) { |
| 2934 (void)ud; (void)osize; /* not used */ |
| 2935 if (nsize == 0) { |
| 2936 free(ptr); |
| 2937 return NULL; |
| 2938 } |
| 2939 else |
| 2940 return realloc(ptr, nsize); |
| 2941 } |
| 2942 </pre><p> |
| 2943 Note that Standard C ensures |
| 2944 that <code>free(NULL)</code> has no effect and that |
| 2945 <code>realloc(NULL, size)</code> is equivalent to <code>malloc(size)</code>. |
| 2946 This code assumes that <code>realloc</code> does not fail when shrinking a block
. |
| 2947 (Although Standard C does not ensure this behavior, |
| 2948 it seems to be a safe assumption.) |
| 2949 |
| 2950 |
| 2951 |
| 2952 |
| 2953 |
| 2954 <hr><h3><a name="lua_arith"><code>lua_arith</code></a></h3><p> |
| 2955 <span class="apii">[-(2|1), +1, <em>e</em>]</span> |
| 2956 <pre>void lua_arith (lua_State *L, int op);</pre> |
| 2957 |
| 2958 <p> |
| 2959 Performs an arithmetic operation over the two values |
| 2960 (or one, in the case of negation) |
| 2961 at the top of the stack, |
| 2962 with the value at the top being the second operand, |
| 2963 pops these values, and pushes the result of the operation. |
| 2964 The function follows the semantics of the corresponding Lua operator |
| 2965 (that is, it may call metamethods). |
| 2966 |
| 2967 |
| 2968 <p> |
| 2969 The value of <code>op</code> must be one of the following constants: |
| 2970 |
| 2971 <ul> |
| 2972 |
| 2973 <li><b><a name="pdf-LUA_OPADD"><code>LUA_OPADD</code></a>: </b> performs additio
n (<code>+</code>)</li> |
| 2974 <li><b><a name="pdf-LUA_OPSUB"><code>LUA_OPSUB</code></a>: </b> performs subtrac
tion (<code>-</code>)</li> |
| 2975 <li><b><a name="pdf-LUA_OPMUL"><code>LUA_OPMUL</code></a>: </b> performs multipl
ication (<code>*</code>)</li> |
| 2976 <li><b><a name="pdf-LUA_OPDIV"><code>LUA_OPDIV</code></a>: </b> performs divisio
n (<code>/</code>)</li> |
| 2977 <li><b><a name="pdf-LUA_OPMOD"><code>LUA_OPMOD</code></a>: </b> performs modulo
(<code>%</code>)</li> |
| 2978 <li><b><a name="pdf-LUA_OPPOW"><code>LUA_OPPOW</code></a>: </b> performs exponen
tiation (<code>^</code>)</li> |
| 2979 <li><b><a name="pdf-LUA_OPUNM"><code>LUA_OPUNM</code></a>: </b> performs mathema
tical negation (unary <code>-</code>)</li> |
| 2980 |
| 2981 </ul> |
| 2982 |
| 2983 |
| 2984 |
| 2985 |
| 2986 <hr><h3><a name="lua_atpanic"><code>lua_atpanic</code></a></h3><p> |
| 2987 <span class="apii">[-0, +0, –]</span> |
| 2988 <pre>lua_CFunction lua_atpanic (lua_State *L, lua_CFunction panicf);</pre> |
| 2989 |
| 2990 <p> |
| 2991 Sets a new panic function and returns the old one (see <a href="#4.6">§4.6<
/a>). |
| 2992 |
| 2993 |
| 2994 |
| 2995 |
| 2996 |
| 2997 <hr><h3><a name="lua_call"><code>lua_call</code></a></h3><p> |
| 2998 <span class="apii">[-(nargs+1), +nresults, <em>e</em>]</span> |
| 2999 <pre>void lua_call (lua_State *L, int nargs, int nresults);</pre> |
| 3000 |
| 3001 <p> |
| 3002 Calls a function. |
| 3003 |
| 3004 |
| 3005 <p> |
| 3006 To call a function you must use the following protocol: |
| 3007 first, the function to be called is pushed onto the stack; |
| 3008 then, the arguments to the function are pushed |
| 3009 in direct order; |
| 3010 that is, the first argument is pushed first. |
| 3011 Finally you call <a href="#lua_call"><code>lua_call</code></a>; |
| 3012 <code>nargs</code> is the number of arguments that you pushed onto the stack. |
| 3013 All arguments and the function value are popped from the stack |
| 3014 when the function is called. |
| 3015 The function results are pushed onto the stack when the function returns. |
| 3016 The number of results is adjusted to <code>nresults</code>, |
| 3017 unless <code>nresults</code> is <a name="pdf-LUA_MULTRET"><code>LUA_MULTRET</cod
e></a>. |
| 3018 In this case, all results from the function are pushed. |
| 3019 Lua takes care that the returned values fit into the stack space. |
| 3020 The function results are pushed onto the stack in direct order |
| 3021 (the first result is pushed first), |
| 3022 so that after the call the last result is on the top of the stack. |
| 3023 |
| 3024 |
| 3025 <p> |
| 3026 Any error inside the called function is propagated upwards |
| 3027 (with a <code>longjmp</code>). |
| 3028 |
| 3029 |
| 3030 <p> |
| 3031 The following example shows how the host program can do the |
| 3032 equivalent to this Lua code: |
| 3033 |
| 3034 <pre> |
| 3035 a = f("how", t.x, 14) |
| 3036 </pre><p> |
| 3037 Here it is in C: |
| 3038 |
| 3039 <pre> |
| 3040 lua_getglobal(L, "f"); /* function to be called */ |
| 3041 lua_pushstring(L, "how"); /* 1st argument */ |
| 3042 lua_getglobal(L, "t"); /* table to be indexed */ |
| 3043 lua_getfield(L, -1, "x"); /* push result of t.x (2nd arg) */ |
| 3044 lua_remove(L, -2); /* remove 't' from the stack */ |
| 3045 lua_pushinteger(L, 14); /* 3rd argument */ |
| 3046 lua_call(L, 3, 1); /* call 'f' with 3 arguments and 1 result */ |
| 3047 lua_setglobal(L, "a"); /* set global 'a' */ |
| 3048 </pre><p> |
| 3049 Note that the code above is "balanced": |
| 3050 at its end, the stack is back to its original configuration. |
| 3051 This is considered good programming practice. |
| 3052 |
| 3053 |
| 3054 |
| 3055 |
| 3056 |
| 3057 <hr><h3><a name="lua_callk"><code>lua_callk</code></a></h3><p> |
| 3058 <span class="apii">[-(nargs + 1), +nresults, <em>e</em>]</span> |
| 3059 <pre>void lua_callk (lua_State *L, int nargs, int nresults, int ctx, |
| 3060 lua_CFunction k);</pre> |
| 3061 |
| 3062 <p> |
| 3063 This function behaves exactly like <a href="#lua_call"><code>lua_call</code></a>
, |
| 3064 but allows the called function to yield (see <a href="#4.7">§4.7</a>). |
| 3065 |
| 3066 |
| 3067 |
| 3068 |
| 3069 |
| 3070 <hr><h3><a name="lua_CFunction"><code>lua_CFunction</code></a></h3> |
| 3071 <pre>typedef int (*lua_CFunction) (lua_State *L);</pre> |
| 3072 |
| 3073 <p> |
| 3074 Type for C functions. |
| 3075 |
| 3076 |
| 3077 <p> |
| 3078 In order to communicate properly with Lua, |
| 3079 a C function must use the following protocol, |
| 3080 which defines the way parameters and results are passed: |
| 3081 a C function receives its arguments from Lua in its stack |
| 3082 in direct order (the first argument is pushed first). |
| 3083 So, when the function starts, |
| 3084 <code>lua_gettop(L)</code> returns the number of arguments received by the funct
ion. |
| 3085 The first argument (if any) is at index 1 |
| 3086 and its last argument is at index <code>lua_gettop(L)</code>. |
| 3087 To return values to Lua, a C function just pushes them onto the stack, |
| 3088 in direct order (the first result is pushed first), |
| 3089 and returns the number of results. |
| 3090 Any other value in the stack below the results will be properly |
| 3091 discarded by Lua. |
| 3092 Like a Lua function, a C function called by Lua can also return |
| 3093 many results. |
| 3094 |
| 3095 |
| 3096 <p> |
| 3097 As an example, the following function receives a variable number |
| 3098 of numerical arguments and returns their average and sum: |
| 3099 |
| 3100 <pre> |
| 3101 static int foo (lua_State *L) { |
| 3102 int n = lua_gettop(L); /* number of arguments */ |
| 3103 lua_Number sum = 0; |
| 3104 int i; |
| 3105 for (i = 1; i <= n; i++) { |
| 3106 if (!lua_isnumber(L, i)) { |
| 3107 lua_pushstring(L, "incorrect argument"); |
| 3108 lua_error(L); |
| 3109 } |
| 3110 sum += lua_tonumber(L, i); |
| 3111 } |
| 3112 lua_pushnumber(L, sum/n); /* first result */ |
| 3113 lua_pushnumber(L, sum); /* second result */ |
| 3114 return 2; /* number of results */ |
| 3115 } |
| 3116 </pre> |
| 3117 |
| 3118 |
| 3119 |
| 3120 |
| 3121 <hr><h3><a name="lua_checkstack"><code>lua_checkstack</code></a></h3><p> |
| 3122 <span class="apii">[-0, +0, –]</span> |
| 3123 <pre>int lua_checkstack (lua_State *L, int extra);</pre> |
| 3124 |
| 3125 <p> |
| 3126 Ensures that there are at least <code>extra</code> free stack slots in the stack
. |
| 3127 It returns false if it cannot fulfill the request, |
| 3128 because it would cause the stack to be larger than a fixed maximum size |
| 3129 (typically at least a few thousand elements) or |
| 3130 because it cannot allocate memory for the new stack size. |
| 3131 This function never shrinks the stack; |
| 3132 if the stack is already larger than the new size, |
| 3133 it is left unchanged. |
| 3134 |
| 3135 |
| 3136 |
| 3137 |
| 3138 |
| 3139 <hr><h3><a name="lua_close"><code>lua_close</code></a></h3><p> |
| 3140 <span class="apii">[-0, +0, –]</span> |
| 3141 <pre>void lua_close (lua_State *L);</pre> |
| 3142 |
| 3143 <p> |
| 3144 Destroys all objects in the given Lua state |
| 3145 (calling the corresponding garbage-collection metamethods, if any) |
| 3146 and frees all dynamic memory used by this state. |
| 3147 On several platforms, you may not need to call this function, |
| 3148 because all resources are naturally released when the host program ends. |
| 3149 On the other hand, long-running programs that create multiple states, |
| 3150 such as daemons or web servers, |
| 3151 might need to close states as soon as they are not needed. |
| 3152 |
| 3153 |
| 3154 |
| 3155 |
| 3156 |
| 3157 <hr><h3><a name="lua_compare"><code>lua_compare</code></a></h3><p> |
| 3158 <span class="apii">[-0, +0, <em>e</em>]</span> |
| 3159 <pre>int lua_compare (lua_State *L, int index1, int index2, int op);</pre> |
| 3160 |
| 3161 <p> |
| 3162 Compares two Lua values. |
| 3163 Returns 1 if the value at index <code>index1</code> satisfies <code>op</code> |
| 3164 when compared with the value at index <code>index2</code>, |
| 3165 following the semantics of the corresponding Lua operator |
| 3166 (that is, it may call metamethods). |
| 3167 Otherwise returns 0. |
| 3168 Also returns 0 if any of the indices is non valid. |
| 3169 |
| 3170 |
| 3171 <p> |
| 3172 The value of <code>op</code> must be one of the following constants: |
| 3173 |
| 3174 <ul> |
| 3175 |
| 3176 <li><b><a name="pdf-LUA_OPEQ"><code>LUA_OPEQ</code></a>: </b> compares for equal
ity (<code>==</code>)</li> |
| 3177 <li><b><a name="pdf-LUA_OPLT"><code>LUA_OPLT</code></a>: </b> compares for less
than (<code><</code>)</li> |
| 3178 <li><b><a name="pdf-LUA_OPLE"><code>LUA_OPLE</code></a>: </b> compares for less
or equal (<code><=</code>)</li> |
| 3179 |
| 3180 </ul> |
| 3181 |
| 3182 |
| 3183 |
| 3184 |
| 3185 <hr><h3><a name="lua_concat"><code>lua_concat</code></a></h3><p> |
| 3186 <span class="apii">[-n, +1, <em>e</em>]</span> |
| 3187 <pre>void lua_concat (lua_State *L, int n);</pre> |
| 3188 |
| 3189 <p> |
| 3190 Concatenates the <code>n</code> values at the top of the stack, |
| 3191 pops them, and leaves the result at the top. |
| 3192 If <code>n</code> is 1, the result is the single value on the stack |
| 3193 (that is, the function does nothing); |
| 3194 if <code>n</code> is 0, the result is the empty string. |
| 3195 Concatenation is performed following the usual semantics of Lua |
| 3196 (see <a href="#3.4.5">§3.4.5</a>). |
| 3197 |
| 3198 |
| 3199 |
| 3200 |
| 3201 |
| 3202 <hr><h3><a name="lua_copy"><code>lua_copy</code></a></h3><p> |
| 3203 <span class="apii">[-0, +0, –]</span> |
| 3204 <pre>void lua_copy (lua_State *L, int fromidx, int toidx);</pre> |
| 3205 |
| 3206 <p> |
| 3207 Moves the element at index <code>fromidx</code> |
| 3208 into the valid index <code>toidx</code> |
| 3209 without shifting any element |
| 3210 (therefore replacing the value at that position). |
| 3211 |
| 3212 |
| 3213 |
| 3214 |
| 3215 |
| 3216 <hr><h3><a name="lua_createtable"><code>lua_createtable</code></a></h3><p> |
| 3217 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 3218 <pre>void lua_createtable (lua_State *L, int narr, int nrec);</pre> |
| 3219 |
| 3220 <p> |
| 3221 Creates a new empty table and pushes it onto the stack. |
| 3222 Parameter <code>narr</code> is a hint for how many elements the table |
| 3223 will have as a sequence; |
| 3224 parameter <code>nrec</code> is a hint for how many other elements |
| 3225 the table will have. |
| 3226 Lua may use these hints to preallocate memory for the new table. |
| 3227 This pre-allocation is useful for performance when you know in advance |
| 3228 how many elements the table will have. |
| 3229 Otherwise you can use the function <a href="#lua_newtable"><code>lua_newtable</c
ode></a>. |
| 3230 |
| 3231 |
| 3232 |
| 3233 |
| 3234 |
| 3235 <hr><h3><a name="lua_dump"><code>lua_dump</code></a></h3><p> |
| 3236 <span class="apii">[-0, +0, <em>e</em>]</span> |
| 3237 <pre>int lua_dump (lua_State *L, lua_Writer writer, void *data);</pre> |
| 3238 |
| 3239 <p> |
| 3240 Dumps a function as a binary chunk. |
| 3241 Receives a Lua function on the top of the stack |
| 3242 and produces a binary chunk that, |
| 3243 if loaded again, |
| 3244 results in a function equivalent to the one dumped. |
| 3245 As it produces parts of the chunk, |
| 3246 <a href="#lua_dump"><code>lua_dump</code></a> calls function <code>writer</code>
(see <a href="#lua_Writer"><code>lua_Writer</code></a>) |
| 3247 with the given <code>data</code> |
| 3248 to write them. |
| 3249 |
| 3250 |
| 3251 <p> |
| 3252 The value returned is the error code returned by the last |
| 3253 call to the writer; |
| 3254 0 means no errors. |
| 3255 |
| 3256 |
| 3257 <p> |
| 3258 This function does not pop the Lua function from the stack. |
| 3259 |
| 3260 |
| 3261 |
| 3262 |
| 3263 |
| 3264 <hr><h3><a name="lua_error"><code>lua_error</code></a></h3><p> |
| 3265 <span class="apii">[-1, +0, <em>v</em>]</span> |
| 3266 <pre>int lua_error (lua_State *L);</pre> |
| 3267 |
| 3268 <p> |
| 3269 Generates a Lua error. |
| 3270 The error message (which can actually be a Lua value of any type) |
| 3271 must be on the stack top. |
| 3272 This function does a long jump, |
| 3273 and therefore never returns |
| 3274 (see <a href="#luaL_error"><code>luaL_error</code></a>). |
| 3275 |
| 3276 |
| 3277 |
| 3278 |
| 3279 |
| 3280 <hr><h3><a name="lua_gc"><code>lua_gc</code></a></h3><p> |
| 3281 <span class="apii">[-0, +0, <em>e</em>]</span> |
| 3282 <pre>int lua_gc (lua_State *L, int what, int data);</pre> |
| 3283 |
| 3284 <p> |
| 3285 Controls the garbage collector. |
| 3286 |
| 3287 |
| 3288 <p> |
| 3289 This function performs several tasks, |
| 3290 according to the value of the parameter <code>what</code>: |
| 3291 |
| 3292 <ul> |
| 3293 |
| 3294 <li><b><code>LUA_GCSTOP</code>: </b> |
| 3295 stops the garbage collector. |
| 3296 </li> |
| 3297 |
| 3298 <li><b><code>LUA_GCRESTART</code>: </b> |
| 3299 restarts the garbage collector. |
| 3300 </li> |
| 3301 |
| 3302 <li><b><code>LUA_GCCOLLECT</code>: </b> |
| 3303 performs a full garbage-collection cycle. |
| 3304 </li> |
| 3305 |
| 3306 <li><b><code>LUA_GCCOUNT</code>: </b> |
| 3307 returns the current amount of memory (in Kbytes) in use by Lua. |
| 3308 </li> |
| 3309 |
| 3310 <li><b><code>LUA_GCCOUNTB</code>: </b> |
| 3311 returns the remainder of dividing the current amount of bytes of |
| 3312 memory in use by Lua by 1024. |
| 3313 </li> |
| 3314 |
| 3315 <li><b><code>LUA_GCSTEP</code>: </b> |
| 3316 performs an incremental step of garbage collection. |
| 3317 The step "size" is controlled by <code>data</code> |
| 3318 (larger values mean more steps) in a non-specified way. |
| 3319 If you want to control the step size |
| 3320 you must experimentally tune the value of <code>data</code>. |
| 3321 The function returns 1 if the step finished a |
| 3322 garbage-collection cycle. |
| 3323 </li> |
| 3324 |
| 3325 <li><b><code>LUA_GCSETPAUSE</code>: </b> |
| 3326 sets <code>data</code> as the new value |
| 3327 for the <em>pause</em> of the collector (see <a href="#2.5">§2.5</a>). |
| 3328 The function returns the previous value of the pause. |
| 3329 </li> |
| 3330 |
| 3331 <li><b><code>LUA_GCSETSTEPMUL</code>: </b> |
| 3332 sets <code>data</code> as the new value for the <em>step multiplier</em> of |
| 3333 the collector (see <a href="#2.5">§2.5</a>). |
| 3334 The function returns the previous value of the step multiplier. |
| 3335 </li> |
| 3336 |
| 3337 <li><b><code>LUA_GCISRUNNING</code>: </b> |
| 3338 returns a boolean that tells whether the collector is running |
| 3339 (i.e., not stopped). |
| 3340 </li> |
| 3341 |
| 3342 <li><b><code>LUA_GCGEN</code>: </b> |
| 3343 changes the collector to generational mode |
| 3344 (see <a href="#2.5">§2.5</a>). |
| 3345 </li> |
| 3346 |
| 3347 <li><b><code>LUA_GCINC</code>: </b> |
| 3348 changes the collector to incremental mode. |
| 3349 This is the default mode. |
| 3350 </li> |
| 3351 |
| 3352 </ul> |
| 3353 |
| 3354 <p> |
| 3355 For more details about these options, |
| 3356 see <a href="#pdf-collectgarbage"><code>collectgarbage</code></a>. |
| 3357 |
| 3358 |
| 3359 |
| 3360 |
| 3361 |
| 3362 <hr><h3><a name="lua_getallocf"><code>lua_getallocf</code></a></h3><p> |
| 3363 <span class="apii">[-0, +0, –]</span> |
| 3364 <pre>lua_Alloc lua_getallocf (lua_State *L, void **ud);</pre> |
| 3365 |
| 3366 <p> |
| 3367 Returns the memory-allocation function of a given state. |
| 3368 If <code>ud</code> is not <code>NULL</code>, Lua stores in <code>*ud</code> the |
| 3369 opaque pointer passed to <a href="#lua_newstate"><code>lua_newstate</code></a>. |
| 3370 |
| 3371 |
| 3372 |
| 3373 |
| 3374 |
| 3375 <hr><h3><a name="lua_getctx"><code>lua_getctx</code></a></h3><p> |
| 3376 <span class="apii">[-0, +0, –]</span> |
| 3377 <pre>int lua_getctx (lua_State *L, int *ctx);</pre> |
| 3378 |
| 3379 <p> |
| 3380 This function is called by a continuation function (see <a href="#4.7">§4.7
</a>) |
| 3381 to retrieve the status of the thread and a context information. |
| 3382 |
| 3383 |
| 3384 <p> |
| 3385 When called in the original function, |
| 3386 <a href="#lua_getctx"><code>lua_getctx</code></a> always returns <a href="#pdf-L
UA_OK"><code>LUA_OK</code></a> |
| 3387 and does not change the value of its argument <code>ctx</code>. |
| 3388 When called inside a continuation function, |
| 3389 <a href="#lua_getctx"><code>lua_getctx</code></a> returns <a href="#pdf-LUA_YIEL
D"><code>LUA_YIELD</code></a> and sets |
| 3390 the value of <code>ctx</code> to be the context information |
| 3391 (the value passed as the <code>ctx</code> argument |
| 3392 to the callee together with the continuation function). |
| 3393 |
| 3394 |
| 3395 <p> |
| 3396 When the callee is <a href="#lua_pcallk"><code>lua_pcallk</code></a>, |
| 3397 Lua may also call its continuation function |
| 3398 to handle errors during the call. |
| 3399 That is, upon an error in the function called by <a href="#lua_pcallk"><code>lua
_pcallk</code></a>, |
| 3400 Lua may not return to the original function |
| 3401 but instead may call the continuation function. |
| 3402 In that case, a call to <a href="#lua_getctx"><code>lua_getctx</code></a> will r
eturn the error code |
| 3403 (the value that would be returned by <a href="#lua_pcallk"><code>lua_pcallk</cod
e></a>); |
| 3404 the value of <code>ctx</code> will be set to the context information, |
| 3405 as in the case of a yield. |
| 3406 |
| 3407 |
| 3408 |
| 3409 |
| 3410 |
| 3411 <hr><h3><a name="lua_getfield"><code>lua_getfield</code></a></h3><p> |
| 3412 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 3413 <pre>void lua_getfield (lua_State *L, int index, const char *k);</pre> |
| 3414 |
| 3415 <p> |
| 3416 Pushes onto the stack the value <code>t[k]</code>, |
| 3417 where <code>t</code> is the value at the given index. |
| 3418 As in Lua, this function may trigger a metamethod |
| 3419 for the "index" event (see <a href="#2.4">§2.4</a>). |
| 3420 |
| 3421 |
| 3422 |
| 3423 |
| 3424 |
| 3425 <hr><h3><a name="lua_getglobal"><code>lua_getglobal</code></a></h3><p> |
| 3426 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 3427 <pre>void lua_getglobal (lua_State *L, const char *name);</pre> |
| 3428 |
| 3429 <p> |
| 3430 Pushes onto the stack the value of the global <code>name</code>. |
| 3431 |
| 3432 |
| 3433 |
| 3434 |
| 3435 |
| 3436 <hr><h3><a name="lua_getmetatable"><code>lua_getmetatable</code></a></h3><p> |
| 3437 <span class="apii">[-0, +(0|1), –]</span> |
| 3438 <pre>int lua_getmetatable (lua_State *L, int index);</pre> |
| 3439 |
| 3440 <p> |
| 3441 Pushes onto the stack the metatable of the value at the given index. |
| 3442 If the value does not have a metatable, |
| 3443 the function returns 0 and pushes nothing on the stack. |
| 3444 |
| 3445 |
| 3446 |
| 3447 |
| 3448 |
| 3449 <hr><h3><a name="lua_gettable"><code>lua_gettable</code></a></h3><p> |
| 3450 <span class="apii">[-1, +1, <em>e</em>]</span> |
| 3451 <pre>void lua_gettable (lua_State *L, int index);</pre> |
| 3452 |
| 3453 <p> |
| 3454 Pushes onto the stack the value <code>t[k]</code>, |
| 3455 where <code>t</code> is the value at the given index |
| 3456 and <code>k</code> is the value at the top of the stack. |
| 3457 |
| 3458 |
| 3459 <p> |
| 3460 This function pops the key from the stack |
| 3461 (putting the resulting value in its place). |
| 3462 As in Lua, this function may trigger a metamethod |
| 3463 for the "index" event (see <a href="#2.4">§2.4</a>). |
| 3464 |
| 3465 |
| 3466 |
| 3467 |
| 3468 |
| 3469 <hr><h3><a name="lua_gettop"><code>lua_gettop</code></a></h3><p> |
| 3470 <span class="apii">[-0, +0, –]</span> |
| 3471 <pre>int lua_gettop (lua_State *L);</pre> |
| 3472 |
| 3473 <p> |
| 3474 Returns the index of the top element in the stack. |
| 3475 Because indices start at 1, |
| 3476 this result is equal to the number of elements in the stack |
| 3477 (and so 0 means an empty stack). |
| 3478 |
| 3479 |
| 3480 |
| 3481 |
| 3482 |
| 3483 <hr><h3><a name="lua_getuservalue"><code>lua_getuservalue</code></a></h3><p> |
| 3484 <span class="apii">[-0, +1, –]</span> |
| 3485 <pre>void lua_getuservalue (lua_State *L, int index);</pre> |
| 3486 |
| 3487 <p> |
| 3488 Pushes onto the stack the Lua value associated with the userdata |
| 3489 at the given index. |
| 3490 This Lua value must be a table or <b>nil</b>. |
| 3491 |
| 3492 |
| 3493 |
| 3494 |
| 3495 |
| 3496 <hr><h3><a name="lua_insert"><code>lua_insert</code></a></h3><p> |
| 3497 <span class="apii">[-1, +1, –]</span> |
| 3498 <pre>void lua_insert (lua_State *L, int index);</pre> |
| 3499 |
| 3500 <p> |
| 3501 Moves the top element into the given valid index, |
| 3502 shifting up the elements above this index to open space. |
| 3503 This function cannot be called with a pseudo-index, |
| 3504 because a pseudo-index is not an actual stack position. |
| 3505 |
| 3506 |
| 3507 |
| 3508 |
| 3509 |
| 3510 <hr><h3><a name="lua_Integer"><code>lua_Integer</code></a></h3> |
| 3511 <pre>typedef ptrdiff_t lua_Integer;</pre> |
| 3512 |
| 3513 <p> |
| 3514 The type used by the Lua API to represent signed integral values. |
| 3515 |
| 3516 |
| 3517 <p> |
| 3518 By default it is a <code>ptrdiff_t</code>, |
| 3519 which is usually the largest signed integral type the machine handles |
| 3520 "comfortably". |
| 3521 |
| 3522 |
| 3523 |
| 3524 |
| 3525 |
| 3526 <hr><h3><a name="lua_isboolean"><code>lua_isboolean</code></a></h3><p> |
| 3527 <span class="apii">[-0, +0, –]</span> |
| 3528 <pre>int lua_isboolean (lua_State *L, int index);</pre> |
| 3529 |
| 3530 <p> |
| 3531 Returns 1 if the value at the given index is a boolean, |
| 3532 and 0 otherwise. |
| 3533 |
| 3534 |
| 3535 |
| 3536 |
| 3537 |
| 3538 <hr><h3><a name="lua_iscfunction"><code>lua_iscfunction</code></a></h3><p> |
| 3539 <span class="apii">[-0, +0, –]</span> |
| 3540 <pre>int lua_iscfunction (lua_State *L, int index);</pre> |
| 3541 |
| 3542 <p> |
| 3543 Returns 1 if the value at the given index is a C function, |
| 3544 and 0 otherwise. |
| 3545 |
| 3546 |
| 3547 |
| 3548 |
| 3549 |
| 3550 <hr><h3><a name="lua_isfunction"><code>lua_isfunction</code></a></h3><p> |
| 3551 <span class="apii">[-0, +0, –]</span> |
| 3552 <pre>int lua_isfunction (lua_State *L, int index);</pre> |
| 3553 |
| 3554 <p> |
| 3555 Returns 1 if the value at the given index is a function |
| 3556 (either C or Lua), and 0 otherwise. |
| 3557 |
| 3558 |
| 3559 |
| 3560 |
| 3561 |
| 3562 <hr><h3><a name="lua_islightuserdata"><code>lua_islightuserdata</code></a></h3><
p> |
| 3563 <span class="apii">[-0, +0, –]</span> |
| 3564 <pre>int lua_islightuserdata (lua_State *L, int index);</pre> |
| 3565 |
| 3566 <p> |
| 3567 Returns 1 if the value at the given index is a light userdata, |
| 3568 and 0 otherwise. |
| 3569 |
| 3570 |
| 3571 |
| 3572 |
| 3573 |
| 3574 <hr><h3><a name="lua_isnil"><code>lua_isnil</code></a></h3><p> |
| 3575 <span class="apii">[-0, +0, –]</span> |
| 3576 <pre>int lua_isnil (lua_State *L, int index);</pre> |
| 3577 |
| 3578 <p> |
| 3579 Returns 1 if the value at the given index is <b>nil</b>, |
| 3580 and 0 otherwise. |
| 3581 |
| 3582 |
| 3583 |
| 3584 |
| 3585 |
| 3586 <hr><h3><a name="lua_isnone"><code>lua_isnone</code></a></h3><p> |
| 3587 <span class="apii">[-0, +0, –]</span> |
| 3588 <pre>int lua_isnone (lua_State *L, int index);</pre> |
| 3589 |
| 3590 <p> |
| 3591 Returns 1 if the given index is not valid, |
| 3592 and 0 otherwise. |
| 3593 |
| 3594 |
| 3595 |
| 3596 |
| 3597 |
| 3598 <hr><h3><a name="lua_isnoneornil"><code>lua_isnoneornil</code></a></h3><p> |
| 3599 <span class="apii">[-0, +0, –]</span> |
| 3600 <pre>int lua_isnoneornil (lua_State *L, int index);</pre> |
| 3601 |
| 3602 <p> |
| 3603 Returns 1 if the given index is not valid |
| 3604 or if the value at this index is <b>nil</b>, |
| 3605 and 0 otherwise. |
| 3606 |
| 3607 |
| 3608 |
| 3609 |
| 3610 |
| 3611 <hr><h3><a name="lua_isnumber"><code>lua_isnumber</code></a></h3><p> |
| 3612 <span class="apii">[-0, +0, –]</span> |
| 3613 <pre>int lua_isnumber (lua_State *L, int index);</pre> |
| 3614 |
| 3615 <p> |
| 3616 Returns 1 if the value at the given index is a number |
| 3617 or a string convertible to a number, |
| 3618 and 0 otherwise. |
| 3619 |
| 3620 |
| 3621 |
| 3622 |
| 3623 |
| 3624 <hr><h3><a name="lua_isstring"><code>lua_isstring</code></a></h3><p> |
| 3625 <span class="apii">[-0, +0, –]</span> |
| 3626 <pre>int lua_isstring (lua_State *L, int index);</pre> |
| 3627 |
| 3628 <p> |
| 3629 Returns 1 if the value at the given index is a string |
| 3630 or a number (which is always convertible to a string), |
| 3631 and 0 otherwise. |
| 3632 |
| 3633 |
| 3634 |
| 3635 |
| 3636 |
| 3637 <hr><h3><a name="lua_istable"><code>lua_istable</code></a></h3><p> |
| 3638 <span class="apii">[-0, +0, –]</span> |
| 3639 <pre>int lua_istable (lua_State *L, int index);</pre> |
| 3640 |
| 3641 <p> |
| 3642 Returns 1 if the value at the given index is a table, |
| 3643 and 0 otherwise. |
| 3644 |
| 3645 |
| 3646 |
| 3647 |
| 3648 |
| 3649 <hr><h3><a name="lua_isthread"><code>lua_isthread</code></a></h3><p> |
| 3650 <span class="apii">[-0, +0, –]</span> |
| 3651 <pre>int lua_isthread (lua_State *L, int index);</pre> |
| 3652 |
| 3653 <p> |
| 3654 Returns 1 if the value at the given index is a thread, |
| 3655 and 0 otherwise. |
| 3656 |
| 3657 |
| 3658 |
| 3659 |
| 3660 |
| 3661 <hr><h3><a name="lua_isuserdata"><code>lua_isuserdata</code></a></h3><p> |
| 3662 <span class="apii">[-0, +0, –]</span> |
| 3663 <pre>int lua_isuserdata (lua_State *L, int index);</pre> |
| 3664 |
| 3665 <p> |
| 3666 Returns 1 if the value at the given index is a userdata |
| 3667 (either full or light), and 0 otherwise. |
| 3668 |
| 3669 |
| 3670 |
| 3671 |
| 3672 |
| 3673 <hr><h3><a name="lua_len"><code>lua_len</code></a></h3><p> |
| 3674 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 3675 <pre>void lua_len (lua_State *L, int index);</pre> |
| 3676 |
| 3677 <p> |
| 3678 Returns the "length" of the value at the given index; |
| 3679 it is equivalent to the '<code>#</code>' operator in Lua (see <a href="#3.4.6">&
sect;3.4.6</a>). |
| 3680 The result is pushed on the stack. |
| 3681 |
| 3682 |
| 3683 |
| 3684 |
| 3685 |
| 3686 <hr><h3><a name="lua_load"><code>lua_load</code></a></h3><p> |
| 3687 <span class="apii">[-0, +1, –]</span> |
| 3688 <pre>int lua_load (lua_State *L, |
| 3689 lua_Reader reader, |
| 3690 void *data, |
| 3691 const char *source, |
| 3692 const char *mode);</pre> |
| 3693 |
| 3694 <p> |
| 3695 Loads a Lua chunk (without running it). |
| 3696 If there are no errors, |
| 3697 <code>lua_load</code> pushes the compiled chunk as a Lua |
| 3698 function on top of the stack. |
| 3699 Otherwise, it pushes an error message. |
| 3700 |
| 3701 |
| 3702 <p> |
| 3703 The return values of <code>lua_load</code> are: |
| 3704 |
| 3705 <ul> |
| 3706 |
| 3707 <li><b><a href="#pdf-LUA_OK"><code>LUA_OK</code></a>: </b> no errors;</li> |
| 3708 |
| 3709 <li><b><a name="pdf-LUA_ERRSYNTAX"><code>LUA_ERRSYNTAX</code></a>: </b> |
| 3710 syntax error during precompilation;</li> |
| 3711 |
| 3712 <li><b><a href="#pdf-LUA_ERRMEM"><code>LUA_ERRMEM</code></a>: </b> |
| 3713 memory allocation error;</li> |
| 3714 |
| 3715 <li><b><a href="#pdf-LUA_ERRGCMM"><code>LUA_ERRGCMM</code></a>: </b> |
| 3716 error while running a <code>__gc</code> metamethod. |
| 3717 (This error has no relation with the chunk being loaded. |
| 3718 It is generated by the garbage collector.) |
| 3719 </li> |
| 3720 |
| 3721 </ul> |
| 3722 |
| 3723 <p> |
| 3724 The <code>lua_load</code> function uses a user-supplied <code>reader</code> func
tion |
| 3725 to read the chunk (see <a href="#lua_Reader"><code>lua_Reader</code></a>). |
| 3726 The <code>data</code> argument is an opaque value passed to the reader function. |
| 3727 |
| 3728 |
| 3729 <p> |
| 3730 The <code>source</code> argument gives a name to the chunk, |
| 3731 which is used for error messages and in debug information (see <a href="#4.9">&s
ect;4.9</a>). |
| 3732 |
| 3733 |
| 3734 <p> |
| 3735 <code>lua_load</code> automatically detects whether the chunk is text or binary |
| 3736 and loads it accordingly (see program <code>luac</code>). |
| 3737 The string <code>mode</code> works as in function <a href="#pdf-load"><code>load
</code></a>, |
| 3738 with the addition that |
| 3739 a <code>NULL</code> value is equivalent to the string "<code>bt</code>". |
| 3740 |
| 3741 |
| 3742 <p> |
| 3743 <code>lua_load</code> uses the stack internally, |
| 3744 so the reader function should always leave the stack |
| 3745 unmodified when returning. |
| 3746 |
| 3747 |
| 3748 <p> |
| 3749 If the resulting function has one upvalue, |
| 3750 this upvalue is set to the value of the global environment |
| 3751 stored at index <code>LUA_RIDX_GLOBALS</code> in the registry (see <a href="#4.5
">§4.5</a>). |
| 3752 When loading main chunks, |
| 3753 this upvalue will be the <code>_ENV</code> variable (see <a href="#2.2">§2.
2</a>). |
| 3754 |
| 3755 |
| 3756 |
| 3757 |
| 3758 |
| 3759 <hr><h3><a name="lua_newstate"><code>lua_newstate</code></a></h3><p> |
| 3760 <span class="apii">[-0, +0, –]</span> |
| 3761 <pre>lua_State *lua_newstate (lua_Alloc f, void *ud);</pre> |
| 3762 |
| 3763 <p> |
| 3764 Creates a new thread running in a new, independent state. |
| 3765 Returns <code>NULL</code> if cannot create the thread or the state |
| 3766 (due to lack of memory). |
| 3767 The argument <code>f</code> is the allocator function; |
| 3768 Lua does all memory allocation for this state through this function. |
| 3769 The second argument, <code>ud</code>, is an opaque pointer that Lua |
| 3770 passes to the allocator in every call. |
| 3771 |
| 3772 |
| 3773 |
| 3774 |
| 3775 |
| 3776 <hr><h3><a name="lua_newtable"><code>lua_newtable</code></a></h3><p> |
| 3777 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 3778 <pre>void lua_newtable (lua_State *L);</pre> |
| 3779 |
| 3780 <p> |
| 3781 Creates a new empty table and pushes it onto the stack. |
| 3782 It is equivalent to <code>lua_createtable(L, 0, 0)</code>. |
| 3783 |
| 3784 |
| 3785 |
| 3786 |
| 3787 |
| 3788 <hr><h3><a name="lua_newthread"><code>lua_newthread</code></a></h3><p> |
| 3789 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 3790 <pre>lua_State *lua_newthread (lua_State *L);</pre> |
| 3791 |
| 3792 <p> |
| 3793 Creates a new thread, pushes it on the stack, |
| 3794 and returns a pointer to a <a href="#lua_State"><code>lua_State</code></a> that
represents this new thread. |
| 3795 The new thread returned by this function shares with the original thread |
| 3796 its global environment, |
| 3797 but has an independent execution stack. |
| 3798 |
| 3799 |
| 3800 <p> |
| 3801 There is no explicit function to close or to destroy a thread. |
| 3802 Threads are subject to garbage collection, |
| 3803 like any Lua object. |
| 3804 |
| 3805 |
| 3806 |
| 3807 |
| 3808 |
| 3809 <hr><h3><a name="lua_newuserdata"><code>lua_newuserdata</code></a></h3><p> |
| 3810 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 3811 <pre>void *lua_newuserdata (lua_State *L, size_t size);</pre> |
| 3812 |
| 3813 <p> |
| 3814 This function allocates a new block of memory with the given size, |
| 3815 pushes onto the stack a new full userdata with the block address, |
| 3816 and returns this address. |
| 3817 The host program can freely use this memory. |
| 3818 |
| 3819 |
| 3820 |
| 3821 |
| 3822 |
| 3823 <hr><h3><a name="lua_next"><code>lua_next</code></a></h3><p> |
| 3824 <span class="apii">[-1, +(2|0), <em>e</em>]</span> |
| 3825 <pre>int lua_next (lua_State *L, int index);</pre> |
| 3826 |
| 3827 <p> |
| 3828 Pops a key from the stack, |
| 3829 and pushes a key–value pair from the table at the given index |
| 3830 (the "next" pair after the given key). |
| 3831 If there are no more elements in the table, |
| 3832 then <a href="#lua_next"><code>lua_next</code></a> returns 0 (and pushes nothing
). |
| 3833 |
| 3834 |
| 3835 <p> |
| 3836 A typical traversal looks like this: |
| 3837 |
| 3838 <pre> |
| 3839 /* table is in the stack at index 't' */ |
| 3840 lua_pushnil(L); /* first key */ |
| 3841 while (lua_next(L, t) != 0) { |
| 3842 /* uses 'key' (at index -2) and 'value' (at index -1) */ |
| 3843 printf("%s - %s\n", |
| 3844 lua_typename(L, lua_type(L, -2)), |
| 3845 lua_typename(L, lua_type(L, -1))); |
| 3846 /* removes 'value'; keeps 'key' for next iteration */ |
| 3847 lua_pop(L, 1); |
| 3848 } |
| 3849 </pre> |
| 3850 |
| 3851 <p> |
| 3852 While traversing a table, |
| 3853 do not call <a href="#lua_tolstring"><code>lua_tolstring</code></a> directly on
a key, |
| 3854 unless you know that the key is actually a string. |
| 3855 Recall that <a href="#lua_tolstring"><code>lua_tolstring</code></a> may change |
| 3856 the value at the given index; |
| 3857 this confuses the next call to <a href="#lua_next"><code>lua_next</code></a>. |
| 3858 |
| 3859 |
| 3860 <p> |
| 3861 See function <a href="#pdf-next"><code>next</code></a> for the caveats of modify
ing |
| 3862 the table during its traversal. |
| 3863 |
| 3864 |
| 3865 |
| 3866 |
| 3867 |
| 3868 <hr><h3><a name="lua_Number"><code>lua_Number</code></a></h3> |
| 3869 <pre>typedef double lua_Number;</pre> |
| 3870 |
| 3871 <p> |
| 3872 The type of numbers in Lua. |
| 3873 By default, it is double, but that can be changed in <code>luaconf.h</code>. |
| 3874 Through this configuration file you can change |
| 3875 Lua to operate with another type for numbers (e.g., float or long). |
| 3876 |
| 3877 |
| 3878 |
| 3879 |
| 3880 |
| 3881 <hr><h3><a name="lua_pcall"><code>lua_pcall</code></a></h3><p> |
| 3882 <span class="apii">[-(nargs + 1), +(nresults|1), –]</span> |
| 3883 <pre>int lua_pcall (lua_State *L, int nargs, int nresults, int msgh);</pre> |
| 3884 |
| 3885 <p> |
| 3886 Calls a function in protected mode. |
| 3887 |
| 3888 |
| 3889 <p> |
| 3890 Both <code>nargs</code> and <code>nresults</code> have the same meaning as |
| 3891 in <a href="#lua_call"><code>lua_call</code></a>. |
| 3892 If there are no errors during the call, |
| 3893 <a href="#lua_pcall"><code>lua_pcall</code></a> behaves exactly like <a href="#l
ua_call"><code>lua_call</code></a>. |
| 3894 However, if there is any error, |
| 3895 <a href="#lua_pcall"><code>lua_pcall</code></a> catches it, |
| 3896 pushes a single value on the stack (the error message), |
| 3897 and returns an error code. |
| 3898 Like <a href="#lua_call"><code>lua_call</code></a>, |
| 3899 <a href="#lua_pcall"><code>lua_pcall</code></a> always removes the function |
| 3900 and its arguments from the stack. |
| 3901 |
| 3902 |
| 3903 <p> |
| 3904 If <code>msgh</code> is 0, |
| 3905 then the error message returned on the stack |
| 3906 is exactly the original error message. |
| 3907 Otherwise, <code>msgh</code> is the stack index of a |
| 3908 <em>message handler</em>. |
| 3909 (In the current implementation, this index cannot be a pseudo-index.) |
| 3910 In case of runtime errors, |
| 3911 this function will be called with the error message |
| 3912 and its return value will be the message |
| 3913 returned on the stack by <a href="#lua_pcall"><code>lua_pcall</code></a>. |
| 3914 |
| 3915 |
| 3916 <p> |
| 3917 Typically, the message handler is used to add more debug |
| 3918 information to the error message, such as a stack traceback. |
| 3919 Such information cannot be gathered after the return of <a href="#lua_pcall"><co
de>lua_pcall</code></a>, |
| 3920 since by then the stack has unwound. |
| 3921 |
| 3922 |
| 3923 <p> |
| 3924 The <a href="#lua_pcall"><code>lua_pcall</code></a> function returns one of the
following codes |
| 3925 (defined in <code>lua.h</code>): |
| 3926 |
| 3927 <ul> |
| 3928 |
| 3929 <li><b><a name="pdf-LUA_OK"><code>LUA_OK</code></a> (0): </b> |
| 3930 success.</li> |
| 3931 |
| 3932 <li><b><a name="pdf-LUA_ERRRUN"><code>LUA_ERRRUN</code></a>: </b> |
| 3933 a runtime error. |
| 3934 </li> |
| 3935 |
| 3936 <li><b><a name="pdf-LUA_ERRMEM"><code>LUA_ERRMEM</code></a>: </b> |
| 3937 memory allocation error. |
| 3938 For such errors, Lua does not call the message handler. |
| 3939 </li> |
| 3940 |
| 3941 <li><b><a name="pdf-LUA_ERRERR"><code>LUA_ERRERR</code></a>: </b> |
| 3942 error while running the message handler. |
| 3943 </li> |
| 3944 |
| 3945 <li><b><a name="pdf-LUA_ERRGCMM"><code>LUA_ERRGCMM</code></a>: </b> |
| 3946 error while running a <code>__gc</code> metamethod. |
| 3947 (This error typically has no relation with the function being called. |
| 3948 It is generated by the garbage collector.) |
| 3949 </li> |
| 3950 |
| 3951 </ul> |
| 3952 |
| 3953 |
| 3954 |
| 3955 |
| 3956 <hr><h3><a name="lua_pcallk"><code>lua_pcallk</code></a></h3><p> |
| 3957 <span class="apii">[-(nargs + 1), +(nresults|1), –]</span> |
| 3958 <pre>int lua_pcallk (lua_State *L, |
| 3959 int nargs, |
| 3960 int nresults, |
| 3961 int errfunc, |
| 3962 int ctx, |
| 3963 lua_CFunction k);</pre> |
| 3964 |
| 3965 <p> |
| 3966 This function behaves exactly like <a href="#lua_pcall"><code>lua_pcall</code></
a>, |
| 3967 but allows the called function to yield (see <a href="#4.7">§4.7</a>). |
| 3968 |
| 3969 |
| 3970 |
| 3971 |
| 3972 |
| 3973 <hr><h3><a name="lua_pop"><code>lua_pop</code></a></h3><p> |
| 3974 <span class="apii">[-n, +0, –]</span> |
| 3975 <pre>void lua_pop (lua_State *L, int n);</pre> |
| 3976 |
| 3977 <p> |
| 3978 Pops <code>n</code> elements from the stack. |
| 3979 |
| 3980 |
| 3981 |
| 3982 |
| 3983 |
| 3984 <hr><h3><a name="lua_pushboolean"><code>lua_pushboolean</code></a></h3><p> |
| 3985 <span class="apii">[-0, +1, –]</span> |
| 3986 <pre>void lua_pushboolean (lua_State *L, int b);</pre> |
| 3987 |
| 3988 <p> |
| 3989 Pushes a boolean value with value <code>b</code> onto the stack. |
| 3990 |
| 3991 |
| 3992 |
| 3993 |
| 3994 |
| 3995 <hr><h3><a name="lua_pushcclosure"><code>lua_pushcclosure</code></a></h3><p> |
| 3996 <span class="apii">[-n, +1, <em>e</em>]</span> |
| 3997 <pre>void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n);</pre> |
| 3998 |
| 3999 <p> |
| 4000 Pushes a new C closure onto the stack. |
| 4001 |
| 4002 |
| 4003 <p> |
| 4004 When a C function is created, |
| 4005 it is possible to associate some values with it, |
| 4006 thus creating a C closure (see <a href="#4.4">§4.4</a>); |
| 4007 these values are then accessible to the function whenever it is called. |
| 4008 To associate values with a C function, |
| 4009 first these values should be pushed onto the stack |
| 4010 (when there are multiple values, the first value is pushed first). |
| 4011 Then <a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a> |
| 4012 is called to create and push the C function onto the stack, |
| 4013 with the argument <code>n</code> telling how many values should be |
| 4014 associated with the function. |
| 4015 <a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a> also pops these va
lues from the stack. |
| 4016 |
| 4017 |
| 4018 <p> |
| 4019 The maximum value for <code>n</code> is 255. |
| 4020 |
| 4021 |
| 4022 <p> |
| 4023 When <code>n</code> is zero, |
| 4024 this function creates a <em>light C function</em>, |
| 4025 which is just a pointer to the C function. |
| 4026 In that case, it never throws a memory error. |
| 4027 |
| 4028 |
| 4029 |
| 4030 |
| 4031 |
| 4032 <hr><h3><a name="lua_pushcfunction"><code>lua_pushcfunction</code></a></h3><p> |
| 4033 <span class="apii">[-0, +1, –]</span> |
| 4034 <pre>void lua_pushcfunction (lua_State *L, lua_CFunction f);</pre> |
| 4035 |
| 4036 <p> |
| 4037 Pushes a C function onto the stack. |
| 4038 This function receives a pointer to a C function |
| 4039 and pushes onto the stack a Lua value of type <code>function</code> that, |
| 4040 when called, invokes the corresponding C function. |
| 4041 |
| 4042 |
| 4043 <p> |
| 4044 Any function to be registered in Lua must |
| 4045 follow the correct protocol to receive its parameters |
| 4046 and return its results (see <a href="#lua_CFunction"><code>lua_CFunction</code><
/a>). |
| 4047 |
| 4048 |
| 4049 <p> |
| 4050 <code>lua_pushcfunction</code> is defined as a macro: |
| 4051 |
| 4052 <pre> |
| 4053 #define lua_pushcfunction(L,f) lua_pushcclosure(L,f,0) |
| 4054 </pre><p> |
| 4055 Note that <code>f</code> is used twice. |
| 4056 |
| 4057 |
| 4058 |
| 4059 |
| 4060 |
| 4061 <hr><h3><a name="lua_pushfstring"><code>lua_pushfstring</code></a></h3><p> |
| 4062 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 4063 <pre>const char *lua_pushfstring (lua_State *L, const char *fmt, ...);</pre> |
| 4064 |
| 4065 <p> |
| 4066 Pushes onto the stack a formatted string |
| 4067 and returns a pointer to this string. |
| 4068 It is similar to the ANSI C function <code>sprintf</code>, |
| 4069 but has some important differences: |
| 4070 |
| 4071 <ul> |
| 4072 |
| 4073 <li> |
| 4074 You do not have to allocate space for the result: |
| 4075 the result is a Lua string and Lua takes care of memory allocation |
| 4076 (and deallocation, through garbage collection). |
| 4077 </li> |
| 4078 |
| 4079 <li> |
| 4080 The conversion specifiers are quite restricted. |
| 4081 There are no flags, widths, or precisions. |
| 4082 The conversion specifiers can only be |
| 4083 '<code>%%</code>' (inserts a '<code>%</code>' in the string), |
| 4084 '<code>%s</code>' (inserts a zero-terminated string, with no size restrictions), |
| 4085 '<code>%f</code>' (inserts a <a href="#lua_Number"><code>lua_Number</code></a>), |
| 4086 '<code>%p</code>' (inserts a pointer as a hexadecimal numeral), |
| 4087 '<code>%d</code>' (inserts an <code>int</code>), and |
| 4088 '<code>%c</code>' (inserts an <code>int</code> as a byte). |
| 4089 </li> |
| 4090 |
| 4091 </ul> |
| 4092 |
| 4093 |
| 4094 |
| 4095 |
| 4096 <hr><h3><a name="lua_pushglobaltable"><code>lua_pushglobaltable</code></a></h3><
p> |
| 4097 <span class="apii">[-0, +1, –]</span> |
| 4098 <pre>void lua_pushglobaltable (lua_State *L);</pre> |
| 4099 |
| 4100 <p> |
| 4101 Pushes the global environment onto the stack. |
| 4102 |
| 4103 |
| 4104 |
| 4105 |
| 4106 |
| 4107 <hr><h3><a name="lua_pushinteger"><code>lua_pushinteger</code></a></h3><p> |
| 4108 <span class="apii">[-0, +1, –]</span> |
| 4109 <pre>void lua_pushinteger (lua_State *L, lua_Integer n);</pre> |
| 4110 |
| 4111 <p> |
| 4112 Pushes a number with value <code>n</code> onto the stack. |
| 4113 |
| 4114 |
| 4115 |
| 4116 |
| 4117 |
| 4118 <hr><h3><a name="lua_pushlightuserdata"><code>lua_pushlightuserdata</code></a></
h3><p> |
| 4119 <span class="apii">[-0, +1, –]</span> |
| 4120 <pre>void lua_pushlightuserdata (lua_State *L, void *p);</pre> |
| 4121 |
| 4122 <p> |
| 4123 Pushes a light userdata onto the stack. |
| 4124 |
| 4125 |
| 4126 <p> |
| 4127 Userdata represent C values in Lua. |
| 4128 A <em>light userdata</em> represents a pointer, a <code>void*</code>. |
| 4129 It is a value (like a number): |
| 4130 you do not create it, it has no individual metatable, |
| 4131 and it is not collected (as it was never created). |
| 4132 A light userdata is equal to "any" |
| 4133 light userdata with the same C address. |
| 4134 |
| 4135 |
| 4136 |
| 4137 |
| 4138 |
| 4139 <hr><h3><a name="lua_pushliteral"><code>lua_pushliteral</code></a></h3><p> |
| 4140 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 4141 <pre>const char *lua_pushliteral (lua_State *L, const char *s);</pre> |
| 4142 |
| 4143 <p> |
| 4144 This macro is equivalent to <a href="#lua_pushlstring"><code>lua_pushlstring</co
de></a>, |
| 4145 but can be used only when <code>s</code> is a literal string. |
| 4146 It automatically provides the string length. |
| 4147 |
| 4148 |
| 4149 |
| 4150 |
| 4151 |
| 4152 <hr><h3><a name="lua_pushlstring"><code>lua_pushlstring</code></a></h3><p> |
| 4153 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 4154 <pre>const char *lua_pushlstring (lua_State *L, const char *s, size_t len);</pre
> |
| 4155 |
| 4156 <p> |
| 4157 Pushes the string pointed to by <code>s</code> with size <code>len</code> |
| 4158 onto the stack. |
| 4159 Lua makes (or reuses) an internal copy of the given string, |
| 4160 so the memory at <code>s</code> can be freed or reused immediately after |
| 4161 the function returns. |
| 4162 The string can contain any binary data, |
| 4163 including embedded zeros. |
| 4164 |
| 4165 |
| 4166 <p> |
| 4167 Returns a pointer to the internal copy of the string. |
| 4168 |
| 4169 |
| 4170 |
| 4171 |
| 4172 |
| 4173 <hr><h3><a name="lua_pushnil"><code>lua_pushnil</code></a></h3><p> |
| 4174 <span class="apii">[-0, +1, –]</span> |
| 4175 <pre>void lua_pushnil (lua_State *L);</pre> |
| 4176 |
| 4177 <p> |
| 4178 Pushes a nil value onto the stack. |
| 4179 |
| 4180 |
| 4181 |
| 4182 |
| 4183 |
| 4184 <hr><h3><a name="lua_pushnumber"><code>lua_pushnumber</code></a></h3><p> |
| 4185 <span class="apii">[-0, +1, –]</span> |
| 4186 <pre>void lua_pushnumber (lua_State *L, lua_Number n);</pre> |
| 4187 |
| 4188 <p> |
| 4189 Pushes a number with value <code>n</code> onto the stack. |
| 4190 |
| 4191 |
| 4192 |
| 4193 |
| 4194 |
| 4195 <hr><h3><a name="lua_pushstring"><code>lua_pushstring</code></a></h3><p> |
| 4196 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 4197 <pre>const char *lua_pushstring (lua_State *L, const char *s);</pre> |
| 4198 |
| 4199 <p> |
| 4200 Pushes the zero-terminated string pointed to by <code>s</code> |
| 4201 onto the stack. |
| 4202 Lua makes (or reuses) an internal copy of the given string, |
| 4203 so the memory at <code>s</code> can be freed or reused immediately after |
| 4204 the function returns. |
| 4205 |
| 4206 |
| 4207 <p> |
| 4208 Returns a pointer to the internal copy of the string. |
| 4209 |
| 4210 |
| 4211 <p> |
| 4212 If <code>s</code> is <code>NULL</code>, pushes <b>nil</b> and returns <code>NULL
</code>. |
| 4213 |
| 4214 |
| 4215 |
| 4216 |
| 4217 |
| 4218 <hr><h3><a name="lua_pushthread"><code>lua_pushthread</code></a></h3><p> |
| 4219 <span class="apii">[-0, +1, –]</span> |
| 4220 <pre>int lua_pushthread (lua_State *L);</pre> |
| 4221 |
| 4222 <p> |
| 4223 Pushes the thread represented by <code>L</code> onto the stack. |
| 4224 Returns 1 if this thread is the main thread of its state. |
| 4225 |
| 4226 |
| 4227 |
| 4228 |
| 4229 |
| 4230 <hr><h3><a name="lua_pushunsigned"><code>lua_pushunsigned</code></a></h3><p> |
| 4231 <span class="apii">[-0, +1, –]</span> |
| 4232 <pre>void lua_pushunsigned (lua_State *L, lua_Unsigned n);</pre> |
| 4233 |
| 4234 <p> |
| 4235 Pushes a number with value <code>n</code> onto the stack. |
| 4236 |
| 4237 |
| 4238 |
| 4239 |
| 4240 |
| 4241 <hr><h3><a name="lua_pushvalue"><code>lua_pushvalue</code></a></h3><p> |
| 4242 <span class="apii">[-0, +1, –]</span> |
| 4243 <pre>void lua_pushvalue (lua_State *L, int index);</pre> |
| 4244 |
| 4245 <p> |
| 4246 Pushes a copy of the element at the given index |
| 4247 onto the stack. |
| 4248 |
| 4249 |
| 4250 |
| 4251 |
| 4252 |
| 4253 <hr><h3><a name="lua_pushvfstring"><code>lua_pushvfstring</code></a></h3><p> |
| 4254 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 4255 <pre>const char *lua_pushvfstring (lua_State *L, |
| 4256 const char *fmt, |
| 4257 va_list argp);</pre> |
| 4258 |
| 4259 <p> |
| 4260 Equivalent to <a href="#lua_pushfstring"><code>lua_pushfstring</code></a>, excep
t that it receives a <code>va_list</code> |
| 4261 instead of a variable number of arguments. |
| 4262 |
| 4263 |
| 4264 |
| 4265 |
| 4266 |
| 4267 <hr><h3><a name="lua_rawequal"><code>lua_rawequal</code></a></h3><p> |
| 4268 <span class="apii">[-0, +0, –]</span> |
| 4269 <pre>int lua_rawequal (lua_State *L, int index1, int index2);</pre> |
| 4270 |
| 4271 <p> |
| 4272 Returns 1 if the two values in indices <code>index1</code> and |
| 4273 <code>index2</code> are primitively equal |
| 4274 (that is, without calling metamethods). |
| 4275 Otherwise returns 0. |
| 4276 Also returns 0 if any of the indices are non valid. |
| 4277 |
| 4278 |
| 4279 |
| 4280 |
| 4281 |
| 4282 <hr><h3><a name="lua_rawget"><code>lua_rawget</code></a></h3><p> |
| 4283 <span class="apii">[-1, +1, –]</span> |
| 4284 <pre>void lua_rawget (lua_State *L, int index);</pre> |
| 4285 |
| 4286 <p> |
| 4287 Similar to <a href="#lua_gettable"><code>lua_gettable</code></a>, but does a raw
access |
| 4288 (i.e., without metamethods). |
| 4289 |
| 4290 |
| 4291 |
| 4292 |
| 4293 |
| 4294 <hr><h3><a name="lua_rawgeti"><code>lua_rawgeti</code></a></h3><p> |
| 4295 <span class="apii">[-0, +1, –]</span> |
| 4296 <pre>void lua_rawgeti (lua_State *L, int index, int n);</pre> |
| 4297 |
| 4298 <p> |
| 4299 Pushes onto the stack the value <code>t[n]</code>, |
| 4300 where <code>t</code> is the table at the given index. |
| 4301 The access is raw; |
| 4302 that is, it does not invoke metamethods. |
| 4303 |
| 4304 |
| 4305 |
| 4306 |
| 4307 |
| 4308 <hr><h3><a name="lua_rawgetp"><code>lua_rawgetp</code></a></h3><p> |
| 4309 <span class="apii">[-0, +1, –]</span> |
| 4310 <pre>void lua_rawgetp (lua_State *L, int index, const void *p);</pre> |
| 4311 |
| 4312 <p> |
| 4313 Pushes onto the stack the value <code>t[k]</code>, |
| 4314 where <code>t</code> is the table at the given index and |
| 4315 <code>k</code> is the pointer <code>p</code> represented as a light userdata. |
| 4316 The access is raw; |
| 4317 that is, it does not invoke metamethods. |
| 4318 |
| 4319 |
| 4320 |
| 4321 |
| 4322 |
| 4323 <hr><h3><a name="lua_rawlen"><code>lua_rawlen</code></a></h3><p> |
| 4324 <span class="apii">[-0, +0, –]</span> |
| 4325 <pre>size_t lua_rawlen (lua_State *L, int index);</pre> |
| 4326 |
| 4327 <p> |
| 4328 Returns the raw "length" of the value at the given index: |
| 4329 for strings, this is the string length; |
| 4330 for tables, this is the result of the length operator ('<code>#</code>') |
| 4331 with no metamethods; |
| 4332 for userdata, this is the size of the block of memory allocated |
| 4333 for the userdata; |
| 4334 for other values, it is 0. |
| 4335 |
| 4336 |
| 4337 |
| 4338 |
| 4339 |
| 4340 <hr><h3><a name="lua_rawset"><code>lua_rawset</code></a></h3><p> |
| 4341 <span class="apii">[-2, +0, <em>e</em>]</span> |
| 4342 <pre>void lua_rawset (lua_State *L, int index);</pre> |
| 4343 |
| 4344 <p> |
| 4345 Similar to <a href="#lua_settable"><code>lua_settable</code></a>, but does a raw
assignment |
| 4346 (i.e., without metamethods). |
| 4347 |
| 4348 |
| 4349 |
| 4350 |
| 4351 |
| 4352 <hr><h3><a name="lua_rawseti"><code>lua_rawseti</code></a></h3><p> |
| 4353 <span class="apii">[-1, +0, <em>e</em>]</span> |
| 4354 <pre>void lua_rawseti (lua_State *L, int index, int n);</pre> |
| 4355 |
| 4356 <p> |
| 4357 Does the equivalent of <code>t[n] = v</code>, |
| 4358 where <code>t</code> is the table at the given index |
| 4359 and <code>v</code> is the value at the top of the stack. |
| 4360 |
| 4361 |
| 4362 <p> |
| 4363 This function pops the value from the stack. |
| 4364 The assignment is raw; |
| 4365 that is, it does not invoke metamethods. |
| 4366 |
| 4367 |
| 4368 |
| 4369 |
| 4370 |
| 4371 <hr><h3><a name="lua_rawsetp"><code>lua_rawsetp</code></a></h3><p> |
| 4372 <span class="apii">[-1, +0, <em>e</em>]</span> |
| 4373 <pre>void lua_rawsetp (lua_State *L, int index, const void *p);</pre> |
| 4374 |
| 4375 <p> |
| 4376 Does the equivalent of <code>t[k] = v</code>, |
| 4377 where <code>t</code> is the table at the given index, |
| 4378 <code>k</code> is the pointer <code>p</code> represented as a light userdata, |
| 4379 and <code>v</code> is the value at the top of the stack. |
| 4380 |
| 4381 |
| 4382 <p> |
| 4383 This function pops the value from the stack. |
| 4384 The assignment is raw; |
| 4385 that is, it does not invoke metamethods. |
| 4386 |
| 4387 |
| 4388 |
| 4389 |
| 4390 |
| 4391 <hr><h3><a name="lua_Reader"><code>lua_Reader</code></a></h3> |
| 4392 <pre>typedef const char * (*lua_Reader) (lua_State *L, |
| 4393 void *data, |
| 4394 size_t *size);</pre> |
| 4395 |
| 4396 <p> |
| 4397 The reader function used by <a href="#lua_load"><code>lua_load</code></a>. |
| 4398 Every time it needs another piece of the chunk, |
| 4399 <a href="#lua_load"><code>lua_load</code></a> calls the reader, |
| 4400 passing along its <code>data</code> parameter. |
| 4401 The reader must return a pointer to a block of memory |
| 4402 with a new piece of the chunk |
| 4403 and set <code>size</code> to the block size. |
| 4404 The block must exist until the reader function is called again. |
| 4405 To signal the end of the chunk, |
| 4406 the reader must return <code>NULL</code> or set <code>size</code> to zero. |
| 4407 The reader function may return pieces of any size greater than zero. |
| 4408 |
| 4409 |
| 4410 |
| 4411 |
| 4412 |
| 4413 <hr><h3><a name="lua_register"><code>lua_register</code></a></h3><p> |
| 4414 <span class="apii">[-0, +0, <em>e</em>]</span> |
| 4415 <pre>void lua_register (lua_State *L, const char *name, lua_CFunction f);</pre> |
| 4416 |
| 4417 <p> |
| 4418 Sets the C function <code>f</code> as the new value of global <code>name</code>. |
| 4419 It is defined as a macro: |
| 4420 |
| 4421 <pre> |
| 4422 #define lua_register(L,n,f) \ |
| 4423 (lua_pushcfunction(L, f), lua_setglobal(L, n)) |
| 4424 </pre> |
| 4425 |
| 4426 |
| 4427 |
| 4428 |
| 4429 <hr><h3><a name="lua_remove"><code>lua_remove</code></a></h3><p> |
| 4430 <span class="apii">[-1, +0, –]</span> |
| 4431 <pre>void lua_remove (lua_State *L, int index);</pre> |
| 4432 |
| 4433 <p> |
| 4434 Removes the element at the given valid index, |
| 4435 shifting down the elements above this index to fill the gap. |
| 4436 This function cannot be called with a pseudo-index, |
| 4437 because a pseudo-index is not an actual stack position. |
| 4438 |
| 4439 |
| 4440 |
| 4441 |
| 4442 |
| 4443 <hr><h3><a name="lua_replace"><code>lua_replace</code></a></h3><p> |
| 4444 <span class="apii">[-1, +0, –]</span> |
| 4445 <pre>void lua_replace (lua_State *L, int index);</pre> |
| 4446 |
| 4447 <p> |
| 4448 Moves the top element into the given valid index |
| 4449 without shifting any element |
| 4450 (therefore replacing the value at the given index), |
| 4451 and then pops the top element. |
| 4452 |
| 4453 |
| 4454 |
| 4455 |
| 4456 |
| 4457 <hr><h3><a name="lua_resume"><code>lua_resume</code></a></h3><p> |
| 4458 <span class="apii">[-?, +?, –]</span> |
| 4459 <pre>int lua_resume (lua_State *L, lua_State *from, int nargs);</pre> |
| 4460 |
| 4461 <p> |
| 4462 Starts and resumes a coroutine in a given thread. |
| 4463 |
| 4464 |
| 4465 <p> |
| 4466 To start a coroutine, |
| 4467 you push onto the thread stack the main function plus any arguments; |
| 4468 then you call <a href="#lua_resume"><code>lua_resume</code></a>, |
| 4469 with <code>nargs</code> being the number of arguments. |
| 4470 This call returns when the coroutine suspends or finishes its execution. |
| 4471 When it returns, the stack contains all values passed to <a href="#lua_yield"><c
ode>lua_yield</code></a>, |
| 4472 or all values returned by the body function. |
| 4473 <a href="#lua_resume"><code>lua_resume</code></a> returns |
| 4474 <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a> if the coroutine yields, |
| 4475 <a href="#pdf-LUA_OK"><code>LUA_OK</code></a> if the coroutine finishes its exec
ution |
| 4476 without errors, |
| 4477 or an error code in case of errors (see <a href="#lua_pcall"><code>lua_pcall</co
de></a>). |
| 4478 |
| 4479 |
| 4480 <p> |
| 4481 In case of errors, |
| 4482 the stack is not unwound, |
| 4483 so you can use the debug API over it. |
| 4484 The error message is on the top of the stack. |
| 4485 |
| 4486 |
| 4487 <p> |
| 4488 To resume a coroutine, |
| 4489 you remove any results from the last <a href="#lua_yield"><code>lua_yield</code>
</a>, |
| 4490 put on its stack only the values to |
| 4491 be passed as results from <code>yield</code>, |
| 4492 and then call <a href="#lua_resume"><code>lua_resume</code></a>. |
| 4493 |
| 4494 |
| 4495 <p> |
| 4496 The parameter <code>from</code> represents the coroutine that is resuming <code>
L</code>. |
| 4497 If there is no such coroutine, |
| 4498 this parameter can be <code>NULL</code>. |
| 4499 |
| 4500 |
| 4501 |
| 4502 |
| 4503 |
| 4504 <hr><h3><a name="lua_setallocf"><code>lua_setallocf</code></a></h3><p> |
| 4505 <span class="apii">[-0, +0, –]</span> |
| 4506 <pre>void lua_setallocf (lua_State *L, lua_Alloc f, void *ud);</pre> |
| 4507 |
| 4508 <p> |
| 4509 Changes the allocator function of a given state to <code>f</code> |
| 4510 with user data <code>ud</code>. |
| 4511 |
| 4512 |
| 4513 |
| 4514 |
| 4515 |
| 4516 <hr><h3><a name="lua_setfield"><code>lua_setfield</code></a></h3><p> |
| 4517 <span class="apii">[-1, +0, <em>e</em>]</span> |
| 4518 <pre>void lua_setfield (lua_State *L, int index, const char *k);</pre> |
| 4519 |
| 4520 <p> |
| 4521 Does the equivalent to <code>t[k] = v</code>, |
| 4522 where <code>t</code> is the value at the given index |
| 4523 and <code>v</code> is the value at the top of the stack. |
| 4524 |
| 4525 |
| 4526 <p> |
| 4527 This function pops the value from the stack. |
| 4528 As in Lua, this function may trigger a metamethod |
| 4529 for the "newindex" event (see <a href="#2.4">§2.4</a>). |
| 4530 |
| 4531 |
| 4532 |
| 4533 |
| 4534 |
| 4535 <hr><h3><a name="lua_setglobal"><code>lua_setglobal</code></a></h3><p> |
| 4536 <span class="apii">[-1, +0, <em>e</em>]</span> |
| 4537 <pre>void lua_setglobal (lua_State *L, const char *name);</pre> |
| 4538 |
| 4539 <p> |
| 4540 Pops a value from the stack and |
| 4541 sets it as the new value of global <code>name</code>. |
| 4542 |
| 4543 |
| 4544 |
| 4545 |
| 4546 |
| 4547 <hr><h3><a name="lua_setmetatable"><code>lua_setmetatable</code></a></h3><p> |
| 4548 <span class="apii">[-1, +0, –]</span> |
| 4549 <pre>void lua_setmetatable (lua_State *L, int index);</pre> |
| 4550 |
| 4551 <p> |
| 4552 Pops a table from the stack and |
| 4553 sets it as the new metatable for the value at the given index. |
| 4554 |
| 4555 |
| 4556 |
| 4557 |
| 4558 |
| 4559 <hr><h3><a name="lua_settable"><code>lua_settable</code></a></h3><p> |
| 4560 <span class="apii">[-2, +0, <em>e</em>]</span> |
| 4561 <pre>void lua_settable (lua_State *L, int index);</pre> |
| 4562 |
| 4563 <p> |
| 4564 Does the equivalent to <code>t[k] = v</code>, |
| 4565 where <code>t</code> is the value at the given index, |
| 4566 <code>v</code> is the value at the top of the stack, |
| 4567 and <code>k</code> is the value just below the top. |
| 4568 |
| 4569 |
| 4570 <p> |
| 4571 This function pops both the key and the value from the stack. |
| 4572 As in Lua, this function may trigger a metamethod |
| 4573 for the "newindex" event (see <a href="#2.4">§2.4</a>). |
| 4574 |
| 4575 |
| 4576 |
| 4577 |
| 4578 |
| 4579 <hr><h3><a name="lua_settop"><code>lua_settop</code></a></h3><p> |
| 4580 <span class="apii">[-?, +?, –]</span> |
| 4581 <pre>void lua_settop (lua_State *L, int index);</pre> |
| 4582 |
| 4583 <p> |
| 4584 Accepts any index, or 0, |
| 4585 and sets the stack top to this index. |
| 4586 If the new top is larger than the old one, |
| 4587 then the new elements are filled with <b>nil</b>. |
| 4588 If <code>index</code> is 0, then all stack elements are removed. |
| 4589 |
| 4590 |
| 4591 |
| 4592 |
| 4593 |
| 4594 <hr><h3><a name="lua_setuservalue"><code>lua_setuservalue</code></a></h3><p> |
| 4595 <span class="apii">[-1, +0, –]</span> |
| 4596 <pre>void lua_setuservalue (lua_State *L, int index);</pre> |
| 4597 |
| 4598 <p> |
| 4599 Pops a table or <b>nil</b> from the stack and sets it as |
| 4600 the new value associated to the userdata at the given index. |
| 4601 |
| 4602 |
| 4603 |
| 4604 |
| 4605 |
| 4606 <hr><h3><a name="lua_State"><code>lua_State</code></a></h3> |
| 4607 <pre>typedef struct lua_State lua_State;</pre> |
| 4608 |
| 4609 <p> |
| 4610 An opaque structure that points to a thread and indirectly |
| 4611 (through the thread) to the whole state of a Lua interpreter. |
| 4612 The Lua library is fully reentrant: |
| 4613 it has no global variables. |
| 4614 All information about a state is accessible through this structure. |
| 4615 |
| 4616 |
| 4617 <p> |
| 4618 A pointer to this structure must be passed as the first argument to |
| 4619 every function in the library, except to <a href="#lua_newstate"><code>lua_newst
ate</code></a>, |
| 4620 which creates a Lua state from scratch. |
| 4621 |
| 4622 |
| 4623 |
| 4624 |
| 4625 |
| 4626 <hr><h3><a name="lua_status"><code>lua_status</code></a></h3><p> |
| 4627 <span class="apii">[-0, +0, –]</span> |
| 4628 <pre>int lua_status (lua_State *L);</pre> |
| 4629 |
| 4630 <p> |
| 4631 Returns the status of the thread <code>L</code>. |
| 4632 |
| 4633 |
| 4634 <p> |
| 4635 The status can be 0 (<a href="#pdf-LUA_OK"><code>LUA_OK</code></a>) for a normal
thread, |
| 4636 an error code if the thread finished the execution |
| 4637 of a <a href="#lua_resume"><code>lua_resume</code></a> with an error, |
| 4638 or <a name="pdf-LUA_YIELD"><code>LUA_YIELD</code></a> if the thread is suspended
. |
| 4639 |
| 4640 |
| 4641 <p> |
| 4642 You can only call functions in threads with status <a href="#pdf-LUA_OK"><code>L
UA_OK</code></a>. |
| 4643 You can resume threads with status <a href="#pdf-LUA_OK"><code>LUA_OK</code></a> |
| 4644 (to start a new coroutine) or <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a
> |
| 4645 (to resume a coroutine). |
| 4646 |
| 4647 |
| 4648 |
| 4649 |
| 4650 |
| 4651 <hr><h3><a name="lua_toboolean"><code>lua_toboolean</code></a></h3><p> |
| 4652 <span class="apii">[-0, +0, –]</span> |
| 4653 <pre>int lua_toboolean (lua_State *L, int index);</pre> |
| 4654 |
| 4655 <p> |
| 4656 Converts the Lua value at the given index to a C boolean |
| 4657 value (0 or 1). |
| 4658 Like all tests in Lua, |
| 4659 <a href="#lua_toboolean"><code>lua_toboolean</code></a> returns true for any Lua
value |
| 4660 different from <b>false</b> and <b>nil</b>; |
| 4661 otherwise it returns false. |
| 4662 (If you want to accept only actual boolean values, |
| 4663 use <a href="#lua_isboolean"><code>lua_isboolean</code></a> to test the value's
type.) |
| 4664 |
| 4665 |
| 4666 |
| 4667 |
| 4668 |
| 4669 <hr><h3><a name="lua_tocfunction"><code>lua_tocfunction</code></a></h3><p> |
| 4670 <span class="apii">[-0, +0, –]</span> |
| 4671 <pre>lua_CFunction lua_tocfunction (lua_State *L, int index);</pre> |
| 4672 |
| 4673 <p> |
| 4674 Converts a value at the given index to a C function. |
| 4675 That value must be a C function; |
| 4676 otherwise, returns <code>NULL</code>. |
| 4677 |
| 4678 |
| 4679 |
| 4680 |
| 4681 |
| 4682 <hr><h3><a name="lua_tointeger"><code>lua_tointeger</code></a></h3><p> |
| 4683 <span class="apii">[-0, +0, –]</span> |
| 4684 <pre>lua_Integer lua_tointeger (lua_State *L, int index);</pre> |
| 4685 |
| 4686 <p> |
| 4687 Equivalent to <a href="#lua_tointegerx"><code>lua_tointegerx</code></a> with <co
de>isnum</code> equal to <code>NULL</code>. |
| 4688 |
| 4689 |
| 4690 |
| 4691 |
| 4692 |
| 4693 <hr><h3><a name="lua_tointegerx"><code>lua_tointegerx</code></a></h3><p> |
| 4694 <span class="apii">[-0, +0, –]</span> |
| 4695 <pre>lua_Integer lua_tointegerx (lua_State *L, int index, int *isnum);</pre> |
| 4696 |
| 4697 <p> |
| 4698 Converts the Lua value at the given index |
| 4699 to the signed integral type <a href="#lua_Integer"><code>lua_Integer</code></a>. |
| 4700 The Lua value must be a number or a string convertible to a number |
| 4701 (see <a href="#3.4.2">§3.4.2</a>); |
| 4702 otherwise, <code>lua_tointegerx</code> returns 0. |
| 4703 |
| 4704 |
| 4705 <p> |
| 4706 If the number is not an integer, |
| 4707 it is truncated in some non-specified way. |
| 4708 |
| 4709 |
| 4710 <p> |
| 4711 If <code>isnum</code> is not <code>NULL</code>, |
| 4712 its referent is assigned a boolean value that |
| 4713 indicates whether the operation succeeded. |
| 4714 |
| 4715 |
| 4716 |
| 4717 |
| 4718 |
| 4719 <hr><h3><a name="lua_tolstring"><code>lua_tolstring</code></a></h3><p> |
| 4720 <span class="apii">[-0, +0, <em>e</em>]</span> |
| 4721 <pre>const char *lua_tolstring (lua_State *L, int index, size_t *len);</pre> |
| 4722 |
| 4723 <p> |
| 4724 Converts the Lua value at the given index to a C string. |
| 4725 If <code>len</code> is not <code>NULL</code>, |
| 4726 it also sets <code>*len</code> with the string length. |
| 4727 The Lua value must be a string or a number; |
| 4728 otherwise, the function returns <code>NULL</code>. |
| 4729 If the value is a number, |
| 4730 then <code>lua_tolstring</code> also |
| 4731 <em>changes the actual value in the stack to a string</em>. |
| 4732 (This change confuses <a href="#lua_next"><code>lua_next</code></a> |
| 4733 when <code>lua_tolstring</code> is applied to keys during a table traversal.) |
| 4734 |
| 4735 |
| 4736 <p> |
| 4737 <code>lua_tolstring</code> returns a fully aligned pointer |
| 4738 to a string inside the Lua state. |
| 4739 This string always has a zero ('<code>\0</code>') |
| 4740 after its last character (as in C), |
| 4741 but can contain other zeros in its body. |
| 4742 Because Lua has garbage collection, |
| 4743 there is no guarantee that the pointer returned by <code>lua_tolstring</code> |
| 4744 will be valid after the corresponding value is removed from the stack. |
| 4745 |
| 4746 |
| 4747 |
| 4748 |
| 4749 |
| 4750 <hr><h3><a name="lua_tonumber"><code>lua_tonumber</code></a></h3><p> |
| 4751 <span class="apii">[-0, +0, –]</span> |
| 4752 <pre>lua_Number lua_tonumber (lua_State *L, int index);</pre> |
| 4753 |
| 4754 <p> |
| 4755 Equivalent to <a href="#lua_tonumberx"><code>lua_tonumberx</code></a> with <code
>isnum</code> equal to <code>NULL</code>. |
| 4756 |
| 4757 |
| 4758 |
| 4759 |
| 4760 |
| 4761 <hr><h3><a name="lua_tonumberx"><code>lua_tonumberx</code></a></h3><p> |
| 4762 <span class="apii">[-0, +0, –]</span> |
| 4763 <pre>lua_Number lua_tonumberx (lua_State *L, int index, int *isnum);</pre> |
| 4764 |
| 4765 <p> |
| 4766 Converts the Lua value at the given index |
| 4767 to the C type <a href="#lua_Number"><code>lua_Number</code></a> (see <a hre
f="#lua_Number"><code>lua_Number</code></a>). |
| 4768 The Lua value must be a number or a string convertible to a number |
| 4769 (see <a href="#3.4.2">§3.4.2</a>); |
| 4770 otherwise, <a href="#lua_tonumberx"><code>lua_tonumberx</code></a> returns
0. |
| 4771 |
| 4772 |
| 4773 <p> |
| 4774 If <code>isnum</code> is not <code>NULL</code>, |
| 4775 its referent is assigned a boolean value that |
| 4776 indicates whether the operation succeeded. |
| 4777 |
| 4778 |
| 4779 |
| 4780 |
| 4781 |
| 4782 <hr><h3><a name="lua_topointer"><code>lua_topointer</code></a></h3><p> |
| 4783 <span class="apii">[-0, +0, –]</span> |
| 4784 <pre>const void *lua_topointer (lua_State *L, int index);</pre> |
| 4785 |
| 4786 <p> |
| 4787 Converts the value at the given index to a generic |
| 4788 C pointer (<code>void*</code>). |
| 4789 The value can be a userdata, a table, a thread, or a function; |
| 4790 otherwise, <code>lua_topointer</code> returns <code>NULL</code>. |
| 4791 Different objects will give different pointers. |
| 4792 There is no way to convert the pointer back to its original value. |
| 4793 |
| 4794 |
| 4795 <p> |
| 4796 Typically this function is used only for debug information. |
| 4797 |
| 4798 |
| 4799 |
| 4800 |
| 4801 |
| 4802 <hr><h3><a name="lua_tostring"><code>lua_tostring</code></a></h3><p> |
| 4803 <span class="apii">[-0, +0, <em>e</em>]</span> |
| 4804 <pre>const char *lua_tostring (lua_State *L, int index);</pre> |
| 4805 |
| 4806 <p> |
| 4807 Equivalent to <a href="#lua_tolstring"><code>lua_tolstring</code></a> with <code
>len</code> equal to <code>NULL</code>. |
| 4808 |
| 4809 |
| 4810 |
| 4811 |
| 4812 |
| 4813 <hr><h3><a name="lua_tothread"><code>lua_tothread</code></a></h3><p> |
| 4814 <span class="apii">[-0, +0, –]</span> |
| 4815 <pre>lua_State *lua_tothread (lua_State *L, int index);</pre> |
| 4816 |
| 4817 <p> |
| 4818 Converts the value at the given index to a Lua thread |
| 4819 (represented as <code>lua_State*</code>). |
| 4820 This value must be a thread; |
| 4821 otherwise, the function returns <code>NULL</code>. |
| 4822 |
| 4823 |
| 4824 |
| 4825 |
| 4826 |
| 4827 <hr><h3><a name="lua_tounsigned"><code>lua_tounsigned</code></a></h3><p> |
| 4828 <span class="apii">[-0, +0, –]</span> |
| 4829 <pre>lua_Unsigned lua_tounsigned (lua_State *L, int index);</pre> |
| 4830 |
| 4831 <p> |
| 4832 Equivalent to <a href="#lua_tounsignedx"><code>lua_tounsignedx</code></a> with <
code>isnum</code> equal to <code>NULL</code>. |
| 4833 |
| 4834 |
| 4835 |
| 4836 |
| 4837 |
| 4838 <hr><h3><a name="lua_tounsignedx"><code>lua_tounsignedx</code></a></h3><p> |
| 4839 <span class="apii">[-0, +0, –]</span> |
| 4840 <pre>lua_Unsigned lua_tounsignedx (lua_State *L, int index, int *isnum);</pre> |
| 4841 |
| 4842 <p> |
| 4843 Converts the Lua value at the given index |
| 4844 to the unsigned integral type <a href="#lua_Unsigned"><code>lua_Unsigned</code><
/a>. |
| 4845 The Lua value must be a number or a string convertible to a number |
| 4846 (see <a href="#3.4.2">§3.4.2</a>); |
| 4847 otherwise, <code>lua_tounsignedx</code> returns 0. |
| 4848 |
| 4849 |
| 4850 <p> |
| 4851 If the number is not an integer, |
| 4852 it is truncated in some non-specified way. |
| 4853 If the number is outside the range of representable values, |
| 4854 it is normalized to the remainder of its division by |
| 4855 one more than the maximum representable value. |
| 4856 |
| 4857 |
| 4858 <p> |
| 4859 If <code>isnum</code> is not <code>NULL</code>, |
| 4860 its referent is assigned a boolean value that |
| 4861 indicates whether the operation succeeded. |
| 4862 |
| 4863 |
| 4864 |
| 4865 |
| 4866 |
| 4867 <hr><h3><a name="lua_touserdata"><code>lua_touserdata</code></a></h3><p> |
| 4868 <span class="apii">[-0, +0, –]</span> |
| 4869 <pre>void *lua_touserdata (lua_State *L, int index);</pre> |
| 4870 |
| 4871 <p> |
| 4872 If the value at the given index is a full userdata, |
| 4873 returns its block address. |
| 4874 If the value is a light userdata, |
| 4875 returns its pointer. |
| 4876 Otherwise, returns <code>NULL</code>. |
| 4877 |
| 4878 |
| 4879 |
| 4880 |
| 4881 |
| 4882 <hr><h3><a name="lua_type"><code>lua_type</code></a></h3><p> |
| 4883 <span class="apii">[-0, +0, –]</span> |
| 4884 <pre>int lua_type (lua_State *L, int index);</pre> |
| 4885 |
| 4886 <p> |
| 4887 Returns the type of the value in the given valid index, |
| 4888 or <code>LUA_TNONE</code> for a non-valid (but acceptable) index. |
| 4889 The types returned by <a href="#lua_type"><code>lua_type</code></a> are coded by
the following constants |
| 4890 defined in <code>lua.h</code>: |
| 4891 <a name="pdf-LUA_TNIL"><code>LUA_TNIL</code></a>, |
| 4892 <a name="pdf-LUA_TNUMBER"><code>LUA_TNUMBER</code></a>, |
| 4893 <a name="pdf-LUA_TBOOLEAN"><code>LUA_TBOOLEAN</code></a>, |
| 4894 <a name="pdf-LUA_TSTRING"><code>LUA_TSTRING</code></a>, |
| 4895 <a name="pdf-LUA_TTABLE"><code>LUA_TTABLE</code></a>, |
| 4896 <a name="pdf-LUA_TFUNCTION"><code>LUA_TFUNCTION</code></a>, |
| 4897 <a name="pdf-LUA_TUSERDATA"><code>LUA_TUSERDATA</code></a>, |
| 4898 <a name="pdf-LUA_TTHREAD"><code>LUA_TTHREAD</code></a>, |
| 4899 and |
| 4900 <a name="pdf-LUA_TLIGHTUSERDATA"><code>LUA_TLIGHTUSERDATA</code></a>. |
| 4901 |
| 4902 |
| 4903 |
| 4904 |
| 4905 |
| 4906 <hr><h3><a name="lua_typename"><code>lua_typename</code></a></h3><p> |
| 4907 <span class="apii">[-0, +0, –]</span> |
| 4908 <pre>const char *lua_typename (lua_State *L, int tp);</pre> |
| 4909 |
| 4910 <p> |
| 4911 Returns the name of the type encoded by the value <code>tp</code>, |
| 4912 which must be one the values returned by <a href="#lua_type"><code>lua_type</cod
e></a>. |
| 4913 |
| 4914 |
| 4915 |
| 4916 |
| 4917 |
| 4918 <hr><h3><a name="lua_Unsigned"><code>lua_Unsigned</code></a></h3> |
| 4919 <pre>typedef unsigned long lua_Unsigned;</pre> |
| 4920 |
| 4921 <p> |
| 4922 The type used by the Lua API to represent unsigned integral values. |
| 4923 It must have at least 32 bits. |
| 4924 |
| 4925 |
| 4926 <p> |
| 4927 By default it is an <code>unsigned int</code> or an <code>unsigned long</code>, |
| 4928 whichever can hold 32-bit values. |
| 4929 |
| 4930 |
| 4931 |
| 4932 |
| 4933 |
| 4934 <hr><h3><a name="lua_upvalueindex"><code>lua_upvalueindex</code></a></h3><p> |
| 4935 <span class="apii">[-0, +0, –]</span> |
| 4936 <pre>int lua_upvalueindex (int i);</pre> |
| 4937 |
| 4938 <p> |
| 4939 Returns the pseudo-index that represents the <code>i</code>-th upvalue of |
| 4940 the running function (see <a href="#4.4">§4.4</a>). |
| 4941 |
| 4942 |
| 4943 |
| 4944 |
| 4945 |
| 4946 <hr><h3><a name="lua_version"><code>lua_version</code></a></h3><p> |
| 4947 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 4948 <pre>const lua_Number *lua_version (lua_State *L);</pre> |
| 4949 |
| 4950 <p> |
| 4951 Returns the address of the version number stored in the Lua core. |
| 4952 When called with a valid <a href="#lua_State"><code>lua_State</code></a>, |
| 4953 returns the address of the version used to create that state. |
| 4954 When called with <code>NULL</code>, |
| 4955 returns the address of the version running the call. |
| 4956 |
| 4957 |
| 4958 |
| 4959 |
| 4960 |
| 4961 <hr><h3><a name="lua_Writer"><code>lua_Writer</code></a></h3> |
| 4962 <pre>typedef int (*lua_Writer) (lua_State *L, |
| 4963 const void* p, |
| 4964 size_t sz, |
| 4965 void* ud);</pre> |
| 4966 |
| 4967 <p> |
| 4968 The type of the writer function used by <a href="#lua_dump"><code>lua_dump</code
></a>. |
| 4969 Every time it produces another piece of chunk, |
| 4970 <a href="#lua_dump"><code>lua_dump</code></a> calls the writer, |
| 4971 passing along the buffer to be written (<code>p</code>), |
| 4972 its size (<code>sz</code>), |
| 4973 and the <code>data</code> parameter supplied to <a href="#lua_dump"><code>lua_du
mp</code></a>. |
| 4974 |
| 4975 |
| 4976 <p> |
| 4977 The writer returns an error code: |
| 4978 0 means no errors; |
| 4979 any other value means an error and stops <a href="#lua_dump"><code>lua_dump</cod
e></a> from |
| 4980 calling the writer again. |
| 4981 |
| 4982 |
| 4983 |
| 4984 |
| 4985 |
| 4986 <hr><h3><a name="lua_xmove"><code>lua_xmove</code></a></h3><p> |
| 4987 <span class="apii">[-?, +?, –]</span> |
| 4988 <pre>void lua_xmove (lua_State *from, lua_State *to, int n);</pre> |
| 4989 |
| 4990 <p> |
| 4991 Exchange values between different threads of the same state. |
| 4992 |
| 4993 |
| 4994 <p> |
| 4995 This function pops <code>n</code> values from the stack <code>from</code>, |
| 4996 and pushes them onto the stack <code>to</code>. |
| 4997 |
| 4998 |
| 4999 |
| 5000 |
| 5001 |
| 5002 <hr><h3><a name="lua_yield"><code>lua_yield</code></a></h3><p> |
| 5003 <span class="apii">[-?, +?, –]</span> |
| 5004 <pre>int lua_yield (lua_State *L, int nresults);</pre> |
| 5005 |
| 5006 <p> |
| 5007 This function is equivalent to <a href="#lua_yieldk"><code>lua_yieldk</code></a>
, |
| 5008 but it has no continuation (see <a href="#4.7">§4.7</a>). |
| 5009 Therefore, when the thread resumes, |
| 5010 it returns to the function that called |
| 5011 the function calling <code>lua_yield</code>. |
| 5012 |
| 5013 |
| 5014 |
| 5015 |
| 5016 |
| 5017 <hr><h3><a name="lua_yieldk"><code>lua_yieldk</code></a></h3><p> |
| 5018 <span class="apii">[-?, +?, –]</span> |
| 5019 <pre>int lua_yieldk (lua_State *L, int nresults, int ctx, lua_CFunction k);</pre
> |
| 5020 |
| 5021 <p> |
| 5022 Yields a coroutine. |
| 5023 |
| 5024 |
| 5025 <p> |
| 5026 This function should only be called as the |
| 5027 return expression of a C function, as follows: |
| 5028 |
| 5029 <pre> |
| 5030 return lua_yieldk (L, n, i, k); |
| 5031 </pre><p> |
| 5032 When a C function calls <a href="#lua_yieldk"><code>lua_yieldk</code></a> i
n that way, |
| 5033 the running coroutine suspends its execution, |
| 5034 and the call to <a href="#lua_resume"><code>lua_resume</code></a> that started t
his coroutine returns. |
| 5035 The parameter <code>nresults</code> is the number of values from the stack |
| 5036 that are passed as results to <a href="#lua_resume"><code>lua_resume</code></a>. |
| 5037 |
| 5038 |
| 5039 <p> |
| 5040 When the coroutine is resumed again, |
| 5041 Lua calls the given continuation function <code>k</code> to continue |
| 5042 the execution of the C function that yielded (see <a href="#4.7">§4.7</a>). |
| 5043 This continuation function receives the same stack |
| 5044 from the previous function, |
| 5045 with the results removed and |
| 5046 replaced by the arguments passed to <a href="#lua_resume"><code>lua_resume</code
></a>. |
| 5047 Moreover, |
| 5048 the continuation function may access the value <code>ctx</code> |
| 5049 by calling <a href="#lua_getctx"><code>lua_getctx</code></a>. |
| 5050 |
| 5051 |
| 5052 |
| 5053 |
| 5054 |
| 5055 |
| 5056 |
| 5057 <h2>4.9 – <a name="4.9">The Debug Interface</a></h2> |
| 5058 |
| 5059 <p> |
| 5060 Lua has no built-in debugging facilities. |
| 5061 Instead, it offers a special interface |
| 5062 by means of functions and <em>hooks</em>. |
| 5063 This interface allows the construction of different |
| 5064 kinds of debuggers, profilers, and other tools |
| 5065 that need "inside information" from the interpreter. |
| 5066 |
| 5067 |
| 5068 |
| 5069 <hr><h3><a name="lua_Debug"><code>lua_Debug</code></a></h3> |
| 5070 <pre>typedef struct lua_Debug { |
| 5071 int event; |
| 5072 const char *name; /* (n) */ |
| 5073 const char *namewhat; /* (n) */ |
| 5074 const char *what; /* (S) */ |
| 5075 const char *source; /* (S) */ |
| 5076 int currentline; /* (l) */ |
| 5077 int linedefined; /* (S) */ |
| 5078 int lastlinedefined; /* (S) */ |
| 5079 unsigned char nups; /* (u) number of upvalues */ |
| 5080 unsigned char nparams; /* (u) number of parameters */ |
| 5081 char isvararg; /* (u) */ |
| 5082 char istailcall; /* (t) */ |
| 5083 char short_src[LUA_IDSIZE]; /* (S) */ |
| 5084 /* private part */ |
| 5085 <em>other fields</em> |
| 5086 } lua_Debug;</pre> |
| 5087 |
| 5088 <p> |
| 5089 A structure used to carry different pieces of |
| 5090 information about a function or an activation record. |
| 5091 <a href="#lua_getstack"><code>lua_getstack</code></a> fills only the private par
t |
| 5092 of this structure, for later use. |
| 5093 To fill the other fields of <a href="#lua_Debug"><code>lua_Debug</code></a> with
useful information, |
| 5094 call <a href="#lua_getinfo"><code>lua_getinfo</code></a>. |
| 5095 |
| 5096 |
| 5097 <p> |
| 5098 The fields of <a href="#lua_Debug"><code>lua_Debug</code></a> have the following
meaning: |
| 5099 |
| 5100 <ul> |
| 5101 |
| 5102 <li><b><code>source</code>: </b> |
| 5103 the source of the chunk that created the function. |
| 5104 If <code>source</code> starts with a '<code>@</code>', |
| 5105 it means that the function was defined in a file where |
| 5106 the file name follows the '<code>@</code>'. |
| 5107 If <code>source</code> starts with a '<code>=</code>', |
| 5108 the remainder of its contents describe the source in a user-dependent manner. |
| 5109 Otherwise, |
| 5110 the function was defined in a string where |
| 5111 <code>source</code> is that string. |
| 5112 </li> |
| 5113 |
| 5114 <li><b><code>short_src</code>: </b> |
| 5115 a "printable" version of <code>source</code>, to be used in error messages. |
| 5116 </li> |
| 5117 |
| 5118 <li><b><code>linedefined</code>: </b> |
| 5119 the line number where the definition of the function starts. |
| 5120 </li> |
| 5121 |
| 5122 <li><b><code>lastlinedefined</code>: </b> |
| 5123 the line number where the definition of the function ends. |
| 5124 </li> |
| 5125 |
| 5126 <li><b><code>what</code>: </b> |
| 5127 the string <code>"Lua"</code> if the function is a Lua function, |
| 5128 <code>"C"</code> if it is a C function, |
| 5129 <code>"main"</code> if it is the main part of a chunk. |
| 5130 </li> |
| 5131 |
| 5132 <li><b><code>currentline</code>: </b> |
| 5133 the current line where the given function is executing. |
| 5134 When no line information is available, |
| 5135 <code>currentline</code> is set to -1. |
| 5136 </li> |
| 5137 |
| 5138 <li><b><code>name</code>: </b> |
| 5139 a reasonable name for the given function. |
| 5140 Because functions in Lua are first-class values, |
| 5141 they do not have a fixed name: |
| 5142 some functions can be the value of multiple global variables, |
| 5143 while others can be stored only in a table field. |
| 5144 The <code>lua_getinfo</code> function checks how the function was |
| 5145 called to find a suitable name. |
| 5146 If it cannot find a name, |
| 5147 then <code>name</code> is set to <code>NULL</code>. |
| 5148 </li> |
| 5149 |
| 5150 <li><b><code>namewhat</code>: </b> |
| 5151 explains the <code>name</code> field. |
| 5152 The value of <code>namewhat</code> can be |
| 5153 <code>"global"</code>, <code>"local"</code>, <code>"method"</code>, |
| 5154 <code>"field"</code>, <code>"upvalue"</code>, or <code>""</code> (the empty stri
ng), |
| 5155 according to how the function was called. |
| 5156 (Lua uses the empty string when no other option seems to apply.) |
| 5157 </li> |
| 5158 |
| 5159 <li><b><code>istailcall</code>: </b> |
| 5160 true if this function invocation was called by a tail call. |
| 5161 In this case, the caller of this level is not in the stack. |
| 5162 </li> |
| 5163 |
| 5164 <li><b><code>nups</code>: </b> |
| 5165 the number of upvalues of the function. |
| 5166 </li> |
| 5167 |
| 5168 <li><b><code>nparams</code>: </b> |
| 5169 the number of fixed parameters of the function |
| 5170 (always 0 for C functions). |
| 5171 </li> |
| 5172 |
| 5173 <li><b><code>isvararg</code>: </b> |
| 5174 true if the function is a vararg function |
| 5175 (always true for C functions). |
| 5176 </li> |
| 5177 |
| 5178 </ul> |
| 5179 |
| 5180 |
| 5181 |
| 5182 |
| 5183 <hr><h3><a name="lua_gethook"><code>lua_gethook</code></a></h3><p> |
| 5184 <span class="apii">[-0, +0, –]</span> |
| 5185 <pre>lua_Hook lua_gethook (lua_State *L);</pre> |
| 5186 |
| 5187 <p> |
| 5188 Returns the current hook function. |
| 5189 |
| 5190 |
| 5191 |
| 5192 |
| 5193 |
| 5194 <hr><h3><a name="lua_gethookcount"><code>lua_gethookcount</code></a></h3><p> |
| 5195 <span class="apii">[-0, +0, –]</span> |
| 5196 <pre>int lua_gethookcount (lua_State *L);</pre> |
| 5197 |
| 5198 <p> |
| 5199 Returns the current hook count. |
| 5200 |
| 5201 |
| 5202 |
| 5203 |
| 5204 |
| 5205 <hr><h3><a name="lua_gethookmask"><code>lua_gethookmask</code></a></h3><p> |
| 5206 <span class="apii">[-0, +0, –]</span> |
| 5207 <pre>int lua_gethookmask (lua_State *L);</pre> |
| 5208 |
| 5209 <p> |
| 5210 Returns the current hook mask. |
| 5211 |
| 5212 |
| 5213 |
| 5214 |
| 5215 |
| 5216 <hr><h3><a name="lua_getinfo"><code>lua_getinfo</code></a></h3><p> |
| 5217 <span class="apii">[-(0|1), +(0|1|2), <em>e</em>]</span> |
| 5218 <pre>int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar);</pre> |
| 5219 |
| 5220 <p> |
| 5221 Gets information about a specific function or function invocation. |
| 5222 |
| 5223 |
| 5224 <p> |
| 5225 To get information about a function invocation, |
| 5226 the parameter <code>ar</code> must be a valid activation record that was |
| 5227 filled by a previous call to <a href="#lua_getstack"><code>lua_getstack</code></
a> or |
| 5228 given as argument to a hook (see <a href="#lua_Hook"><code>lua_Hook</code></a>). |
| 5229 |
| 5230 |
| 5231 <p> |
| 5232 To get information about a function you push it onto the stack |
| 5233 and start the <code>what</code> string with the character '<code>></code>'. |
| 5234 (In that case, |
| 5235 <code>lua_getinfo</code> pops the function from the top of the stack.) |
| 5236 For instance, to know in which line a function <code>f</code> was defined, |
| 5237 you can write the following code: |
| 5238 |
| 5239 <pre> |
| 5240 lua_Debug ar; |
| 5241 lua_getglobal(L, "f"); /* get global 'f' */ |
| 5242 lua_getinfo(L, ">S", &ar); |
| 5243 printf("%d\n", ar.linedefined); |
| 5244 </pre> |
| 5245 |
| 5246 <p> |
| 5247 Each character in the string <code>what</code> |
| 5248 selects some fields of the structure <code>ar</code> to be filled or |
| 5249 a value to be pushed on the stack: |
| 5250 |
| 5251 <ul> |
| 5252 |
| 5253 <li><b>'<code>n</code>': </b> fills in the field <code>name</code> and <code>nam
ewhat</code>; |
| 5254 </li> |
| 5255 |
| 5256 <li><b>'<code>S</code>': </b> |
| 5257 fills in the fields <code>source</code>, <code>short_src</code>, |
| 5258 <code>linedefined</code>, <code>lastlinedefined</code>, and <code>what</code>; |
| 5259 </li> |
| 5260 |
| 5261 <li><b>'<code>l</code>': </b> fills in the field <code>currentline</code>; |
| 5262 </li> |
| 5263 |
| 5264 <li><b>'<code>t</code>': </b> fills in the field <code>istailcall</code>; |
| 5265 </li> |
| 5266 |
| 5267 <li><b>'<code>u</code>': </b> fills in the fields |
| 5268 <code>nups</code>, <code>nparams</code>, and <code>isvararg</code>; |
| 5269 </li> |
| 5270 |
| 5271 <li><b>'<code>f</code>': </b> |
| 5272 pushes onto the stack the function that is |
| 5273 running at the given level; |
| 5274 </li> |
| 5275 |
| 5276 <li><b>'<code>L</code>': </b> |
| 5277 pushes onto the stack a table whose indices are the |
| 5278 numbers of the lines that are valid on the function. |
| 5279 (A <em>valid line</em> is a line with some associated code, |
| 5280 that is, a line where you can put a break point. |
| 5281 Non-valid lines include empty lines and comments.) |
| 5282 </li> |
| 5283 |
| 5284 </ul> |
| 5285 |
| 5286 <p> |
| 5287 This function returns 0 on error |
| 5288 (for instance, an invalid option in <code>what</code>). |
| 5289 |
| 5290 |
| 5291 |
| 5292 |
| 5293 |
| 5294 <hr><h3><a name="lua_getlocal"><code>lua_getlocal</code></a></h3><p> |
| 5295 <span class="apii">[-0, +(0|1), –]</span> |
| 5296 <pre>const char *lua_getlocal (lua_State *L, lua_Debug *ar, int n);</pre> |
| 5297 |
| 5298 <p> |
| 5299 Gets information about a local variable of |
| 5300 a given activation record or a given function. |
| 5301 |
| 5302 |
| 5303 <p> |
| 5304 In the first case, |
| 5305 the parameter <code>ar</code> must be a valid activation record that was |
| 5306 filled by a previous call to <a href="#lua_getstack"><code>lua_getstack</code></
a> or |
| 5307 given as argument to a hook (see <a href="#lua_Hook"><code>lua_Hook</code></a>). |
| 5308 The index <code>n</code> selects which local variable to inspect; |
| 5309 see <a href="#pdf-debug.getlocal"><code>debug.getlocal</code></a> for details ab
out variable indices |
| 5310 and names. |
| 5311 |
| 5312 |
| 5313 <p> |
| 5314 <a href="#lua_getlocal"><code>lua_getlocal</code></a> pushes the variable's valu
e onto the stack |
| 5315 and returns its name. |
| 5316 |
| 5317 |
| 5318 <p> |
| 5319 In the second case, <code>ar</code> should be <code>NULL</code> and the function |
| 5320 to be inspected must be at the top of the stack. |
| 5321 In this case, only parameters of Lua functions are visible |
| 5322 (as there is no information about what variables are active) |
| 5323 and no values are pushed onto the stack. |
| 5324 |
| 5325 |
| 5326 <p> |
| 5327 Returns <code>NULL</code> (and pushes nothing) |
| 5328 when the index is greater than |
| 5329 the number of active local variables. |
| 5330 |
| 5331 |
| 5332 |
| 5333 |
| 5334 |
| 5335 <hr><h3><a name="lua_getstack"><code>lua_getstack</code></a></h3><p> |
| 5336 <span class="apii">[-0, +0, –]</span> |
| 5337 <pre>int lua_getstack (lua_State *L, int level, lua_Debug *ar);</pre> |
| 5338 |
| 5339 <p> |
| 5340 Gets information about the interpreter runtime stack. |
| 5341 |
| 5342 |
| 5343 <p> |
| 5344 This function fills parts of a <a href="#lua_Debug"><code>lua_Debug</code></a> s
tructure with |
| 5345 an identification of the <em>activation record</em> |
| 5346 of the function executing at a given level. |
| 5347 Level 0 is the current running function, |
| 5348 whereas level <em>n+1</em> is the function that has called level <em>n</em> |
| 5349 (except for tail calls, which do not count on the stack). |
| 5350 When there are no errors, <a href="#lua_getstack"><code>lua_getstack</code></a>
returns 1; |
| 5351 when called with a level greater than the stack depth, |
| 5352 it returns 0. |
| 5353 |
| 5354 |
| 5355 |
| 5356 |
| 5357 |
| 5358 <hr><h3><a name="lua_getupvalue"><code>lua_getupvalue</code></a></h3><p> |
| 5359 <span class="apii">[-0, +(0|1), –]</span> |
| 5360 <pre>const char *lua_getupvalue (lua_State *L, int funcindex, int n);</pre> |
| 5361 |
| 5362 <p> |
| 5363 Gets information about a closure's upvalue. |
| 5364 (For Lua functions, |
| 5365 upvalues are the external local variables that the function uses, |
| 5366 and that are consequently included in its closure.) |
| 5367 <a href="#lua_getupvalue"><code>lua_getupvalue</code></a> gets the index <code>n
</code> of an upvalue, |
| 5368 pushes the upvalue's value onto the stack, |
| 5369 and returns its name. |
| 5370 <code>funcindex</code> points to the closure in the stack. |
| 5371 (Upvalues have no particular order, |
| 5372 as they are active through the whole function. |
| 5373 So, they are numbered in an arbitrary order.) |
| 5374 |
| 5375 |
| 5376 <p> |
| 5377 Returns <code>NULL</code> (and pushes nothing) |
| 5378 when the index is greater than the number of upvalues. |
| 5379 For C functions, this function uses the empty string <code>""</code> |
| 5380 as a name for all upvalues. |
| 5381 |
| 5382 |
| 5383 |
| 5384 |
| 5385 |
| 5386 <hr><h3><a name="lua_Hook"><code>lua_Hook</code></a></h3> |
| 5387 <pre>typedef void (*lua_Hook) (lua_State *L, lua_Debug *ar);</pre> |
| 5388 |
| 5389 <p> |
| 5390 Type for debugging hook functions. |
| 5391 |
| 5392 |
| 5393 <p> |
| 5394 Whenever a hook is called, its <code>ar</code> argument has its field |
| 5395 <code>event</code> set to the specific event that triggered the hook. |
| 5396 Lua identifies these events with the following constants: |
| 5397 <a name="pdf-LUA_HOOKCALL"><code>LUA_HOOKCALL</code></a>, <a name="pdf-LUA_HOOKR
ET"><code>LUA_HOOKRET</code></a>, |
| 5398 <a name="pdf-LUA_HOOKTAILCALL"><code>LUA_HOOKTAILCALL</code></a>, <a name="pdf-L
UA_HOOKLINE"><code>LUA_HOOKLINE</code></a>, |
| 5399 and <a name="pdf-LUA_HOOKCOUNT"><code>LUA_HOOKCOUNT</code></a>. |
| 5400 Moreover, for line events, the field <code>currentline</code> is also set. |
| 5401 To get the value of any other field in <code>ar</code>, |
| 5402 the hook must call <a href="#lua_getinfo"><code>lua_getinfo</code></a>. |
| 5403 |
| 5404 |
| 5405 <p> |
| 5406 For call events, <code>event</code> can be <code>LUA_HOOKCALL</code>, |
| 5407 the normal value, or <code>LUA_HOOKTAILCALL</code>, for a tail call; |
| 5408 in this case, there will be no corresponding return event. |
| 5409 |
| 5410 |
| 5411 <p> |
| 5412 While Lua is running a hook, it disables other calls to hooks. |
| 5413 Therefore, if a hook calls back Lua to execute a function or a chunk, |
| 5414 this execution occurs without any calls to hooks. |
| 5415 |
| 5416 |
| 5417 <p> |
| 5418 Hook functions cannot have continuations, |
| 5419 that is, they cannot call <a href="#lua_yieldk"><code>lua_yieldk</code></a>, |
| 5420 <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>. |
| 5421 |
| 5422 |
| 5423 <p> |
| 5424 Hook functions can yield under the following conditions: |
| 5425 Only count and line events can yield |
| 5426 and they cannot yield any value; |
| 5427 to yield a hook function must finish its execution |
| 5428 calling <a href="#lua_yield"><code>lua_yield</code></a> with <code>nresults</cod
e> equal to zero. |
| 5429 |
| 5430 |
| 5431 |
| 5432 |
| 5433 |
| 5434 <hr><h3><a name="lua_sethook"><code>lua_sethook</code></a></h3><p> |
| 5435 <span class="apii">[-0, +0, –]</span> |
| 5436 <pre>int lua_sethook (lua_State *L, lua_Hook f, int mask, int count);</pre> |
| 5437 |
| 5438 <p> |
| 5439 Sets the debugging hook function. |
| 5440 |
| 5441 |
| 5442 <p> |
| 5443 Argument <code>f</code> is the hook function. |
| 5444 <code>mask</code> specifies on which events the hook will be called: |
| 5445 it is formed by a bitwise or of the constants |
| 5446 <a name="pdf-LUA_MASKCALL"><code>LUA_MASKCALL</code></a>, |
| 5447 <a name="pdf-LUA_MASKRET"><code>LUA_MASKRET</code></a>, |
| 5448 <a name="pdf-LUA_MASKLINE"><code>LUA_MASKLINE</code></a>, |
| 5449 and <a name="pdf-LUA_MASKCOUNT"><code>LUA_MASKCOUNT</code></a>. |
| 5450 The <code>count</code> argument is only meaningful when the mask |
| 5451 includes <code>LUA_MASKCOUNT</code>. |
| 5452 For each event, the hook is called as explained below: |
| 5453 |
| 5454 <ul> |
| 5455 |
| 5456 <li><b>The call hook: </b> is called when the interpreter calls a function. |
| 5457 The hook is called just after Lua enters the new function, |
| 5458 before the function gets its arguments. |
| 5459 </li> |
| 5460 |
| 5461 <li><b>The return hook: </b> is called when the interpreter returns from a funct
ion. |
| 5462 The hook is called just before Lua leaves the function. |
| 5463 There is no standard way to access the values |
| 5464 to be returned by the function. |
| 5465 </li> |
| 5466 |
| 5467 <li><b>The line hook: </b> is called when the interpreter is about to |
| 5468 start the execution of a new line of code, |
| 5469 or when it jumps back in the code (even to the same line). |
| 5470 (This event only happens while Lua is executing a Lua function.) |
| 5471 </li> |
| 5472 |
| 5473 <li><b>The count hook: </b> is called after the interpreter executes every |
| 5474 <code>count</code> instructions. |
| 5475 (This event only happens while Lua is executing a Lua function.) |
| 5476 </li> |
| 5477 |
| 5478 </ul> |
| 5479 |
| 5480 <p> |
| 5481 A hook is disabled by setting <code>mask</code> to zero. |
| 5482 |
| 5483 |
| 5484 |
| 5485 |
| 5486 |
| 5487 <hr><h3><a name="lua_setlocal"><code>lua_setlocal</code></a></h3><p> |
| 5488 <span class="apii">[-(0|1), +0, –]</span> |
| 5489 <pre>const char *lua_setlocal (lua_State *L, lua_Debug *ar, int n);</pre> |
| 5490 |
| 5491 <p> |
| 5492 Sets the value of a local variable of a given activation record. |
| 5493 Parameters <code>ar</code> and <code>n</code> are as in <a href="#lua_getlocal">
<code>lua_getlocal</code></a> |
| 5494 (see <a href="#lua_getlocal"><code>lua_getlocal</code></a>). |
| 5495 <a href="#lua_setlocal"><code>lua_setlocal</code></a> assigns the value at the t
op of the stack |
| 5496 to the variable and returns its name. |
| 5497 It also pops the value from the stack. |
| 5498 |
| 5499 |
| 5500 <p> |
| 5501 Returns <code>NULL</code> (and pops nothing) |
| 5502 when the index is greater than |
| 5503 the number of active local variables. |
| 5504 |
| 5505 |
| 5506 |
| 5507 |
| 5508 |
| 5509 <hr><h3><a name="lua_setupvalue"><code>lua_setupvalue</code></a></h3><p> |
| 5510 <span class="apii">[-(0|1), +0, –]</span> |
| 5511 <pre>const char *lua_setupvalue (lua_State *L, int funcindex, int n);</pre> |
| 5512 |
| 5513 <p> |
| 5514 Sets the value of a closure's upvalue. |
| 5515 It assigns the value at the top of the stack |
| 5516 to the upvalue and returns its name. |
| 5517 It also pops the value from the stack. |
| 5518 Parameters <code>funcindex</code> and <code>n</code> are as in the <a href="#lua
_getupvalue"><code>lua_getupvalue</code></a> |
| 5519 (see <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>). |
| 5520 |
| 5521 |
| 5522 <p> |
| 5523 Returns <code>NULL</code> (and pops nothing) |
| 5524 when the index is greater than the number of upvalues. |
| 5525 |
| 5526 |
| 5527 |
| 5528 |
| 5529 |
| 5530 <hr><h3><a name="lua_upvalueid"><code>lua_upvalueid</code></a></h3><p> |
| 5531 <span class="apii">[-0, +0, –]</span> |
| 5532 <pre>void *lua_upvalueid (lua_State *L, int funcindex, int n);</pre> |
| 5533 |
| 5534 <p> |
| 5535 Returns an unique identifier for the upvalue numbered <code>n</code> |
| 5536 from the closure at index <code>funcindex</code>. |
| 5537 Parameters <code>funcindex</code> and <code>n</code> are as in the <a href="#lua
_getupvalue"><code>lua_getupvalue</code></a> |
| 5538 (see <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>) |
| 5539 (but <code>n</code> cannot be greater than the number of upvalues). |
| 5540 |
| 5541 |
| 5542 <p> |
| 5543 These unique identifiers allow a program to check whether different |
| 5544 closures share upvalues. |
| 5545 Lua closures that share an upvalue |
| 5546 (that is, that access a same external local variable) |
| 5547 will return identical ids for those upvalue indices. |
| 5548 |
| 5549 |
| 5550 |
| 5551 |
| 5552 |
| 5553 <hr><h3><a name="lua_upvaluejoin"><code>lua_upvaluejoin</code></a></h3><p> |
| 5554 <span class="apii">[-0, +0, –]</span> |
| 5555 <pre>void lua_upvaluejoin (lua_State *L, int funcindex1, int n1, |
| 5556 int funcindex2, int n2);</pre> |
| 5557 |
| 5558 <p> |
| 5559 Make the <code>n1</code>-th upvalue of the Lua closure at index <code>funcindex1
</code> |
| 5560 refer to the <code>n2</code>-th upvalue of the Lua closure at index <code>funcin
dex2</code>. |
| 5561 |
| 5562 |
| 5563 |
| 5564 |
| 5565 |
| 5566 |
| 5567 |
| 5568 <h1>5 – <a name="5">The Auxiliary Library</a></h1> |
| 5569 |
| 5570 <p> |
| 5571 |
| 5572 The <em>auxiliary library</em> provides several convenient functions |
| 5573 to interface C with Lua. |
| 5574 While the basic API provides the primitive functions for all |
| 5575 interactions between C and Lua, |
| 5576 the auxiliary library provides higher-level functions for some |
| 5577 common tasks. |
| 5578 |
| 5579 |
| 5580 <p> |
| 5581 All functions and types from the auxiliary library |
| 5582 are defined in header file <code>lauxlib.h</code> and |
| 5583 have a prefix <code>luaL_</code>. |
| 5584 |
| 5585 |
| 5586 <p> |
| 5587 All functions in the auxiliary library are built on |
| 5588 top of the basic API, |
| 5589 and so they provide nothing that cannot be done with that API. |
| 5590 Nevertheless, the use of the auxiliary library ensures |
| 5591 more consistency to your code. |
| 5592 |
| 5593 |
| 5594 <p> |
| 5595 Several functions in the auxiliary library use internally some |
| 5596 extra stack slots. |
| 5597 When a function in the auxiliary library uses less than five slots, |
| 5598 it does not check the stack size; |
| 5599 it simply assumes that there are enough slots. |
| 5600 |
| 5601 |
| 5602 <p> |
| 5603 Several functions in the auxiliary library are used to |
| 5604 check C function arguments. |
| 5605 Because the error message is formatted for arguments |
| 5606 (e.g., "<code>bad argument #1</code>"), |
| 5607 you should not use these functions for other stack values. |
| 5608 |
| 5609 |
| 5610 <p> |
| 5611 Functions called <code>luaL_check*</code> |
| 5612 always throw an error if the check is not satisfied. |
| 5613 |
| 5614 |
| 5615 |
| 5616 <h2>5.1 – <a name="5.1">Functions and Types</a></h2> |
| 5617 |
| 5618 <p> |
| 5619 Here we list all functions and types from the auxiliary library |
| 5620 in alphabetical order. |
| 5621 |
| 5622 |
| 5623 |
| 5624 <hr><h3><a name="luaL_addchar"><code>luaL_addchar</code></a></h3><p> |
| 5625 <span class="apii">[-?, +?, <em>e</em>]</span> |
| 5626 <pre>void luaL_addchar (luaL_Buffer *B, char c);</pre> |
| 5627 |
| 5628 <p> |
| 5629 Adds the byte <code>c</code> to the buffer <code>B</code> |
| 5630 (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>). |
| 5631 |
| 5632 |
| 5633 |
| 5634 |
| 5635 |
| 5636 <hr><h3><a name="luaL_addlstring"><code>luaL_addlstring</code></a></h3><p> |
| 5637 <span class="apii">[-?, +?, <em>e</em>]</span> |
| 5638 <pre>void luaL_addlstring (luaL_Buffer *B, const char *s, size_t l);</pre> |
| 5639 |
| 5640 <p> |
| 5641 Adds the string pointed to by <code>s</code> with length <code>l</code> to |
| 5642 the buffer <code>B</code> |
| 5643 (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>). |
| 5644 The string can contain embedded zeros. |
| 5645 |
| 5646 |
| 5647 |
| 5648 |
| 5649 |
| 5650 <hr><h3><a name="luaL_addsize"><code>luaL_addsize</code></a></h3><p> |
| 5651 <span class="apii">[-?, +?, <em>e</em>]</span> |
| 5652 <pre>void luaL_addsize (luaL_Buffer *B, size_t n);</pre> |
| 5653 |
| 5654 <p> |
| 5655 Adds to the buffer <code>B</code> (see <a href="#luaL_Buffer"><code>luaL_Buffer<
/code></a>) |
| 5656 a string of length <code>n</code> previously copied to the |
| 5657 buffer area (see <a href="#luaL_prepbuffer"><code>luaL_prepbuffer</code></a>). |
| 5658 |
| 5659 |
| 5660 |
| 5661 |
| 5662 |
| 5663 <hr><h3><a name="luaL_addstring"><code>luaL_addstring</code></a></h3><p> |
| 5664 <span class="apii">[-?, +?, <em>e</em>]</span> |
| 5665 <pre>void luaL_addstring (luaL_Buffer *B, const char *s);</pre> |
| 5666 |
| 5667 <p> |
| 5668 Adds the zero-terminated string pointed to by <code>s</code> |
| 5669 to the buffer <code>B</code> |
| 5670 (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>). |
| 5671 The string cannot contain embedded zeros. |
| 5672 |
| 5673 |
| 5674 |
| 5675 |
| 5676 |
| 5677 <hr><h3><a name="luaL_addvalue"><code>luaL_addvalue</code></a></h3><p> |
| 5678 <span class="apii">[-1, +?, <em>e</em>]</span> |
| 5679 <pre>void luaL_addvalue (luaL_Buffer *B);</pre> |
| 5680 |
| 5681 <p> |
| 5682 Adds the value at the top of the stack |
| 5683 to the buffer <code>B</code> |
| 5684 (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>). |
| 5685 Pops the value. |
| 5686 |
| 5687 |
| 5688 <p> |
| 5689 This is the only function on string buffers that can (and must) |
| 5690 be called with an extra element on the stack, |
| 5691 which is the value to be added to the buffer. |
| 5692 |
| 5693 |
| 5694 |
| 5695 |
| 5696 |
| 5697 <hr><h3><a name="luaL_argcheck"><code>luaL_argcheck</code></a></h3><p> |
| 5698 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 5699 <pre>void luaL_argcheck (lua_State *L, |
| 5700 int cond, |
| 5701 int arg, |
| 5702 const char *extramsg);</pre> |
| 5703 |
| 5704 <p> |
| 5705 Checks whether <code>cond</code> is true. |
| 5706 If not, raises an error with a standard message. |
| 5707 |
| 5708 |
| 5709 |
| 5710 |
| 5711 |
| 5712 <hr><h3><a name="luaL_argerror"><code>luaL_argerror</code></a></h3><p> |
| 5713 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 5714 <pre>int luaL_argerror (lua_State *L, int arg, const char *extramsg);</pre> |
| 5715 |
| 5716 <p> |
| 5717 Raises an error with a standard message |
| 5718 that includes <code>extramsg</code> as a comment. |
| 5719 |
| 5720 |
| 5721 <p> |
| 5722 This function never returns, |
| 5723 but it is an idiom to use it in C functions |
| 5724 as <code>return luaL_argerror(<em>args</em>)</code>. |
| 5725 |
| 5726 |
| 5727 |
| 5728 |
| 5729 |
| 5730 <hr><h3><a name="luaL_Buffer"><code>luaL_Buffer</code></a></h3> |
| 5731 <pre>typedef struct luaL_Buffer luaL_Buffer;</pre> |
| 5732 |
| 5733 <p> |
| 5734 Type for a <em>string buffer</em>. |
| 5735 |
| 5736 |
| 5737 <p> |
| 5738 A string buffer allows C code to build Lua strings piecemeal. |
| 5739 Its pattern of use is as follows: |
| 5740 |
| 5741 <ul> |
| 5742 |
| 5743 <li>First declare a variable <code>b</code> of type <a href="#luaL_Buffer"><code
>luaL_Buffer</code></a>.</li> |
| 5744 |
| 5745 <li>Then initialize it with a call <code>luaL_buffinit(L, &b)</code>.</li> |
| 5746 |
| 5747 <li> |
| 5748 Then add string pieces to the buffer calling any of |
| 5749 the <code>luaL_add*</code> functions. |
| 5750 </li> |
| 5751 |
| 5752 <li> |
| 5753 Finish by calling <code>luaL_pushresult(&b)</code>. |
| 5754 This call leaves the final string on the top of the stack. |
| 5755 </li> |
| 5756 |
| 5757 </ul> |
| 5758 |
| 5759 <p> |
| 5760 If you know beforehand the total size of the resulting string, |
| 5761 you can use the buffer like this: |
| 5762 |
| 5763 <ul> |
| 5764 |
| 5765 <li>First declare a variable <code>b</code> of type <a href="#luaL_Buffer"><code
>luaL_Buffer</code></a>.</li> |
| 5766 |
| 5767 <li>Then initialize it and preallocate a space of |
| 5768 size <code>sz</code> with a call <code>luaL_buffinitsize(L, &b, sz)</code>.<
/li> |
| 5769 |
| 5770 <li>Then copy the string into that space.</li> |
| 5771 |
| 5772 <li> |
| 5773 Finish by calling <code>luaL_pushresultsize(&b, sz)</code>, |
| 5774 where <code>sz</code> is the total size of the resulting string |
| 5775 copied into that space. |
| 5776 </li> |
| 5777 |
| 5778 </ul> |
| 5779 |
| 5780 <p> |
| 5781 During its normal operation, |
| 5782 a string buffer uses a variable number of stack slots. |
| 5783 So, while using a buffer, you cannot assume that you know where |
| 5784 the top of the stack is. |
| 5785 You can use the stack between successive calls to buffer operations |
| 5786 as long as that use is balanced; |
| 5787 that is, |
| 5788 when you call a buffer operation, |
| 5789 the stack is at the same level |
| 5790 it was immediately after the previous buffer operation. |
| 5791 (The only exception to this rule is <a href="#luaL_addvalue"><code>luaL_addvalue
</code></a>.) |
| 5792 After calling <a href="#luaL_pushresult"><code>luaL_pushresult</code></a> the st
ack is back to its |
| 5793 level when the buffer was initialized, |
| 5794 plus the final string on its top. |
| 5795 |
| 5796 |
| 5797 |
| 5798 |
| 5799 |
| 5800 <hr><h3><a name="luaL_buffinit"><code>luaL_buffinit</code></a></h3><p> |
| 5801 <span class="apii">[-0, +0, –]</span> |
| 5802 <pre>void luaL_buffinit (lua_State *L, luaL_Buffer *B);</pre> |
| 5803 |
| 5804 <p> |
| 5805 Initializes a buffer <code>B</code>. |
| 5806 This function does not allocate any space; |
| 5807 the buffer must be declared as a variable |
| 5808 (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>). |
| 5809 |
| 5810 |
| 5811 |
| 5812 |
| 5813 |
| 5814 <hr><h3><a name="luaL_buffinitsize"><code>luaL_buffinitsize</code></a></h3><p> |
| 5815 <span class="apii">[-?, +?, <em>e</em>]</span> |
| 5816 <pre>char *luaL_buffinitsize (lua_State *L, luaL_Buffer *B, size_t sz);</pre> |
| 5817 |
| 5818 <p> |
| 5819 Equivalent to the sequence |
| 5820 <a href="#luaL_buffinit"><code>luaL_buffinit</code></a>, <a href="#luaL_prepbuff
size"><code>luaL_prepbuffsize</code></a>. |
| 5821 |
| 5822 |
| 5823 |
| 5824 |
| 5825 |
| 5826 <hr><h3><a name="luaL_callmeta"><code>luaL_callmeta</code></a></h3><p> |
| 5827 <span class="apii">[-0, +(0|1), <em>e</em>]</span> |
| 5828 <pre>int luaL_callmeta (lua_State *L, int obj, const char *e);</pre> |
| 5829 |
| 5830 <p> |
| 5831 Calls a metamethod. |
| 5832 |
| 5833 |
| 5834 <p> |
| 5835 If the object at index <code>obj</code> has a metatable and this |
| 5836 metatable has a field <code>e</code>, |
| 5837 this function calls this field passing the object as its only argument. |
| 5838 In this case this function returns true and pushes onto the |
| 5839 stack the value returned by the call. |
| 5840 If there is no metatable or no metamethod, |
| 5841 this function returns false (without pushing any value on the stack). |
| 5842 |
| 5843 |
| 5844 |
| 5845 |
| 5846 |
| 5847 <hr><h3><a name="luaL_checkany"><code>luaL_checkany</code></a></h3><p> |
| 5848 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 5849 <pre>void luaL_checkany (lua_State *L, int arg);</pre> |
| 5850 |
| 5851 <p> |
| 5852 Checks whether the function has an argument |
| 5853 of any type (including <b>nil</b>) at position <code>arg</code>. |
| 5854 |
| 5855 |
| 5856 |
| 5857 |
| 5858 |
| 5859 <hr><h3><a name="luaL_checkint"><code>luaL_checkint</code></a></h3><p> |
| 5860 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 5861 <pre>int luaL_checkint (lua_State *L, int arg);</pre> |
| 5862 |
| 5863 <p> |
| 5864 Checks whether the function argument <code>arg</code> is a number |
| 5865 and returns this number cast to an <code>int</code>. |
| 5866 |
| 5867 |
| 5868 |
| 5869 |
| 5870 |
| 5871 <hr><h3><a name="luaL_checkinteger"><code>luaL_checkinteger</code></a></h3><p> |
| 5872 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 5873 <pre>lua_Integer luaL_checkinteger (lua_State *L, int arg);</pre> |
| 5874 |
| 5875 <p> |
| 5876 Checks whether the function argument <code>arg</code> is a number |
| 5877 and returns this number cast to a <a href="#lua_Integer"><code>lua_Integer</code
></a>. |
| 5878 |
| 5879 |
| 5880 |
| 5881 |
| 5882 |
| 5883 <hr><h3><a name="luaL_checklong"><code>luaL_checklong</code></a></h3><p> |
| 5884 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 5885 <pre>long luaL_checklong (lua_State *L, int arg);</pre> |
| 5886 |
| 5887 <p> |
| 5888 Checks whether the function argument <code>arg</code> is a number |
| 5889 and returns this number cast to a <code>long</code>. |
| 5890 |
| 5891 |
| 5892 |
| 5893 |
| 5894 |
| 5895 <hr><h3><a name="luaL_checklstring"><code>luaL_checklstring</code></a></h3><p> |
| 5896 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 5897 <pre>const char *luaL_checklstring (lua_State *L, int arg, size_t *l);</pre> |
| 5898 |
| 5899 <p> |
| 5900 Checks whether the function argument <code>arg</code> is a string |
| 5901 and returns this string; |
| 5902 if <code>l</code> is not <code>NULL</code> fills <code>*l</code> |
| 5903 with the string's length. |
| 5904 |
| 5905 |
| 5906 <p> |
| 5907 This function uses <a href="#lua_tolstring"><code>lua_tolstring</code></a> to ge
t its result, |
| 5908 so all conversions and caveats of that function apply here. |
| 5909 |
| 5910 |
| 5911 |
| 5912 |
| 5913 |
| 5914 <hr><h3><a name="luaL_checknumber"><code>luaL_checknumber</code></a></h3><p> |
| 5915 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 5916 <pre>lua_Number luaL_checknumber (lua_State *L, int arg);</pre> |
| 5917 |
| 5918 <p> |
| 5919 Checks whether the function argument <code>arg</code> is a number |
| 5920 and returns this number. |
| 5921 |
| 5922 |
| 5923 |
| 5924 |
| 5925 |
| 5926 <hr><h3><a name="luaL_checkoption"><code>luaL_checkoption</code></a></h3><p> |
| 5927 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 5928 <pre>int luaL_checkoption (lua_State *L, |
| 5929 int arg, |
| 5930 const char *def, |
| 5931 const char *const lst[]);</pre> |
| 5932 |
| 5933 <p> |
| 5934 Checks whether the function argument <code>arg</code> is a string and |
| 5935 searches for this string in the array <code>lst</code> |
| 5936 (which must be NULL-terminated). |
| 5937 Returns the index in the array where the string was found. |
| 5938 Raises an error if the argument is not a string or |
| 5939 if the string cannot be found. |
| 5940 |
| 5941 |
| 5942 <p> |
| 5943 If <code>def</code> is not <code>NULL</code>, |
| 5944 the function uses <code>def</code> as a default value when |
| 5945 there is no argument <code>arg</code> or when this argument is <b>nil</b>. |
| 5946 |
| 5947 |
| 5948 <p> |
| 5949 This is a useful function for mapping strings to C enums. |
| 5950 (The usual convention in Lua libraries is |
| 5951 to use strings instead of numbers to select options.) |
| 5952 |
| 5953 |
| 5954 |
| 5955 |
| 5956 |
| 5957 <hr><h3><a name="luaL_checkstack"><code>luaL_checkstack</code></a></h3><p> |
| 5958 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 5959 <pre>void luaL_checkstack (lua_State *L, int sz, const char *msg);</pre> |
| 5960 |
| 5961 <p> |
| 5962 Grows the stack size to <code>top + sz</code> elements, |
| 5963 raising an error if the stack cannot grow to that size. |
| 5964 <code>msg</code> is an additional text to go into the error message |
| 5965 (or <code>NULL</code> for no additional text). |
| 5966 |
| 5967 |
| 5968 |
| 5969 |
| 5970 |
| 5971 <hr><h3><a name="luaL_checkstring"><code>luaL_checkstring</code></a></h3><p> |
| 5972 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 5973 <pre>const char *luaL_checkstring (lua_State *L, int arg);</pre> |
| 5974 |
| 5975 <p> |
| 5976 Checks whether the function argument <code>arg</code> is a string |
| 5977 and returns this string. |
| 5978 |
| 5979 |
| 5980 <p> |
| 5981 This function uses <a href="#lua_tolstring"><code>lua_tolstring</code></a> to ge
t its result, |
| 5982 so all conversions and caveats of that function apply here. |
| 5983 |
| 5984 |
| 5985 |
| 5986 |
| 5987 |
| 5988 <hr><h3><a name="luaL_checktype"><code>luaL_checktype</code></a></h3><p> |
| 5989 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 5990 <pre>void luaL_checktype (lua_State *L, int arg, int t);</pre> |
| 5991 |
| 5992 <p> |
| 5993 Checks whether the function argument <code>arg</code> has type <code>t</code>. |
| 5994 See <a href="#lua_type"><code>lua_type</code></a> for the encoding of types for
<code>t</code>. |
| 5995 |
| 5996 |
| 5997 |
| 5998 |
| 5999 |
| 6000 <hr><h3><a name="luaL_checkudata"><code>luaL_checkudata</code></a></h3><p> |
| 6001 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 6002 <pre>void *luaL_checkudata (lua_State *L, int arg, const char *tname);</pre> |
| 6003 |
| 6004 <p> |
| 6005 Checks whether the function argument <code>arg</code> is a userdata |
| 6006 of the type <code>tname</code> (see <a href="#luaL_newmetatable"><code>luaL_newm
etatable</code></a>) and |
| 6007 returns the userdata address (see <a href="#lua_touserdata"><code>lua_touserdata
</code></a>). |
| 6008 |
| 6009 |
| 6010 |
| 6011 |
| 6012 |
| 6013 <hr><h3><a name="luaL_checkunsigned"><code>luaL_checkunsigned</code></a></h3><p> |
| 6014 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 6015 <pre>lua_Unsigned luaL_checkunsigned (lua_State *L, int arg);</pre> |
| 6016 |
| 6017 <p> |
| 6018 Checks whether the function argument <code>arg</code> is a number |
| 6019 and returns this number cast to a <a href="#lua_Unsigned"><code>lua_Unsigned</co
de></a>. |
| 6020 |
| 6021 |
| 6022 |
| 6023 |
| 6024 |
| 6025 <hr><h3><a name="luaL_checkversion"><code>luaL_checkversion</code></a></h3><p> |
| 6026 <span class="apii">[-0, +0, –]</span> |
| 6027 <pre>void luaL_checkversion (lua_State *L);</pre> |
| 6028 |
| 6029 <p> |
| 6030 Checks whether the core running the call, |
| 6031 the core that created the Lua state, |
| 6032 and the code making the call are all using the same version of Lua. |
| 6033 Also checks whether the core running the call |
| 6034 and the core that created the Lua state |
| 6035 are using the same address space. |
| 6036 |
| 6037 |
| 6038 |
| 6039 |
| 6040 |
| 6041 <hr><h3><a name="luaL_dofile"><code>luaL_dofile</code></a></h3><p> |
| 6042 <span class="apii">[-0, +?, <em>e</em>]</span> |
| 6043 <pre>int luaL_dofile (lua_State *L, const char *filename);</pre> |
| 6044 |
| 6045 <p> |
| 6046 Loads and runs the given file. |
| 6047 It is defined as the following macro: |
| 6048 |
| 6049 <pre> |
| 6050 (luaL_loadfile(L, filename) || lua_pcall(L, 0, LUA_MULTRET, 0)) |
| 6051 </pre><p> |
| 6052 It returns false if there are no errors |
| 6053 or true in case of errors. |
| 6054 |
| 6055 |
| 6056 |
| 6057 |
| 6058 |
| 6059 <hr><h3><a name="luaL_dostring"><code>luaL_dostring</code></a></h3><p> |
| 6060 <span class="apii">[-0, +?, –]</span> |
| 6061 <pre>int luaL_dostring (lua_State *L, const char *str);</pre> |
| 6062 |
| 6063 <p> |
| 6064 Loads and runs the given string. |
| 6065 It is defined as the following macro: |
| 6066 |
| 6067 <pre> |
| 6068 (luaL_loadstring(L, str) || lua_pcall(L, 0, LUA_MULTRET, 0)) |
| 6069 </pre><p> |
| 6070 It returns false if there are no errors |
| 6071 or true in case of errors. |
| 6072 |
| 6073 |
| 6074 |
| 6075 |
| 6076 |
| 6077 <hr><h3><a name="luaL_error"><code>luaL_error</code></a></h3><p> |
| 6078 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 6079 <pre>int luaL_error (lua_State *L, const char *fmt, ...);</pre> |
| 6080 |
| 6081 <p> |
| 6082 Raises an error. |
| 6083 The error message format is given by <code>fmt</code> |
| 6084 plus any extra arguments, |
| 6085 following the same rules of <a href="#lua_pushfstring"><code>lua_pushfstring</co
de></a>. |
| 6086 It also adds at the beginning of the message the file name and |
| 6087 the line number where the error occurred, |
| 6088 if this information is available. |
| 6089 |
| 6090 |
| 6091 <p> |
| 6092 This function never returns, |
| 6093 but it is an idiom to use it in C functions |
| 6094 as <code>return luaL_error(<em>args</em>)</code>. |
| 6095 |
| 6096 |
| 6097 |
| 6098 |
| 6099 |
| 6100 <hr><h3><a name="luaL_execresult"><code>luaL_execresult</code></a></h3><p> |
| 6101 <span class="apii">[-0, +3, <em>e</em>]</span> |
| 6102 <pre>int luaL_execresult (lua_State *L, int stat);</pre> |
| 6103 |
| 6104 <p> |
| 6105 This function produces the return values for |
| 6106 process-related functions in the standard library |
| 6107 (<a href="#pdf-os.execute"><code>os.execute</code></a> and <a href="#pdf-io.clos
e"><code>io.close</code></a>). |
| 6108 |
| 6109 |
| 6110 |
| 6111 |
| 6112 |
| 6113 <hr><h3><a name="luaL_fileresult"><code>luaL_fileresult</code></a></h3><p> |
| 6114 <span class="apii">[-0, +(1|3), <em>e</em>]</span> |
| 6115 <pre>int luaL_fileresult (lua_State *L, int stat, const char *fname);</pre> |
| 6116 |
| 6117 <p> |
| 6118 This function produces the return values for |
| 6119 file-related functions in the standard library |
| 6120 (<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.
). |
| 6121 |
| 6122 |
| 6123 |
| 6124 |
| 6125 |
| 6126 <hr><h3><a name="luaL_getmetafield"><code>luaL_getmetafield</code></a></h3><p> |
| 6127 <span class="apii">[-0, +(0|1), <em>e</em>]</span> |
| 6128 <pre>int luaL_getmetafield (lua_State *L, int obj, const char *e);</pre> |
| 6129 |
| 6130 <p> |
| 6131 Pushes onto the stack the field <code>e</code> from the metatable |
| 6132 of the object at index <code>obj</code>. |
| 6133 If the object does not have a metatable, |
| 6134 or if the metatable does not have this field, |
| 6135 returns false and pushes nothing. |
| 6136 |
| 6137 |
| 6138 |
| 6139 |
| 6140 |
| 6141 <hr><h3><a name="luaL_getmetatable"><code>luaL_getmetatable</code></a></h3><p> |
| 6142 <span class="apii">[-0, +1, –]</span> |
| 6143 <pre>void luaL_getmetatable (lua_State *L, const char *tname);</pre> |
| 6144 |
| 6145 <p> |
| 6146 Pushes onto the stack the metatable associated with name <code>tname</code> |
| 6147 in the registry (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code>
</a>). |
| 6148 |
| 6149 |
| 6150 |
| 6151 |
| 6152 |
| 6153 <hr><h3><a name="luaL_getsubtable"><code>luaL_getsubtable</code></a></h3><p> |
| 6154 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 6155 <pre>int luaL_getsubtable (lua_State *L, int idx, const char *fname);</pre> |
| 6156 |
| 6157 <p> |
| 6158 Ensures that the value <code>t[fname]</code>, |
| 6159 where <code>t</code> is the value at index <code>idx</code>, |
| 6160 is a table, |
| 6161 and pushes that table onto the stack. |
| 6162 Returns true if it finds a previous table there |
| 6163 and false if it creates a new table. |
| 6164 |
| 6165 |
| 6166 |
| 6167 |
| 6168 |
| 6169 <hr><h3><a name="luaL_gsub"><code>luaL_gsub</code></a></h3><p> |
| 6170 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 6171 <pre>const char *luaL_gsub (lua_State *L, |
| 6172 const char *s, |
| 6173 const char *p, |
| 6174 const char *r);</pre> |
| 6175 |
| 6176 <p> |
| 6177 Creates a copy of string <code>s</code> by replacing |
| 6178 any occurrence of the string <code>p</code> |
| 6179 with the string <code>r</code>. |
| 6180 Pushes the resulting string on the stack and returns it. |
| 6181 |
| 6182 |
| 6183 |
| 6184 |
| 6185 |
| 6186 <hr><h3><a name="luaL_len"><code>luaL_len</code></a></h3><p> |
| 6187 <span class="apii">[-0, +0, <em>e</em>]</span> |
| 6188 <pre>int luaL_len (lua_State *L, int index);</pre> |
| 6189 |
| 6190 <p> |
| 6191 Returns the "length" of the value at the given index |
| 6192 as a number; |
| 6193 it is equivalent to the '<code>#</code>' operator in Lua (see <a href="#3.4.6">&
sect;3.4.6</a>). |
| 6194 Raises an error if the result of the operation is not a number. |
| 6195 (This case only can happen through metamethods.) |
| 6196 |
| 6197 |
| 6198 |
| 6199 |
| 6200 |
| 6201 <hr><h3><a name="luaL_loadbuffer"><code>luaL_loadbuffer</code></a></h3><p> |
| 6202 <span class="apii">[-0, +1, –]</span> |
| 6203 <pre>int luaL_loadbuffer (lua_State *L, |
| 6204 const char *buff, |
| 6205 size_t sz, |
| 6206 const char *name);</pre> |
| 6207 |
| 6208 <p> |
| 6209 Equivalent to <a href="#luaL_loadbufferx"><code>luaL_loadbufferx</code></a> with
<code>mode</code> equal to <code>NULL</code>. |
| 6210 |
| 6211 |
| 6212 |
| 6213 |
| 6214 |
| 6215 <hr><h3><a name="luaL_loadbufferx"><code>luaL_loadbufferx</code></a></h3><p> |
| 6216 <span class="apii">[-0, +1, –]</span> |
| 6217 <pre>int luaL_loadbufferx (lua_State *L, |
| 6218 const char *buff, |
| 6219 size_t sz, |
| 6220 const char *name, |
| 6221 const char *mode);</pre> |
| 6222 |
| 6223 <p> |
| 6224 Loads a buffer as a Lua chunk. |
| 6225 This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chu
nk in the |
| 6226 buffer pointed to by <code>buff</code> with size <code>sz</code>. |
| 6227 |
| 6228 |
| 6229 <p> |
| 6230 This function returns the same results as <a href="#lua_load"><code>lua_load</co
de></a>. |
| 6231 <code>name</code> is the chunk name, |
| 6232 used for debug information and error messages. |
| 6233 The string <code>mode</code> works as in function <a href="#lua_load"><code>lua_
load</code></a>. |
| 6234 |
| 6235 |
| 6236 |
| 6237 |
| 6238 |
| 6239 <hr><h3><a name="luaL_loadfile"><code>luaL_loadfile</code></a></h3><p> |
| 6240 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 6241 <pre>int luaL_loadfile (lua_State *L, const char *filename);</pre> |
| 6242 |
| 6243 <p> |
| 6244 Equivalent to <a href="#luaL_loadfilex"><code>luaL_loadfilex</code></a> with <co
de>mode</code> equal to <code>NULL</code>. |
| 6245 |
| 6246 |
| 6247 |
| 6248 |
| 6249 |
| 6250 <hr><h3><a name="luaL_loadfilex"><code>luaL_loadfilex</code></a></h3><p> |
| 6251 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 6252 <pre>int luaL_loadfilex (lua_State *L, const char *filename, |
| 6253 const char *mode);</pre> |
| 6254 |
| 6255 <p> |
| 6256 Loads a file as a Lua chunk. |
| 6257 This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chu
nk in the file |
| 6258 named <code>filename</code>. |
| 6259 If <code>filename</code> is <code>NULL</code>, |
| 6260 then it loads from the standard input. |
| 6261 The first line in the file is ignored if it starts with a <code>#</code>. |
| 6262 |
| 6263 |
| 6264 <p> |
| 6265 The string <code>mode</code> works as in function <a href="#lua_load"><code>lua_
load</code></a>. |
| 6266 |
| 6267 |
| 6268 <p> |
| 6269 This function returns the same results as <a href="#lua_load"><code>lua_load</co
de></a>, |
| 6270 but it has an extra error code <a name="pdf-LUA_ERRFILE"><code>LUA_ERRFILE</code
></a> |
| 6271 if it cannot open/read the file or the file has a wrong mode. |
| 6272 |
| 6273 |
| 6274 <p> |
| 6275 As <a href="#lua_load"><code>lua_load</code></a>, this function only loads the c
hunk; |
| 6276 it does not run it. |
| 6277 |
| 6278 |
| 6279 |
| 6280 |
| 6281 |
| 6282 <hr><h3><a name="luaL_loadstring"><code>luaL_loadstring</code></a></h3><p> |
| 6283 <span class="apii">[-0, +1, –]</span> |
| 6284 <pre>int luaL_loadstring (lua_State *L, const char *s);</pre> |
| 6285 |
| 6286 <p> |
| 6287 Loads a string as a Lua chunk. |
| 6288 This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chu
nk in |
| 6289 the zero-terminated string <code>s</code>. |
| 6290 |
| 6291 |
| 6292 <p> |
| 6293 This function returns the same results as <a href="#lua_load"><code>lua_load</co
de></a>. |
| 6294 |
| 6295 |
| 6296 <p> |
| 6297 Also as <a href="#lua_load"><code>lua_load</code></a>, this function only loads
the chunk; |
| 6298 it does not run it. |
| 6299 |
| 6300 |
| 6301 |
| 6302 |
| 6303 |
| 6304 <hr><h3><a name="luaL_newlib"><code>luaL_newlib</code></a></h3><p> |
| 6305 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 6306 <pre>void luaL_newlib (lua_State *L, const luaL_Reg *l);</pre> |
| 6307 |
| 6308 <p> |
| 6309 Creates a new table and registers there |
| 6310 the functions in list <code>l</code>. |
| 6311 It is implemented as the following macro: |
| 6312 |
| 6313 <pre> |
| 6314 (luaL_newlibtable(L,l), luaL_setfuncs(L,l,0)) |
| 6315 </pre> |
| 6316 |
| 6317 |
| 6318 |
| 6319 |
| 6320 <hr><h3><a name="luaL_newlibtable"><code>luaL_newlibtable</code></a></h3><p> |
| 6321 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 6322 <pre>void luaL_newlibtable (lua_State *L, const luaL_Reg l[]);</pre> |
| 6323 |
| 6324 <p> |
| 6325 Creates a new table with a size optimized |
| 6326 to store all entries in the array <code>l</code> |
| 6327 (but does not actually store them). |
| 6328 It is intended to be used in conjunction with <a href="#luaL_setfuncs"><code>lua
L_setfuncs</code></a> |
| 6329 (see <a href="#luaL_newlib"><code>luaL_newlib</code></a>). |
| 6330 |
| 6331 |
| 6332 <p> |
| 6333 It is implemented as a macro. |
| 6334 The array <code>l</code> must be the actual array, |
| 6335 not a pointer to it. |
| 6336 |
| 6337 |
| 6338 |
| 6339 |
| 6340 |
| 6341 <hr><h3><a name="luaL_newmetatable"><code>luaL_newmetatable</code></a></h3><p> |
| 6342 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 6343 <pre>int luaL_newmetatable (lua_State *L, const char *tname);</pre> |
| 6344 |
| 6345 <p> |
| 6346 If the registry already has the key <code>tname</code>, |
| 6347 returns 0. |
| 6348 Otherwise, |
| 6349 creates a new table to be used as a metatable for userdata, |
| 6350 adds it to the registry with key <code>tname</code>, |
| 6351 and returns 1. |
| 6352 |
| 6353 |
| 6354 <p> |
| 6355 In both cases pushes onto the stack the final value associated |
| 6356 with <code>tname</code> in the registry. |
| 6357 |
| 6358 |
| 6359 |
| 6360 |
| 6361 |
| 6362 <hr><h3><a name="luaL_newstate"><code>luaL_newstate</code></a></h3><p> |
| 6363 <span class="apii">[-0, +0, –]</span> |
| 6364 <pre>lua_State *luaL_newstate (void);</pre> |
| 6365 |
| 6366 <p> |
| 6367 Creates a new Lua state. |
| 6368 It calls <a href="#lua_newstate"><code>lua_newstate</code></a> with an |
| 6369 allocator based on the standard C <code>realloc</code> function |
| 6370 and then sets a panic function (see <a href="#4.6">§4.6</a>) that prints |
| 6371 an error message to the standard error output in case of fatal |
| 6372 errors. |
| 6373 |
| 6374 |
| 6375 <p> |
| 6376 Returns the new state, |
| 6377 or <code>NULL</code> if there is a memory allocation error. |
| 6378 |
| 6379 |
| 6380 |
| 6381 |
| 6382 |
| 6383 <hr><h3><a name="luaL_openlibs"><code>luaL_openlibs</code></a></h3><p> |
| 6384 <span class="apii">[-0, +0, <em>e</em>]</span> |
| 6385 <pre>void luaL_openlibs (lua_State *L);</pre> |
| 6386 |
| 6387 <p> |
| 6388 Opens all standard Lua libraries into the given state. |
| 6389 |
| 6390 |
| 6391 |
| 6392 |
| 6393 |
| 6394 <hr><h3><a name="luaL_optint"><code>luaL_optint</code></a></h3><p> |
| 6395 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 6396 <pre>int luaL_optint (lua_State *L, int arg, int d);</pre> |
| 6397 |
| 6398 <p> |
| 6399 If the function argument <code>arg</code> is a number, |
| 6400 returns this number cast to an <code>int</code>. |
| 6401 If this argument is absent or is <b>nil</b>, |
| 6402 returns <code>d</code>. |
| 6403 Otherwise, raises an error. |
| 6404 |
| 6405 |
| 6406 |
| 6407 |
| 6408 |
| 6409 <hr><h3><a name="luaL_optinteger"><code>luaL_optinteger</code></a></h3><p> |
| 6410 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 6411 <pre>lua_Integer luaL_optinteger (lua_State *L, |
| 6412 int arg, |
| 6413 lua_Integer d);</pre> |
| 6414 |
| 6415 <p> |
| 6416 If the function argument <code>arg</code> is a number, |
| 6417 returns this number cast to a <a href="#lua_Integer"><code>lua_Integer</code></a
>. |
| 6418 If this argument is absent or is <b>nil</b>, |
| 6419 returns <code>d</code>. |
| 6420 Otherwise, raises an error. |
| 6421 |
| 6422 |
| 6423 |
| 6424 |
| 6425 |
| 6426 <hr><h3><a name="luaL_optlong"><code>luaL_optlong</code></a></h3><p> |
| 6427 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 6428 <pre>long luaL_optlong (lua_State *L, int arg, long d);</pre> |
| 6429 |
| 6430 <p> |
| 6431 If the function argument <code>arg</code> is a number, |
| 6432 returns this number cast to a <code>long</code>. |
| 6433 If this argument is absent or is <b>nil</b>, |
| 6434 returns <code>d</code>. |
| 6435 Otherwise, raises an error. |
| 6436 |
| 6437 |
| 6438 |
| 6439 |
| 6440 |
| 6441 <hr><h3><a name="luaL_optlstring"><code>luaL_optlstring</code></a></h3><p> |
| 6442 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 6443 <pre>const char *luaL_optlstring (lua_State *L, |
| 6444 int arg, |
| 6445 const char *d, |
| 6446 size_t *l);</pre> |
| 6447 |
| 6448 <p> |
| 6449 If the function argument <code>arg</code> is a string, |
| 6450 returns this string. |
| 6451 If this argument is absent or is <b>nil</b>, |
| 6452 returns <code>d</code>. |
| 6453 Otherwise, raises an error. |
| 6454 |
| 6455 |
| 6456 <p> |
| 6457 If <code>l</code> is not <code>NULL</code>, |
| 6458 fills the position <code>*l</code> with the result's length. |
| 6459 |
| 6460 |
| 6461 |
| 6462 |
| 6463 |
| 6464 <hr><h3><a name="luaL_optnumber"><code>luaL_optnumber</code></a></h3><p> |
| 6465 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 6466 <pre>lua_Number luaL_optnumber (lua_State *L, int arg, lua_Number d);</pre> |
| 6467 |
| 6468 <p> |
| 6469 If the function argument <code>arg</code> is a number, |
| 6470 returns this number. |
| 6471 If this argument is absent or is <b>nil</b>, |
| 6472 returns <code>d</code>. |
| 6473 Otherwise, raises an error. |
| 6474 |
| 6475 |
| 6476 |
| 6477 |
| 6478 |
| 6479 <hr><h3><a name="luaL_optstring"><code>luaL_optstring</code></a></h3><p> |
| 6480 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 6481 <pre>const char *luaL_optstring (lua_State *L, |
| 6482 int arg, |
| 6483 const char *d);</pre> |
| 6484 |
| 6485 <p> |
| 6486 If the function argument <code>arg</code> is a string, |
| 6487 returns this string. |
| 6488 If this argument is absent or is <b>nil</b>, |
| 6489 returns <code>d</code>. |
| 6490 Otherwise, raises an error. |
| 6491 |
| 6492 |
| 6493 |
| 6494 |
| 6495 |
| 6496 <hr><h3><a name="luaL_optunsigned"><code>luaL_optunsigned</code></a></h3><p> |
| 6497 <span class="apii">[-0, +0, <em>v</em>]</span> |
| 6498 <pre>lua_Unsigned luaL_optunsigned (lua_State *L, |
| 6499 int arg, |
| 6500 lua_Unsigned u);</pre> |
| 6501 |
| 6502 <p> |
| 6503 If the function argument <code>arg</code> is a number, |
| 6504 returns this number cast to a <a href="#lua_Unsigned"><code>lua_Unsigned</code><
/a>. |
| 6505 If this argument is absent or is <b>nil</b>, |
| 6506 returns <code>u</code>. |
| 6507 Otherwise, raises an error. |
| 6508 |
| 6509 |
| 6510 |
| 6511 |
| 6512 |
| 6513 <hr><h3><a name="luaL_prepbuffer"><code>luaL_prepbuffer</code></a></h3><p> |
| 6514 <span class="apii">[-?, +?, <em>e</em>]</span> |
| 6515 <pre>char *luaL_prepbuffer (luaL_Buffer *B);</pre> |
| 6516 |
| 6517 <p> |
| 6518 Equivalent to <a href="#luaL_prepbuffsize"><code>luaL_prepbuffsize</code></a> |
| 6519 with the predefined size <a name="pdf-LUAL_BUFFERSIZE"><code>LUAL_BUFFERSIZE</co
de></a>. |
| 6520 |
| 6521 |
| 6522 |
| 6523 |
| 6524 |
| 6525 <hr><h3><a name="luaL_prepbuffsize"><code>luaL_prepbuffsize</code></a></h3><p> |
| 6526 <span class="apii">[-?, +?, <em>e</em>]</span> |
| 6527 <pre>char *luaL_prepbuffsize (luaL_Buffer *B, size_t sz);</pre> |
| 6528 |
| 6529 <p> |
| 6530 Returns an address to a space of size <code>sz</code> |
| 6531 where you can copy a string to be added to buffer <code>B</code> |
| 6532 (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>). |
| 6533 After copying the string into this space you must call |
| 6534 <a href="#luaL_addsize"><code>luaL_addsize</code></a> with the size of the strin
g to actually add |
| 6535 it to the buffer. |
| 6536 |
| 6537 |
| 6538 |
| 6539 |
| 6540 |
| 6541 <hr><h3><a name="luaL_pushresult"><code>luaL_pushresult</code></a></h3><p> |
| 6542 <span class="apii">[-?, +1, <em>e</em>]</span> |
| 6543 <pre>void luaL_pushresult (luaL_Buffer *B);</pre> |
| 6544 |
| 6545 <p> |
| 6546 Finishes the use of buffer <code>B</code> leaving the final string on |
| 6547 the top of the stack. |
| 6548 |
| 6549 |
| 6550 |
| 6551 |
| 6552 |
| 6553 <hr><h3><a name="luaL_pushresultsize"><code>luaL_pushresultsize</code></a></h3><
p> |
| 6554 <span class="apii">[-?, +1, <em>e</em>]</span> |
| 6555 <pre>void luaL_pushresultsize (luaL_Buffer *B, size_t sz);</pre> |
| 6556 |
| 6557 <p> |
| 6558 Equivalent to the sequence <a href="#luaL_addsize"><code>luaL_addsize</code></a>
, <a href="#luaL_pushresult"><code>luaL_pushresult</code></a>. |
| 6559 |
| 6560 |
| 6561 |
| 6562 |
| 6563 |
| 6564 <hr><h3><a name="luaL_ref"><code>luaL_ref</code></a></h3><p> |
| 6565 <span class="apii">[-1, +0, <em>e</em>]</span> |
| 6566 <pre>int luaL_ref (lua_State *L, int t);</pre> |
| 6567 |
| 6568 <p> |
| 6569 Creates and returns a <em>reference</em>, |
| 6570 in the table at index <code>t</code>, |
| 6571 for the object at the top of the stack (and pops the object). |
| 6572 |
| 6573 |
| 6574 <p> |
| 6575 A reference is a unique integer key. |
| 6576 As long as you do not manually add integer keys into table <code>t</code>, |
| 6577 <a href="#luaL_ref"><code>luaL_ref</code></a> ensures the uniqueness of the key
it returns. |
| 6578 You can retrieve an object referred by reference <code>r</code> |
| 6579 by calling <code>lua_rawgeti(L, t, r)</code>. |
| 6580 Function <a href="#luaL_unref"><code>luaL_unref</code></a> frees a reference and
its associated object. |
| 6581 |
| 6582 |
| 6583 <p> |
| 6584 If the object at the top of the stack is <b>nil</b>, |
| 6585 <a href="#luaL_ref"><code>luaL_ref</code></a> returns the constant <a name="pdf-
LUA_REFNIL"><code>LUA_REFNIL</code></a>. |
| 6586 The constant <a name="pdf-LUA_NOREF"><code>LUA_NOREF</code></a> is guaranteed to
be different |
| 6587 from any reference returned by <a href="#luaL_ref"><code>luaL_ref</code></a>. |
| 6588 |
| 6589 |
| 6590 |
| 6591 |
| 6592 |
| 6593 <hr><h3><a name="luaL_Reg"><code>luaL_Reg</code></a></h3> |
| 6594 <pre>typedef struct luaL_Reg { |
| 6595 const char *name; |
| 6596 lua_CFunction func; |
| 6597 } luaL_Reg;</pre> |
| 6598 |
| 6599 <p> |
| 6600 Type for arrays of functions to be registered by |
| 6601 <a href="#luaL_setfuncs"><code>luaL_setfuncs</code></a>. |
| 6602 <code>name</code> is the function name and <code>func</code> is a pointer to |
| 6603 the function. |
| 6604 Any array of <a href="#luaL_Reg"><code>luaL_Reg</code></a> must end with an sent
inel entry |
| 6605 in which both <code>name</code> and <code>func</code> are <code>NULL</code>. |
| 6606 |
| 6607 |
| 6608 |
| 6609 |
| 6610 |
| 6611 <hr><h3><a name="luaL_requiref"><code>luaL_requiref</code></a></h3><p> |
| 6612 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 6613 <pre>void luaL_requiref (lua_State *L, const char *modname, |
| 6614 lua_CFunction openf, int glb);</pre> |
| 6615 |
| 6616 <p> |
| 6617 Calls function <code>openf</code> with string <code>modname</code> as an argumen
t |
| 6618 and sets the call result in <code>package.loaded[modname]</code>, |
| 6619 as if that function has been called through <a href="#pdf-require"><code>require
</code></a>. |
| 6620 |
| 6621 |
| 6622 <p> |
| 6623 If <code>glb</code> is true, |
| 6624 also stores the result into global <code>modname</code>. |
| 6625 |
| 6626 |
| 6627 <p> |
| 6628 Leaves a copy of that result on the stack. |
| 6629 |
| 6630 |
| 6631 |
| 6632 |
| 6633 |
| 6634 <hr><h3><a name="luaL_setfuncs"><code>luaL_setfuncs</code></a></h3><p> |
| 6635 <span class="apii">[-nup, +0, <em>e</em>]</span> |
| 6636 <pre>void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup);</pre> |
| 6637 |
| 6638 <p> |
| 6639 Registers all functions in the array <code>l</code> |
| 6640 (see <a href="#luaL_Reg"><code>luaL_Reg</code></a>) into the table on the top of
the stack |
| 6641 (below optional upvalues, see next). |
| 6642 |
| 6643 |
| 6644 <p> |
| 6645 When <code>nup</code> is not zero, |
| 6646 all functions are created sharing <code>nup</code> upvalues, |
| 6647 which must be previously pushed on the stack |
| 6648 on top of the library table. |
| 6649 These values are popped from the stack after the registration. |
| 6650 |
| 6651 |
| 6652 |
| 6653 |
| 6654 |
| 6655 <hr><h3><a name="luaL_setmetatable"><code>luaL_setmetatable</code></a></h3><p> |
| 6656 <span class="apii">[-0, +0, –]</span> |
| 6657 <pre>void luaL_setmetatable (lua_State *L, const char *tname);</pre> |
| 6658 |
| 6659 <p> |
| 6660 Sets the metatable of the object at the top of the stack |
| 6661 as the metatable associated with name <code>tname</code> |
| 6662 in the registry (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code>
</a>). |
| 6663 |
| 6664 |
| 6665 |
| 6666 |
| 6667 |
| 6668 <hr><h3><a name="luaL_testudata"><code>luaL_testudata</code></a></h3><p> |
| 6669 <span class="apii">[-0, +0, <em>e</em>]</span> |
| 6670 <pre>void *luaL_testudata (lua_State *L, int arg, const char *tname);</pre> |
| 6671 |
| 6672 <p> |
| 6673 This function works like <a href="#luaL_checkudata"><code>luaL_checkudata</code>
</a>, |
| 6674 except that, when the test fails, |
| 6675 it returns <code>NULL</code> instead of throwing an error. |
| 6676 |
| 6677 |
| 6678 |
| 6679 |
| 6680 |
| 6681 <hr><h3><a name="luaL_tolstring"><code>luaL_tolstring</code></a></h3><p> |
| 6682 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 6683 <pre>const char *luaL_tolstring (lua_State *L, int idx, size_t *len);</pre> |
| 6684 |
| 6685 <p> |
| 6686 Converts any Lua value at the given index to a C string |
| 6687 in a reasonable format. |
| 6688 The resulting string is pushed onto the stack and also |
| 6689 returned by the function. |
| 6690 If <code>len</code> is not <code>NULL</code>, |
| 6691 the function also sets <code>*len</code> with the string length. |
| 6692 |
| 6693 |
| 6694 <p> |
| 6695 If the value has a metatable with a <code>"__tostring"</code> field, |
| 6696 then <code>luaL_tolstring</code> calls the corresponding metamethod |
| 6697 with the value as argument, |
| 6698 and uses the result of the call as its result. |
| 6699 |
| 6700 |
| 6701 |
| 6702 |
| 6703 |
| 6704 <hr><h3><a name="luaL_traceback"><code>luaL_traceback</code></a></h3><p> |
| 6705 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 6706 <pre>void luaL_traceback (lua_State *L, lua_State *L1, const char *msg, |
| 6707 int level);</pre> |
| 6708 |
| 6709 <p> |
| 6710 Creates and pushes a traceback of the stack <code>L1</code>. |
| 6711 If <code>msg</code> is not <code>NULL</code> it is appended |
| 6712 at the beginning of the traceback. |
| 6713 The <code>level</code> parameter tells at which level |
| 6714 to start the traceback. |
| 6715 |
| 6716 |
| 6717 |
| 6718 |
| 6719 |
| 6720 <hr><h3><a name="luaL_typename"><code>luaL_typename</code></a></h3><p> |
| 6721 <span class="apii">[-0, +0, –]</span> |
| 6722 <pre>const char *luaL_typename (lua_State *L, int index);</pre> |
| 6723 |
| 6724 <p> |
| 6725 Returns the name of the type of the value at the given index. |
| 6726 |
| 6727 |
| 6728 |
| 6729 |
| 6730 |
| 6731 <hr><h3><a name="luaL_unref"><code>luaL_unref</code></a></h3><p> |
| 6732 <span class="apii">[-0, +0, –]</span> |
| 6733 <pre>void luaL_unref (lua_State *L, int t, int ref);</pre> |
| 6734 |
| 6735 <p> |
| 6736 Releases reference <code>ref</code> from the table at index <code>t</code> |
| 6737 (see <a href="#luaL_ref"><code>luaL_ref</code></a>). |
| 6738 The entry is removed from the table, |
| 6739 so that the referred object can be collected. |
| 6740 The reference <code>ref</code> is also freed to be used again. |
| 6741 |
| 6742 |
| 6743 <p> |
| 6744 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>, |
| 6745 <a href="#luaL_unref"><code>luaL_unref</code></a> does nothing. |
| 6746 |
| 6747 |
| 6748 |
| 6749 |
| 6750 |
| 6751 <hr><h3><a name="luaL_where"><code>luaL_where</code></a></h3><p> |
| 6752 <span class="apii">[-0, +1, <em>e</em>]</span> |
| 6753 <pre>void luaL_where (lua_State *L, int lvl);</pre> |
| 6754 |
| 6755 <p> |
| 6756 Pushes onto the stack a string identifying the current position |
| 6757 of the control at level <code>lvl</code> in the call stack. |
| 6758 Typically this string has the following format: |
| 6759 |
| 6760 <pre> |
| 6761 <em>chunkname</em>:<em>currentline</em>: |
| 6762 </pre><p> |
| 6763 Level 0 is the running function, |
| 6764 level 1 is the function that called the running function, |
| 6765 etc. |
| 6766 |
| 6767 |
| 6768 <p> |
| 6769 This function is used to build a prefix for error messages. |
| 6770 |
| 6771 |
| 6772 |
| 6773 |
| 6774 |
| 6775 |
| 6776 |
| 6777 <h1>6 – <a name="6">Standard Libraries</a></h1> |
| 6778 |
| 6779 <p> |
| 6780 The standard Lua libraries provide useful functions |
| 6781 that are implemented directly through the C API. |
| 6782 Some of these functions provide essential services to the language |
| 6783 (e.g., <a href="#pdf-type"><code>type</code></a> and <a href="#pdf-getmetatable"
><code>getmetatable</code></a>); |
| 6784 others provide access to "outside" services (e.g., I/O); |
| 6785 and others could be implemented in Lua itself, |
| 6786 but are quite useful or have critical performance requirements that |
| 6787 deserve an implementation in C (e.g., <a href="#pdf-table.sort"><code>table.sort
</code></a>). |
| 6788 |
| 6789 |
| 6790 <p> |
| 6791 All libraries are implemented through the official C API |
| 6792 and are provided as separate C modules. |
| 6793 Currently, Lua has the following standard libraries: |
| 6794 |
| 6795 <ul> |
| 6796 |
| 6797 <li>basic library (<a href="#6.1">§6.1</a>);</li> |
| 6798 |
| 6799 <li>coroutine library (<a href="#6.2">§6.2</a>);</li> |
| 6800 |
| 6801 <li>package library (<a href="#6.3">§6.3</a>);</li> |
| 6802 |
| 6803 <li>string manipulation (<a href="#6.4">§6.4</a>);</li> |
| 6804 |
| 6805 <li>table manipulation (<a href="#6.5">§6.5</a>);</li> |
| 6806 |
| 6807 <li>mathematical functions (<a href="#6.6">§6.6</a>) (sin, log, etc.);</li> |
| 6808 |
| 6809 <li>bitwise operations (<a href="#6.7">§6.7</a>);</li> |
| 6810 |
| 6811 <li>input and output (<a href="#6.8">§6.8</a>);</li> |
| 6812 |
| 6813 <li>operating system facilities (<a href="#6.9">§6.9</a>);</li> |
| 6814 |
| 6815 <li>debug facilities (<a href="#6.10">§6.10</a>).</li> |
| 6816 |
| 6817 </ul><p> |
| 6818 Except for the basic and the package libraries, |
| 6819 each library provides all its functions as fields of a global table |
| 6820 or as methods of its objects. |
| 6821 |
| 6822 |
| 6823 <p> |
| 6824 To have access to these libraries, |
| 6825 the C host program should call the <a href="#luaL_openlibs"><code>luaL_open
libs</code></a> function, |
| 6826 which opens all standard libraries. |
| 6827 Alternatively, |
| 6828 the host program can open them individually by using |
| 6829 <a href="#luaL_requiref"><code>luaL_requiref</code></a> to call |
| 6830 <a name="pdf-luaopen_base"><code>luaopen_base</code></a> (for the basic library)
, |
| 6831 <a name="pdf-luaopen_package"><code>luaopen_package</code></a> (for the package
library), |
| 6832 <a name="pdf-luaopen_coroutine"><code>luaopen_coroutine</code></a> (for the coro
utine library), |
| 6833 <a name="pdf-luaopen_string"><code>luaopen_string</code></a> (for the string lib
rary), |
| 6834 <a name="pdf-luaopen_table"><code>luaopen_table</code></a> (for the table librar
y), |
| 6835 <a name="pdf-luaopen_math"><code>luaopen_math</code></a> (for the mathematical l
ibrary), |
| 6836 <a name="pdf-luaopen_bit32"><code>luaopen_bit32</code></a> (for the bit library)
, |
| 6837 <a name="pdf-luaopen_io"><code>luaopen_io</code></a> (for the I/O library), |
| 6838 <a name="pdf-luaopen_os"><code>luaopen_os</code></a> (for the Operating System l
ibrary), |
| 6839 and <a name="pdf-luaopen_debug"><code>luaopen_debug</code></a> (for the debug li
brary). |
| 6840 These functions are declared in <a name="pdf-lualib.h"><code>lualib.h</code></a>
. |
| 6841 |
| 6842 |
| 6843 |
| 6844 <h2>6.1 – <a name="6.1">Basic Functions</a></h2> |
| 6845 |
| 6846 <p> |
| 6847 The basic library provides core functions to Lua. |
| 6848 If you do not include this library in your application, |
| 6849 you should check carefully whether you need to provide |
| 6850 implementations for some of its facilities. |
| 6851 |
| 6852 |
| 6853 <p> |
| 6854 <hr><h3><a name="pdf-assert"><code>assert (v [, message])</code></a></h3> |
| 6855 Issues an error when |
| 6856 the value of its argument <code>v</code> is false (i.e., <b>nil</b> or <b>false<
/b>); |
| 6857 otherwise, returns all its arguments. |
| 6858 <code>message</code> is an error message; |
| 6859 when absent, it defaults to "assertion failed!" |
| 6860 |
| 6861 |
| 6862 |
| 6863 |
| 6864 <p> |
| 6865 <hr><h3><a name="pdf-collectgarbage"><code>collectgarbage ([opt [, arg]])</code>
</a></h3> |
| 6866 |
| 6867 |
| 6868 <p> |
| 6869 This function is a generic interface to the garbage collector. |
| 6870 It performs different functions according to its first argument, <code>opt</code
>: |
| 6871 |
| 6872 <ul> |
| 6873 |
| 6874 <li><b>"<code>collect</code>": </b> |
| 6875 performs a full garbage-collection cycle. |
| 6876 This is the default option. |
| 6877 </li> |
| 6878 |
| 6879 <li><b>"<code>stop</code>": </b> |
| 6880 stops automatic execution of the garbage collector. |
| 6881 The collector will run only when explicitly invoked, |
| 6882 until a call to restart it. |
| 6883 </li> |
| 6884 |
| 6885 <li><b>"<code>restart</code>": </b> |
| 6886 restarts automatic execution of the garbage collector. |
| 6887 </li> |
| 6888 |
| 6889 <li><b>"<code>count</code>": </b> |
| 6890 returns the total memory in use by Lua (in Kbytes) and |
| 6891 a second value with the total memory in bytes modulo 1024. |
| 6892 The first value has a fractional part, |
| 6893 so the following equality is always true: |
| 6894 |
| 6895 <pre> |
| 6896 k, b = collectgarbage("count") |
| 6897 assert(k*1024 == math.floor(k)*1024 + b) |
| 6898 </pre><p> |
| 6899 (The second result is useful when Lua is compiled |
| 6900 with a non floating-point type for numbers.) |
| 6901 </li> |
| 6902 |
| 6903 <li><b>"<code>step</code>": </b> |
| 6904 performs a garbage-collection step. |
| 6905 The step "size" is controlled by <code>arg</code> |
| 6906 (larger values mean more steps) in a non-specified way. |
| 6907 If you want to control the step size |
| 6908 you must experimentally tune the value of <code>arg</code>. |
| 6909 Returns <b>true</b> if the step finished a collection cycle. |
| 6910 </li> |
| 6911 |
| 6912 <li><b>"<code>setpause</code>": </b> |
| 6913 sets <code>arg</code> as the new value for the <em>pause</em> of |
| 6914 the collector (see <a href="#2.5">§2.5</a>). |
| 6915 Returns the previous value for <em>pause</em>. |
| 6916 </li> |
| 6917 |
| 6918 <li><b>"<code>setstepmul</code>": </b> |
| 6919 sets <code>arg</code> as the new value for the <em>step multiplier</em> of |
| 6920 the collector (see <a href="#2.5">§2.5</a>). |
| 6921 Returns the previous value for <em>step</em>. |
| 6922 </li> |
| 6923 |
| 6924 <li><b>"<code>isrunning</code>": </b> |
| 6925 returns a boolean that tells whether the collector is running |
| 6926 (i.e., not stopped). |
| 6927 </li> |
| 6928 |
| 6929 <li><b>"<code>generational</code>": </b> |
| 6930 changes the collector to generational mode. |
| 6931 This is an experimental feature (see <a href="#2.5">§2.5</a>). |
| 6932 </li> |
| 6933 |
| 6934 <li><b>"<code>incremental</code>": </b> |
| 6935 changes the collector to incremental mode. |
| 6936 This is the default mode. |
| 6937 </li> |
| 6938 |
| 6939 </ul> |
| 6940 |
| 6941 |
| 6942 |
| 6943 <p> |
| 6944 <hr><h3><a name="pdf-dofile"><code>dofile ([filename])</code></a></h3> |
| 6945 Opens the named file and executes its contents as a Lua chunk. |
| 6946 When called without arguments, |
| 6947 <code>dofile</code> executes the contents of the standard input (<code>stdin</co
de>). |
| 6948 Returns all values returned by the chunk. |
| 6949 In case of errors, <code>dofile</code> propagates the error |
| 6950 to its caller (that is, <code>dofile</code> does not run in protected mode). |
| 6951 |
| 6952 |
| 6953 |
| 6954 |
| 6955 <p> |
| 6956 <hr><h3><a name="pdf-error"><code>error (message [, level])</code></a></h3> |
| 6957 Terminates the last protected function called |
| 6958 and returns <code>message</code> as the error message. |
| 6959 Function <code>error</code> never returns. |
| 6960 |
| 6961 |
| 6962 <p> |
| 6963 Usually, <code>error</code> adds some information about the error position |
| 6964 at the beginning of the message, if the message is a string. |
| 6965 The <code>level</code> argument specifies how to get the error position. |
| 6966 With level 1 (the default), the error position is where the |
| 6967 <code>error</code> function was called. |
| 6968 Level 2 points the error to where the function |
| 6969 that called <code>error</code> was called; and so on. |
| 6970 Passing a level 0 avoids the addition of error position information |
| 6971 to the message. |
| 6972 |
| 6973 |
| 6974 |
| 6975 |
| 6976 <p> |
| 6977 <hr><h3><a name="pdf-_G"><code>_G</code></a></h3> |
| 6978 A global variable (not a function) that |
| 6979 holds the global environment (see <a href="#2.2">§2.2</a>). |
| 6980 Lua itself does not use this variable; |
| 6981 changing its value does not affect any environment, |
| 6982 nor vice-versa. |
| 6983 |
| 6984 |
| 6985 |
| 6986 |
| 6987 <p> |
| 6988 <hr><h3><a name="pdf-getmetatable"><code>getmetatable (object)</code></a></h3> |
| 6989 |
| 6990 |
| 6991 <p> |
| 6992 If <code>object</code> does not have a metatable, returns <b>nil</b>. |
| 6993 Otherwise, |
| 6994 if the object's metatable has a <code>"__metatable"</code> field, |
| 6995 returns the associated value. |
| 6996 Otherwise, returns the metatable of the given object. |
| 6997 |
| 6998 |
| 6999 |
| 7000 |
| 7001 <p> |
| 7002 <hr><h3><a name="pdf-ipairs"><code>ipairs (t)</code></a></h3> |
| 7003 |
| 7004 |
| 7005 <p> |
| 7006 If <code>t</code> has a metamethod <code>__ipairs</code>, |
| 7007 calls it with <code>t</code> as argument and returns the first three |
| 7008 results from the call. |
| 7009 |
| 7010 |
| 7011 <p> |
| 7012 Otherwise, |
| 7013 returns three values: an iterator function, the table <code>t</code>, and 0, |
| 7014 so that the construction |
| 7015 |
| 7016 <pre> |
| 7017 for i,v in ipairs(t) do <em>body</em> end |
| 7018 </pre><p> |
| 7019 will iterate over the pairs (<code>1,t[1]</code>), (<code>2,t[2]</code>), ..., |
| 7020 up to the first integer key absent from the table. |
| 7021 |
| 7022 |
| 7023 |
| 7024 |
| 7025 <p> |
| 7026 <hr><h3><a name="pdf-load"><code>load (ld [, source [, mode [, env]]])</code></a
></h3> |
| 7027 |
| 7028 |
| 7029 <p> |
| 7030 Loads a chunk. |
| 7031 |
| 7032 |
| 7033 <p> |
| 7034 If <code>ld</code> is a string, the chunk is this string. |
| 7035 If <code>ld</code> is a function, |
| 7036 <code>load</code> calls it repeatedly to get the chunk pieces. |
| 7037 Each call to <code>ld</code> must return a string that concatenates |
| 7038 with previous results. |
| 7039 A return of an empty string, <b>nil</b>, or no value signals the end of the chun
k. |
| 7040 |
| 7041 |
| 7042 <p> |
| 7043 If there are no syntactic errors, |
| 7044 returns the compiled chunk as a function; |
| 7045 otherwise, returns <b>nil</b> plus the error message. |
| 7046 |
| 7047 |
| 7048 <p> |
| 7049 If the resulting function has upvalues, |
| 7050 the first upvalue is set to the value of <code>env</code>, |
| 7051 if that parameter is given, |
| 7052 or to the value of the global environment. |
| 7053 (When you load a main chunk, |
| 7054 the resulting function will always have exactly one upvalue, |
| 7055 the <code>_ENV</code> variable (see <a href="#2.2">§2.2</a>). |
| 7056 When you load a binary chunk created from a function (see <a href="#pdf-string.d
ump"><code>string.dump</code></a>), |
| 7057 the resulting function can have arbitrary upvalues.) |
| 7058 |
| 7059 |
| 7060 <p> |
| 7061 <code>source</code> is used as the source of the chunk for error messages |
| 7062 and debug information (see <a href="#4.9">§4.9</a>). |
| 7063 When absent, |
| 7064 it defaults to <code>ld</code>, if <code>ld</code> is a string, |
| 7065 or to "<code>=(load)</code>" otherwise. |
| 7066 |
| 7067 |
| 7068 <p> |
| 7069 The string <code>mode</code> controls whether the chunk can be text or binary |
| 7070 (that is, a precompiled chunk). |
| 7071 It may be the string "<code>b</code>" (only binary chunks), |
| 7072 "<code>t</code>" (only text chunks), |
| 7073 or "<code>bt</code>" (both binary and text). |
| 7074 The default is "<code>bt</code>". |
| 7075 |
| 7076 |
| 7077 |
| 7078 |
| 7079 <p> |
| 7080 <hr><h3><a name="pdf-loadfile"><code>loadfile ([filename [, mode [, env]]])</cod
e></a></h3> |
| 7081 |
| 7082 |
| 7083 <p> |
| 7084 Similar to <a href="#pdf-load"><code>load</code></a>, |
| 7085 but gets the chunk from file <code>filename</code> |
| 7086 or from the standard input, |
| 7087 if no file name is given. |
| 7088 |
| 7089 |
| 7090 |
| 7091 |
| 7092 <p> |
| 7093 <hr><h3><a name="pdf-next"><code>next (table [, index])</code></a></h3> |
| 7094 |
| 7095 |
| 7096 <p> |
| 7097 Allows a program to traverse all fields of a table. |
| 7098 Its first argument is a table and its second argument |
| 7099 is an index in this table. |
| 7100 <code>next</code> returns the next index of the table |
| 7101 and its associated value. |
| 7102 When called with <b>nil</b> as its second argument, |
| 7103 <code>next</code> returns an initial index |
| 7104 and its associated value. |
| 7105 When called with the last index, |
| 7106 or with <b>nil</b> in an empty table, |
| 7107 <code>next</code> returns <b>nil</b>. |
| 7108 If the second argument is absent, then it is interpreted as <b>nil</b>. |
| 7109 In particular, |
| 7110 you can use <code>next(t)</code> to check whether a table is empty. |
| 7111 |
| 7112 |
| 7113 <p> |
| 7114 The order in which the indices are enumerated is not specified, |
| 7115 <em>even for numeric indices</em>. |
| 7116 (To traverse a table in numeric order, |
| 7117 use a numerical <b>for</b>.) |
| 7118 |
| 7119 |
| 7120 <p> |
| 7121 The behavior of <code>next</code> is undefined if, |
| 7122 during the traversal, |
| 7123 you assign any value to a non-existent field in the table. |
| 7124 You may however modify existing fields. |
| 7125 In particular, you may clear existing fields. |
| 7126 |
| 7127 |
| 7128 |
| 7129 |
| 7130 <p> |
| 7131 <hr><h3><a name="pdf-pairs"><code>pairs (t)</code></a></h3> |
| 7132 |
| 7133 |
| 7134 <p> |
| 7135 If <code>t</code> has a metamethod <code>__pairs</code>, |
| 7136 calls it with <code>t</code> as argument and returns the first three |
| 7137 results from the call. |
| 7138 |
| 7139 |
| 7140 <p> |
| 7141 Otherwise, |
| 7142 returns three values: the <a href="#pdf-next"><code>next</code></a> function, th
e table <code>t</code>, and <b>nil</b>, |
| 7143 so that the construction |
| 7144 |
| 7145 <pre> |
| 7146 for k,v in pairs(t) do <em>body</em> end |
| 7147 </pre><p> |
| 7148 will iterate over all key–value pairs of table <code>t</code>. |
| 7149 |
| 7150 |
| 7151 <p> |
| 7152 See function <a href="#pdf-next"><code>next</code></a> for the caveats of modify
ing |
| 7153 the table during its traversal. |
| 7154 |
| 7155 |
| 7156 |
| 7157 |
| 7158 <p> |
| 7159 <hr><h3><a name="pdf-pcall"><code>pcall (f [, arg1, ···])</
code></a></h3> |
| 7160 |
| 7161 |
| 7162 <p> |
| 7163 Calls function <code>f</code> with |
| 7164 the given arguments in <em>protected mode</em>. |
| 7165 This means that any error inside <code>f</code> is not propagated; |
| 7166 instead, <code>pcall</code> catches the error |
| 7167 and returns a status code. |
| 7168 Its first result is the status code (a boolean), |
| 7169 which is true if the call succeeds without errors. |
| 7170 In such case, <code>pcall</code> also returns all results from the call, |
| 7171 after this first result. |
| 7172 In case of any error, <code>pcall</code> returns <b>false</b> plus the error mes
sage. |
| 7173 |
| 7174 |
| 7175 |
| 7176 |
| 7177 <p> |
| 7178 <hr><h3><a name="pdf-print"><code>print (···)</code></a></h
3> |
| 7179 Receives any number of arguments |
| 7180 and prints their values to <code>stdout</code>, |
| 7181 using the <a href="#pdf-tostring"><code>tostring</code></a> function to convert
each argument to a string. |
| 7182 <code>print</code> is not intended for formatted output, |
| 7183 but only as a quick way to show a value, |
| 7184 for instance for debugging. |
| 7185 For complete control over the output, |
| 7186 use <a href="#pdf-string.format"><code>string.format</code></a> and <a href="#pd
f-io.write"><code>io.write</code></a>. |
| 7187 |
| 7188 |
| 7189 |
| 7190 |
| 7191 <p> |
| 7192 <hr><h3><a name="pdf-rawequal"><code>rawequal (v1, v2)</code></a></h3> |
| 7193 Checks whether <code>v1</code> is equal to <code>v2</code>, |
| 7194 without invoking any metamethod. |
| 7195 Returns a boolean. |
| 7196 |
| 7197 |
| 7198 |
| 7199 |
| 7200 <p> |
| 7201 <hr><h3><a name="pdf-rawget"><code>rawget (table, index)</code></a></h3> |
| 7202 Gets the real value of <code>table[index]</code>, |
| 7203 without invoking any metamethod. |
| 7204 <code>table</code> must be a table; |
| 7205 <code>index</code> may be any value. |
| 7206 |
| 7207 |
| 7208 |
| 7209 |
| 7210 <p> |
| 7211 <hr><h3><a name="pdf-rawlen"><code>rawlen (v)</code></a></h3> |
| 7212 Returns the length of the object <code>v</code>, |
| 7213 which must be a table or a string, |
| 7214 without invoking any metamethod. |
| 7215 Returns an integer number. |
| 7216 |
| 7217 |
| 7218 |
| 7219 |
| 7220 <p> |
| 7221 <hr><h3><a name="pdf-rawset"><code>rawset (table, index, value)</code></a></h3> |
| 7222 Sets the real value of <code>table[index]</code> to <code>value</code>, |
| 7223 without invoking any metamethod. |
| 7224 <code>table</code> must be a table, |
| 7225 <code>index</code> any value different from <b>nil</b> and NaN, |
| 7226 and <code>value</code> any Lua value. |
| 7227 |
| 7228 |
| 7229 <p> |
| 7230 This function returns <code>table</code>. |
| 7231 |
| 7232 |
| 7233 |
| 7234 |
| 7235 <p> |
| 7236 <hr><h3><a name="pdf-select"><code>select (index, ···)</cod
e></a></h3> |
| 7237 |
| 7238 |
| 7239 <p> |
| 7240 If <code>index</code> is a number, |
| 7241 returns all arguments after argument number <code>index</code>; |
| 7242 a negative number indexes from the end (-1 is the last argument). |
| 7243 Otherwise, <code>index</code> must be the string <code>"#"</code>, |
| 7244 and <code>select</code> returns the total number of extra arguments it received. |
| 7245 |
| 7246 |
| 7247 |
| 7248 |
| 7249 <p> |
| 7250 <hr><h3><a name="pdf-setmetatable"><code>setmetatable (table, metatable)</code><
/a></h3> |
| 7251 |
| 7252 |
| 7253 <p> |
| 7254 Sets the metatable for the given table. |
| 7255 (You cannot change the metatable of other types from Lua, only from C.) |
| 7256 If <code>metatable</code> is <b>nil</b>, |
| 7257 removes the metatable of the given table. |
| 7258 If the original metatable has a <code>"__metatable"</code> field, |
| 7259 raises an error. |
| 7260 |
| 7261 |
| 7262 <p> |
| 7263 This function returns <code>table</code>. |
| 7264 |
| 7265 |
| 7266 |
| 7267 |
| 7268 <p> |
| 7269 <hr><h3><a name="pdf-tonumber"><code>tonumber (e [, base])</code></a></h3> |
| 7270 |
| 7271 |
| 7272 <p> |
| 7273 When called with no <code>base</code>, |
| 7274 <code>tonumber</code> tries to convert its argument to a number. |
| 7275 If the argument is already a number or |
| 7276 a string convertible to a number (see <a href="#3.4.2">§3.4.2</a>), |
| 7277 then <code>tonumber</code> returns this number; |
| 7278 otherwise, it returns <b>nil</b>. |
| 7279 |
| 7280 |
| 7281 <p> |
| 7282 When called with <code>base</code>, |
| 7283 then <code>e</code> should be a string to be interpreted as |
| 7284 an integer numeral in that base. |
| 7285 The base may be any integer between 2 and 36, inclusive. |
| 7286 In bases above 10, the letter '<code>A</code>' (in either upper or lower ca
se) |
| 7287 represents 10, '<code>B</code>' represents 11, and so forth, |
| 7288 with '<code>Z</code>' representing 35. |
| 7289 If the string <code>e</code> is not a valid numeral in the given base, |
| 7290 the function returns <b>nil</b>. |
| 7291 |
| 7292 |
| 7293 |
| 7294 |
| 7295 <p> |
| 7296 <hr><h3><a name="pdf-tostring"><code>tostring (v)</code></a></h3> |
| 7297 Receives a value of any type and |
| 7298 converts it to a string in a reasonable format. |
| 7299 (For complete control of how numbers are converted, |
| 7300 use <a href="#pdf-string.format"><code>string.format</code></a>.) |
| 7301 |
| 7302 |
| 7303 <p> |
| 7304 If the metatable of <code>v</code> has a <code>"__tostring"</code> field, |
| 7305 then <code>tostring</code> calls the corresponding value |
| 7306 with <code>v</code> as argument, |
| 7307 and uses the result of the call as its result. |
| 7308 |
| 7309 |
| 7310 |
| 7311 |
| 7312 <p> |
| 7313 <hr><h3><a name="pdf-type"><code>type (v)</code></a></h3> |
| 7314 Returns the type of its only argument, coded as a string. |
| 7315 The possible results of this function are |
| 7316 "<code>nil</code>" (a string, not the value <b>nil</b>), |
| 7317 "<code>number</code>", |
| 7318 "<code>string</code>", |
| 7319 "<code>boolean</code>", |
| 7320 "<code>table</code>", |
| 7321 "<code>function</code>", |
| 7322 "<code>thread</code>", |
| 7323 and "<code>userdata</code>". |
| 7324 |
| 7325 |
| 7326 |
| 7327 |
| 7328 <p> |
| 7329 <hr><h3><a name="pdf-_VERSION"><code>_VERSION</code></a></h3> |
| 7330 A global variable (not a function) that |
| 7331 holds a string containing the current interpreter version. |
| 7332 The current contents of this variable is "<code>Lua 5.2</code>". |
| 7333 |
| 7334 |
| 7335 |
| 7336 |
| 7337 <p> |
| 7338 <hr><h3><a name="pdf-xpcall"><code>xpcall (f, msgh [, arg1, ··&mid
dot;])</code></a></h3> |
| 7339 |
| 7340 |
| 7341 <p> |
| 7342 This function is similar to <a href="#pdf-pcall"><code>pcall</code></a>, |
| 7343 except that it sets a new message handler <code>msgh</code>. |
| 7344 |
| 7345 |
| 7346 |
| 7347 |
| 7348 |
| 7349 |
| 7350 |
| 7351 <h2>6.2 – <a name="6.2">Coroutine Manipulation</a></h2> |
| 7352 |
| 7353 <p> |
| 7354 The operations related to coroutines comprise a sub-library of |
| 7355 the basic library and come inside the table <a name="pdf-coroutine"><code>corout
ine</code></a>. |
| 7356 See <a href="#2.6">§2.6</a> for a general description of coroutines. |
| 7357 |
| 7358 |
| 7359 <p> |
| 7360 <hr><h3><a name="pdf-coroutine.create"><code>coroutine.create (f)</code></a></h3
> |
| 7361 |
| 7362 |
| 7363 <p> |
| 7364 Creates a new coroutine, with body <code>f</code>. |
| 7365 <code>f</code> must be a Lua function. |
| 7366 Returns this new coroutine, |
| 7367 an object with type <code>"thread"</code>. |
| 7368 |
| 7369 |
| 7370 |
| 7371 |
| 7372 <p> |
| 7373 <hr><h3><a name="pdf-coroutine.resume"><code>coroutine.resume (co [, val1, &midd
ot;··])</code></a></h3> |
| 7374 |
| 7375 |
| 7376 <p> |
| 7377 Starts or continues the execution of coroutine <code>co</code>. |
| 7378 The first time you resume a coroutine, |
| 7379 it starts running its body. |
| 7380 The values <code>val1</code>, ... are passed |
| 7381 as the arguments to the body function. |
| 7382 If the coroutine has yielded, |
| 7383 <code>resume</code> restarts it; |
| 7384 the values <code>val1</code>, ... are passed |
| 7385 as the results from the yield. |
| 7386 |
| 7387 |
| 7388 <p> |
| 7389 If the coroutine runs without any errors, |
| 7390 <code>resume</code> returns <b>true</b> plus any values passed to <code>yield</c
ode> |
| 7391 (if the coroutine yields) or any values returned by the body function |
| 7392 (if the coroutine terminates). |
| 7393 If there is any error, |
| 7394 <code>resume</code> returns <b>false</b> plus the error message. |
| 7395 |
| 7396 |
| 7397 |
| 7398 |
| 7399 <p> |
| 7400 <hr><h3><a name="pdf-coroutine.running"><code>coroutine.running ()</code></a></h
3> |
| 7401 |
| 7402 |
| 7403 <p> |
| 7404 Returns the running coroutine plus a boolean, |
| 7405 true when the running coroutine is the main one. |
| 7406 |
| 7407 |
| 7408 |
| 7409 |
| 7410 <p> |
| 7411 <hr><h3><a name="pdf-coroutine.status"><code>coroutine.status (co)</code></a></h
3> |
| 7412 |
| 7413 |
| 7414 <p> |
| 7415 Returns the status of coroutine <code>co</code>, as a string: |
| 7416 <code>"running"</code>, |
| 7417 if the coroutine is running (that is, it called <code>status</code>); |
| 7418 <code>"suspended"</code>, if the coroutine is suspended in a call to <code>yield
</code>, |
| 7419 or if it has not started running yet; |
| 7420 <code>"normal"</code> if the coroutine is active but not running |
| 7421 (that is, it has resumed another coroutine); |
| 7422 and <code>"dead"</code> if the coroutine has finished its body function, |
| 7423 or if it has stopped with an error. |
| 7424 |
| 7425 |
| 7426 |
| 7427 |
| 7428 <p> |
| 7429 <hr><h3><a name="pdf-coroutine.wrap"><code>coroutine.wrap (f)</code></a></h3> |
| 7430 |
| 7431 |
| 7432 <p> |
| 7433 Creates a new coroutine, with body <code>f</code>. |
| 7434 <code>f</code> must be a Lua function. |
| 7435 Returns a function that resumes the coroutine each time it is called. |
| 7436 Any arguments passed to the function behave as the |
| 7437 extra arguments to <code>resume</code>. |
| 7438 Returns the same values returned by <code>resume</code>, |
| 7439 except the first boolean. |
| 7440 In case of error, propagates the error. |
| 7441 |
| 7442 |
| 7443 |
| 7444 |
| 7445 <p> |
| 7446 <hr><h3><a name="pdf-coroutine.yield"><code>coroutine.yield (··&mi
ddot;)</code></a></h3> |
| 7447 |
| 7448 |
| 7449 <p> |
| 7450 Suspends the execution of the calling coroutine. |
| 7451 Any arguments to <code>yield</code> are passed as extra results to <code>resume<
/code>. |
| 7452 |
| 7453 |
| 7454 |
| 7455 |
| 7456 |
| 7457 |
| 7458 |
| 7459 <h2>6.3 – <a name="6.3">Modules</a></h2> |
| 7460 |
| 7461 <p> |
| 7462 The package library provides basic |
| 7463 facilities for loading modules in Lua. |
| 7464 It exports one function directly in the global environment: |
| 7465 <a href="#pdf-require"><code>require</code></a>. |
| 7466 Everything else is exported in a table <a name="pdf-package"><code>package</code
></a>. |
| 7467 |
| 7468 |
| 7469 <p> |
| 7470 <hr><h3><a name="pdf-require"><code>require (modname)</code></a></h3> |
| 7471 |
| 7472 |
| 7473 <p> |
| 7474 Loads the given module. |
| 7475 The function starts by looking into the <a href="#pdf-package.loaded"><code>pack
age.loaded</code></a> table |
| 7476 to determine whether <code>modname</code> is already loaded. |
| 7477 If it is, then <code>require</code> returns the value stored |
| 7478 at <code>package.loaded[modname]</code>. |
| 7479 Otherwise, it tries to find a <em>loader</em> for the module. |
| 7480 |
| 7481 |
| 7482 <p> |
| 7483 To find a loader, |
| 7484 <code>require</code> is guided by the <a href="#pdf-package.searchers"><code>pac
kage.searchers</code></a> sequence. |
| 7485 By changing this sequence, |
| 7486 we can change how <code>require</code> looks for a module. |
| 7487 The following explanation is based on the default configuration |
| 7488 for <a href="#pdf-package.searchers"><code>package.searchers</code></a>. |
| 7489 |
| 7490 |
| 7491 <p> |
| 7492 First <code>require</code> queries <code>package.preload[modname]</code>. |
| 7493 If it has a value, |
| 7494 this value (which should be a function) is the loader. |
| 7495 Otherwise <code>require</code> searches for a Lua loader using the |
| 7496 path stored in <a href="#pdf-package.path"><code>package.path</code></a>. |
| 7497 If that also fails, it searches for a C loader using the |
| 7498 path stored in <a href="#pdf-package.cpath"><code>package.cpath</code></a>. |
| 7499 If that also fails, |
| 7500 it tries an <em>all-in-one</em> loader (see <a href="#pdf-package.searchers"><co
de>package.searchers</code></a>). |
| 7501 |
| 7502 |
| 7503 <p> |
| 7504 Once a loader is found, |
| 7505 <code>require</code> calls the loader with two arguments: |
| 7506 <code>modname</code> and an extra value dependent on how it got the loader. |
| 7507 (If the loader came from a file, |
| 7508 this extra value is the file name.) |
| 7509 If the loader returns any non-nil value, |
| 7510 <code>require</code> assigns the returned value to <code>package.loaded[modname]
</code>. |
| 7511 If the loader does not return a non-nil value and |
| 7512 has not assigned any value to <code>package.loaded[modname]</code>, |
| 7513 then <code>require</code> assigns <b>true</b> to this entry. |
| 7514 In any case, <code>require</code> returns the |
| 7515 final value of <code>package.loaded[modname]</code>. |
| 7516 |
| 7517 |
| 7518 <p> |
| 7519 If there is any error loading or running the module, |
| 7520 or if it cannot find any loader for the module, |
| 7521 then <code>require</code> raises an error. |
| 7522 |
| 7523 |
| 7524 |
| 7525 |
| 7526 <p> |
| 7527 <hr><h3><a name="pdf-package.config"><code>package.config</code></a></h3> |
| 7528 |
| 7529 |
| 7530 <p> |
| 7531 A string describing some compile-time configurations for packages. |
| 7532 This string is a sequence of lines: |
| 7533 |
| 7534 <ul> |
| 7535 |
| 7536 <li>The first line is the directory separator string. |
| 7537 Default is '<code>\</code>' for Windows and '<code>/</code>' for all other syste
ms.</li> |
| 7538 |
| 7539 <li>The second line is the character that separates templates in a path. |
| 7540 Default is '<code>;</code>'.</li> |
| 7541 |
| 7542 <li>The third line is the string that marks the |
| 7543 substitution points in a template. |
| 7544 Default is '<code>?</code>'.</li> |
| 7545 |
| 7546 <li>The fourth line is a string that, in a path in Windows, |
| 7547 is replaced by the executable's directory. |
| 7548 Default is '<code>!</code>'.</li> |
| 7549 |
| 7550 <li>The fifth line is a mark to ignore all text before it |
| 7551 when building the <code>luaopen_</code> function name. |
| 7552 Default is '<code>-</code>'.</li> |
| 7553 |
| 7554 </ul> |
| 7555 |
| 7556 |
| 7557 |
| 7558 <p> |
| 7559 <hr><h3><a name="pdf-package.cpath"><code>package.cpath</code></a></h3> |
| 7560 |
| 7561 |
| 7562 <p> |
| 7563 The path used by <a href="#pdf-require"><code>require</code></a> to search for a
C loader. |
| 7564 |
| 7565 |
| 7566 <p> |
| 7567 Lua initializes the C path <a href="#pdf-package.cpath"><code>package.cpath
</code></a> in the same way |
| 7568 it initializes the Lua path <a href="#pdf-package.path"><code>package.path</code
></a>, |
| 7569 using the environment variable <a name="pdf-LUA_CPATH_5_2"><code>LUA_CPATH_5_2</
code></a> |
| 7570 or the environment variable <a name="pdf-LUA_CPATH"><code>LUA_CPATH</code></a> |
| 7571 or a default path defined in <code>luaconf.h</code>. |
| 7572 |
| 7573 |
| 7574 |
| 7575 |
| 7576 <p> |
| 7577 <hr><h3><a name="pdf-package.loaded"><code>package.loaded</code></a></h3> |
| 7578 |
| 7579 |
| 7580 <p> |
| 7581 A table used by <a href="#pdf-require"><code>require</code></a> to control which |
| 7582 modules are already loaded. |
| 7583 When you require a module <code>modname</code> and |
| 7584 <code>package.loaded[modname]</code> is not false, |
| 7585 <a href="#pdf-require"><code>require</code></a> simply returns the value stored
there. |
| 7586 |
| 7587 |
| 7588 <p> |
| 7589 This variable is only a reference to the real table; |
| 7590 assignments to this variable do not change the |
| 7591 table used by <a href="#pdf-require"><code>require</code></a>. |
| 7592 |
| 7593 |
| 7594 |
| 7595 |
| 7596 <p> |
| 7597 <hr><h3><a name="pdf-package.loadlib"><code>package.loadlib (libname, funcname)<
/code></a></h3> |
| 7598 |
| 7599 |
| 7600 <p> |
| 7601 Dynamically links the host program with the C library <code>libname</code>. |
| 7602 |
| 7603 |
| 7604 <p> |
| 7605 If <code>funcname</code> is "<code>*</code>", |
| 7606 then it only links with the library, |
| 7607 making the symbols exported by the library |
| 7608 available to other dynamically linked libraries. |
| 7609 Otherwise, |
| 7610 it looks for a function <code>funcname</code> inside the library |
| 7611 and returns this function as a C function. |
| 7612 So, <code>funcname</code> must follow the <a href="#lua_CFunction"><code>lua_CFu
nction</code></a> prototype |
| 7613 (see <a href="#lua_CFunction"><code>lua_CFunction</code></a>). |
| 7614 |
| 7615 |
| 7616 <p> |
| 7617 This is a low-level function. |
| 7618 It completely bypasses the package and module system. |
| 7619 Unlike <a href="#pdf-require"><code>require</code></a>, |
| 7620 it does not perform any path searching and |
| 7621 does not automatically adds extensions. |
| 7622 <code>libname</code> must be the complete file name of the C library, |
| 7623 including if necessary a path and an extension. |
| 7624 <code>funcname</code> must be the exact name exported by the C library |
| 7625 (which may depend on the C compiler and linker used). |
| 7626 |
| 7627 |
| 7628 <p> |
| 7629 This function is not supported by Standard C. |
| 7630 As such, it is only available on some platforms |
| 7631 (Windows, Linux, Mac OS X, Solaris, BSD, |
| 7632 plus other Unix systems that support the <code>dlfcn</code> standard). |
| 7633 |
| 7634 |
| 7635 |
| 7636 |
| 7637 <p> |
| 7638 <hr><h3><a name="pdf-package.path"><code>package.path</code></a></h3> |
| 7639 |
| 7640 |
| 7641 <p> |
| 7642 The path used by <a href="#pdf-require"><code>require</code></a> to search for a
Lua loader. |
| 7643 |
| 7644 |
| 7645 <p> |
| 7646 At start-up, Lua initializes this variable with |
| 7647 the value of the environment variable <a name="pdf-LUA_PATH_5_2"><code>LUA_PATH_
5_2</code></a> or |
| 7648 the environment variable <a name="pdf-LUA_PATH"><code>LUA_PATH</code></a> or |
| 7649 with a default path defined in <code>luaconf.h</code>, |
| 7650 if those environment variables are not defined. |
| 7651 Any "<code>;;</code>" in the value of the environment variable |
| 7652 is replaced by the default path. |
| 7653 |
| 7654 |
| 7655 |
| 7656 |
| 7657 <p> |
| 7658 <hr><h3><a name="pdf-package.preload"><code>package.preload</code></a></h3> |
| 7659 |
| 7660 |
| 7661 <p> |
| 7662 A table to store loaders for specific modules |
| 7663 (see <a href="#pdf-require"><code>require</code></a>). |
| 7664 |
| 7665 |
| 7666 <p> |
| 7667 This variable is only a reference to the real table; |
| 7668 assignments to this variable do not change the |
| 7669 table used by <a href="#pdf-require"><code>require</code></a>. |
| 7670 |
| 7671 |
| 7672 |
| 7673 |
| 7674 <p> |
| 7675 <hr><h3><a name="pdf-package.searchers"><code>package.searchers</code></a></h3> |
| 7676 |
| 7677 |
| 7678 <p> |
| 7679 A table used by <a href="#pdf-require"><code>require</code></a> to control how t
o load modules. |
| 7680 |
| 7681 |
| 7682 <p> |
| 7683 Each entry in this table is a <em>searcher function</em>. |
| 7684 When looking for a module, |
| 7685 <a href="#pdf-require"><code>require</code></a> calls each of these searchers in
ascending order, |
| 7686 with the module name (the argument given to <a href="#pdf-require"><code>require
</code></a>) as its |
| 7687 sole parameter. |
| 7688 The function can return another function (the module <em>loader</em>) |
| 7689 plus an extra value that will be passed to that loader, |
| 7690 or a string explaining why it did not find that module |
| 7691 (or <b>nil</b> if it has nothing to say). |
| 7692 |
| 7693 |
| 7694 <p> |
| 7695 Lua initializes this table with four searcher functions. |
| 7696 |
| 7697 |
| 7698 <p> |
| 7699 The first searcher simply looks for a loader in the |
| 7700 <a href="#pdf-package.preload"><code>package.preload</code></a> table. |
| 7701 |
| 7702 |
| 7703 <p> |
| 7704 The second searcher looks for a loader as a Lua library, |
| 7705 using the path stored at <a href="#pdf-package.path"><code>package.path</code></
a>. |
| 7706 The search is done as described in function <a href="#pdf-package.searchpath"><c
ode>package.searchpath</code></a>. |
| 7707 |
| 7708 |
| 7709 <p> |
| 7710 The third searcher looks for a loader as a C library, |
| 7711 using the path given by the variable <a href="#pdf-package.cpath"><code>package.
cpath</code></a>. |
| 7712 Again, |
| 7713 the search is done as described in function <a href="#pdf-package.searchpath"><c
ode>package.searchpath</code></a>. |
| 7714 For instance, |
| 7715 if the C path is the string |
| 7716 |
| 7717 <pre> |
| 7718 "./?.so;./?.dll;/usr/local/?/init.so" |
| 7719 </pre><p> |
| 7720 the searcher for module <code>foo</code> |
| 7721 will try to open the files <code>./foo.so</code>, <code>./foo.dll</code>, |
| 7722 and <code>/usr/local/foo/init.so</code>, in that order. |
| 7723 Once it finds a C library, |
| 7724 this searcher first uses a dynamic link facility to link the |
| 7725 application with the library. |
| 7726 Then it tries to find a C function inside the library to |
| 7727 be used as the loader. |
| 7728 The name of this C function is the string "<code>luaopen_</code>" |
| 7729 concatenated with a copy of the module name where each dot |
| 7730 is replaced by an underscore. |
| 7731 Moreover, if the module name has a hyphen, |
| 7732 its prefix up to (and including) the first hyphen is removed. |
| 7733 For instance, if the module name is <code>a.v1-b.c</code>, |
| 7734 the function name will be <code>luaopen_b_c</code>. |
| 7735 |
| 7736 |
| 7737 <p> |
| 7738 The fourth searcher tries an <em>all-in-one loader</em>. |
| 7739 It searches the C path for a library for |
| 7740 the root name of the given module. |
| 7741 For instance, when requiring <code>a.b.c</code>, |
| 7742 it will search for a C library for <code>a</code>. |
| 7743 If found, it looks into it for an open function for |
| 7744 the submodule; |
| 7745 in our example, that would be <code>luaopen_a_b_c</code>. |
| 7746 With this facility, a package can pack several C submodules |
| 7747 into one single library, |
| 7748 with each submodule keeping its original open function. |
| 7749 |
| 7750 |
| 7751 <p> |
| 7752 All searchers except the first one (preload) return as the extra value |
| 7753 the file name where the module was found, |
| 7754 as returned by <a href="#pdf-package.searchpath"><code>package.searchpath</code>
</a>. |
| 7755 The first searcher returns no extra value. |
| 7756 |
| 7757 |
| 7758 |
| 7759 |
| 7760 <p> |
| 7761 <hr><h3><a name="pdf-package.searchpath"><code>package.searchpath (name, path [,
sep [, rep]])</code></a></h3> |
| 7762 |
| 7763 |
| 7764 <p> |
| 7765 Searches for the given <code>name</code> in the given <code>path</code>. |
| 7766 |
| 7767 |
| 7768 <p> |
| 7769 A path is a string containing a sequence of |
| 7770 <em>templates</em> separated by semicolons. |
| 7771 For each template, |
| 7772 the function replaces each interrogation mark (if any) |
| 7773 in the template with a copy of <code>name</code> |
| 7774 wherein all occurrences of <code>sep</code> |
| 7775 (a dot, by default) |
| 7776 were replaced by <code>rep</code> |
| 7777 (the system's directory separator, by default), |
| 7778 and then tries to open the resulting file name. |
| 7779 |
| 7780 |
| 7781 <p> |
| 7782 For instance, if the path is the string |
| 7783 |
| 7784 <pre> |
| 7785 "./?.lua;./?.lc;/usr/local/?/init.lua" |
| 7786 </pre><p> |
| 7787 the search for the name <code>foo.a</code> |
| 7788 will try to open the files |
| 7789 <code>./foo/a.lua</code>, <code>./foo/a.lc</code>, and |
| 7790 <code>/usr/local/foo/a/init.lua</code>, in that order. |
| 7791 |
| 7792 |
| 7793 <p> |
| 7794 Returns the resulting name of the first file that it can |
| 7795 open in read mode (after closing the file), |
| 7796 or <b>nil</b> plus an error message if none succeeds. |
| 7797 (This error message lists all file names it tried to open.) |
| 7798 |
| 7799 |
| 7800 |
| 7801 |
| 7802 |
| 7803 |
| 7804 |
| 7805 <h2>6.4 – <a name="6.4">String Manipulation</a></h2> |
| 7806 |
| 7807 <p> |
| 7808 This library provides generic functions for string manipulation, |
| 7809 such as finding and extracting substrings, and pattern matching. |
| 7810 When indexing a string in Lua, the first character is at position 1 |
| 7811 (not at 0, as in C). |
| 7812 Indices are allowed to be negative and are interpreted as indexing backwards, |
| 7813 from the end of the string. |
| 7814 Thus, the last character is at position -1, and so on. |
| 7815 |
| 7816 |
| 7817 <p> |
| 7818 The string library provides all its functions inside the table |
| 7819 <a name="pdf-string"><code>string</code></a>. |
| 7820 It also sets a metatable for strings |
| 7821 where the <code>__index</code> field points to the <code>string</code> table. |
| 7822 Therefore, you can use the string functions in object-oriented style. |
| 7823 For instance, <code>string.byte(s,i)</code> |
| 7824 can be written as <code>s:byte(i)</code>. |
| 7825 |
| 7826 |
| 7827 <p> |
| 7828 The string library assumes one-byte character encodings. |
| 7829 |
| 7830 |
| 7831 <p> |
| 7832 <hr><h3><a name="pdf-string.byte"><code>string.byte (s [, i [, j]])</code></a></
h3> |
| 7833 Returns the internal numerical codes of the characters <code>s[i]</code>, |
| 7834 <code>s[i+1]</code>, ..., <code>s[j]</code>. |
| 7835 The default value for <code>i</code> is 1; |
| 7836 the default value for <code>j</code> is <code>i</code>. |
| 7837 These indices are corrected |
| 7838 following the same rules of function <a href="#pdf-string.sub"><code>string.sub<
/code></a>. |
| 7839 |
| 7840 |
| 7841 <p> |
| 7842 Numerical codes are not necessarily portable across platforms. |
| 7843 |
| 7844 |
| 7845 |
| 7846 |
| 7847 <p> |
| 7848 <hr><h3><a name="pdf-string.char"><code>string.char (···)</
code></a></h3> |
| 7849 Receives zero or more integers. |
| 7850 Returns a string with length equal to the number of arguments, |
| 7851 in which each character has the internal numerical code equal |
| 7852 to its corresponding argument. |
| 7853 |
| 7854 |
| 7855 <p> |
| 7856 Numerical codes are not necessarily portable across platforms. |
| 7857 |
| 7858 |
| 7859 |
| 7860 |
| 7861 <p> |
| 7862 <hr><h3><a name="pdf-string.dump"><code>string.dump (function)</code></a></h3> |
| 7863 |
| 7864 |
| 7865 <p> |
| 7866 Returns a string containing a binary representation of the given function, |
| 7867 so that a later <a href="#pdf-load"><code>load</code></a> on this string returns |
| 7868 a copy of the function (but with new upvalues). |
| 7869 |
| 7870 |
| 7871 |
| 7872 |
| 7873 <p> |
| 7874 <hr><h3><a name="pdf-string.find"><code>string.find (s, pattern [, init [, plain
]])</code></a></h3> |
| 7875 |
| 7876 |
| 7877 <p> |
| 7878 Looks for the first match of |
| 7879 <code>pattern</code> in the string <code>s</code>. |
| 7880 If it finds a match, then <code>find</code> returns the indices of <code>s<
/code> |
| 7881 where this occurrence starts and ends; |
| 7882 otherwise, it returns <b>nil</b>. |
| 7883 A third, optional numerical argument <code>init</code> specifies |
| 7884 where to start the search; |
| 7885 its default value is 1 and can be negative. |
| 7886 A value of <b>true</b> as a fourth, optional argument <code>plain</code> |
| 7887 turns off the pattern matching facilities, |
| 7888 so the function does a plain "find substring" operation, |
| 7889 with no characters in <code>pattern</code> being considered magic. |
| 7890 Note that if <code>plain</code> is given, then <code>init</code> must be given a
s well. |
| 7891 |
| 7892 |
| 7893 <p> |
| 7894 If the pattern has captures, |
| 7895 then in a successful match |
| 7896 the captured values are also returned, |
| 7897 after the two indices. |
| 7898 |
| 7899 |
| 7900 |
| 7901 |
| 7902 <p> |
| 7903 <hr><h3><a name="pdf-string.format"><code>string.format (formatstring, ·&
middot;·)</code></a></h3> |
| 7904 |
| 7905 |
| 7906 <p> |
| 7907 Returns a formatted version of its variable number of arguments |
| 7908 following the description given in its first argument (which must be a string). |
| 7909 The format string follows the same rules as the ANSI C function <code>sprin
tf</code>. |
| 7910 The only differences are that the options/modifiers |
| 7911 <code>*</code>, <code>h</code>, <code>L</code>, <code>l</code>, <code>n</code>, |
| 7912 and <code>p</code> are not supported |
| 7913 and that there is an extra option, <code>q</code>. |
| 7914 The <code>q</code> option formats a string between double quotes, |
| 7915 using escape sequences when necessary to ensure that |
| 7916 it can safely be read back by the Lua interpreter. |
| 7917 For instance, the call |
| 7918 |
| 7919 <pre> |
| 7920 string.format('%q', 'a string with "quotes" and \n new line') |
| 7921 </pre><p> |
| 7922 may produce the string: |
| 7923 |
| 7924 <pre> |
| 7925 "a string with \"quotes\" and \ |
| 7926 new line" |
| 7927 </pre> |
| 7928 |
| 7929 <p> |
| 7930 Options |
| 7931 <code>A</code> and <code>a</code> (when available), |
| 7932 <code>E</code>, <code>e</code>, <code>f</code>, |
| 7933 <code>G</code>, and <code>g</code> all expect a number as argument. |
| 7934 Options <code>c</code>, <code>d</code>, |
| 7935 <code>i</code>, <code>o</code>, <code>u</code>, <code>X</code>, and <code>x</cod
e> |
| 7936 also expect a number, |
| 7937 but the range of that number may be limited by |
| 7938 the underlying C implementation. |
| 7939 For options <code>o</code>, <code>u</code>, <code>X</code>, and <code>x</code>, |
| 7940 the number cannot be negative. |
| 7941 Option <code>q</code> expects a string; |
| 7942 option <code>s</code> expects a string without embedded zeros. |
| 7943 If the argument to option <code>s</code> is not a string, |
| 7944 it is converted to one following the same rules of <a href="#pdf-tostring"><code
>tostring</code></a>. |
| 7945 |
| 7946 |
| 7947 |
| 7948 |
| 7949 <p> |
| 7950 <hr><h3><a name="pdf-string.gmatch"><code>string.gmatch (s, pattern)</code></a><
/h3> |
| 7951 Returns an iterator function that, |
| 7952 each time it is called, |
| 7953 returns the next captures from <code>pattern</code> over the string <code>s</cod
e>. |
| 7954 If <code>pattern</code> specifies no captures, |
| 7955 then the whole match is produced in each call. |
| 7956 |
| 7957 |
| 7958 <p> |
| 7959 As an example, the following loop |
| 7960 will iterate over all the words from string <code>s</code>, |
| 7961 printing one per line: |
| 7962 |
| 7963 <pre> |
| 7964 s = "hello world from Lua" |
| 7965 for w in string.gmatch(s, "%a+") do |
| 7966 print(w) |
| 7967 end |
| 7968 </pre><p> |
| 7969 The next example collects all pairs <code>key=value</code> from the |
| 7970 given string into a table: |
| 7971 |
| 7972 <pre> |
| 7973 t = {} |
| 7974 s = "from=world, to=Lua" |
| 7975 for k, v in string.gmatch(s, "(%w+)=(%w+)") do |
| 7976 t[k] = v |
| 7977 end |
| 7978 </pre> |
| 7979 |
| 7980 <p> |
| 7981 For this function, a caret '<code>^</code>' at the start of a pattern does not |
| 7982 work as an anchor, as this would prevent the iteration. |
| 7983 |
| 7984 |
| 7985 |
| 7986 |
| 7987 <p> |
| 7988 <hr><h3><a name="pdf-string.gsub"><code>string.gsub (s, pattern, repl [, n])</co
de></a></h3> |
| 7989 Returns a copy of <code>s</code> |
| 7990 in which all (or the first <code>n</code>, if given) |
| 7991 occurrences of the <code>pattern</code> have been |
| 7992 replaced by a replacement string specified by <code>repl</code>, |
| 7993 which can be a string, a table, or a function. |
| 7994 <code>gsub</code> also returns, as its second value, |
| 7995 the total number of matches that occurred. |
| 7996 The name <code>gsub</code> comes from <em>Global SUBstitution</em>. |
| 7997 |
| 7998 |
| 7999 <p> |
| 8000 If <code>repl</code> is a string, then its value is used for replacement. |
| 8001 The character <code>%</code> works as an escape character: |
| 8002 any sequence in <code>repl</code> of the form <code>%<em>d</em></code>, |
| 8003 with <em>d</em> between 1 and 9, |
| 8004 stands for the value of the <em>d</em>-th captured substring. |
| 8005 The sequence <code>%0</code> stands for the whole match. |
| 8006 The sequence <code>%%</code> stands for a single <code>%</code>. |
| 8007 |
| 8008 |
| 8009 <p> |
| 8010 If <code>repl</code> is a table, then the table is queried for every match, |
| 8011 using the first capture as the key. |
| 8012 |
| 8013 |
| 8014 <p> |
| 8015 If <code>repl</code> is a function, then this function is called every time a |
| 8016 match occurs, with all captured substrings passed as arguments, |
| 8017 in order. |
| 8018 |
| 8019 |
| 8020 <p> |
| 8021 In any case, |
| 8022 if the pattern specifies no captures, |
| 8023 then it behaves as if the whole pattern was inside a capture. |
| 8024 |
| 8025 |
| 8026 <p> |
| 8027 If the value returned by the table query or by the function call |
| 8028 is a string or a number, |
| 8029 then it is used as the replacement string; |
| 8030 otherwise, if it is <b>false</b> or <b>nil</b>, |
| 8031 then there is no replacement |
| 8032 (that is, the original match is kept in the string). |
| 8033 |
| 8034 |
| 8035 <p> |
| 8036 Here are some examples: |
| 8037 |
| 8038 <pre> |
| 8039 x = string.gsub("hello world", "(%w+)", "%1 %1") |
| 8040 --> x="hello hello world world" |
| 8041 |
| 8042 x = string.gsub("hello world", "%w+", "%0 %0", 1) |
| 8043 --> x="hello hello world" |
| 8044 |
| 8045 x = string.gsub("hello world from Lua", "(%w+)%s*(%w+)", "%2 %1") |
| 8046 --> x="world hello Lua from" |
| 8047 |
| 8048 x = string.gsub("home = $HOME, user = $USER", "%$(%w+)", os.getenv) |
| 8049 --> x="home = /home/roberto, user = roberto" |
| 8050 |
| 8051 x = string.gsub("4+5 = $return 4+5$", "%$(.-)%$", function (s) |
| 8052 return load(s)() |
| 8053 end) |
| 8054 --> x="4+5 = 9" |
| 8055 |
| 8056 local t = {name="lua", version="5.2"} |
| 8057 x = string.gsub("$name-$version.tar.gz", "%$(%w+)", t) |
| 8058 --> x="lua-5.2.tar.gz" |
| 8059 </pre> |
| 8060 |
| 8061 |
| 8062 |
| 8063 <p> |
| 8064 <hr><h3><a name="pdf-string.len"><code>string.len (s)</code></a></h3> |
| 8065 Receives a string and returns its length. |
| 8066 The empty string <code>""</code> has length 0. |
| 8067 Embedded zeros are counted, |
| 8068 so <code>"a\000bc\000"</code> has length 5. |
| 8069 |
| 8070 |
| 8071 |
| 8072 |
| 8073 <p> |
| 8074 <hr><h3><a name="pdf-string.lower"><code>string.lower (s)</code></a></h3> |
| 8075 Receives a string and returns a copy of this string with all |
| 8076 uppercase letters changed to lowercase. |
| 8077 All other characters are left unchanged. |
| 8078 The definition of what an uppercase letter is depends on the current locale. |
| 8079 |
| 8080 |
| 8081 |
| 8082 |
| 8083 <p> |
| 8084 <hr><h3><a name="pdf-string.match"><code>string.match (s, pattern [, init])</cod
e></a></h3> |
| 8085 Looks for the first <em>match</em> of |
| 8086 <code>pattern</code> in the string <code>s</code>. |
| 8087 If it finds one, then <code>match</code> returns |
| 8088 the captures from the pattern; |
| 8089 otherwise it returns <b>nil</b>. |
| 8090 If <code>pattern</code> specifies no captures, |
| 8091 then the whole match is returned. |
| 8092 A third, optional numerical argument <code>init</code> specifies |
| 8093 where to start the search; |
| 8094 its default value is 1 and can be negative. |
| 8095 |
| 8096 |
| 8097 |
| 8098 |
| 8099 <p> |
| 8100 <hr><h3><a name="pdf-string.rep"><code>string.rep (s, n [, sep])</code></a></h3> |
| 8101 Returns a string that is the concatenation of <code>n</code> copies of |
| 8102 the string <code>s</code> separated by the string <code>sep</code>. |
| 8103 The default value for <code>sep</code> is the empty string |
| 8104 (that is, no separator). |
| 8105 |
| 8106 |
| 8107 |
| 8108 |
| 8109 <p> |
| 8110 <hr><h3><a name="pdf-string.reverse"><code>string.reverse (s)</code></a></h3> |
| 8111 Returns a string that is the string <code>s</code> reversed. |
| 8112 |
| 8113 |
| 8114 |
| 8115 |
| 8116 <p> |
| 8117 <hr><h3><a name="pdf-string.sub"><code>string.sub (s, i [, j])</code></a></h3> |
| 8118 Returns the substring of <code>s</code> that |
| 8119 starts at <code>i</code> and continues until <code>j</code>; |
| 8120 <code>i</code> and <code>j</code> can be negative. |
| 8121 If <code>j</code> is absent, then it is assumed to be equal to -1 |
| 8122 (which is the same as the string length). |
| 8123 In particular, |
| 8124 the call <code>string.sub(s,1,j)</code> returns a prefix of <code>s</code> |
| 8125 with length <code>j</code>, |
| 8126 and <code>string.sub(s, -i)</code> returns a suffix of <code>s</code> |
| 8127 with length <code>i</code>. |
| 8128 |
| 8129 |
| 8130 <p> |
| 8131 If, after the translation of negative indices, |
| 8132 <code>i</code> is less than 1, |
| 8133 it is corrected to 1. |
| 8134 If <code>j</code> is greater than the string length, |
| 8135 it is corrected to that length. |
| 8136 If, after these corrections, |
| 8137 <code>i</code> is greater than <code>j</code>, |
| 8138 the function returns the empty string. |
| 8139 |
| 8140 |
| 8141 |
| 8142 |
| 8143 <p> |
| 8144 <hr><h3><a name="pdf-string.upper"><code>string.upper (s)</code></a></h3> |
| 8145 Receives a string and returns a copy of this string with all |
| 8146 lowercase letters changed to uppercase. |
| 8147 All other characters are left unchanged. |
| 8148 The definition of what a lowercase letter is depends on the current locale. |
| 8149 |
| 8150 |
| 8151 |
| 8152 <h3>6.4.1 – <a name="6.4.1">Patterns</a></h3> |
| 8153 |
| 8154 |
| 8155 <h4>Character Class:</h4><p> |
| 8156 A <em>character class</em> is used to represent a set of characters. |
| 8157 The following combinations are allowed in describing a character class: |
| 8158 |
| 8159 <ul> |
| 8160 |
| 8161 <li><b><em>x</em>: </b> |
| 8162 (where <em>x</em> is not one of the <em>magic characters</em> |
| 8163 <code>^$()%.[]*+-?</code>) |
| 8164 represents the character <em>x</em> itself. |
| 8165 </li> |
| 8166 |
| 8167 <li><b><code>.</code>: </b> (a dot) represents all characters.</li> |
| 8168 |
| 8169 <li><b><code>%a</code>: </b> represents all letters.</li> |
| 8170 |
| 8171 <li><b><code>%c</code>: </b> represents all control characters.</li> |
| 8172 |
| 8173 <li><b><code>%d</code>: </b> represents all digits.</li> |
| 8174 |
| 8175 <li><b><code>%g</code>: </b> represents all printable characters except space.</
li> |
| 8176 |
| 8177 <li><b><code>%l</code>: </b> represents all lowercase letters.</li> |
| 8178 |
| 8179 <li><b><code>%p</code>: </b> represents all punctuation characters.</li> |
| 8180 |
| 8181 <li><b><code>%s</code>: </b> represents all space characters.</li> |
| 8182 |
| 8183 <li><b><code>%u</code>: </b> represents all uppercase letters.</li> |
| 8184 |
| 8185 <li><b><code>%w</code>: </b> represents all alphanumeric characters.</li> |
| 8186 |
| 8187 <li><b><code>%x</code>: </b> represents all hexadecimal digits.</li> |
| 8188 |
| 8189 <li><b><code>%<em>x</em></code>: </b> (where <em>x</em> is any non-alphanumeric
character) |
| 8190 represents the character <em>x</em>. |
| 8191 This is the standard way to escape the magic characters. |
| 8192 Any punctuation character (even the non magic) |
| 8193 can be preceded by a '<code>%</code>' |
| 8194 when used to represent itself in a pattern. |
| 8195 </li> |
| 8196 |
| 8197 <li><b><code>[<em>set</em>]</code>: </b> |
| 8198 represents the class which is the union of all |
| 8199 characters in <em>set</em>. |
| 8200 A range of characters can be specified by |
| 8201 separating the end characters of the range, |
| 8202 in ascending order, with a '<code>-</code>', |
| 8203 All classes <code>%</code><em>x</em> described above can also be used as |
| 8204 components in <em>set</em>. |
| 8205 All other characters in <em>set</em> represent themselves. |
| 8206 For example, <code>[%w_]</code> (or <code>[_%w]</code>) |
| 8207 represents all alphanumeric characters plus the underscore, |
| 8208 <code>[0-7]</code> represents the octal digits, |
| 8209 and <code>[0-7%l%-]</code> represents the octal digits plus |
| 8210 the lowercase letters plus the '<code>-</code>' character. |
| 8211 |
| 8212 |
| 8213 <p> |
| 8214 The interaction between ranges and classes is not defined. |
| 8215 Therefore, patterns like <code>[%a-z]</code> or <code>[a-%%]</code> |
| 8216 have no meaning. |
| 8217 </li> |
| 8218 |
| 8219 <li><b><code>[^<em>set</em>]</code>: </b> |
| 8220 represents the complement of <em>set</em>, |
| 8221 where <em>set</em> is interpreted as above. |
| 8222 </li> |
| 8223 |
| 8224 </ul><p> |
| 8225 For all classes represented by single letters (<code>%a</code>, <code>%c</code>,
etc.), |
| 8226 the corresponding uppercase letter represents the complement of the class. |
| 8227 For instance, <code>%S</code> represents all non-space characters. |
| 8228 |
| 8229 |
| 8230 <p> |
| 8231 The definitions of letter, space, and other character groups |
| 8232 depend on the current locale. |
| 8233 In particular, the class <code>[a-z]</code> may not be equivalent to <code>%l</c
ode>. |
| 8234 |
| 8235 |
| 8236 |
| 8237 |
| 8238 |
| 8239 <h4>Pattern Item:</h4><p> |
| 8240 A <em>pattern item</em> can be |
| 8241 |
| 8242 <ul> |
| 8243 |
| 8244 <li> |
| 8245 a single character class, |
| 8246 which matches any single character in the class; |
| 8247 </li> |
| 8248 |
| 8249 <li> |
| 8250 a single character class followed by '<code>*</code>', |
| 8251 which matches 0 or more repetitions of characters in the class. |
| 8252 These repetition items will always match the longest possible sequence; |
| 8253 </li> |
| 8254 |
| 8255 <li> |
| 8256 a single character class followed by '<code>+</code>', |
| 8257 which matches 1 or more repetitions of characters in the class. |
| 8258 These repetition items will always match the longest possible sequence; |
| 8259 </li> |
| 8260 |
| 8261 <li> |
| 8262 a single character class followed by '<code>-</code>', |
| 8263 which also matches 0 or more repetitions of characters in the class. |
| 8264 Unlike '<code>*</code>', |
| 8265 these repetition items will always match the shortest possible sequence; |
| 8266 </li> |
| 8267 |
| 8268 <li> |
| 8269 a single character class followed by '<code>?</code>', |
| 8270 which matches 0 or 1 occurrence of a character in the class; |
| 8271 </li> |
| 8272 |
| 8273 <li> |
| 8274 <code>%<em>n</em></code>, for <em>n</em> between 1 and 9; |
| 8275 such item matches a substring equal to the <em>n</em>-th captured string |
| 8276 (see below); |
| 8277 </li> |
| 8278 |
| 8279 <li> |
| 8280 <code>%b<em>xy</em></code>, where <em>x</em> and <em>y</em> are two distinct cha
racters; |
| 8281 such item matches strings that start with <em>x</em>, end with <em>y</
em>, |
| 8282 and where the <em>x</em> and <em>y</em> are <em>balanced</em>. |
| 8283 This means that, if one reads the string from left to right, |
| 8284 counting <em>+1</em> for an <em>x</em> and <em>-1</em> for a <em>y</em>, |
| 8285 the ending <em>y</em> is the first <em>y</em> where the count reaches 0. |
| 8286 For instance, the item <code>%b()</code> matches expressions with |
| 8287 balanced parentheses. |
| 8288 </li> |
| 8289 |
| 8290 <li> |
| 8291 <code>%f[<em>set</em>]</code>, a <em>frontier pattern</em>; |
| 8292 such item matches an empty string at any position such that |
| 8293 the next character belongs to <em>set</em> |
| 8294 and the previous character does not belong to <em>set</em>. |
| 8295 The set <em>set</em> is interpreted as previously described. |
| 8296 The beginning and the end of the subject are handled as if |
| 8297 they were the character '<code>\0</code>'. |
| 8298 </li> |
| 8299 |
| 8300 </ul> |
| 8301 |
| 8302 |
| 8303 |
| 8304 |
| 8305 <h4>Pattern:</h4><p> |
| 8306 A <em>pattern</em> is a sequence of pattern items. |
| 8307 A caret '<code>^</code>' at the beginning of a pattern anchors the match at the |
| 8308 beginning of the subject string. |
| 8309 A '<code>$</code>' at the end of a pattern anchors the match at the |
| 8310 end of the subject string. |
| 8311 At other positions, |
| 8312 '<code>^</code>' and '<code>$</code>' have no special meaning and represent them
selves. |
| 8313 |
| 8314 |
| 8315 |
| 8316 |
| 8317 |
| 8318 <h4>Captures:</h4><p> |
| 8319 A pattern can contain sub-patterns enclosed in parentheses; |
| 8320 they describe <em>captures</em>. |
| 8321 When a match succeeds, the substrings of the subject string |
| 8322 that match captures are stored (<em>captured</em>) for future use. |
| 8323 Captures are numbered according to their left parentheses. |
| 8324 For instance, in the pattern <code>"(a*(.)%w(%s*))"</code>, |
| 8325 the part of the string matching <code>"a*(.)%w(%s*)"</code> is |
| 8326 stored as the first capture (and therefore has number 1); |
| 8327 the character matching "<code>.</code>" is captured with number 2, |
| 8328 and the part matching "<code>%s*</code>" has number 3. |
| 8329 |
| 8330 |
| 8331 <p> |
| 8332 As a special case, the empty capture <code>()</code> captures |
| 8333 the current string position (a number). |
| 8334 For instance, if we apply the pattern <code>"()aa()"</code> on the |
| 8335 string <code>"flaaap"</code>, there will be two captures: 3 and 5. |
| 8336 |
| 8337 |
| 8338 |
| 8339 |
| 8340 |
| 8341 |
| 8342 |
| 8343 |
| 8344 |
| 8345 |
| 8346 |
| 8347 <h2>6.5 – <a name="6.5">Table Manipulation</a></h2> |
| 8348 |
| 8349 <p> |
| 8350 This library provides generic functions for table manipulation. |
| 8351 It provides all its functions inside the table <a name="pdf-table"><code>table</
code></a>. |
| 8352 |
| 8353 |
| 8354 <p> |
| 8355 Remember that, whenever an operation needs the length of a table, |
| 8356 the table should be a proper sequence |
| 8357 or have a <code>__len</code> metamethod (see <a href="#3.4.6">§3.4.6</a>). |
| 8358 All functions ignore non-numeric keys |
| 8359 in tables given as arguments. |
| 8360 |
| 8361 |
| 8362 <p> |
| 8363 For performance reasons, |
| 8364 all table accesses (get/set) performed by these functions are raw. |
| 8365 |
| 8366 |
| 8367 <p> |
| 8368 <hr><h3><a name="pdf-table.concat"><code>table.concat (list [, sep [, i [, j]]])
</code></a></h3> |
| 8369 |
| 8370 |
| 8371 <p> |
| 8372 Given a list where all elements are strings or numbers, |
| 8373 returns the string <code>list[i]..sep..list[i+1] ··· sep..l
ist[j]</code>. |
| 8374 The default value for <code>sep</code> is the empty string, |
| 8375 the default for <code>i</code> is 1, |
| 8376 and the default for <code>j</code> is <code>#list</code>. |
| 8377 If <code>i</code> is greater than <code>j</code>, returns the empty string. |
| 8378 |
| 8379 |
| 8380 |
| 8381 |
| 8382 <p> |
| 8383 <hr><h3><a name="pdf-table.insert"><code>table.insert (list, [pos,] value)</code
></a></h3> |
| 8384 |
| 8385 |
| 8386 <p> |
| 8387 Inserts element <code>value</code> at position <code>pos</code> in <code>list</c
ode>, |
| 8388 shifting up the elements |
| 8389 <code>list[pos], list[pos+1], ···, list[#list]</code>. |
| 8390 The default value for <code>pos</code> is <code>#list+1</code>, |
| 8391 so that a call <code>table.insert(t,x)</code> inserts <code>x</code> at the end |
| 8392 of list <code>t</code>. |
| 8393 |
| 8394 |
| 8395 |
| 8396 |
| 8397 <p> |
| 8398 <hr><h3><a name="pdf-table.pack"><code>table.pack (···)</co
de></a></h3> |
| 8399 |
| 8400 |
| 8401 <p> |
| 8402 Returns a new table with all parameters stored into keys 1, 2, etc. |
| 8403 and with a field "<code>n</code>" with the total number of parameters. |
| 8404 Note that the resulting table may not be a sequence. |
| 8405 |
| 8406 |
| 8407 |
| 8408 |
| 8409 <p> |
| 8410 <hr><h3><a name="pdf-table.remove"><code>table.remove (list [, pos])</code></a><
/h3> |
| 8411 |
| 8412 |
| 8413 <p> |
| 8414 Removes from <code>list</code> the element at position <code>pos</code>, |
| 8415 returning the value of the removed element. |
| 8416 When <code>pos</code> is an integer between 1 and <code>#list</code>, |
| 8417 it shifts down the elements |
| 8418 <code>list[pos+1], list[pos+2], ···, list[#list]</code> |
| 8419 and erases element <code>list[#list]</code>; |
| 8420 The index <code>pos</code> can also be 0 when <code>#list</code> is 0, |
| 8421 or <code>#list + 1</code>; |
| 8422 in those cases, the function erases the element <code>list[pos]</code>. |
| 8423 |
| 8424 |
| 8425 <p> |
| 8426 The default value for <code>pos</code> is <code>#list</code>, |
| 8427 so that a call <code>table.remove(t)</code> removes the last element |
| 8428 of list <code>t</code>. |
| 8429 |
| 8430 |
| 8431 |
| 8432 |
| 8433 <p> |
| 8434 <hr><h3><a name="pdf-table.sort"><code>table.sort (list [, comp])</code></a></h3
> |
| 8435 |
| 8436 |
| 8437 <p> |
| 8438 Sorts list elements in a given order, <em>in-place</em>, |
| 8439 from <code>list[1]</code> to <code>list[#list]</code>. |
| 8440 If <code>comp</code> is given, |
| 8441 then it must be a function that receives two list elements |
| 8442 and returns true when the first element must come |
| 8443 before the second in the final order |
| 8444 (so that <code>not comp(list[i+1],list[i])</code> will be true after the sort). |
| 8445 If <code>comp</code> is not given, |
| 8446 then the standard Lua operator <code><</code> is used instead. |
| 8447 |
| 8448 |
| 8449 <p> |
| 8450 The sort algorithm is not stable; |
| 8451 that is, elements considered equal by the given order |
| 8452 may have their relative positions changed by the sort. |
| 8453 |
| 8454 |
| 8455 |
| 8456 |
| 8457 <p> |
| 8458 <hr><h3><a name="pdf-table.unpack"><code>table.unpack (list [, i [, j]])</code><
/a></h3> |
| 8459 |
| 8460 |
| 8461 <p> |
| 8462 Returns the elements from the given table. |
| 8463 This function is equivalent to |
| 8464 |
| 8465 <pre> |
| 8466 return list[i], list[i+1], ···, list[j] |
| 8467 </pre><p> |
| 8468 By default, <code>i</code> is 1 and <code>j</code> is <code>#list</code>. |
| 8469 |
| 8470 |
| 8471 |
| 8472 |
| 8473 |
| 8474 |
| 8475 |
| 8476 <h2>6.6 – <a name="6.6">Mathematical Functions</a></h2> |
| 8477 |
| 8478 <p> |
| 8479 This library is an interface to the standard C math library. |
| 8480 It provides all its functions inside the table <a name="pdf-math"><code>math</co
de></a>. |
| 8481 |
| 8482 |
| 8483 <p> |
| 8484 <hr><h3><a name="pdf-math.abs"><code>math.abs (x)</code></a></h3> |
| 8485 |
| 8486 |
| 8487 <p> |
| 8488 Returns the absolute value of <code>x</code>. |
| 8489 |
| 8490 |
| 8491 |
| 8492 |
| 8493 <p> |
| 8494 <hr><h3><a name="pdf-math.acos"><code>math.acos (x)</code></a></h3> |
| 8495 |
| 8496 |
| 8497 <p> |
| 8498 Returns the arc cosine of <code>x</code> (in radians). |
| 8499 |
| 8500 |
| 8501 |
| 8502 |
| 8503 <p> |
| 8504 <hr><h3><a name="pdf-math.asin"><code>math.asin (x)</code></a></h3> |
| 8505 |
| 8506 |
| 8507 <p> |
| 8508 Returns the arc sine of <code>x</code> (in radians). |
| 8509 |
| 8510 |
| 8511 |
| 8512 |
| 8513 <p> |
| 8514 <hr><h3><a name="pdf-math.atan"><code>math.atan (x)</code></a></h3> |
| 8515 |
| 8516 |
| 8517 <p> |
| 8518 Returns the arc tangent of <code>x</code> (in radians). |
| 8519 |
| 8520 |
| 8521 |
| 8522 |
| 8523 <p> |
| 8524 <hr><h3><a name="pdf-math.atan2"><code>math.atan2 (y, x)</code></a></h3> |
| 8525 |
| 8526 |
| 8527 <p> |
| 8528 Returns the arc tangent of <code>y/x</code> (in radians), |
| 8529 but uses the signs of both parameters to find the |
| 8530 quadrant of the result. |
| 8531 (It also handles correctly the case of <code>x</code> being zero.) |
| 8532 |
| 8533 |
| 8534 |
| 8535 |
| 8536 <p> |
| 8537 <hr><h3><a name="pdf-math.ceil"><code>math.ceil (x)</code></a></h3> |
| 8538 |
| 8539 |
| 8540 <p> |
| 8541 Returns the smallest integer larger than or equal to <code>x</code>. |
| 8542 |
| 8543 |
| 8544 |
| 8545 |
| 8546 <p> |
| 8547 <hr><h3><a name="pdf-math.cos"><code>math.cos (x)</code></a></h3> |
| 8548 |
| 8549 |
| 8550 <p> |
| 8551 Returns the cosine of <code>x</code> (assumed to be in radians). |
| 8552 |
| 8553 |
| 8554 |
| 8555 |
| 8556 <p> |
| 8557 <hr><h3><a name="pdf-math.cosh"><code>math.cosh (x)</code></a></h3> |
| 8558 |
| 8559 |
| 8560 <p> |
| 8561 Returns the hyperbolic cosine of <code>x</code>. |
| 8562 |
| 8563 |
| 8564 |
| 8565 |
| 8566 <p> |
| 8567 <hr><h3><a name="pdf-math.deg"><code>math.deg (x)</code></a></h3> |
| 8568 |
| 8569 |
| 8570 <p> |
| 8571 Returns the angle <code>x</code> (given in radians) in degrees. |
| 8572 |
| 8573 |
| 8574 |
| 8575 |
| 8576 <p> |
| 8577 <hr><h3><a name="pdf-math.exp"><code>math.exp (x)</code></a></h3> |
| 8578 |
| 8579 |
| 8580 <p> |
| 8581 Returns the value <em>e<sup>x</sup></em>. |
| 8582 |
| 8583 |
| 8584 |
| 8585 |
| 8586 <p> |
| 8587 <hr><h3><a name="pdf-math.floor"><code>math.floor (x)</code></a></h3> |
| 8588 |
| 8589 |
| 8590 <p> |
| 8591 Returns the largest integer smaller than or equal to <code>x</code>. |
| 8592 |
| 8593 |
| 8594 |
| 8595 |
| 8596 <p> |
| 8597 <hr><h3><a name="pdf-math.fmod"><code>math.fmod (x, y)</code></a></h3> |
| 8598 |
| 8599 |
| 8600 <p> |
| 8601 Returns the remainder of the division of <code>x</code> by <code>y</code> |
| 8602 that rounds the quotient towards zero. |
| 8603 |
| 8604 |
| 8605 |
| 8606 |
| 8607 <p> |
| 8608 <hr><h3><a name="pdf-math.frexp"><code>math.frexp (x)</code></a></h3> |
| 8609 |
| 8610 |
| 8611 <p> |
| 8612 Returns <code>m</code> and <code>e</code> such that <em>x = m2<sup>e</sup></em>, |
| 8613 <code>e</code> is an integer and the absolute value of <code>m</code> is |
| 8614 in the range <em>[0.5, 1)</em> |
| 8615 (or zero when <code>x</code> is zero). |
| 8616 |
| 8617 |
| 8618 |
| 8619 |
| 8620 <p> |
| 8621 <hr><h3><a name="pdf-math.huge"><code>math.huge</code></a></h3> |
| 8622 |
| 8623 |
| 8624 <p> |
| 8625 The value <code>HUGE_VAL</code>, |
| 8626 a value larger than or equal to any other numerical value. |
| 8627 |
| 8628 |
| 8629 |
| 8630 |
| 8631 <p> |
| 8632 <hr><h3><a name="pdf-math.ldexp"><code>math.ldexp (m, e)</code></a></h3> |
| 8633 |
| 8634 |
| 8635 <p> |
| 8636 Returns <em>m2<sup>e</sup></em> (<code>e</code> should be an integer). |
| 8637 |
| 8638 |
| 8639 |
| 8640 |
| 8641 <p> |
| 8642 <hr><h3><a name="pdf-math.log"><code>math.log (x [, base])</code></a></h3> |
| 8643 |
| 8644 |
| 8645 <p> |
| 8646 Returns the logarithm of <code>x</code> in the given base. |
| 8647 The default for <code>base</code> is <em>e</em> |
| 8648 (so that the function returns the natural logarithm of <code>x</code>). |
| 8649 |
| 8650 |
| 8651 |
| 8652 |
| 8653 <p> |
| 8654 <hr><h3><a name="pdf-math.max"><code>math.max (x, ···)</cod
e></a></h3> |
| 8655 |
| 8656 |
| 8657 <p> |
| 8658 Returns the maximum value among its arguments. |
| 8659 |
| 8660 |
| 8661 |
| 8662 |
| 8663 <p> |
| 8664 <hr><h3><a name="pdf-math.min"><code>math.min (x, ···)</cod
e></a></h3> |
| 8665 |
| 8666 |
| 8667 <p> |
| 8668 Returns the minimum value among its arguments. |
| 8669 |
| 8670 |
| 8671 |
| 8672 |
| 8673 <p> |
| 8674 <hr><h3><a name="pdf-math.modf"><code>math.modf (x)</code></a></h3> |
| 8675 |
| 8676 |
| 8677 <p> |
| 8678 Returns two numbers, |
| 8679 the integral part of <code>x</code> and the fractional part of <code>x</code>. |
| 8680 |
| 8681 |
| 8682 |
| 8683 |
| 8684 <p> |
| 8685 <hr><h3><a name="pdf-math.pi"><code>math.pi</code></a></h3> |
| 8686 |
| 8687 |
| 8688 <p> |
| 8689 The value of <em>π</em>. |
| 8690 |
| 8691 |
| 8692 |
| 8693 |
| 8694 <p> |
| 8695 <hr><h3><a name="pdf-math.pow"><code>math.pow (x, y)</code></a></h3> |
| 8696 |
| 8697 |
| 8698 <p> |
| 8699 Returns <em>x<sup>y</sup></em>. |
| 8700 (You can also use the expression <code>x^y</code> to compute this value.) |
| 8701 |
| 8702 |
| 8703 |
| 8704 |
| 8705 <p> |
| 8706 <hr><h3><a name="pdf-math.rad"><code>math.rad (x)</code></a></h3> |
| 8707 |
| 8708 |
| 8709 <p> |
| 8710 Returns the angle <code>x</code> (given in degrees) in radians. |
| 8711 |
| 8712 |
| 8713 |
| 8714 |
| 8715 <p> |
| 8716 <hr><h3><a name="pdf-math.random"><code>math.random ([m [, n]])</code></a></h3> |
| 8717 |
| 8718 |
| 8719 <p> |
| 8720 This function is an interface to the simple |
| 8721 pseudo-random generator function <code>rand</code> provided by Standard C. |
| 8722 (No guarantees can be given for its statistical properties.) |
| 8723 |
| 8724 |
| 8725 <p> |
| 8726 When called without arguments, |
| 8727 returns a uniform pseudo-random real number |
| 8728 in the range <em>[0,1)</em>. |
| 8729 When called with an integer number <code>m</code>, |
| 8730 <code>math.random</code> returns |
| 8731 a uniform pseudo-random integer in the range <em>[1, m]</em>. |
| 8732 When called with two integer numbers <code>m</code> and <code>n</code>, |
| 8733 <code>math.random</code> returns a uniform pseudo-random |
| 8734 integer in the range <em>[m, n]</em>. |
| 8735 |
| 8736 |
| 8737 |
| 8738 |
| 8739 <p> |
| 8740 <hr><h3><a name="pdf-math.randomseed"><code>math.randomseed (x)</code></a></h3> |
| 8741 |
| 8742 |
| 8743 <p> |
| 8744 Sets <code>x</code> as the "seed" |
| 8745 for the pseudo-random generator: |
| 8746 equal seeds produce equal sequences of numbers. |
| 8747 |
| 8748 |
| 8749 |
| 8750 |
| 8751 <p> |
| 8752 <hr><h3><a name="pdf-math.sin"><code>math.sin (x)</code></a></h3> |
| 8753 |
| 8754 |
| 8755 <p> |
| 8756 Returns the sine of <code>x</code> (assumed to be in radians). |
| 8757 |
| 8758 |
| 8759 |
| 8760 |
| 8761 <p> |
| 8762 <hr><h3><a name="pdf-math.sinh"><code>math.sinh (x)</code></a></h3> |
| 8763 |
| 8764 |
| 8765 <p> |
| 8766 Returns the hyperbolic sine of <code>x</code>. |
| 8767 |
| 8768 |
| 8769 |
| 8770 |
| 8771 <p> |
| 8772 <hr><h3><a name="pdf-math.sqrt"><code>math.sqrt (x)</code></a></h3> |
| 8773 |
| 8774 |
| 8775 <p> |
| 8776 Returns the square root of <code>x</code>. |
| 8777 (You can also use the expression <code>x^0.5</code> to compute this value.) |
| 8778 |
| 8779 |
| 8780 |
| 8781 |
| 8782 <p> |
| 8783 <hr><h3><a name="pdf-math.tan"><code>math.tan (x)</code></a></h3> |
| 8784 |
| 8785 |
| 8786 <p> |
| 8787 Returns the tangent of <code>x</code> (assumed to be in radians). |
| 8788 |
| 8789 |
| 8790 |
| 8791 |
| 8792 <p> |
| 8793 <hr><h3><a name="pdf-math.tanh"><code>math.tanh (x)</code></a></h3> |
| 8794 |
| 8795 |
| 8796 <p> |
| 8797 Returns the hyperbolic tangent of <code>x</code>. |
| 8798 |
| 8799 |
| 8800 |
| 8801 |
| 8802 |
| 8803 |
| 8804 |
| 8805 <h2>6.7 – <a name="6.7">Bitwise Operations</a></h2> |
| 8806 |
| 8807 <p> |
| 8808 This library provides bitwise operations. |
| 8809 It provides all its functions inside the table <a name="pdf-bit32"><code>bit32</
code></a>. |
| 8810 |
| 8811 |
| 8812 <p> |
| 8813 Unless otherwise stated, |
| 8814 all functions accept numeric arguments in the range |
| 8815 <em>(-2<sup>51</sup>,+2<sup>51</sup>)</em>; |
| 8816 each argument is normalized to |
| 8817 the remainder of its division by <em>2<sup>32</sup></em> |
| 8818 and truncated to an integer (in some unspecified way), |
| 8819 so that its final value falls in the range <em>[0,2<sup>32</sup> - 1]</em>. |
| 8820 Similarly, all results are in the range <em>[0,2<sup>32</sup> - 1]</em>. |
| 8821 Note that <code>bit32.bnot(0)</code> is <code>0xFFFFFFFF</code>, |
| 8822 which is different from <code>-1</code>. |
| 8823 |
| 8824 |
| 8825 <p> |
| 8826 <hr><h3><a name="pdf-bit32.arshift"><code>bit32.arshift (x, disp)</code></a></h3
> |
| 8827 |
| 8828 |
| 8829 <p> |
| 8830 Returns the number <code>x</code> shifted <code>disp</code> bits to the right. |
| 8831 The number <code>disp</code> may be any representable integer. |
| 8832 Negative displacements shift to the left. |
| 8833 |
| 8834 |
| 8835 <p> |
| 8836 This shift operation is what is called arithmetic shift. |
| 8837 Vacant bits on the left are filled |
| 8838 with copies of the higher bit of <code>x</code>; |
| 8839 vacant bits on the right are filled with zeros. |
| 8840 In particular, |
| 8841 displacements with absolute values higher than 31 |
| 8842 result in zero or <code>0xFFFFFFFF</code> (all original bits are shifted out). |
| 8843 |
| 8844 |
| 8845 |
| 8846 |
| 8847 <p> |
| 8848 <hr><h3><a name="pdf-bit32.band"><code>bit32.band (···)</co
de></a></h3> |
| 8849 |
| 8850 |
| 8851 <p> |
| 8852 Returns the bitwise <em>and</em> of its operands. |
| 8853 |
| 8854 |
| 8855 |
| 8856 |
| 8857 <p> |
| 8858 <hr><h3><a name="pdf-bit32.bnot"><code>bit32.bnot (x)</code></a></h3> |
| 8859 |
| 8860 |
| 8861 <p> |
| 8862 Returns the bitwise negation of <code>x</code>. |
| 8863 For any integer <code>x</code>, |
| 8864 the following identity holds: |
| 8865 |
| 8866 <pre> |
| 8867 assert(bit32.bnot(x) == (-1 - x) % 2^32) |
| 8868 </pre> |
| 8869 |
| 8870 |
| 8871 |
| 8872 <p> |
| 8873 <hr><h3><a name="pdf-bit32.bor"><code>bit32.bor (···)</code
></a></h3> |
| 8874 |
| 8875 |
| 8876 <p> |
| 8877 Returns the bitwise <em>or</em> of its operands. |
| 8878 |
| 8879 |
| 8880 |
| 8881 |
| 8882 <p> |
| 8883 <hr><h3><a name="pdf-bit32.btest"><code>bit32.btest (···)</
code></a></h3> |
| 8884 |
| 8885 |
| 8886 <p> |
| 8887 Returns a boolean signaling |
| 8888 whether the bitwise <em>and</em> of its operands is different from zero. |
| 8889 |
| 8890 |
| 8891 |
| 8892 |
| 8893 <p> |
| 8894 <hr><h3><a name="pdf-bit32.bxor"><code>bit32.bxor (···)</co
de></a></h3> |
| 8895 |
| 8896 |
| 8897 <p> |
| 8898 Returns the bitwise <em>exclusive or</em> of its operands. |
| 8899 |
| 8900 |
| 8901 |
| 8902 |
| 8903 <p> |
| 8904 <hr><h3><a name="pdf-bit32.extract"><code>bit32.extract (n, field [, width])</co
de></a></h3> |
| 8905 |
| 8906 |
| 8907 <p> |
| 8908 Returns the unsigned number formed by the bits |
| 8909 <code>field</code> to <code>field + width - 1</code> from <code>n</code>. |
| 8910 Bits are numbered from 0 (least significant) to 31 (most significant). |
| 8911 All accessed bits must be in the range <em>[0, 31]</em>. |
| 8912 |
| 8913 |
| 8914 <p> |
| 8915 The default for <code>width</code> is 1. |
| 8916 |
| 8917 |
| 8918 |
| 8919 |
| 8920 <p> |
| 8921 <hr><h3><a name="pdf-bit32.replace"><code>bit32.replace (n, v, field [, width])<
/code></a></h3> |
| 8922 |
| 8923 |
| 8924 <p> |
| 8925 Returns a copy of <code>n</code> with |
| 8926 the bits <code>field</code> to <code>field + width - 1</code> |
| 8927 replaced by the value <code>v</code>. |
| 8928 See <a href="#pdf-bit32.extract"><code>bit32.extract</code></a> for details abou
t <code>field</code> and <code>width</code>. |
| 8929 |
| 8930 |
| 8931 |
| 8932 |
| 8933 <p> |
| 8934 <hr><h3><a name="pdf-bit32.lrotate"><code>bit32.lrotate (x, disp)</code></a></h3
> |
| 8935 |
| 8936 |
| 8937 <p> |
| 8938 Returns the number <code>x</code> rotated <code>disp</code> bits to the left. |
| 8939 The number <code>disp</code> may be any representable integer. |
| 8940 |
| 8941 |
| 8942 <p> |
| 8943 For any valid displacement, |
| 8944 the following identity holds: |
| 8945 |
| 8946 <pre> |
| 8947 assert(bit32.lrotate(x, disp) == bit32.lrotate(x, disp % 32)) |
| 8948 </pre><p> |
| 8949 In particular, |
| 8950 negative displacements rotate to the right. |
| 8951 |
| 8952 |
| 8953 |
| 8954 |
| 8955 <p> |
| 8956 <hr><h3><a name="pdf-bit32.lshift"><code>bit32.lshift (x, disp)</code></a></h3> |
| 8957 |
| 8958 |
| 8959 <p> |
| 8960 Returns the number <code>x</code> shifted <code>disp</code> bits to the left. |
| 8961 The number <code>disp</code> may be any representable integer. |
| 8962 Negative displacements shift to the right. |
| 8963 In any direction, vacant bits are filled with zeros. |
| 8964 In particular, |
| 8965 displacements with absolute values higher than 31 |
| 8966 result in zero (all bits are shifted out). |
| 8967 |
| 8968 |
| 8969 <p> |
| 8970 For positive displacements, |
| 8971 the following equality holds: |
| 8972 |
| 8973 <pre> |
| 8974 assert(bit32.lshift(b, disp) == (b * 2^disp) % 2^32) |
| 8975 </pre> |
| 8976 |
| 8977 |
| 8978 |
| 8979 <p> |
| 8980 <hr><h3><a name="pdf-bit32.rrotate"><code>bit32.rrotate (x, disp)</code></a></h3
> |
| 8981 |
| 8982 |
| 8983 <p> |
| 8984 Returns the number <code>x</code> rotated <code>disp</code> bits to the right. |
| 8985 The number <code>disp</code> may be any representable integer. |
| 8986 |
| 8987 |
| 8988 <p> |
| 8989 For any valid displacement, |
| 8990 the following identity holds: |
| 8991 |
| 8992 <pre> |
| 8993 assert(bit32.rrotate(x, disp) == bit32.rrotate(x, disp % 32)) |
| 8994 </pre><p> |
| 8995 In particular, |
| 8996 negative displacements rotate to the left. |
| 8997 |
| 8998 |
| 8999 |
| 9000 |
| 9001 <p> |
| 9002 <hr><h3><a name="pdf-bit32.rshift"><code>bit32.rshift (x, disp)</code></a></h3> |
| 9003 |
| 9004 |
| 9005 <p> |
| 9006 Returns the number <code>x</code> shifted <code>disp</code> bits to the right. |
| 9007 The number <code>disp</code> may be any representable integer. |
| 9008 Negative displacements shift to the left. |
| 9009 In any direction, vacant bits are filled with zeros. |
| 9010 In particular, |
| 9011 displacements with absolute values higher than 31 |
| 9012 result in zero (all bits are shifted out). |
| 9013 |
| 9014 |
| 9015 <p> |
| 9016 For positive displacements, |
| 9017 the following equality holds: |
| 9018 |
| 9019 <pre> |
| 9020 assert(bit32.rshift(b, disp) == math.floor(b % 2^32 / 2^disp)) |
| 9021 </pre> |
| 9022 |
| 9023 <p> |
| 9024 This shift operation is what is called logical shift. |
| 9025 |
| 9026 |
| 9027 |
| 9028 |
| 9029 |
| 9030 |
| 9031 |
| 9032 <h2>6.8 – <a name="6.8">Input and Output Facilities</a></h2> |
| 9033 |
| 9034 <p> |
| 9035 The I/O library provides two different styles for file manipulation. |
| 9036 The first one uses implicit file descriptors; |
| 9037 that is, there are operations to set a default input file and a |
| 9038 default output file, |
| 9039 and all input/output operations are over these default files. |
| 9040 The second style uses explicit file descriptors. |
| 9041 |
| 9042 |
| 9043 <p> |
| 9044 When using implicit file descriptors, |
| 9045 all operations are supplied by table <a name="pdf-io"><code>io</code></a>. |
| 9046 When using explicit file descriptors, |
| 9047 the operation <a href="#pdf-io.open"><code>io.open</code></a> returns a file des
criptor |
| 9048 and then all operations are supplied as methods of the file descriptor. |
| 9049 |
| 9050 |
| 9051 <p> |
| 9052 The table <code>io</code> also provides |
| 9053 three predefined file descriptors with their usual meanings from C: |
| 9054 <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>. |
| 9055 The I/O library never closes these files. |
| 9056 |
| 9057 |
| 9058 <p> |
| 9059 Unless otherwise stated, |
| 9060 all I/O functions return <b>nil</b> on failure |
| 9061 (plus an error message as a second result and |
| 9062 a system-dependent error code as a third result) |
| 9063 and some value different from <b>nil</b> on success. |
| 9064 On non-Posix systems, |
| 9065 the computation of the error message and error code |
| 9066 in case of errors |
| 9067 may be not thread safe, |
| 9068 because they rely on the global C variable <code>errno</code>. |
| 9069 |
| 9070 |
| 9071 <p> |
| 9072 <hr><h3><a name="pdf-io.close"><code>io.close ([file])</code></a></h3> |
| 9073 |
| 9074 |
| 9075 <p> |
| 9076 Equivalent to <code>file:close()</code>. |
| 9077 Without a <code>file</code>, closes the default output file. |
| 9078 |
| 9079 |
| 9080 |
| 9081 |
| 9082 <p> |
| 9083 <hr><h3><a name="pdf-io.flush"><code>io.flush ()</code></a></h3> |
| 9084 |
| 9085 |
| 9086 <p> |
| 9087 Equivalent to <code>io.output():flush()</code>. |
| 9088 |
| 9089 |
| 9090 |
| 9091 |
| 9092 <p> |
| 9093 <hr><h3><a name="pdf-io.input"><code>io.input ([file])</code></a></h3> |
| 9094 |
| 9095 |
| 9096 <p> |
| 9097 When called with a file name, it opens the named file (in text mode), |
| 9098 and sets its handle as the default input file. |
| 9099 When called with a file handle, |
| 9100 it simply sets this file handle as the default input file. |
| 9101 When called without parameters, |
| 9102 it returns the current default input file. |
| 9103 |
| 9104 |
| 9105 <p> |
| 9106 In case of errors this function raises the error, |
| 9107 instead of returning an error code. |
| 9108 |
| 9109 |
| 9110 |
| 9111 |
| 9112 <p> |
| 9113 <hr><h3><a name="pdf-io.lines"><code>io.lines ([filename ···
;])</code></a></h3> |
| 9114 |
| 9115 |
| 9116 <p> |
| 9117 Opens the given file name in read mode |
| 9118 and returns an iterator function that |
| 9119 works like <code>file:lines(···)</code> over the opened fil
e. |
| 9120 When the iterator function detects the end of file, |
| 9121 it returns <b>nil</b> (to finish the loop) and automatically closes the file. |
| 9122 |
| 9123 |
| 9124 <p> |
| 9125 The call <code>io.lines()</code> (with no file name) is equivalent |
| 9126 to <code>io.input():lines()</code>; |
| 9127 that is, it iterates over the lines of the default input file. |
| 9128 In this case it does not close the file when the loop ends. |
| 9129 |
| 9130 |
| 9131 <p> |
| 9132 In case of errors this function raises the error, |
| 9133 instead of returning an error code. |
| 9134 |
| 9135 |
| 9136 |
| 9137 |
| 9138 <p> |
| 9139 <hr><h3><a name="pdf-io.open"><code>io.open (filename [, mode])</code></a></h3> |
| 9140 |
| 9141 |
| 9142 <p> |
| 9143 This function opens a file, |
| 9144 in the mode specified in the string <code>mode</code>. |
| 9145 It returns a new file handle, |
| 9146 or, in case of errors, <b>nil</b> plus an error message. |
| 9147 |
| 9148 |
| 9149 <p> |
| 9150 The <code>mode</code> string can be any of the following: |
| 9151 |
| 9152 <ul> |
| 9153 <li><b>"<code>r</code>": </b> read mode (the default);</li> |
| 9154 <li><b>"<code>w</code>": </b> write mode;</li> |
| 9155 <li><b>"<code>a</code>": </b> append mode;</li> |
| 9156 <li><b>"<code>r+</code>": </b> update mode, all previous data is preserved;</li> |
| 9157 <li><b>"<code>w+</code>": </b> update mode, all previous data is erased;</li> |
| 9158 <li><b>"<code>a+</code>": </b> append update mode, previous data is preserved, |
| 9159 writing is only allowed at the end of file.</li> |
| 9160 </ul><p> |
| 9161 The <code>mode</code> string can also have a '<code>b</code>' at the end, |
| 9162 which is needed in some systems to open the file in binary mode. |
| 9163 |
| 9164 |
| 9165 |
| 9166 |
| 9167 <p> |
| 9168 <hr><h3><a name="pdf-io.output"><code>io.output ([file])</code></a></h3> |
| 9169 |
| 9170 |
| 9171 <p> |
| 9172 Similar to <a href="#pdf-io.input"><code>io.input</code></a>, but operates over
the default output file. |
| 9173 |
| 9174 |
| 9175 |
| 9176 |
| 9177 <p> |
| 9178 <hr><h3><a name="pdf-io.popen"><code>io.popen (prog [, mode])</code></a></h3> |
| 9179 |
| 9180 |
| 9181 <p> |
| 9182 This function is system dependent and is not available |
| 9183 on all platforms. |
| 9184 |
| 9185 |
| 9186 <p> |
| 9187 Starts program <code>prog</code> in a separated process and returns |
| 9188 a file handle that you can use to read data from this program |
| 9189 (if <code>mode</code> is <code>"r"</code>, the default) |
| 9190 or to write data to this program |
| 9191 (if <code>mode</code> is <code>"w"</code>). |
| 9192 |
| 9193 |
| 9194 |
| 9195 |
| 9196 <p> |
| 9197 <hr><h3><a name="pdf-io.read"><code>io.read (···)</code></a
></h3> |
| 9198 |
| 9199 |
| 9200 <p> |
| 9201 Equivalent to <code>io.input():read(···)</code>. |
| 9202 |
| 9203 |
| 9204 |
| 9205 |
| 9206 <p> |
| 9207 <hr><h3><a name="pdf-io.tmpfile"><code>io.tmpfile ()</code></a></h3> |
| 9208 |
| 9209 |
| 9210 <p> |
| 9211 Returns a handle for a temporary file. |
| 9212 This file is opened in update mode |
| 9213 and it is automatically removed when the program ends. |
| 9214 |
| 9215 |
| 9216 |
| 9217 |
| 9218 <p> |
| 9219 <hr><h3><a name="pdf-io.type"><code>io.type (obj)</code></a></h3> |
| 9220 |
| 9221 |
| 9222 <p> |
| 9223 Checks whether <code>obj</code> is a valid file handle. |
| 9224 Returns the string <code>"file"</code> if <code>obj</code> is an open file handl
e, |
| 9225 <code>"closed file"</code> if <code>obj</code> is a closed file handle, |
| 9226 or <b>nil</b> if <code>obj</code> is not a file handle. |
| 9227 |
| 9228 |
| 9229 |
| 9230 |
| 9231 <p> |
| 9232 <hr><h3><a name="pdf-io.write"><code>io.write (···)</code><
/a></h3> |
| 9233 |
| 9234 |
| 9235 <p> |
| 9236 Equivalent to <code>io.output():write(···)</code>. |
| 9237 |
| 9238 |
| 9239 |
| 9240 |
| 9241 <p> |
| 9242 <hr><h3><a name="pdf-file:close"><code>file:close ()</code></a></h3> |
| 9243 |
| 9244 |
| 9245 <p> |
| 9246 Closes <code>file</code>. |
| 9247 Note that files are automatically closed when |
| 9248 their handles are garbage collected, |
| 9249 but that takes an unpredictable amount of time to happen. |
| 9250 |
| 9251 |
| 9252 <p> |
| 9253 When closing a file handle created with <a href="#pdf-io.popen"><code>io.popen</
code></a>, |
| 9254 <a href="#pdf-file:close"><code>file:close</code></a> returns the same values |
| 9255 returned by <a href="#pdf-os.execute"><code>os.execute</code></a>. |
| 9256 |
| 9257 |
| 9258 |
| 9259 |
| 9260 <p> |
| 9261 <hr><h3><a name="pdf-file:flush"><code>file:flush ()</code></a></h3> |
| 9262 |
| 9263 |
| 9264 <p> |
| 9265 Saves any written data to <code>file</code>. |
| 9266 |
| 9267 |
| 9268 |
| 9269 |
| 9270 <p> |
| 9271 <hr><h3><a name="pdf-file:lines"><code>file:lines (···)</co
de></a></h3> |
| 9272 |
| 9273 |
| 9274 <p> |
| 9275 Returns an iterator function that, |
| 9276 each time it is called, |
| 9277 reads the file according to the given formats. |
| 9278 When no format is given, |
| 9279 uses "*l" as a default. |
| 9280 As an example, the construction |
| 9281 |
| 9282 <pre> |
| 9283 for c in file:lines(1) do <em>body</em> end |
| 9284 </pre><p> |
| 9285 will iterate over all characters of the file, |
| 9286 starting at the current position. |
| 9287 Unlike <a href="#pdf-io.lines"><code>io.lines</code></a>, this function does not
close the file |
| 9288 when the loop ends. |
| 9289 |
| 9290 |
| 9291 <p> |
| 9292 In case of errors this function raises the error, |
| 9293 instead of returning an error code. |
| 9294 |
| 9295 |
| 9296 |
| 9297 |
| 9298 <p> |
| 9299 <hr><h3><a name="pdf-file:read"><code>file:read (···)</code
></a></h3> |
| 9300 |
| 9301 |
| 9302 <p> |
| 9303 Reads the file <code>file</code>, |
| 9304 according to the given formats, which specify what to read. |
| 9305 For each format, |
| 9306 the function returns a string (or a number) with the characters read, |
| 9307 or <b>nil</b> if it cannot read data with the specified format. |
| 9308 When called without formats, |
| 9309 it uses a default format that reads the next line |
| 9310 (see below). |
| 9311 |
| 9312 |
| 9313 <p> |
| 9314 The available formats are |
| 9315 |
| 9316 <ul> |
| 9317 |
| 9318 <li><b>"<code>*n</code>": </b> |
| 9319 reads a number; |
| 9320 this is the only format that returns a number instead of a string. |
| 9321 </li> |
| 9322 |
| 9323 <li><b>"<code>*a</code>": </b> |
| 9324 reads the whole file, starting at the current position. |
| 9325 On end of file, it returns the empty string. |
| 9326 </li> |
| 9327 |
| 9328 <li><b>"<code>*l</code>": </b> |
| 9329 reads the next line skipping the end of line, |
| 9330 returning <b>nil</b> on end of file. |
| 9331 This is the default format. |
| 9332 </li> |
| 9333 |
| 9334 <li><b>"<code>*L</code>": </b> |
| 9335 reads the next line keeping the end of line (if present), |
| 9336 returning <b>nil</b> on end of file. |
| 9337 </li> |
| 9338 |
| 9339 <li><b><em>number</em>: </b> |
| 9340 reads a string with up to this number of bytes, |
| 9341 returning <b>nil</b> on end of file. |
| 9342 If number is zero, |
| 9343 it reads nothing and returns an empty string, |
| 9344 or <b>nil</b> on end of file. |
| 9345 </li> |
| 9346 |
| 9347 </ul> |
| 9348 |
| 9349 |
| 9350 |
| 9351 <p> |
| 9352 <hr><h3><a name="pdf-file:seek"><code>file:seek ([whence [, offset]])</code></a>
</h3> |
| 9353 |
| 9354 |
| 9355 <p> |
| 9356 Sets and gets the file position, |
| 9357 measured from the beginning of the file, |
| 9358 to the position given by <code>offset</code> plus a base |
| 9359 specified by the string <code>whence</code>, as follows: |
| 9360 |
| 9361 <ul> |
| 9362 <li><b>"<code>set</code>": </b> base is position 0 (beginning of the file);</li> |
| 9363 <li><b>"<code>cur</code>": </b> base is current position;</li> |
| 9364 <li><b>"<code>end</code>": </b> base is end of file;</li> |
| 9365 </ul><p> |
| 9366 In case of success, <code>seek</code> returns the final file position, |
| 9367 measured in bytes from the beginning of the file. |
| 9368 If <code>seek</code> fails, it returns <b>nil</b>, |
| 9369 plus a string describing the error. |
| 9370 |
| 9371 |
| 9372 <p> |
| 9373 The default value for <code>whence</code> is <code>"cur"</code>, |
| 9374 and for <code>offset</code> is 0. |
| 9375 Therefore, the call <code>file:seek()</code> returns the current |
| 9376 file position, without changing it; |
| 9377 the call <code>file:seek("set")</code> sets the position to the |
| 9378 beginning of the file (and returns 0); |
| 9379 and the call <code>file:seek("end")</code> sets the position to the |
| 9380 end of the file, and returns its size. |
| 9381 |
| 9382 |
| 9383 |
| 9384 |
| 9385 <p> |
| 9386 <hr><h3><a name="pdf-file:setvbuf"><code>file:setvbuf (mode [, size])</code></a>
</h3> |
| 9387 |
| 9388 |
| 9389 <p> |
| 9390 Sets the buffering mode for an output file. |
| 9391 There are three available modes: |
| 9392 |
| 9393 <ul> |
| 9394 |
| 9395 <li><b>"<code>no</code>": </b> |
| 9396 no buffering; the result of any output operation appears immediately. |
| 9397 </li> |
| 9398 |
| 9399 <li><b>"<code>full</code>": </b> |
| 9400 full buffering; output operation is performed only |
| 9401 when the buffer is full or when |
| 9402 you explicitly <code>flush</code> the file (see <a href="#pdf-io.flush"><code>io
.flush</code></a>). |
| 9403 </li> |
| 9404 |
| 9405 <li><b>"<code>line</code>": </b> |
| 9406 line buffering; output is buffered until a newline is output |
| 9407 or there is any input from some special files |
| 9408 (such as a terminal device). |
| 9409 </li> |
| 9410 |
| 9411 </ul><p> |
| 9412 For the last two cases, <code>size</code> |
| 9413 specifies the size of the buffer, in bytes. |
| 9414 The default is an appropriate size. |
| 9415 |
| 9416 |
| 9417 |
| 9418 |
| 9419 <p> |
| 9420 <hr><h3><a name="pdf-file:write"><code>file:write (···)</co
de></a></h3> |
| 9421 |
| 9422 |
| 9423 <p> |
| 9424 Writes the value of each of its arguments to <code>file</code>. |
| 9425 The arguments must be strings or numbers. |
| 9426 |
| 9427 |
| 9428 <p> |
| 9429 In case of success, this function returns <code>file</code>. |
| 9430 Otherwise it returns <b>nil</b> plus a string describing the error. |
| 9431 |
| 9432 |
| 9433 |
| 9434 |
| 9435 |
| 9436 |
| 9437 |
| 9438 <h2>6.9 – <a name="6.9">Operating System Facilities</a></h2> |
| 9439 |
| 9440 <p> |
| 9441 This library is implemented through table <a name="pdf-os"><code>os</code></a>. |
| 9442 |
| 9443 |
| 9444 <p> |
| 9445 <hr><h3><a name="pdf-os.clock"><code>os.clock ()</code></a></h3> |
| 9446 |
| 9447 |
| 9448 <p> |
| 9449 Returns an approximation of the amount in seconds of CPU time |
| 9450 used by the program. |
| 9451 |
| 9452 |
| 9453 |
| 9454 |
| 9455 <p> |
| 9456 <hr><h3><a name="pdf-os.date"><code>os.date ([format [, time]])</code></a></h3> |
| 9457 |
| 9458 |
| 9459 <p> |
| 9460 Returns a string or a table containing date and time, |
| 9461 formatted according to the given string <code>format</code>. |
| 9462 |
| 9463 |
| 9464 <p> |
| 9465 If the <code>time</code> argument is present, |
| 9466 this is the time to be formatted |
| 9467 (see the <a href="#pdf-os.time"><code>os.time</code></a> function for a descript
ion of this value). |
| 9468 Otherwise, <code>date</code> formats the current time. |
| 9469 |
| 9470 |
| 9471 <p> |
| 9472 If <code>format</code> starts with '<code>!</code>', |
| 9473 then the date is formatted in Coordinated Universal Time. |
| 9474 After this optional character, |
| 9475 if <code>format</code> is the string "<code>*t</code>", |
| 9476 then <code>date</code> returns a table with the following fields: |
| 9477 <code>year</code> (four digits), <code>month</code> (1–12), <code>day</cod
e> (1–31), |
| 9478 <code>hour</code> (0–23), <code>min</code> (0–59), <code>sec</code>
(0–61), |
| 9479 <code>wday</code> (weekday, Sunday is 1), |
| 9480 <code>yday</code> (day of the year), |
| 9481 and <code>isdst</code> (daylight saving flag, a boolean). |
| 9482 This last field may be absent |
| 9483 if the information is not available. |
| 9484 |
| 9485 |
| 9486 <p> |
| 9487 If <code>format</code> is not "<code>*t</code>", |
| 9488 then <code>date</code> returns the date as a string, |
| 9489 formatted according to the same rules as the ANSI C function <code>strftime
</code>. |
| 9490 |
| 9491 |
| 9492 <p> |
| 9493 When called without arguments, |
| 9494 <code>date</code> returns a reasonable date and time representation that depends
on |
| 9495 the host system and on the current locale |
| 9496 (that is, <code>os.date()</code> is equivalent to <code>os.date("%c")</code>). |
| 9497 |
| 9498 |
| 9499 <p> |
| 9500 On non-Posix systems, |
| 9501 this function may be not thread safe |
| 9502 because of its reliance on C function <code>gmtime</code> and C functi
on <code>localtime</code>. |
| 9503 |
| 9504 |
| 9505 |
| 9506 |
| 9507 <p> |
| 9508 <hr><h3><a name="pdf-os.difftime"><code>os.difftime (t2, t1)</code></a></h3> |
| 9509 |
| 9510 |
| 9511 <p> |
| 9512 Returns the number of seconds from time <code>t1</code> to time <code>t2</code>. |
| 9513 In POSIX, Windows, and some other systems, |
| 9514 this value is exactly <code>t2</code><em>-</em><code>t1</code>. |
| 9515 |
| 9516 |
| 9517 |
| 9518 |
| 9519 <p> |
| 9520 <hr><h3><a name="pdf-os.execute"><code>os.execute ([command])</code></a></h3> |
| 9521 |
| 9522 |
| 9523 <p> |
| 9524 This function is equivalent to the ANSI C function <code>system</code>. |
| 9525 It passes <code>command</code> to be executed by an operating system shell. |
| 9526 Its first result is <b>true</b> |
| 9527 if the command terminated successfully, |
| 9528 or <b>nil</b> otherwise. |
| 9529 After this first result |
| 9530 the function returns a string and a number, |
| 9531 as follows: |
| 9532 |
| 9533 <ul> |
| 9534 |
| 9535 <li><b>"<code>exit</code>": </b> |
| 9536 the command terminated normally; |
| 9537 the following number is the exit status of the command. |
| 9538 </li> |
| 9539 |
| 9540 <li><b>"<code>signal</code>": </b> |
| 9541 the command was terminated by a signal; |
| 9542 the following number is the signal that terminated the command. |
| 9543 </li> |
| 9544 |
| 9545 </ul> |
| 9546 |
| 9547 <p> |
| 9548 When called without a <code>command</code>, |
| 9549 <code>os.execute</code> returns a boolean that is true if a shell is available. |
| 9550 |
| 9551 |
| 9552 |
| 9553 |
| 9554 <p> |
| 9555 <hr><h3><a name="pdf-os.exit"><code>os.exit ([code [, close])</code></a></h3> |
| 9556 |
| 9557 |
| 9558 <p> |
| 9559 Calls the ANSI C function <code>exit</code> to terminate the host program. |
| 9560 If <code>code</code> is <b>true</b>, |
| 9561 the returned status is <code>EXIT_SUCCESS</code>; |
| 9562 if <code>code</code> is <b>false</b>, |
| 9563 the returned status is <code>EXIT_FAILURE</code>; |
| 9564 if <code>code</code> is a number, |
| 9565 the returned status is this number. |
| 9566 The default value for <code>code</code> is <b>true</b>. |
| 9567 |
| 9568 |
| 9569 <p> |
| 9570 If the optional second argument <code>close</code> is true, |
| 9571 closes the Lua state before exiting. |
| 9572 |
| 9573 |
| 9574 |
| 9575 |
| 9576 <p> |
| 9577 <hr><h3><a name="pdf-os.getenv"><code>os.getenv (varname)</code></a></h3> |
| 9578 |
| 9579 |
| 9580 <p> |
| 9581 Returns the value of the process environment variable <code>varname</code>, |
| 9582 or <b>nil</b> if the variable is not defined. |
| 9583 |
| 9584 |
| 9585 |
| 9586 |
| 9587 <p> |
| 9588 <hr><h3><a name="pdf-os.remove"><code>os.remove (filename)</code></a></h3> |
| 9589 |
| 9590 |
| 9591 <p> |
| 9592 Deletes the file (or empty directory, on POSIX systems) |
| 9593 with the given name. |
| 9594 If this function fails, it returns <b>nil</b>, |
| 9595 plus a string describing the error and the error code. |
| 9596 |
| 9597 |
| 9598 |
| 9599 |
| 9600 <p> |
| 9601 <hr><h3><a name="pdf-os.rename"><code>os.rename (oldname, newname)</code></a></h
3> |
| 9602 |
| 9603 |
| 9604 <p> |
| 9605 Renames file or directory named <code>oldname</code> to <code>newname</code>. |
| 9606 If this function fails, it returns <b>nil</b>, |
| 9607 plus a string describing the error and the error code. |
| 9608 |
| 9609 |
| 9610 |
| 9611 |
| 9612 <p> |
| 9613 <hr><h3><a name="pdf-os.setlocale"><code>os.setlocale (locale [, category])</cod
e></a></h3> |
| 9614 |
| 9615 |
| 9616 <p> |
| 9617 Sets the current locale of the program. |
| 9618 <code>locale</code> is a system-dependent string specifying a locale; |
| 9619 <code>category</code> is an optional string describing which category to change: |
| 9620 <code>"all"</code>, <code>"collate"</code>, <code>"ctype"</code>, |
| 9621 <code>"monetary"</code>, <code>"numeric"</code>, or <code>"time"</code>; |
| 9622 the default category is <code>"all"</code>. |
| 9623 The function returns the name of the new locale, |
| 9624 or <b>nil</b> if the request cannot be honored. |
| 9625 |
| 9626 |
| 9627 <p> |
| 9628 If <code>locale</code> is the empty string, |
| 9629 the current locale is set to an implementation-defined native locale. |
| 9630 If <code>locale</code> is the string "<code>C</code>", |
| 9631 the current locale is set to the standard C locale. |
| 9632 |
| 9633 |
| 9634 <p> |
| 9635 When called with <b>nil</b> as the first argument, |
| 9636 this function only returns the name of the current locale |
| 9637 for the given category. |
| 9638 |
| 9639 |
| 9640 <p> |
| 9641 This function may be not thread safe |
| 9642 because of its reliance on C function <code>setlocale</code>. |
| 9643 |
| 9644 |
| 9645 |
| 9646 |
| 9647 <p> |
| 9648 <hr><h3><a name="pdf-os.time"><code>os.time ([table])</code></a></h3> |
| 9649 |
| 9650 |
| 9651 <p> |
| 9652 Returns the current time when called without arguments, |
| 9653 or a time representing the date and time specified by the given table. |
| 9654 This table must have fields <code>year</code>, <code>month</code>, and <code>day
</code>, |
| 9655 and may have fields |
| 9656 <code>hour</code> (default is 12), |
| 9657 <code>min</code> (default is 0), |
| 9658 <code>sec</code> (default is 0), |
| 9659 and <code>isdst</code> (default is <b>nil</b>). |
| 9660 For a description of these fields, see the <a href="#pdf-os.date"><code>os.date<
/code></a> function. |
| 9661 |
| 9662 |
| 9663 <p> |
| 9664 The returned value is a number, whose meaning depends on your system. |
| 9665 In POSIX, Windows, and some other systems, |
| 9666 this number counts the number |
| 9667 of seconds since some given start time (the "epoch"). |
| 9668 In other systems, the meaning is not specified, |
| 9669 and the number returned by <code>time</code> can be used only as an argument to |
| 9670 <a href="#pdf-os.date"><code>os.date</code></a> and <a href="#pdf-os.difftime"><
code>os.difftime</code></a>. |
| 9671 |
| 9672 |
| 9673 |
| 9674 |
| 9675 <p> |
| 9676 <hr><h3><a name="pdf-os.tmpname"><code>os.tmpname ()</code></a></h3> |
| 9677 |
| 9678 |
| 9679 <p> |
| 9680 Returns a string with a file name that can |
| 9681 be used for a temporary file. |
| 9682 The file must be explicitly opened before its use |
| 9683 and explicitly removed when no longer needed. |
| 9684 |
| 9685 |
| 9686 <p> |
| 9687 On POSIX systems, |
| 9688 this function also creates a file with that name, |
| 9689 to avoid security risks. |
| 9690 (Someone else might create the file with wrong permissions |
| 9691 in the time between getting the name and creating the file.) |
| 9692 You still have to open the file to use it |
| 9693 and to remove it (even if you do not use it). |
| 9694 |
| 9695 |
| 9696 <p> |
| 9697 When possible, |
| 9698 you may prefer to use <a href="#pdf-io.tmpfile"><code>io.tmpfile</code></a>, |
| 9699 which automatically removes the file when the program ends. |
| 9700 |
| 9701 |
| 9702 |
| 9703 |
| 9704 |
| 9705 |
| 9706 |
| 9707 <h2>6.10 – <a name="6.10">The Debug Library</a></h2> |
| 9708 |
| 9709 <p> |
| 9710 This library provides |
| 9711 the functionality of the debug interface (<a href="#4.9">§4.9</a>) to Lua p
rograms. |
| 9712 You should exert care when using this library. |
| 9713 Several of its functions |
| 9714 violate basic assumptions about Lua code |
| 9715 (e.g., that variables local to a function |
| 9716 cannot be accessed from outside; |
| 9717 that userdata metatables cannot be changed by Lua code; |
| 9718 that Lua programs do not crash) |
| 9719 and therefore can compromise otherwise secure code. |
| 9720 Moreover, some functions in this library may be slow. |
| 9721 |
| 9722 |
| 9723 <p> |
| 9724 All functions in this library are provided |
| 9725 inside the <a name="pdf-debug"><code>debug</code></a> table. |
| 9726 All functions that operate over a thread |
| 9727 have an optional first argument which is the |
| 9728 thread to operate over. |
| 9729 The default is always the current thread. |
| 9730 |
| 9731 |
| 9732 <p> |
| 9733 <hr><h3><a name="pdf-debug.debug"><code>debug.debug ()</code></a></h3> |
| 9734 |
| 9735 |
| 9736 <p> |
| 9737 Enters an interactive mode with the user, |
| 9738 running each string that the user enters. |
| 9739 Using simple commands and other debug facilities, |
| 9740 the user can inspect global and local variables, |
| 9741 change their values, evaluate expressions, and so on. |
| 9742 A line containing only the word <code>cont</code> finishes this function, |
| 9743 so that the caller continues its execution. |
| 9744 |
| 9745 |
| 9746 <p> |
| 9747 Note that commands for <code>debug.debug</code> are not lexically nested |
| 9748 within any function and so have no direct access to local variables. |
| 9749 |
| 9750 |
| 9751 |
| 9752 |
| 9753 <p> |
| 9754 <hr><h3><a name="pdf-debug.gethook"><code>debug.gethook ([thread])</code></a></h
3> |
| 9755 |
| 9756 |
| 9757 <p> |
| 9758 Returns the current hook settings of the thread, as three values: |
| 9759 the current hook function, the current hook mask, |
| 9760 and the current hook count |
| 9761 (as set by the <a href="#pdf-debug.sethook"><code>debug.sethook</code></a> funct
ion). |
| 9762 |
| 9763 |
| 9764 |
| 9765 |
| 9766 <p> |
| 9767 <hr><h3><a name="pdf-debug.getinfo"><code>debug.getinfo ([thread,] f [, what])</
code></a></h3> |
| 9768 |
| 9769 |
| 9770 <p> |
| 9771 Returns a table with information about a function. |
| 9772 You can give the function directly |
| 9773 or you can give a number as the value of <code>f</code>, |
| 9774 which means the function running at level <code>f</code> of the call stack |
| 9775 of the given thread: |
| 9776 level 0 is the current function (<code>getinfo</code> itself); |
| 9777 level 1 is the function that called <code>getinfo</code> |
| 9778 (except for tail calls, which do not count on the stack); |
| 9779 and so on. |
| 9780 If <code>f</code> is a number larger than the number of active functions, |
| 9781 then <code>getinfo</code> returns <b>nil</b>. |
| 9782 |
| 9783 |
| 9784 <p> |
| 9785 The returned table can contain all the fields returned by <a href="#lua_getinfo"
><code>lua_getinfo</code></a>, |
| 9786 with the string <code>what</code> describing which fields to fill in. |
| 9787 The default for <code>what</code> is to get all information available, |
| 9788 except the table of valid lines. |
| 9789 If present, |
| 9790 the option '<code>f</code>' |
| 9791 adds a field named <code>func</code> with the function itself. |
| 9792 If present, |
| 9793 the option '<code>L</code>' |
| 9794 adds a field named <code>activelines</code> with the table of |
| 9795 valid lines. |
| 9796 |
| 9797 |
| 9798 <p> |
| 9799 For instance, the expression <code>debug.getinfo(1,"n").name</code> returns |
| 9800 a table with a name for the current function, |
| 9801 if a reasonable name can be found, |
| 9802 and the expression <code>debug.getinfo(print)</code> |
| 9803 returns a table with all available information |
| 9804 about the <a href="#pdf-print"><code>print</code></a> function. |
| 9805 |
| 9806 |
| 9807 |
| 9808 |
| 9809 <p> |
| 9810 <hr><h3><a name="pdf-debug.getlocal"><code>debug.getlocal ([thread,] f, local)</
code></a></h3> |
| 9811 |
| 9812 |
| 9813 <p> |
| 9814 This function returns the name and the value of the local variable |
| 9815 with index <code>local</code> of the function at level <code>f</code> of the sta
ck. |
| 9816 This function accesses not only explicit local variables, |
| 9817 but also parameters, temporaries, etc. |
| 9818 |
| 9819 |
| 9820 <p> |
| 9821 The first parameter or local variable has index 1, and so on, |
| 9822 until the last active variable. |
| 9823 Negative indices refer to vararg parameters; |
| 9824 -1 is the first vararg parameter. |
| 9825 The function returns <b>nil</b> if there is no variable with the given index, |
| 9826 and raises an error when called with a level out of range. |
| 9827 (You can call <a href="#pdf-debug.getinfo"><code>debug.getinfo</code></a> to che
ck whether the level is valid.) |
| 9828 |
| 9829 |
| 9830 <p> |
| 9831 Variable names starting with '<code>(</code>' (open parenthesis) |
| 9832 represent internal variables |
| 9833 (loop control variables, temporaries, varargs, and C function locals). |
| 9834 |
| 9835 |
| 9836 <p> |
| 9837 The parameter <code>f</code> may also be a function. |
| 9838 In that case, <code>getlocal</code> returns only the name of function parameters
. |
| 9839 |
| 9840 |
| 9841 |
| 9842 |
| 9843 <p> |
| 9844 <hr><h3><a name="pdf-debug.getmetatable"><code>debug.getmetatable (value)</code>
</a></h3> |
| 9845 |
| 9846 |
| 9847 <p> |
| 9848 Returns the metatable of the given <code>value</code> |
| 9849 or <b>nil</b> if it does not have a metatable. |
| 9850 |
| 9851 |
| 9852 |
| 9853 |
| 9854 <p> |
| 9855 <hr><h3><a name="pdf-debug.getregistry"><code>debug.getregistry ()</code></a></h
3> |
| 9856 |
| 9857 |
| 9858 <p> |
| 9859 Returns the registry table (see <a href="#4.5">§4.5</a>). |
| 9860 |
| 9861 |
| 9862 |
| 9863 |
| 9864 <p> |
| 9865 <hr><h3><a name="pdf-debug.getupvalue"><code>debug.getupvalue (f, up)</code></a>
</h3> |
| 9866 |
| 9867 |
| 9868 <p> |
| 9869 This function returns the name and the value of the upvalue |
| 9870 with index <code>up</code> of the function <code>f</code>. |
| 9871 The function returns <b>nil</b> if there is no upvalue with the given index. |
| 9872 |
| 9873 |
| 9874 |
| 9875 |
| 9876 <p> |
| 9877 <hr><h3><a name="pdf-debug.getuservalue"><code>debug.getuservalue (u)</code></a>
</h3> |
| 9878 |
| 9879 |
| 9880 <p> |
| 9881 Returns the Lua value associated to <code>u</code>. |
| 9882 If <code>u</code> is not a userdata, |
| 9883 returns <b>nil</b>. |
| 9884 |
| 9885 |
| 9886 |
| 9887 |
| 9888 <p> |
| 9889 <hr><h3><a name="pdf-debug.sethook"><code>debug.sethook ([thread,] hook, mask [,
count])</code></a></h3> |
| 9890 |
| 9891 |
| 9892 <p> |
| 9893 Sets the given function as a hook. |
| 9894 The string <code>mask</code> and the number <code>count</code> describe |
| 9895 when the hook will be called. |
| 9896 The string mask may have the following characters, |
| 9897 with the given meaning: |
| 9898 |
| 9899 <ul> |
| 9900 <li><b>'<code>c</code>': </b> the hook is called every time Lua calls a function
;</li> |
| 9901 <li><b>'<code>r</code>': </b> the hook is called every time Lua returns from a f
unction;</li> |
| 9902 <li><b>'<code>l</code>': </b> the hook is called every time Lua enters a new lin
e of code.</li> |
| 9903 </ul><p> |
| 9904 With a <code>count</code> different from zero, |
| 9905 the hook is called after every <code>count</code> instructions. |
| 9906 |
| 9907 |
| 9908 <p> |
| 9909 When called without arguments, |
| 9910 <a href="#pdf-debug.sethook"><code>debug.sethook</code></a> turns off the hook. |
| 9911 |
| 9912 |
| 9913 <p> |
| 9914 When the hook is called, its first parameter is a string |
| 9915 describing the event that has triggered its call: |
| 9916 <code>"call"</code> (or <code>"tail call"</code>), |
| 9917 <code>"return"</code>, |
| 9918 <code>"line"</code>, and <code>"count"</code>. |
| 9919 For line events, |
| 9920 the hook also gets the new line number as its second parameter. |
| 9921 Inside a hook, |
| 9922 you can call <code>getinfo</code> with level 2 to get more information abou
t |
| 9923 the running function |
| 9924 (level 0 is the <code>getinfo</code> function, |
| 9925 and level 1 is the hook function). |
| 9926 |
| 9927 |
| 9928 |
| 9929 |
| 9930 <p> |
| 9931 <hr><h3><a name="pdf-debug.setlocal"><code>debug.setlocal ([thread,] level, loca
l, value)</code></a></h3> |
| 9932 |
| 9933 |
| 9934 <p> |
| 9935 This function assigns the value <code>value</code> to the local variable |
| 9936 with index <code>local</code> of the function at level <code>level</code> of the
stack. |
| 9937 The function returns <b>nil</b> if there is no local |
| 9938 variable with the given index, |
| 9939 and raises an error when called with a <code>level</code> out of range. |
| 9940 (You can call <code>getinfo</code> to check whether the level is valid.) |
| 9941 Otherwise, it returns the name of the local variable. |
| 9942 |
| 9943 |
| 9944 <p> |
| 9945 See <a href="#pdf-debug.getlocal"><code>debug.getlocal</code></a> for more infor
mation about |
| 9946 variable indices and names. |
| 9947 |
| 9948 |
| 9949 |
| 9950 |
| 9951 <p> |
| 9952 <hr><h3><a name="pdf-debug.setmetatable"><code>debug.setmetatable (value, table)
</code></a></h3> |
| 9953 |
| 9954 |
| 9955 <p> |
| 9956 Sets the metatable for the given <code>value</code> to the given <code>table</co
de> |
| 9957 (which can be <b>nil</b>). |
| 9958 Returns <code>value</code>. |
| 9959 |
| 9960 |
| 9961 |
| 9962 |
| 9963 <p> |
| 9964 <hr><h3><a name="pdf-debug.setupvalue"><code>debug.setupvalue (f, up, value)</co
de></a></h3> |
| 9965 |
| 9966 |
| 9967 <p> |
| 9968 This function assigns the value <code>value</code> to the upvalue |
| 9969 with index <code>up</code> of the function <code>f</code>. |
| 9970 The function returns <b>nil</b> if there is no upvalue |
| 9971 with the given index. |
| 9972 Otherwise, it returns the name of the upvalue. |
| 9973 |
| 9974 |
| 9975 |
| 9976 |
| 9977 <p> |
| 9978 <hr><h3><a name="pdf-debug.setuservalue"><code>debug.setuservalue (udata, value)
</code></a></h3> |
| 9979 |
| 9980 |
| 9981 <p> |
| 9982 Sets the given <code>value</code> as |
| 9983 the Lua value associated to the given <code>udata</code>. |
| 9984 <code>value</code> must be a table or <b>nil</b>; |
| 9985 <code>udata</code> must be a full userdata. |
| 9986 |
| 9987 |
| 9988 <p> |
| 9989 Returns <code>udata</code>. |
| 9990 |
| 9991 |
| 9992 |
| 9993 |
| 9994 <p> |
| 9995 <hr><h3><a name="pdf-debug.traceback"><code>debug.traceback ([thread,] [message
[, level]])</code></a></h3> |
| 9996 |
| 9997 |
| 9998 <p> |
| 9999 If <code>message</code> is present but is neither a string nor <b>nil</b>, |
| 10000 this function returns <code>message</code> without further processing. |
| 10001 Otherwise, |
| 10002 it returns a string with a traceback of the call stack. |
| 10003 An optional <code>message</code> string is appended |
| 10004 at the beginning of the traceback. |
| 10005 An optional <code>level</code> number tells at which level |
| 10006 to start the traceback |
| 10007 (default is 1, the function calling <code>traceback</code>). |
| 10008 |
| 10009 |
| 10010 |
| 10011 |
| 10012 <p> |
| 10013 <hr><h3><a name="pdf-debug.upvalueid"><code>debug.upvalueid (f, n)</code></a></h
3> |
| 10014 |
| 10015 |
| 10016 <p> |
| 10017 Returns an unique identifier (as a light userdata) |
| 10018 for the upvalue numbered <code>n</code> |
| 10019 from the given function. |
| 10020 |
| 10021 |
| 10022 <p> |
| 10023 These unique identifiers allow a program to check whether different |
| 10024 closures share upvalues. |
| 10025 Lua closures that share an upvalue |
| 10026 (that is, that access a same external local variable) |
| 10027 will return identical ids for those upvalue indices. |
| 10028 |
| 10029 |
| 10030 |
| 10031 |
| 10032 <p> |
| 10033 <hr><h3><a name="pdf-debug.upvaluejoin"><code>debug.upvaluejoin (f1, n1, f2, n2)
</code></a></h3> |
| 10034 |
| 10035 |
| 10036 <p> |
| 10037 Make the <code>n1</code>-th upvalue of the Lua closure <code>f1</code> |
| 10038 refer to the <code>n2</code>-th upvalue of the Lua closure <code>f2</code>. |
| 10039 |
| 10040 |
| 10041 |
| 10042 |
| 10043 |
| 10044 |
| 10045 |
| 10046 <h1>7 – <a name="7">Lua Standalone</a></h1> |
| 10047 |
| 10048 <p> |
| 10049 Although Lua has been designed as an extension language, |
| 10050 to be embedded in a host C program, |
| 10051 it is also frequently used as a standalone language. |
| 10052 An interpreter for Lua as a standalone language, |
| 10053 called simply <code>lua</code>, |
| 10054 is provided with the standard distribution. |
| 10055 The standalone interpreter includes |
| 10056 all standard libraries, including the debug library. |
| 10057 Its usage is: |
| 10058 |
| 10059 <pre> |
| 10060 lua [options] [script [args]] |
| 10061 </pre><p> |
| 10062 The options are: |
| 10063 |
| 10064 <ul> |
| 10065 <li><b><code>-e <em>stat</em></code>: </b> executes string <em>stat</em>;</li> |
| 10066 <li><b><code>-l <em>mod</em></code>: </b> "requires" <em>mod</em>;</li> |
| 10067 <li><b><code>-i</code>: </b> enters interactive mode after running <em>script</e
m>;</li> |
| 10068 <li><b><code>-v</code>: </b> prints version information;</li> |
| 10069 <li><b><code>-E</code>: </b> ignores environment variables;</li> |
| 10070 <li><b><code>--</code>: </b> stops handling options;</li> |
| 10071 <li><b><code>-</code>: </b> executes <code>stdin</code> as a file and stops hand
ling options.</li> |
| 10072 </ul><p> |
| 10073 After handling its options, <code>lua</code> runs the given <em>script</em>, |
| 10074 passing to it the given <em>args</em> as string arguments. |
| 10075 When called without arguments, |
| 10076 <code>lua</code> behaves as <code>lua -v -i</code> |
| 10077 when the standard input (<code>stdin</code>) is a terminal, |
| 10078 and as <code>lua -</code> otherwise. |
| 10079 |
| 10080 |
| 10081 <p> |
| 10082 When called without option <code>-E</code>, |
| 10083 the interpreter checks for an environment variable <a name="pdf-LUA_INIT_5_2"><c
ode>LUA_INIT_5_2</code></a> |
| 10084 (or <a name="pdf-LUA_INIT"><code>LUA_INIT</code></a> if it is not defined) |
| 10085 before running any argument. |
| 10086 If the variable content has the format <code>@<em>filename</em></code>, |
| 10087 then <code>lua</code> executes the file. |
| 10088 Otherwise, <code>lua</code> executes the string itself. |
| 10089 |
| 10090 |
| 10091 <p> |
| 10092 When called with option <code>-E</code>, |
| 10093 besides ignoring <code>LUA_INIT</code>, |
| 10094 Lua also ignores |
| 10095 the values of <code>LUA_PATH</code> and <code>LUA_CPATH</code>, |
| 10096 setting the values of |
| 10097 <a href="#pdf-package.path"><code>package.path</code></a> and <a href="#pdf-pack
age.cpath"><code>package.cpath</code></a> |
| 10098 with the default paths defined in <code>luaconf.h</code>. |
| 10099 |
| 10100 |
| 10101 <p> |
| 10102 All options are handled in order, except <code>-i</code> and <code>-E</code>. |
| 10103 For instance, an invocation like |
| 10104 |
| 10105 <pre> |
| 10106 $ lua -e'a=1' -e 'print(a)' script.lua |
| 10107 </pre><p> |
| 10108 will first set <code>a</code> to 1, then print the value of <code>a</code>, |
| 10109 and finally run the file <code>script.lua</code> with no arguments. |
| 10110 (Here <code>$</code> is the shell prompt. Your prompt may be different.) |
| 10111 |
| 10112 |
| 10113 <p> |
| 10114 Before starting to run the script, |
| 10115 <code>lua</code> collects all arguments in the command line |
| 10116 in a global table called <code>arg</code>. |
| 10117 The script name is stored at index 0, |
| 10118 the first argument after the script name goes to index 1, |
| 10119 and so on. |
| 10120 Any arguments before the script name |
| 10121 (that is, the interpreter name plus the options) |
| 10122 go to negative indices. |
| 10123 For instance, in the call |
| 10124 |
| 10125 <pre> |
| 10126 $ lua -la b.lua t1 t2 |
| 10127 </pre><p> |
| 10128 the interpreter first runs the file <code>a.lua</code>, |
| 10129 then creates a table |
| 10130 |
| 10131 <pre> |
| 10132 arg = { [-2] = "lua", [-1] = "-la", |
| 10133 [0] = "b.lua", |
| 10134 [1] = "t1", [2] = "t2" } |
| 10135 </pre><p> |
| 10136 and finally runs the file <code>b.lua</code>. |
| 10137 The script is called with <code>arg[1]</code>, <code>arg[2]</code>, ... |
| 10138 as arguments; |
| 10139 it can also access these arguments with the vararg expression '<code>...</code>'
. |
| 10140 |
| 10141 |
| 10142 <p> |
| 10143 In interactive mode, |
| 10144 if you write an incomplete statement, |
| 10145 the interpreter waits for its completion |
| 10146 by issuing a different prompt. |
| 10147 |
| 10148 |
| 10149 <p> |
| 10150 In case of unprotected errors in the script, |
| 10151 the interpreter reports the error to the standard error stream. |
| 10152 If the error object is a string, |
| 10153 the interpreter adds a stack traceback to it. |
| 10154 Otherwise, if the error object has a metamethod <code>__tostring</code>, |
| 10155 the interpreter calls this metamethod to produce the final message. |
| 10156 Finally, if the error object is <b>nil</b>, |
| 10157 the interpreter does not report the error. |
| 10158 |
| 10159 |
| 10160 <p> |
| 10161 When finishing normally, |
| 10162 the interpreter closes its main Lua state |
| 10163 (see <a href="#lua_close"><code>lua_close</code></a>). |
| 10164 The script can avoid this step by |
| 10165 calling <a href="#pdf-os.exit"><code>os.exit</code></a> to terminate. |
| 10166 |
| 10167 |
| 10168 <p> |
| 10169 To allow the use of Lua as a |
| 10170 script interpreter in Unix systems, |
| 10171 the standalone interpreter skips |
| 10172 the first line of a chunk if it starts with <code>#</code>. |
| 10173 Therefore, Lua scripts can be made into executable programs |
| 10174 by using <code>chmod +x</code> and the <code>#!</code> form, |
| 10175 as in |
| 10176 |
| 10177 <pre> |
| 10178 #!/usr/local/bin/lua |
| 10179 </pre><p> |
| 10180 (Of course, |
| 10181 the location of the Lua interpreter may be different in your machine. |
| 10182 If <code>lua</code> is in your <code>PATH</code>, |
| 10183 then |
| 10184 |
| 10185 <pre> |
| 10186 #!/usr/bin/env lua |
| 10187 </pre><p> |
| 10188 is a more portable solution.) |
| 10189 |
| 10190 |
| 10191 |
| 10192 <h1>8 – <a name="8">Incompatibilities with the Previous Version</a></h1> |
| 10193 |
| 10194 <p> |
| 10195 Here we list the incompatibilities that you may find when moving a program |
| 10196 from Lua 5.1 to Lua 5.2. |
| 10197 You can avoid some incompatibilities by compiling Lua with |
| 10198 appropriate options (see file <code>luaconf.h</code>). |
| 10199 However, |
| 10200 all these compatibility options will be removed in the next version of Lua. |
| 10201 Similarly, |
| 10202 all features marked as deprecated in Lua 5.1 |
| 10203 have been removed in Lua 5.2. |
| 10204 |
| 10205 |
| 10206 |
| 10207 <h2>8.1 – <a name="8.1">Changes in the Language</a></h2> |
| 10208 <ul> |
| 10209 |
| 10210 <li> |
| 10211 The concept of <em>environment</em> changed. |
| 10212 Only Lua functions have environments. |
| 10213 To set the environment of a Lua function, |
| 10214 use the variable <code>_ENV</code> or the function <a href="#pdf-load"><code>loa
d</code></a>. |
| 10215 |
| 10216 |
| 10217 <p> |
| 10218 C functions no longer have environments. |
| 10219 Use an upvalue with a shared table if you need to keep |
| 10220 shared state among several C functions. |
| 10221 (You may use <a href="#luaL_setfuncs"><code>luaL_setfuncs</code></a> to open a C
library |
| 10222 with all functions sharing a common upvalue.) |
| 10223 |
| 10224 |
| 10225 <p> |
| 10226 To manipulate the "environment" of a userdata |
| 10227 (which is now called user value), |
| 10228 use the new functions |
| 10229 <a href="#lua_getuservalue"><code>lua_getuservalue</code></a> and <a href="#lua_
setuservalue"><code>lua_setuservalue</code></a>. |
| 10230 </li> |
| 10231 |
| 10232 <li> |
| 10233 Lua identifiers cannot use locale-dependent letters. |
| 10234 </li> |
| 10235 |
| 10236 <li> |
| 10237 Doing a step or a full collection in the garbage collector |
| 10238 does not restart the collector if it has been stopped. |
| 10239 </li> |
| 10240 |
| 10241 <li> |
| 10242 Weak tables with weak keys now perform like <em>ephemeron tables</em>. |
| 10243 </li> |
| 10244 |
| 10245 <li> |
| 10246 The event <em>tail return</em> in debug hooks was removed. |
| 10247 Instead, tail calls generate a special new event, |
| 10248 <em>tail call</em>, so that the debugger can know that |
| 10249 there will not be a corresponding return event. |
| 10250 </li> |
| 10251 |
| 10252 <li> |
| 10253 Equality between function values has changed. |
| 10254 Now, a function definition may not create a new value; |
| 10255 it may reuse some previous value if there is no |
| 10256 observable difference to the new function. |
| 10257 </li> |
| 10258 |
| 10259 </ul> |
| 10260 |
| 10261 |
| 10262 |
| 10263 |
| 10264 <h2>8.2 – <a name="8.2">Changes in the Libraries</a></h2> |
| 10265 <ul> |
| 10266 |
| 10267 <li> |
| 10268 Function <code>module</code> is deprecated. |
| 10269 It is easy to set up a module with regular Lua code. |
| 10270 Modules are not expected to set global variables. |
| 10271 </li> |
| 10272 |
| 10273 <li> |
| 10274 Functions <code>setfenv</code> and <code>getfenv</code> were removed, |
| 10275 because of the changes in environments. |
| 10276 </li> |
| 10277 |
| 10278 <li> |
| 10279 Function <code>math.log10</code> is deprecated. |
| 10280 Use <a href="#pdf-math.log"><code>math.log</code></a> with 10 as its second argu
ment, instead. |
| 10281 </li> |
| 10282 |
| 10283 <li> |
| 10284 Function <code>loadstring</code> is deprecated. |
| 10285 Use <code>load</code> instead; it now accepts string arguments |
| 10286 and are exactly equivalent to <code>loadstring</code>. |
| 10287 </li> |
| 10288 |
| 10289 <li> |
| 10290 Function <code>table.maxn</code> is deprecated. |
| 10291 Write it in Lua if you really need it. |
| 10292 </li> |
| 10293 |
| 10294 <li> |
| 10295 Function <code>os.execute</code> now returns <b>true</b> when command |
| 10296 terminates successfully and <b>nil</b> plus error information |
| 10297 otherwise. |
| 10298 </li> |
| 10299 |
| 10300 <li> |
| 10301 Function <code>unpack</code> was moved into the table library |
| 10302 and therefore must be called as <a href="#pdf-table.unpack"><code>table.unpack</
code></a>. |
| 10303 </li> |
| 10304 |
| 10305 <li> |
| 10306 Character class <code>%z</code> in patterns is deprecated, |
| 10307 as now patterns may contain '<code>\0</code>' as a regular character. |
| 10308 </li> |
| 10309 |
| 10310 <li> |
| 10311 The table <code>package.loaders</code> was renamed <code>package.searchers</code
>. |
| 10312 </li> |
| 10313 |
| 10314 <li> |
| 10315 Lua does not have bytecode verification anymore. |
| 10316 So, all functions that load code |
| 10317 (<a href="#pdf-load"><code>load</code></a> and <a href="#pdf-loadfile"><code>loa
dfile</code></a>) |
| 10318 are potentially insecure when loading untrusted binary data. |
| 10319 (Actually, those functions were already insecure because |
| 10320 of flaws in the verification algorithm.) |
| 10321 When in doubt, |
| 10322 use the <code>mode</code> argument of those functions |
| 10323 to restrict them to loading textual chunks. |
| 10324 </li> |
| 10325 |
| 10326 <li> |
| 10327 The standard paths in the official distribution may |
| 10328 change between versions. |
| 10329 </li> |
| 10330 |
| 10331 </ul> |
| 10332 |
| 10333 |
| 10334 |
| 10335 |
| 10336 <h2>8.3 – <a name="8.3">Changes in the API</a></h2> |
| 10337 <ul> |
| 10338 |
| 10339 <li> |
| 10340 Pseudoindex <code>LUA_GLOBALSINDEX</code> was removed. |
| 10341 You must get the global environment from the registry |
| 10342 (see <a href="#4.5">§4.5</a>). |
| 10343 </li> |
| 10344 |
| 10345 <li> |
| 10346 Pseudoindex <code>LUA_ENVIRONINDEX</code> |
| 10347 and functions <code>lua_getfenv</code>/<code>lua_setfenv</code> |
| 10348 were removed, |
| 10349 as C functions no longer have environments. |
| 10350 </li> |
| 10351 |
| 10352 <li> |
| 10353 Function <code>luaL_register</code> is deprecated. |
| 10354 Use <a href="#luaL_setfuncs"><code>luaL_setfuncs</code></a> so that your module
does not create globals. |
| 10355 (Modules are not expected to set global variables anymore.) |
| 10356 </li> |
| 10357 |
| 10358 <li> |
| 10359 The <code>osize</code> argument to the allocation function |
| 10360 may not be zero when creating a new block, |
| 10361 that is, when <code>ptr</code> is <code>NULL</code> |
| 10362 (see <a href="#lua_Alloc"><code>lua_Alloc</code></a>). |
| 10363 Use only the test <code>ptr == NULL</code> to check whether |
| 10364 the block is new. |
| 10365 </li> |
| 10366 |
| 10367 <li> |
| 10368 Finalizers (<code>__gc</code> metamethods) for userdata are called in the |
| 10369 reverse order that they were marked for finalization, |
| 10370 not that they were created (see <a href="#2.5.1">§2.5.1</a>). |
| 10371 (Most userdata are marked immediately after they are created.) |
| 10372 Moreover, |
| 10373 if the metatable does not have a <code>__gc</code> field when set, |
| 10374 the finalizer will not be called, |
| 10375 even if it is set later. |
| 10376 </li> |
| 10377 |
| 10378 <li> |
| 10379 <code>luaL_typerror</code> was removed. |
| 10380 Write your own version if you need it. |
| 10381 </li> |
| 10382 |
| 10383 <li> |
| 10384 Function <code>lua_cpcall</code> is deprecated. |
| 10385 You can simply push the function with <a href="#lua_pushcfunction"><code>lua_pus
hcfunction</code></a> |
| 10386 and call it with <a href="#lua_pcall"><code>lua_pcall</code></a>. |
| 10387 </li> |
| 10388 |
| 10389 <li> |
| 10390 Functions <code>lua_equal</code> and <code>lua_lessthan</code> are deprecated. |
| 10391 Use the new <a href="#lua_compare"><code>lua_compare</code></a> with appropriate
options instead. |
| 10392 </li> |
| 10393 |
| 10394 <li> |
| 10395 Function <code>lua_objlen</code> was renamed <a href="#lua_rawlen"><code>lua_raw
len</code></a>. |
| 10396 </li> |
| 10397 |
| 10398 <li> |
| 10399 Function <a href="#lua_load"><code>lua_load</code></a> has an extra parameter, <
code>mode</code>. |
| 10400 Pass <code>NULL</code> to simulate the old behavior. |
| 10401 </li> |
| 10402 |
| 10403 <li> |
| 10404 Function <a href="#lua_resume"><code>lua_resume</code></a> has an extra paramete
r, <code>from</code>. |
| 10405 Pass <code>NULL</code> or the thread doing the call. |
| 10406 </li> |
| 10407 |
| 10408 </ul> |
| 10409 |
| 10410 |
| 10411 |
| 10412 |
| 10413 <h1>9 – <a name="9">The Complete Syntax of Lua</a></h1> |
| 10414 |
| 10415 <p> |
| 10416 Here is the complete syntax of Lua in extended BNF. |
| 10417 (It does not describe operator precedences.) |
| 10418 |
| 10419 |
| 10420 |
| 10421 |
| 10422 <pre> |
| 10423 |
| 10424 chunk ::= block |
| 10425 |
| 10426 block ::= {stat} [retstat] |
| 10427 |
| 10428 stat ::= ‘<b>;</b>’ | |
| 10429 varlist ‘<b>=</b>’ explist | |
| 10430 functioncall | |
| 10431 label | |
| 10432 <b>break</b> | |
| 10433 <b>goto</b> Name | |
| 10434 <b>do</b> block <b>end</b> | |
| 10435 <b>while</b> exp <b>do</b> block <b>end</b> | |
| 10436 <b>repeat</b> block <b>until</b> exp | |
| 10437 <b>if</b> exp <b>then</b> block {<b>elseif</b> exp <b>then</b>
block} [<b>else</b> block] <b>end</b> | |
| 10438 <b>for</b> Name ‘<b>=</b>’ exp ‘<b>,</b>&rsqu
o; exp [‘<b>,</b>’ exp] <b>do</b> block <b>end</b> | |
| 10439 <b>for</b> namelist <b>in</b> explist <b>do</b> block <b>end</b
> | |
| 10440 <b>function</b> funcname funcbody | |
| 10441 <b>local</b> <b>function</b> Name funcbody | |
| 10442 <b>local</b> namelist [‘<b>=</b>’ explist] |
| 10443 |
| 10444 retstat ::= <b>return</b> [explist] [‘<b>;</b>’] |
| 10445 |
| 10446 label ::= ‘<b>::</b>’ Name ‘<b>::</b>’ |
| 10447 |
| 10448 funcname ::= Name {‘<b>.</b>’ Name} [‘<b>:</b>’
Name] |
| 10449 |
| 10450 varlist ::= var {‘<b>,</b>’ var} |
| 10451 |
| 10452 var ::= Name | prefixexp ‘<b>[</b>’ exp ‘<b>]</b>&rsq
uo; | prefixexp ‘<b>.</b>’ Name |
| 10453 |
| 10454 namelist ::= Name {‘<b>,</b>’ Name} |
| 10455 |
| 10456 explist ::= exp {‘<b>,</b>’ exp} |
| 10457 |
| 10458 exp ::= <b>nil</b> | <b>false</b> | <b>true</b> | Number | String | &ls
quo;<b>...</b>’ | functiondef | |
| 10459 prefixexp | tableconstructor | exp binop exp | unop exp |
| 10460 |
| 10461 prefixexp ::= var | functioncall | ‘<b>(</b>’ exp ‘<b>
)</b>’ |
| 10462 |
| 10463 functioncall ::= prefixexp args | prefixexp ‘<b>:</b>’ Name
args |
| 10464 |
| 10465 args ::= ‘<b>(</b>’ [explist] ‘<b>)</b>’ | tabl
econstructor | String |
| 10466 |
| 10467 functiondef ::= <b>function</b> funcbody |
| 10468 |
| 10469 funcbody ::= ‘<b>(</b>’ [parlist] ‘<b>)</b>’ blo
ck <b>end</b> |
| 10470 |
| 10471 parlist ::= namelist [‘<b>,</b>’ ‘<b>...</b>’] |
‘<b>...</b>’ |
| 10472 |
| 10473 tableconstructor ::= ‘<b>{</b>’ [fieldlist] ‘<b>}</b>&
rsquo; |
| 10474 |
| 10475 fieldlist ::= field {fieldsep field} [fieldsep] |
| 10476 |
| 10477 field ::= ‘<b>[</b>’ exp ‘<b>]</b>’ ‘<b>=<
/b>’ exp | Name ‘<b>=</b>’ exp | exp |
| 10478 |
| 10479 fieldsep ::= ‘<b>,</b>’ | ‘<b>;</b>’ |
| 10480 |
| 10481 binop ::= ‘<b>+</b>’ | ‘<b>-</b>’ | ‘<b>*<
/b>’ | ‘<b>/</b>’ | ‘<b>^</b>’ | ‘<b>%</b>&r
squo; | ‘<b>..</b>’ | |
| 10482 ‘<b><</b>’ | ‘<b><=</b>’ | &lsquo
;<b>></b>’ | ‘<b>>=</b>’ | ‘<b>==</b>’ | &ls
quo;<b>~=</b>’ | |
| 10483 <b>and</b> | <b>or</b> |
| 10484 |
| 10485 unop ::= ‘<b>-</b>’ | <b>not</b> | ‘<b>#</b>’ |
| 10486 |
| 10487 </pre> |
| 10488 |
| 10489 <p> |
| 10490 |
| 10491 |
| 10492 |
| 10493 |
| 10494 |
| 10495 |
| 10496 |
| 10497 <HR> |
| 10498 <SMALL CLASS="footer"> |
| 10499 Last update: |
| 10500 Thu Mar 21 12:58:59 BRT 2013 |
| 10501 </SMALL> |
| 10502 <!-- |
| 10503 Last change: revised for Lua 5.2.2 |
| 10504 --> |
| 10505 |
| 10506 </body></html> |
| 10507 |
| OLD | NEW |
|---|
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