+Lua 5.1 Reference Manual
+
+Lua 5.1 Reference Manual
++ +++ +Lua 5.1 Reference Manual +
by R. Ierusalimschy, L. H. de Figueiredo, W. Celes +
Lua.org, August 2006 +
ISBN 85-903798-3-3 +
++
+
+ +Buy a copy of this book and +help to support +the Lua project. +
+ +The reference manual is the official definition of the Lua language. +For a complete introduction to Lua programming, see the book +Programming in Lua. +
+ +start +· +contents +· +index +· +português +· +español +
+ +
+
+
+
+
+
+
+
+ +
+The given +options +(see below) +are executed and then +the Lua program in file +script +is loaded and executed. +The given +args +are available to +script +as strings in a global table named +arg. +If these arguments contain spaces or other characters special to the shell, +then they should be quoted +(but note that the quotes will be removed by the shell). +The arguments in +arg +start at 0, +which contains the string +'script'. +The index of the last argument is stored in +arg.n. +The arguments given in the command line before +script, +including the name of the interpreter, +are available in negative indices in +arg. +
+At the very start, +before even handling the command line, +lua +executes the contents of the environment variable +LUA_INIT, +if it is defined. +If the value of +LUA_INIT +is of the form +'@filename', +then +filename +is executed. +Otherwise, the string is assumed to be a Lua statement and is executed. +
+Options start with +'-' +and are described below. +You can use +'--' +to signal the end of options. +
+If no arguments are given, +then +"-v -i" +is assumed when the standard input is a terminal; +otherwise, +"-" +is assumed. +
+In interactive mode, +lua +prompts the user, +reads lines from the standard input, +and executes them as they are read. +If a line does not contain a complete statement, +then a secondary prompt is displayed and +lines are read until a complete statement is formed or +a syntax error is found. +So, one way to interrupt the reading of an incomplete statement is +to force a syntax error: +adding a +';' +in the middle of a statement is a sure way of forcing a syntax error +(except inside multiline strings and comments; these must be closed explicitly). +If a line starts with +'=', +then +lua +displays the values of all the expressions in the remainder of the +line. The expressions must be separated by commas. +The primary prompt is the value of the global variable +_PROMPT, +if this value is a string; +otherwise, the default prompt is used. +Similarly, the secondary prompt is the value of the global variable +_PROMPT2. +So, +to change the prompts, +set the corresponding variable to a string of your choice. +You can do that after calling the interpreter +or on the command line +(but in this case you have to be careful with quotes +if the prompt string contains a space; otherwise you may confuse the shell.) +The default prompts are "> " and ">> ". +
+- +load and execute the standard input as a file, +that is, +not interactively, +even when the standard input is a terminal. +
+-e stat +execute statement +stat. +You need to quote +stat +if it contains spaces, quotes, +or other characters special to the shell. +
+-i +enter interactive mode after +script +is executed. +
+-l name +call +require('name') +before executing +script. +Typically used to load libraries. +
+-v +show version information. +
+The main advantages of precompiling chunks are: +faster loading, +protecting source code from accidental user changes, +and +off-line syntax checking. +
+Precompiling does not imply faster execution +because in Lua chunks are always compiled into bytecodes before being executed. +luac +simply allows those bytecodes to be saved in a file for later execution. +
+Precompiled chunks are not necessarily smaller than the corresponding source. +The main goal in precompiling is faster loading. +
+The binary files created by +luac +are portable only among architectures with the same word size and byte order. +
+luac +produces a single output file containing the bytecodes +for all source files given. +By default, +the output file is named +luac.out, +but you can change this with the +-o +option. +
+In the command line, +you can mix +text files containing Lua source and +binary files containing precompiled chunks. +This is useful because several precompiled chunks, +even from different (but compatible) platforms, +can be combined into a single precompiled chunk. +
+You can use +'-' +to indicate the standard input as a source file +and +'--' +to signal the end of options +(that is, +all remaining arguments will be treated as files even if they start with +'-'). +
+The internal format of the binary files produced by +luac +is likely to change when a new version of Lua is released. +So, +save the source files of all Lua programs that you precompile. +
+
+-l +produce a listing of the compiled bytecode for Lua's virtual machine. +Listing bytecodes is useful to learn about Lua's virtual machine. +If no files are given, then +luac +loads +luac.out +and lists its contents. +
+-o file +output to +file, +instead of the default +luac.out. +(You can use +'-' +for standard output, +but not on platforms that open standard output in text mode.) +The output file may be a source file because +all files are loaded before the output file is written. +Be careful not to overwrite precious files. +
+-p +load files but do not generate any output file. +Used mainly for syntax checking and for testing precompiled chunks: +corrupted files will probably generate errors when loaded. +Lua always performs a thorough integrity test on precompiled chunks. +Bytecode that passes this test is completely safe, +in the sense that it will not break the interpreter. +However, +there is no guarantee that such code does anything sensible. +(None can be given, because the halting problem is unsolvable.) +If no files are given, then +luac +loads +luac.out +and tests its contents. +No messages are displayed if the file passes the integrity test. +
+-s +strip debug information before writing the output file. +This saves some space in very large chunks, +but if errors occur when running a stripped chunk, +then the error messages may not contain the full information they usually do. +For instance, +line numbers and names of local variables are lost. +
+-v +show version information. +
+luac.out +default output file +
+Lua 5.1 Reference Manual
++ +Copyright © 2006-2008 Lua.org, PUC-Rio. +Freely available under the terms of the +Lua license. + +
+ + + + + + +
+Lua is an extension programming language designed to support +general procedural programming with data description +facilities. +It also offers good support for object-oriented programming, +functional programming, and data-driven programming. +Lua is intended to be used as a powerful, light-weight +scripting language for any program that needs one. +Lua is implemented as a library, written in clean C +(that is, in the common subset of ANSI C and C++). + + +
+Being an extension language, Lua has no notion of a "main" program:
+it only works embedded in a host client,
+called the embedding program or simply the host.
+This host program can invoke functions to execute a piece of Lua code,
+can write and read Lua variables,
+and can register C functions to be called by Lua code.
+Through the use of C functions, Lua can be augmented to cope with
+a wide range of different domains,
+thus creating customized programming languages sharing a syntactical framework.
+The Lua distribution includes a sample host program called lua,
+which uses the Lua library to offer a complete, stand-alone Lua interpreter.
+
+
+
+Lua is free software,
+and is provided as usual with no guarantees,
+as stated in its license.
+The implementation described in this manual is available
+at Lua's official web site, www.lua.org.
+
+
+
+Like any other reference manual, +this document is dry in places. +For a discussion of the decisions behind the design of Lua, +see the technical papers available at Lua's web site. +For a detailed introduction to programming in Lua, +see Roberto's book, Programming in Lua (Second Edition). + + + +
+This section describes the lexis, the syntax, and the semantics of Lua. +In other words, +this section describes +which tokens are valid, +how they can be combined, +and what their combinations mean. + + +
+The language constructs will be explained using the usual extended BNF notation, +in which +{a} means 0 or more a's, and +[a] means an optional a. +Non-terminals are shown like non-terminal, +keywords are shown like kword, +and other terminal symbols are shown like `=´. +The complete syntax of Lua can be found in §8 +at the end of this manual. + + + +
+Names +(also called identifiers) +in Lua can be any string of letters, +digits, and underscores, +not beginning with a digit. +This coincides with the definition of names in most languages. +(The definition of letter depends on the current locale: +any character considered alphabetic by the current locale +can be used in an identifier.) +Identifiers are used to name variables and table fields. + + +
+The following keywords are reserved +and cannot be used as names: + + +
+ and break do else elseif + end false for function if + in local nil not or + repeat return then true until while ++ +
+Lua is a case-sensitive language:
+and is a reserved word, but And and AND
+are two different, valid names.
+As a convention, names starting with an underscore followed by
+uppercase letters (such as _VERSION)
+are reserved for internal global variables used by Lua.
+
+
+
+The following strings denote other tokens: + +
+ + - * / % ^ #
+ == ~= <= >= < > =
+ ( ) { } [ ]
+ ; : , . .. ...
+
+
+
+Literal strings
+can be delimited by matching single or double quotes,
+and can contain the following C-like escape sequences:
+'\a' (bell),
+'\b' (backspace),
+'\f' (form feed),
+'\n' (newline),
+'\r' (carriage return),
+'\t' (horizontal tab),
+'\v' (vertical tab),
+'\\' (backslash),
+'\"' (quotation mark [double quote]),
+and '\'' (apostrophe [single quote]).
+Moreover, a backslash followed by a real newline
+results in a newline in the string.
+A character in a string can also be specified by its numerical value
+using the escape sequence \ddd,
+where ddd is a sequence of up to three decimal digits.
+(Note that if a numerical escape is to be followed by a digit,
+it must be expressed using exactly three digits.)
+Strings in Lua can contain any 8-bit value, including embedded zeros,
+which can be specified as '\0'.
+
+
+
+Literal strings can also be defined using a long format
+enclosed by long brackets.
+We define an opening long bracket of level n as an opening
+square bracket followed by n equal signs followed by another
+opening square bracket.
+So, an opening long bracket of level 0 is written as [[,
+an opening long bracket of level 1 is written as [=[,
+and so on.
+A closing long bracket is defined similarly;
+for instance, a closing long bracket of level 4 is written as ]====].
+A long string starts with an opening long bracket of any level and
+ends at the first closing long bracket of the same level.
+Literals in this bracketed form can run for several lines,
+do not interpret any escape sequences,
+and ignore long brackets of any other level.
+They can contain anything except a closing bracket of the proper level.
+
+
+
+For convenience,
+when the opening long bracket is immediately followed by a newline,
+the newline is not included in the string.
+As an example, in a system using ASCII
+(in which 'a' is coded as 97,
+newline is coded as 10, and '1' is coded as 49),
+the five literal strings below denote the same string:
+
+
+ a = 'alo\n123"' + a = "alo\n123\"" + a = '\97lo\10\04923"' + a = [[alo + 123"]] + a = [==[ + alo + 123"]==] ++ +
+A numerical constant can be written with an optional decimal part
+and an optional decimal exponent.
+Lua also accepts integer hexadecimal constants,
+by prefixing them with 0x.
+Examples of valid numerical constants are
+
+
+ 3 3.0 3.1416 314.16e-2 0.31416E1 0xff 0x56 ++ +
+A comment starts with a double hyphen (--)
+anywhere outside a string.
+If the text immediately after -- is not an opening long bracket,
+the comment is a short comment,
+which runs until the end of the line.
+Otherwise, it is a long comment,
+which runs until the corresponding closing long bracket.
+Long comments are frequently used to disable code temporarily.
+
+
+
+
+
+
+Lua is a dynamically typed language. +This means that +variables do not have types; only values do. +There are no type definitions in the language. +All values carry their own type. + + +
+All values in Lua are first-class values. +This means that all values can be stored in variables, +passed as arguments to other functions, and returned as results. + + +
+There are eight basic types in Lua:
+nil, boolean, number,
+string, function, userdata,
+thread, and table.
+Nil is the type of the value nil,
+whose main property is to be different from any other value;
+it usually represents the absence of a useful value.
+Boolean is the type of the values false and true.
+Both nil and false make a condition false;
+any other value makes it true.
+Number represents real (double-precision floating-point) numbers.
+(It is easy to build Lua interpreters that use other
+internal representations for numbers,
+such as single-precision float or long integers;
+see file luaconf.h.)
+String represents arrays of characters.
+
+Lua is 8-bit clean:
+strings can contain any 8-bit character,
+including embedded zeros ('\0') (see §2.1).
+
+
+
+Lua can call (and manipulate) functions written in Lua and +functions written in C +(see §2.5.8). + + +
+The type userdata is provided to allow arbitrary C data to +be stored in Lua variables. +This type corresponds to a block of raw memory +and has no pre-defined operations in Lua, +except assignment and identity test. +However, by using metatables, +the programmer can define operations for userdata values +(see §2.8). +Userdata values cannot be created or modified in Lua, +only through the C API. +This guarantees the integrity of data owned by the host program. + + +
+The type thread represents independent threads of execution +and it is used to implement coroutines (see §2.11). +Do not confuse Lua threads with operating-system threads. +Lua supports coroutines on all systems, +even those that do not support threads. + + +
+The type table implements associative arrays,
+that is, arrays that can be indexed not only with numbers,
+but with any value (except nil).
+Tables can be heterogeneous;
+that is, they can contain values of all types (except nil).
+Tables are the sole data structuring mechanism in Lua;
+they can be used to represent ordinary arrays,
+symbol tables, sets, records, graphs, trees, etc.
+To represent records, Lua uses the field name as an index.
+The language supports this representation by
+providing a.name as syntactic sugar for a["name"].
+There are several convenient ways to create tables in Lua
+(see §2.5.7).
+
+
+
+Like indices, +the value of a table field can be of any type (except nil). +In particular, +because functions are first-class values, +table fields can contain functions. +Thus tables can also carry methods (see §2.5.9). + + +
+Tables, functions, threads, and (full) userdata values are objects: +variables do not actually contain these values, +only references to them. +Assignment, parameter passing, and function returns +always manipulate references to such values; +these operations do not imply any kind of copy. + + +
+The library function type returns a string describing the type
+of a given value.
+
+
+
+
+Lua provides automatic conversion between
+string and number values at run time.
+Any arithmetic operation applied to a string tries to convert
+this string to a number, following the usual conversion rules.
+Conversely, whenever a number is used where a string is expected,
+the number is converted to a string, in a reasonable format.
+For complete control over how numbers are converted to strings,
+use the format function from the string library
+(see string.format).
+
+
+
+
+
+
+
+
+Variables are places that store values. + +There are three kinds of variables in Lua: +global variables, local variables, and table fields. + + +
+A single name can denote a global variable or a local variable +(or a function's formal parameter, +which is a particular kind of local variable): + +
+ var ::= Name +
+Name denotes identifiers, as defined in §2.1. + + +
+Any variable is assumed to be global unless explicitly declared +as a local (see §2.4.7). +Local variables are lexically scoped: +local variables can be freely accessed by functions +defined inside their scope (see §2.6). + + +
+Before the first assignment to a variable, its value is nil. + + +
+Square brackets are used to index a table: + +
+ var ::= prefixexp `[´ exp `]´ +
+The meaning of accesses to global variables
+and table fields can be changed via metatables.
+An access to an indexed variable t[i] is equivalent to
+a call gettable_event(t,i).
+(See §2.8 for a complete description of the
+gettable_event function.
+This function is not defined or callable in Lua.
+We use it here only for explanatory purposes.)
+
+
+
+The syntax var.Name is just syntactic sugar for
+var["Name"]:
+
+
+ var ::= prefixexp `.´ Name ++ +
+All global variables live as fields in ordinary Lua tables,
+called environment tables or simply
+environments (see §2.9).
+Each function has its own reference to an environment,
+so that all global variables in this function
+will refer to this environment table.
+When a function is created,
+it inherits the environment from the function that created it.
+To get the environment table of a Lua function,
+you call getfenv.
+To replace it,
+you call setfenv.
+(You can only manipulate the environment of C functions
+through the debug library; (see §5.9).)
+
+
+
+An access to a global variable x
+is equivalent to _env.x,
+which in turn is equivalent to
+
+
+ gettable_event(_env, "x") +
+where _env is the environment of the running function.
+(See §2.8 for a complete description of the
+gettable_event function.
+This function is not defined or callable in Lua.
+Similarly, the _env variable is not defined in Lua.
+We use them here only for explanatory purposes.)
+
+
+
+
+
+
+Lua supports an almost conventional set of statements, +similar to those in Pascal or C. +This set includes +assignments, control structures, function calls, +and variable declarations. + + + +
+The unit of execution of Lua is called a chunk. +A chunk is simply a sequence of statements, +which are executed sequentially. +Each statement can be optionally followed by a semicolon: + +
+ chunk ::= {stat [`;´]}
+
+There are no empty statements and thus ';;' is not legal.
+
+
+
+Lua handles a chunk as the body of an anonymous function +with a variable number of arguments +(see §2.5.9). +As such, chunks can define local variables, +receive arguments, and return values. + + +
+A chunk can be stored in a file or in a string inside the host program. +To execute a chunk, +Lua first pre-compiles the chunk into instructions for a virtual machine, +and then it executes the compiled code +with an interpreter for the virtual machine. + + +
+Chunks can also be pre-compiled into binary form;
+see program luac for details.
+Programs in source and compiled forms are interchangeable;
+Lua automatically detects the file type and acts accordingly.
+
+
+
+
+
+
+
+A block is a list of statements; +syntactically, a block is the same as a chunk: + +
+ block ::= chunk ++ +
+A block can be explicitly delimited to produce a single statement: + +
+ stat ::= do block end +
+Explicit blocks are useful +to control the scope of variable declarations. +Explicit blocks are also sometimes used to +add a return or break statement in the middle +of another block (see §2.4.4). + + + + + +
+Lua allows multiple assignments. +Therefore, the syntax for assignment +defines a list of variables on the left side +and a list of expressions on the right side. +The elements in both lists are separated by commas: + +
+ stat ::= varlist `=´ explist
+ varlist ::= var {`,´ var}
+ explist ::= exp {`,´ exp}
++Expressions are discussed in §2.5. + + +
+Before the assignment, +the list of values is adjusted to the length of +the list of variables. +If there are more values than needed, +the excess values are thrown away. +If there are fewer values than needed, +the list is extended with as many nil's as needed. +If the list of expressions ends with a function call, +then all values returned by that call enter the list of values, +before the adjustment +(except when the call is enclosed in parentheses; see §2.5). + + +
+The assignment statement first evaluates all its expressions +and only then are the assignments performed. +Thus the code + +
+ i = 3 + i, a[i] = i+1, 20 +
+sets a[3] to 20, without affecting a[4]
+because the i in a[i] is evaluated (to 3)
+before it is assigned 4.
+Similarly, the line
+
+
+ x, y = y, x +
+exchanges the values of x and y,
+and
+
+
+ x, y, z = y, z, x +
+cyclically permutes the values of x, y, and z.
+
+
+
+The meaning of assignments to global variables
+and table fields can be changed via metatables.
+An assignment to an indexed variable t[i] = val is equivalent to
+settable_event(t,i,val).
+(See §2.8 for a complete description of the
+settable_event function.
+This function is not defined or callable in Lua.
+We use it here only for explanatory purposes.)
+
+
+
+An assignment to a global variable x = val
+is equivalent to the assignment
+_env.x = val,
+which in turn is equivalent to
+
+
+ settable_event(_env, "x", val) +
+where _env is the environment of the running function.
+(The _env variable is not defined in Lua.
+We use it here only for explanatory purposes.)
+
+
+
+
+
+
+The control structures +if, while, and repeat have the usual meaning and +familiar syntax: + + + + +
+ stat ::= while exp do block end
+ stat ::= repeat block until exp
+ stat ::= if exp then block {elseif exp then block} [else block] end
++Lua also has a for statement, in two flavors (see §2.4.5). + + +
+The condition expression of a +control structure can return any value. +Both false and nil are considered false. +All values different from nil and false are considered true +(in particular, the number 0 and the empty string are also true). + + +
+In the repeat–until loop, +the inner block does not end at the until keyword, +but only after the condition. +So, the condition can refer to local variables +declared inside the loop block. + + +
+The return statement is used to return values +from a function or a chunk (which is just a function). + +Functions and chunks can return more than one value, +and so the syntax for the return statement is + +
+ stat ::= return [explist] ++ +
+The break statement is used to terminate the execution of a +while, repeat, or for loop, +skipping to the next statement after the loop: + + +
+ stat ::= break +
+A break ends the innermost enclosing loop. + + +
+The return and break
+statements can only be written as the last statement of a block.
+If it is really necessary to return or break in the
+middle of a block,
+then an explicit inner block can be used,
+as in the idioms
+do return end and do break end,
+because now return and break are the last statements in
+their (inner) blocks.
+
+
+
+
+
+
+ +The for statement has two forms: +one numeric and one generic. + + +
+The numeric for loop repeats a block of code while a +control variable runs through an arithmetic progression. +It has the following syntax: + +
+ stat ::= for Name `=´ exp `,´ exp [`,´ exp] do block end +
+The block is repeated for name starting at the value of +the first exp, until it passes the second exp by steps of the +third exp. +More precisely, a for statement like + +
+ for v = e1, e2, e3 do block end +
+is equivalent to the code: + +
+ do + local var, limit, step = tonumber(e1), tonumber(e2), tonumber(e3) + if not (var and limit and step) then error() end + while (step > 0 and var <= limit) or (step <= 0 and var >= limit) do + local v = var + block + var = var + step + end + end +
+Note the following: + +
var, limit, and step are invisible variables.
+The names shown here are for explanatory purposes only.
+v is local to the loop;
+you cannot use its value after the for ends or is broken.
+If you need this value,
+assign it to another variable before breaking or exiting the loop.
++The generic for statement works over functions, +called iterators. +On each iteration, the iterator function is called to produce a new value, +stopping when this new value is nil. +The generic for loop has the following syntax: + +
+ stat ::= for namelist in explist do block end
+ namelist ::= Name {`,´ Name}
++A for statement like + +
+ for var_1, ···, var_n in explist do block end +
+is equivalent to the code: + +
+ do + local f, s, var = explist + while true do + local var_1, ···, var_n = f(s, var) + var = var_1 + if var == nil then break end + block + end + end +
+Note the following: + +
explist is evaluated only once.
+Its results are an iterator function,
+a state,
+and an initial value for the first iterator variable.
+f, s, and var are invisible variables.
+The names are here for explanatory purposes only.
+var_i are local to the loop;
+you cannot use their values after the for ends.
+If you need these values,
+then assign them to other variables before breaking or exiting the loop.
++To allow possible side-effects, +function calls can be executed as statements: + +
+ stat ::= functioncall +
+In this case, all returned values are thrown away. +Function calls are explained in §2.5.8. + + + + + +
+Local variables can be declared anywhere inside a block. +The declaration can include an initial assignment: + +
+ stat ::= local namelist [`=´ explist] +
+If present, an initial assignment has the same semantics +of a multiple assignment (see §2.4.3). +Otherwise, all variables are initialized with nil. + + +
+A chunk is also a block (see §2.4.1), +and so local variables can be declared in a chunk outside any explicit block. +The scope of such local variables extends until the end of the chunk. + + +
+The visibility rules for local variables are explained in §2.6. + + + + + + + +
+The basic expressions in Lua are the following: + +
+ exp ::= prefixexp + exp ::= nil | false | true + exp ::= Number + exp ::= String + exp ::= function + exp ::= tableconstructor + exp ::= `...´ + exp ::= exp binop exp + exp ::= unop exp + prefixexp ::= var | functioncall | `(´ exp `)´ ++ +
+Numbers and literal strings are explained in §2.1;
+variables are explained in §2.3;
+function definitions are explained in §2.5.9;
+function calls are explained in §2.5.8;
+table constructors are explained in §2.5.7.
+Vararg expressions,
+denoted by three dots ('...'), can only be used when
+directly inside a vararg function;
+they are explained in §2.5.9.
+
+
+
+Binary operators comprise arithmetic operators (see §2.5.1), +relational operators (see §2.5.2), logical operators (see §2.5.3), +and the concatenation operator (see §2.5.4). +Unary operators comprise the unary minus (see §2.5.1), +the unary not (see §2.5.3), +and the unary length operator (see §2.5.5). + + +
+Both function calls and vararg expressions can result in multiple values. +If an expression is used as a statement +(only possible for function calls (see §2.4.6)), +then its return list is adjusted to zero elements, +thus discarding all returned values. +If an expression is used as the last (or the only) element +of a list of expressions, +then no adjustment is made +(unless the call is enclosed in parentheses). +In all other contexts, +Lua adjusts the result list to one element, +discarding all values except the first one. + + +
+Here are some examples: + +
+ f() -- adjusted to 0 results
+ g(f(), x) -- f() is adjusted to 1 result
+ g(x, f()) -- g gets x plus all results from f()
+ a,b,c = f(), x -- f() is adjusted to 1 result (c gets nil)
+ a,b = ... -- a gets the first vararg parameter, b gets
+ -- the second (both a and b can get nil if there
+ -- is no corresponding vararg parameter)
+
+ a,b,c = x, f() -- f() is adjusted to 2 results
+ a,b,c = f() -- f() is adjusted to 3 results
+ return f() -- returns all results from f()
+ return ... -- returns all received vararg parameters
+ return x,y,f() -- returns x, y, and all results from f()
+ {f()} -- creates a list with all results from f()
+ {...} -- creates a list with all vararg parameters
+ {f(), nil} -- f() is adjusted to 1 result
+
+
+
+Any expression enclosed in parentheses always results in only one value.
+Thus,
+(f(x,y,z)) is always a single value,
+even if f returns several values.
+(The value of (f(x,y,z)) is the first value returned by f
+or nil if f does not return any values.)
+
+
+
+
+Lua supports the usual arithmetic operators:
+the binary + (addition),
+- (subtraction), * (multiplication),
+/ (division), % (modulo), and ^ (exponentiation);
+and unary - (negation).
+If the operands are numbers, or strings that can be converted to
+numbers (see §2.2.1),
+then all operations have the usual meaning.
+Exponentiation works for any exponent.
+For instance, x^(-0.5) computes the inverse of the square root of x.
+Modulo is defined as
+
+
+ a % b == a - math.floor(a/b)*b +
+That is, it is the remainder of a division that rounds +the quotient towards minus infinity. + + + + + +
+The relational operators in Lua are + +
+ == ~= < > <= >= +
+These operators always result in false or true. + + +
+Equality (==) first compares the type of its operands.
+If the types are different, then the result is false.
+Otherwise, the values of the operands are compared.
+Numbers and strings are compared in the usual way.
+Objects (tables, userdata, threads, and functions)
+are compared by reference:
+two objects are considered equal only if they are the same object.
+Every time you create a new object
+(a table, userdata, thread, or function),
+this new object is different from any previously existing object.
+
+
+
+You can change the way that Lua compares tables and userdata +by using the "eq" metamethod (see §2.8). + + +
+The conversion rules of §2.2.1
+do not apply to equality comparisons.
+Thus, "0"==0 evaluates to false,
+and t[0] and t["0"] denote different
+entries in a table.
+
+
+
+The operator ~= is exactly the negation of equality (==).
+
+
+
+The order operators work as follows.
+If both arguments are numbers, then they are compared as such.
+Otherwise, if both arguments are strings,
+then their values are compared according to the current locale.
+Otherwise, Lua tries to call the "lt" or the "le"
+metamethod (see §2.8).
+A comparison a > b is translated to b < a
+and a >= b is translated to b <= a.
+
+
+
+
+
+
+The logical operators in Lua are +and, or, and not. +Like the control structures (see §2.4.4), +all logical operators consider both false and nil as false +and anything else as true. + + +
+The negation operator not always returns false or true. +The conjunction operator and returns its first argument +if this value is false or nil; +otherwise, and returns its second argument. +The disjunction operator or returns its first argument +if this value is different from nil and false; +otherwise, or returns its second argument. +Both and and or use short-cut evaluation; +that is, +the second operand is evaluated only if necessary. +Here are some examples: + +
+ 10 or 20 --> 10 + 10 or error() --> 10 + nil or "a" --> "a" + nil and 10 --> nil + false and error() --> false + false and nil --> false + false or nil --> nil + 10 and 20 --> 20 +
+(In this manual,
+--> indicates the result of the preceding expression.)
+
+
+
+
+
+
+The string concatenation operator in Lua is
+denoted by two dots ('..').
+If both operands are strings or numbers, then they are converted to
+strings according to the rules mentioned in §2.2.1.
+Otherwise, the "concat" metamethod is called (see §2.8).
+
+
+
+
+
+
+The length operator is denoted by the unary operator #.
+The length of a string is its number of bytes
+(that is, the usual meaning of string length when each
+character is one byte).
+
+
+
+The length of a table t is defined to be any
+integer index n
+such that t[n] is not nil and t[n+1] is nil;
+moreover, if t[1] is nil, n can be zero.
+For a regular array, with non-nil values from 1 to a given n,
+its length is exactly that n,
+the index of its last value.
+If the array has "holes"
+(that is, nil values between other non-nil values),
+then #t can be any of the indices that
+directly precedes a nil value
+(that is, it may consider any such nil value as the end of
+the array).
+
+
+
+
+
+
+Operator precedence in Lua follows the table below, +from lower to higher priority: + +
+ or + and + < > <= >= ~= == + .. + + - + * / % + not # - (unary) + ^ +
+As usual,
+you can use parentheses to change the precedences of an expression.
+The concatenation ('..') and exponentiation ('^')
+operators are right associative.
+All other binary operators are left associative.
+
+
+
+
+
+
+Table constructors are expressions that create tables. +Every time a constructor is evaluated, a new table is created. +A constructor can be used to create an empty table +or to create a table and initialize some of its fields. +The general syntax for constructors is + +
+ tableconstructor ::= `{´ [fieldlist] `}´
+ fieldlist ::= field {fieldsep field} [fieldsep]
+ field ::= `[´ exp `]´ `=´ exp | Name `=´ exp | exp
+ fieldsep ::= `,´ | `;´
+
+
+
+Each field of the form [exp1] = exp2 adds to the new table an entry
+with key exp1 and value exp2.
+A field of the form name = exp is equivalent to
+["name"] = exp.
+Finally, fields of the form exp are equivalent to
+[i] = exp, where i are consecutive numerical integers,
+starting with 1.
+Fields in the other formats do not affect this counting.
+For example,
+
+
+ a = { [f(1)] = g; "x", "y"; x = 1, f(x), [30] = 23; 45 }
++is equivalent to + +
+ do
+ local t = {}
+ t[f(1)] = g
+ t[1] = "x" -- 1st exp
+ t[2] = "y" -- 2nd exp
+ t.x = 1 -- t["x"] = 1
+ t[3] = f(x) -- 3rd exp
+ t[30] = 23
+ t[4] = 45 -- 4th exp
+ a = t
+ end
+
+
+
+If the last field in the list has the form exp
+and the expression is a function call or a vararg expression,
+then all values returned by this expression enter the list consecutively
+(see §2.5.8).
+To avoid this,
+enclose the function call or the vararg expression
+in parentheses (see §2.5).
+
+
+
+The field list can have an optional trailing separator, +as a convenience for machine-generated code. + + + + + +
+A function call in Lua has the following syntax: + +
+ functioncall ::= prefixexp args +
+In a function call, +first prefixexp and args are evaluated. +If the value of prefixexp has type function, +then this function is called +with the given arguments. +Otherwise, the prefixexp "call" metamethod is called, +having as first parameter the value of prefixexp, +followed by the original call arguments +(see §2.8). + + +
+The form + +
+ functioncall ::= prefixexp `:´ Name args +
+can be used to call "methods".
+A call v:name(args)
+is syntactic sugar for v.name(v,args),
+except that v is evaluated only once.
+
+
+
+Arguments have the following syntax: + +
+ args ::= `(´ [explist] `)´ + args ::= tableconstructor + args ::= String +
+All argument expressions are evaluated before the call.
+A call of the form f{fields} is
+syntactic sugar for f({fields});
+that is, the argument list is a single new table.
+A call of the form f'string'
+(or f"string" or f[[string]])
+is syntactic sugar for f('string');
+that is, the argument list is a single literal string.
+
+
+
+As an exception to the free-format syntax of Lua,
+you cannot put a line break before the '(' in a function call.
+This restriction avoids some ambiguities in the language.
+If you write
+
+
+ a = f + (g).x(a) +
+Lua would see that as a single statement, a = f(g).x(a).
+So, if you want two statements, you must add a semi-colon between them.
+If you actually want to call f,
+you must remove the line break before (g).
+
+
+
+A call of the form return functioncall is called
+a tail call.
+Lua implements proper tail calls
+(or proper tail recursion):
+in a tail call,
+the called function reuses the stack entry of the calling function.
+Therefore, there is no limit on the number of nested tail calls that
+a program can execute.
+However, a tail call erases any debug information about the
+calling function.
+Note that a tail call only happens with a particular syntax,
+where the return has one single function call as argument;
+this syntax makes the calling function return exactly
+the returns of the called function.
+So, none of the following examples are tail calls:
+
+
+ return (f(x)) -- results adjusted to 1 + return 2 * f(x) + return x, f(x) -- additional results + f(x); return -- results discarded + return x or f(x) -- results adjusted to 1 ++ + + + +
+The syntax for function definition is + +
+ function ::= function funcbody + funcbody ::= `(´ [parlist] `)´ block end ++ +
+The following syntactic sugar simplifies function definitions: + +
+ stat ::= function funcname funcbody
+ stat ::= local function Name funcbody
+ funcname ::= Name {`.´ Name} [`:´ Name]
++The statement + +
+ function f () body end +
+translates to + +
+ f = function () body end +
+The statement + +
+ function t.a.b.c.f () body end +
+translates to + +
+ t.a.b.c.f = function () body end +
+The statement + +
+ local function f () body end +
+translates to + +
+ local f; f = function () body end +
+not to + +
+ local f = function () body end +
+(This only makes a difference when the body of the function
+contains references to f.)
+
+
+
+A function definition is an executable expression, +whose value has type function. +When Lua pre-compiles a chunk, +all its function bodies are pre-compiled too. +Then, whenever Lua executes the function definition, +the function is instantiated (or closed). +This function instance (or closure) +is the final value of the expression. +Different instances of the same function +can refer to different external local variables +and can have different environment tables. + + +
+Parameters act as local variables that are +initialized with the argument values: + +
+ parlist ::= namelist [`,´ `...´] | `...´ +
+When a function is called,
+the list of arguments is adjusted to
+the length of the list of parameters,
+unless the function is a variadic or vararg function,
+which is
+indicated by three dots ('...') at the end of its parameter list.
+A vararg function does not adjust its argument list;
+instead, it collects all extra arguments and supplies them
+to the function through a vararg expression,
+which is also written as three dots.
+The value of this expression is a list of all actual extra arguments,
+similar to a function with multiple results.
+If a vararg expression is used inside another expression
+or in the middle of a list of expressions,
+then its return list is adjusted to one element.
+If the expression is used as the last element of a list of expressions,
+then no adjustment is made
+(unless that last expression is enclosed in parentheses).
+
+
+
+As an example, consider the following definitions: + +
+ function f(a, b) end + function g(a, b, ...) end + function r() return 1,2,3 end +
+Then, we have the following mapping from arguments to parameters and +to the vararg expression: + +
+ CALL PARAMETERS + + f(3) a=3, b=nil + f(3, 4) a=3, b=4 + f(3, 4, 5) a=3, b=4 + f(r(), 10) a=1, b=10 + f(r()) a=1, b=2 + + g(3) a=3, b=nil, ... --> (nothing) + g(3, 4) a=3, b=4, ... --> (nothing) + g(3, 4, 5, 8) a=3, b=4, ... --> 5 8 + g(5, r()) a=5, b=1, ... --> 2 3 ++ +
+Results are returned using the return statement (see §2.4.4). +If control reaches the end of a function +without encountering a return statement, +then the function returns with no results. + + +
+The colon syntax
+is used for defining methods,
+that is, functions that have an implicit extra parameter self.
+Thus, the statement
+
+
+ function t.a.b.c:f (params) body end +
+is syntactic sugar for + +
+ t.a.b.c.f = function (self, params) body end ++ + + + + + +
+ +Lua is a lexically scoped language. +The scope of variables begins at the first statement after +their declaration and lasts until the end of the innermost block that +includes the declaration. +Consider the following example: + +
+ x = 10 -- global variable + do -- new block + local x = x -- new 'x', with value 10 + print(x) --> 10 + x = x+1 + do -- another block + local x = x+1 -- another 'x' + print(x) --> 12 + end + print(x) --> 11 + end + print(x) --> 10 (the global one) ++ +
+Notice that, in a declaration like local x = x,
+the new x being declared is not in scope yet,
+and so the second x refers to the outside variable.
+
+
+
+Because of the lexical scoping rules, +local variables can be freely accessed by functions +defined inside their scope. +A local variable used by an inner function is called +an upvalue, or external local variable, +inside the inner function. + + +
+Notice that each execution of a local statement +defines new local variables. +Consider the following example: + +
+ a = {}
+ local x = 20
+ for i=1,10 do
+ local y = 0
+ a[i] = function () y=y+1; return x+y end
+ end
+
+The loop creates ten closures
+(that is, ten instances of the anonymous function).
+Each of these closures uses a different y variable,
+while all of them share the same x.
+
+
+
+
+
+
+Because Lua is an embedded extension language,
+all Lua actions start from C code in the host program
+calling a function from the Lua library (see lua_pcall).
+Whenever an error occurs during Lua compilation or execution,
+control returns to C,
+which can take appropriate measures
+(such as printing an error message).
+
+
+
+Lua code can explicitly generate an error by calling the
+error function.
+If you need to catch errors in Lua,
+you can use the pcall function.
+
+
+
+
+
+
+Every value in Lua can have a metatable.
+This metatable is an ordinary Lua table
+that defines the behavior of the original value
+under certain special operations.
+You can change several aspects of the behavior
+of operations over a value by setting specific fields in its metatable.
+For instance, when a non-numeric value is the operand of an addition,
+Lua checks for a function in the field "__add" in its metatable.
+If it finds one,
+Lua calls this function to perform the addition.
+
+
+
+We call the keys in a metatable events
+and the values metamethods.
+In the previous example, the event is "add"
+and the metamethod is the function that performs the addition.
+
+
+
+You can query the metatable of any value
+through the getmetatable function.
+
+
+
+You can replace the metatable of tables
+through the setmetatable
+function.
+You cannot change the metatable of other types from Lua
+(except by using the debug library);
+you must use the C API for that.
+
+
+
+Tables and full userdata have individual metatables +(although multiple tables and userdata can share their metatables). +Values of all other types share one single metatable per type; +that is, there is one single metatable for all numbers, +one for all strings, etc. + + +
+A metatable controls how an object behaves in arithmetic operations, +order comparisons, concatenation, length operation, and indexing. +A metatable also can define a function to be called when a userdata +is garbage collected. +For each of these operations Lua associates a specific key +called an event. +When Lua performs one of these operations over a value, +it checks whether this value has a metatable with the corresponding event. +If so, the value associated with that key (the metamethod) +controls how Lua will perform the operation. + + +
+Metatables control the operations listed next.
+Each operation is identified by its corresponding name.
+The key for each operation is a string with its name prefixed by
+two underscores, '__';
+for instance, the key for operation "add" is the
+string "__add".
+The semantics of these operations is better explained by a Lua function
+describing how the interpreter executes the operation.
+
+
+
+The code shown here in Lua is only illustrative;
+the real behavior is hard coded in the interpreter
+and it is much more efficient than this simulation.
+All functions used in these descriptions
+(rawget, tonumber, etc.)
+are described in §5.1.
+In particular, to retrieve the metamethod of a given object,
+we use the expression
+
+
+ metatable(obj)[event] +
+This should be read as + +
+ rawget(getmetatable(obj) or {}, event)
++ +That is, the access to a metamethod does not invoke other metamethods, +and the access to objects with no metatables does not fail +(it simply results in nil). + + + +
+ operation.
+
+
+
+
+The function getbinhandler below defines how Lua chooses a handler
+for a binary operation.
+First, Lua tries the first operand.
+If its type does not define a handler for the operation,
+then Lua tries the second operand.
+
+
+ function getbinhandler (op1, op2, event) + return metatable(op1)[event] or metatable(op2)[event] + end +
+By using this function,
+the behavior of the op1 + op2 is
+
+
+ function add_event (op1, op2) + local o1, o2 = tonumber(op1), tonumber(op2) + if o1 and o2 then -- both operands are numeric? + return o1 + o2 -- '+' here is the primitive 'add' + else -- at least one of the operands is not numeric + local h = getbinhandler(op1, op2, "__add") + if h then + -- call the handler with both operands + return (h(op1, op2)) + else -- no handler available: default behavior + error(···) + end + end + end +
+
- operation.
+
+Behavior similar to the "add" operation.
+* operation.
+
+Behavior similar to the "add" operation.
+/ operation.
+
+Behavior similar to the "add" operation.
+% operation.
+
+Behavior similar to the "add" operation,
+with the operation
+o1 - floor(o1/o2)*o2 as the primitive operation.
+^ (exponentiation) operation.
+
+Behavior similar to the "add" operation,
+with the function pow (from the C math library)
+as the primitive operation.
+- operation.
+
+
++ function unm_event (op) + local o = tonumber(op) + if o then -- operand is numeric? + return -o -- '-' here is the primitive 'unm' + else -- the operand is not numeric. + -- Try to get a handler from the operand + local h = metatable(op).__unm + if h then + -- call the handler with the operand + return (h(op)) + else -- no handler available: default behavior + error(···) + end + end + end +
+
.. (concatenation) operation.
+
+
++ function concat_event (op1, op2) + if (type(op1) == "string" or type(op1) == "number") and + (type(op2) == "string" or type(op2) == "number") then + return op1 .. op2 -- primitive string concatenation + else + local h = getbinhandler(op1, op2, "__concat") + if h then + return (h(op1, op2)) + else + error(···) + end + end + end +
+
# operation.
+
+
++ function len_event (op) + if type(op) == "string" then + return strlen(op) -- primitive string length + elseif type(op) == "table" then + return #op -- primitive table length + else + local h = metatable(op).__len + if h then + -- call the handler with the operand + return (h(op)) + else -- no handler available: default behavior + error(···) + end + end + end +
+See §2.5.5 for a description of the length of a table. +
== operation.
+
+The function getcomphandler defines how Lua chooses a metamethod
+for comparison operators.
+A metamethod only is selected when both objects
+being compared have the same type
+and the same metamethod for the selected operation.
+
++ function getcomphandler (op1, op2, event) + if type(op1) ~= type(op2) then return nil end + local mm1 = metatable(op1)[event] + local mm2 = metatable(op2)[event] + if mm1 == mm2 then return mm1 else return nil end + end +
+The "eq" event is defined as follows: + +
+ function eq_event (op1, op2) + if type(op1) ~= type(op2) then -- different types? + return false -- different objects + end + if op1 == op2 then -- primitive equal? + return true -- objects are equal + end + -- try metamethod + local h = getcomphandler(op1, op2, "__eq") + if h then + return (h(op1, op2)) + else + return false + end + end +
+a ~= b is equivalent to not (a == b).
+
< operation.
+
+
++ function lt_event (op1, op2) + if type(op1) == "number" and type(op2) == "number" then + return op1 < op2 -- numeric comparison + elseif type(op1) == "string" and type(op2) == "string" then + return op1 < op2 -- lexicographic comparison + else + local h = getcomphandler(op1, op2, "__lt") + if h then + return (h(op1, op2)) + else + error(···) + end + end + end +
+a > b is equivalent to b < a.
+
<= operation.
+
+
++ function le_event (op1, op2) + if type(op1) == "number" and type(op2) == "number" then + return op1 <= op2 -- numeric comparison + elseif type(op1) == "string" and type(op2) == "string" then + return op1 <= op2 -- lexicographic comparison + else + local h = getcomphandler(op1, op2, "__le") + if h then + return (h(op1, op2)) + else + h = getcomphandler(op1, op2, "__lt") + if h then + return not h(op2, op1) + else + error(···) + end + end + end + end +
+a >= b is equivalent to b <= a.
+Note that, in the absence of a "le" metamethod,
+Lua tries the "lt", assuming that a <= b is
+equivalent to not (b < a).
+
table[key].
+
+
++ function gettable_event (table, key) + local h + if type(table) == "table" then + local v = rawget(table, key) + if v ~= nil then return v end + h = metatable(table).__index + if h == nil then return nil end + else + h = metatable(table).__index + if h == nil then + error(···) + end + end + if type(h) == "function" then + return (h(table, key)) -- call the handler + else return h[key] -- or repeat operation on it + end + end +
+
table[key] = value.
+
+
++ function settable_event (table, key, value) + local h + if type(table) == "table" then + local v = rawget(table, key) + if v ~= nil then rawset(table, key, value); return end + h = metatable(table).__newindex + if h == nil then rawset(table, key, value); return end + else + h = metatable(table).__newindex + if h == nil then + error(···) + end + end + if type(h) == "function" then + h(table, key,value) -- call the handler + else h[key] = value -- or repeat operation on it + end + end +
+
+ function function_event (func, ...) + if type(func) == "function" then + return func(...) -- primitive call + else + local h = metatable(func).__call + if h then + return h(func, ...) + else + error(···) + end + end + end +
+
+Besides metatables, +objects of types thread, function, and userdata +have another table associated with them, +called their environment. +Like metatables, environments are regular tables and +multiple objects can share the same environment. + + +
+Threads are created sharing the environment of the creating thread.
+Userdata and C functions are created sharing the environment
+of the creating C function.
+Non-nested Lua functions
+(created by loadfile, loadstring or load)
+are created sharing the environment of the creating thread.
+Nested Lua functions are created sharing the environment of
+the creating Lua function.
+
+
+
+Environments associated with userdata have no meaning for Lua. +It is only a convenience feature for programmers to associate a table to +a userdata. + + +
+Environments associated with threads are called +global environments. +They are used as the default environment for threads and +non-nested Lua functions created by the thread +and can be directly accessed by C code (see §3.3). + + +
+The environment associated with a C function can be directly +accessed by C code (see §3.3). +It is used as the default environment for other C functions +and userdata created by the function. + + +
+Environments associated with Lua functions are used to resolve +all accesses to global variables within the function (see §2.3). +They are used as the default environment for nested Lua functions +created by the function. + + +
+You can change the environment of a Lua function or the
+running thread by calling setfenv.
+You can get the environment of a Lua function or the running thread
+by calling getfenv.
+To manipulate the environment of other objects
+(userdata, C functions, other threads) you must
+use the C API.
+
+
+
+
+
+
+Lua performs automatic memory management. +This means that +you have to worry neither about allocating memory for new objects +nor about freeing it when the objects are no longer needed. +Lua manages memory automatically by running +a garbage collector from time to time +to collect all dead objects +(that is, objects that are no longer accessible from Lua). +All memory used by Lua is subject to automatic management: +tables, userdata, functions, threads, strings, etc. + + +
+Lua implements an incremental mark-and-sweep collector. +It uses two numbers to control its garbage-collection cycles: +the garbage-collector pause and +the garbage-collector step multiplier. +Both use percentage points as units +(so that a value of 100 means an internal value of 1). + + +
+The garbage-collector pause +controls how long the collector waits before starting a new cycle. +Larger values make the collector less aggressive. +Values smaller than 100 mean the collector will not wait to +start a new cycle. +A value of 200 means that the collector waits for the total memory in use +to double before starting a new cycle. + + +
+The step multiplier +controls the relative speed of the collector relative to +memory allocation. +Larger values make the collector more aggressive but also increase +the size of each incremental step. +Values smaller than 100 make the collector too slow and +can result in the collector never finishing a cycle. +The default, 200, means that the collector runs at "twice" +the speed of memory allocation. + + +
+You can change these numbers by calling lua_gc in C
+or collectgarbage in Lua.
+With these functions you can also control
+the collector directly (e.g., stop and restart it).
+
+
+
+
+Using the C API, +you can set garbage-collector metamethods for userdata (see §2.8). +These metamethods are also called finalizers. +Finalizers allow you to coordinate Lua's garbage collection +with external resource management +(such as closing files, network or database connections, +or freeing your own memory). + + +
+Garbage userdata with a field __gc in their metatables are not
+collected immediately by the garbage collector.
+Instead, Lua puts them in a list.
+After the collection,
+Lua does the equivalent of the following function
+for each userdata in that list:
+
+
+ function gc_event (udata) + local h = metatable(udata).__gc + if h then + h(udata) + end + end ++ +
+At the end of each garbage-collection cycle, +the finalizers for userdata are called in reverse +order of their creation, +among those collected in that cycle. +That is, the first finalizer to be called is the one associated +with the userdata created last in the program. +The userdata itself is freed only in the next garbage-collection cycle. + + + + + +
+A weak table is a table whose elements are +weak references. +A weak reference is ignored by the garbage collector. +In other words, +if the only references to an object are weak references, +then the garbage collector will collect this object. + + +
+A weak table can have weak keys, weak values, or both.
+A table with weak keys allows the collection of its keys,
+but prevents the collection of its values.
+A table with both weak keys and weak values allows the collection of
+both keys and values.
+In any case, if either the key or the value is collected,
+the whole pair is removed from the table.
+The weakness of a table is controlled by the
+__mode field of its metatable.
+If the __mode field is a string containing the character 'k',
+the keys in the table are weak.
+If __mode contains 'v',
+the values in the table are weak.
+
+
+
+After you use a table as a metatable,
+you should not change the value of its __mode field.
+Otherwise, the weak behavior of the tables controlled by this
+metatable is undefined.
+
+
+
+
+
+
+
+
+Lua supports coroutines, +also called collaborative multithreading. +A coroutine in Lua represents an independent thread of execution. +Unlike threads in multithread systems, however, +a coroutine only suspends its execution by explicitly calling +a yield function. + + +
+You create a coroutine with a call to coroutine.create.
+Its sole argument is a function
+that is the main function of the coroutine.
+The create function only creates a new coroutine and
+returns a handle to it (an object of type thread);
+it does not start the coroutine execution.
+
+
+
+When you first call coroutine.resume,
+passing as its first argument
+a thread returned by coroutine.create,
+the coroutine starts its execution,
+at the first line of its main function.
+Extra arguments passed to coroutine.resume are passed on
+to the coroutine main function.
+After the coroutine starts running,
+it runs until it terminates or yields.
+
+
+
+A coroutine can terminate its execution in two ways:
+normally, when its main function returns
+(explicitly or implicitly, after the last instruction);
+and abnormally, if there is an unprotected error.
+In the first case, coroutine.resume returns true,
+plus any values returned by the coroutine main function.
+In case of errors, coroutine.resume returns false
+plus an error message.
+
+
+
+A coroutine yields by calling coroutine.yield.
+When a coroutine yields,
+the corresponding coroutine.resume returns immediately,
+even if the yield happens inside nested function calls
+(that is, not in the main function,
+but in a function directly or indirectly called by the main function).
+In the case of a yield, coroutine.resume also returns true,
+plus any values passed to coroutine.yield.
+The next time you resume the same coroutine,
+it continues its execution from the point where it yielded,
+with the call to coroutine.yield returning any extra
+arguments passed to coroutine.resume.
+
+
+
+Like coroutine.create,
+the coroutine.wrap function also creates a coroutine,
+but instead of returning the coroutine itself,
+it returns a function that, when called, resumes the coroutine.
+Any arguments passed to this function
+go as extra arguments to coroutine.resume.
+coroutine.wrap returns all the values returned by coroutine.resume,
+except the first one (the boolean error code).
+Unlike coroutine.resume,
+coroutine.wrap does not catch errors;
+any error is propagated to the caller.
+
+
+
+As an example, +consider the following code: + +
+ function foo (a)
+ print("foo", a)
+ return coroutine.yield(2*a)
+ end
+
+ co = coroutine.create(function (a,b)
+ print("co-body", a, b)
+ local r = foo(a+1)
+ print("co-body", r)
+ local r, s = coroutine.yield(a+b, a-b)
+ print("co-body", r, s)
+ return b, "end"
+ end)
+
+ print("main", coroutine.resume(co, 1, 10))
+ print("main", coroutine.resume(co, "r"))
+ print("main", coroutine.resume(co, "x", "y"))
+ print("main", coroutine.resume(co, "x", "y"))
++When you run it, it produces the following output: + +
+ co-body 1 10 + foo 2 + + main true 4 + co-body r + main true 11 -9 + co-body x y + main true 10 end + main false cannot resume dead coroutine ++ + + + +
+
+This section describes the C API for Lua, that is,
+the set of C functions available to the host program to communicate
+with Lua.
+All API functions and related types and constants
+are declared in the header file lua.h.
+
+
+
+Even when we use the term "function", +any facility in the API may be provided as a macro instead. +All such macros use each of their arguments exactly once +(except for the first argument, which is always a Lua state), +and so do not generate any hidden side-effects. + + +
+As in most C libraries,
+the Lua API functions do not check their arguments for validity or consistency.
+However, you can change this behavior by compiling Lua
+with a proper definition for the macro luai_apicheck,
+in file luaconf.h.
+
+
+
+
+Lua uses a virtual stack to pass values to and from C. +Each element in this stack represents a Lua value +(nil, number, string, etc.). + + +
+Whenever Lua calls C, the called function gets a new stack,
+which is independent of previous stacks and of stacks of
+C functions that are still active.
+This stack initially contains any arguments to the C function
+and it is where the C function pushes its results
+to be returned to the caller (see lua_CFunction).
+
+
+
+For convenience,
+most query operations in the API do not follow a strict stack discipline.
+Instead, they can refer to any element in the stack
+by using an index:
+A positive index represents an absolute stack position
+(starting at 1);
+a negative index represents an offset relative to the top of the stack.
+More specifically, if the stack has n elements,
+then index 1 represents the first element
+(that is, the element that was pushed onto the stack first)
+and
+index n represents the last element;
+index -1 also represents the last element
+(that is, the element at the top)
+and index -n represents the first element.
+We say that an index is valid
+if it lies between 1 and the stack top
+(that is, if 1 ≤ abs(index) ≤ top).
+
+
+
+
+
+
+
+When you interact with Lua API,
+you are responsible for ensuring consistency.
+In particular,
+you are responsible for controlling stack overflow.
+You can use the function lua_checkstack
+to grow the stack size.
+
+
+
+Whenever Lua calls C,
+it ensures that at least LUA_MINSTACK stack positions are available.
+LUA_MINSTACK is defined as 20,
+so that usually you do not have to worry about stack space
+unless your code has loops pushing elements onto the stack.
+
+
+
+Most query functions accept as indices any value inside the
+available stack space, that is, indices up to the maximum stack size
+you have set through lua_checkstack.
+Such indices are called acceptable indices.
+More formally, we define an acceptable index
+as follows:
+
+
+ (index < 0 && abs(index) <= top) || + (index > 0 && index <= stackspace) +
+Note that 0 is never an acceptable index. + + + + + +
+Unless otherwise noted, +any function that accepts valid indices can also be called with +pseudo-indices, +which represent some Lua values that are accessible to C code +but which are not in the stack. +Pseudo-indices are used to access the thread environment, +the function environment, +the registry, +and the upvalues of a C function (see §3.4). + + +
+The thread environment (where global variables live) is
+always at pseudo-index LUA_GLOBALSINDEX.
+The environment of the running C function is always
+at pseudo-index LUA_ENVIRONINDEX.
+
+
+
+To access and change the value of global variables, +you can use regular table operations over an environment table. +For instance, to access the value of a global variable, do + +
+ lua_getfield(L, LUA_GLOBALSINDEX, varname); ++ + + + +
+When a C function is created,
+it is possible to associate some values with it,
+thus creating a C closure;
+these values are called upvalues and are
+accessible to the function whenever it is called
+(see lua_pushcclosure).
+
+
+
+Whenever a C function is called,
+its upvalues are located at specific pseudo-indices.
+These pseudo-indices are produced by the macro
+lua_upvalueindex.
+The first value associated with a function is at position
+lua_upvalueindex(1), and so on.
+Any access to lua_upvalueindex(n),
+where n is greater than the number of upvalues of the
+current function (but not greater than 256),
+produces an acceptable (but invalid) index.
+
+
+
+
+
+
+Lua provides a registry,
+a pre-defined table that can be used by any C code to
+store whatever Lua value it needs to store.
+This table is always located at pseudo-index
+LUA_REGISTRYINDEX.
+Any C library can store data into this table,
+but it should take care to choose keys different from those used
+by other libraries, to avoid collisions.
+Typically, you should use as key a string containing your library name
+or a light userdata with the address of a C object in your code.
+
+
+
+The integer keys in the registry are used by the reference mechanism, +implemented by the auxiliary library, +and therefore should not be used for other purposes. + + + + + +
+Internally, Lua uses the C longjmp facility to handle errors.
+(You can also choose to use exceptions if you use C++;
+see file luaconf.h.)
+When Lua faces any error
+(such as memory allocation errors, type errors, syntax errors,
+and runtime errors)
+it raises an error;
+that is, it does a long jump.
+A protected environment uses setjmp
+to set a recover point;
+any error jumps to the most recent active recover point.
+
+
+
+Most functions in the API can throw an error, +for instance due to a memory allocation error. +The documentation for each function indicates whether +it can throw errors. + + +
+Inside a C function you can throw an error by calling lua_error.
+
+
+
+
+
+
+Here we list all functions and types from the C API in +alphabetical order. +Each function has an indicator like this: +[-o, +p, x] + + +
+The first field, o,
+is how many elements the function pops from the stack.
+The second field, p,
+is how many elements the function pushes onto the stack.
+(Any function always pushes its results after popping its arguments.)
+A field in the form x|y means the function can push (or pop)
+x or y elements,
+depending on the situation;
+an interrogation mark '?' means that
+we cannot know how many elements the function pops/pushes
+by looking only at its arguments
+(e.g., they may depend on what is on the stack).
+The third field, x,
+tells whether the function may throw errors:
+'-' means the function never throws any error;
+'m' means the function may throw an error
+only due to not enough memory;
+'e' means the function may throw other kinds of errors;
+'v' means the function may throw an error on purpose.
+
+
+
+
lua_Alloctypedef void * (*lua_Alloc) (void *ud, + void *ptr, + size_t osize, + size_t nsize);+ +
+The type of the memory-allocation function used by Lua states.
+The allocator function must provide a
+functionality similar to realloc,
+but not exactly the same.
+Its arguments are
+ud, an opaque pointer passed to lua_newstate;
+ptr, a pointer to the block being allocated/reallocated/freed;
+osize, the original size of the block;
+nsize, the new size of the block.
+ptr is NULL if and only if osize is zero.
+When nsize is zero, the allocator must return NULL;
+if osize is not zero,
+it should free the block pointed to by ptr.
+When nsize is not zero, the allocator returns NULL
+if and only if it cannot fill the request.
+When nsize is not zero and osize is zero,
+the allocator should behave like malloc.
+When nsize and osize are not zero,
+the allocator behaves like realloc.
+Lua assumes that the allocator never fails when
+osize >= nsize.
+
+
+
+Here is a simple implementation for the allocator function.
+It is used in the auxiliary library by luaL_newstate.
+
+
+ static void *l_alloc (void *ud, void *ptr, size_t osize,
+ size_t nsize) {
+ (void)ud; (void)osize; /* not used */
+ if (nsize == 0) {
+ free(ptr);
+ return NULL;
+ }
+ else
+ return realloc(ptr, nsize);
+ }
+
+This code assumes
+that free(NULL) has no effect and that
+realloc(NULL, size) is equivalent to malloc(size).
+ANSI C ensures both behaviors.
+
+
+
+
+
+
lua_atpanic+[-0, +0, -] +
lua_CFunction lua_atpanic (lua_State *L, lua_CFunction panicf);+ +
+Sets a new panic function and returns the old one. + + +
+If an error happens outside any protected environment,
+Lua calls a panic function
+and then calls exit(EXIT_FAILURE),
+thus exiting the host application.
+Your panic function can avoid this exit by
+never returning (e.g., doing a long jump).
+
+
+
+The panic function can access the error message at the top of the stack. + + + + + +
lua_call+[-(nargs + 1), +nresults, e] +
void lua_call (lua_State *L, int nargs, int nresults);+ +
+Calls a function. + + +
+To call a function you must use the following protocol:
+first, the function to be called is pushed onto the stack;
+then, the arguments to the function are pushed
+in direct order;
+that is, the first argument is pushed first.
+Finally you call lua_call;
+nargs is the number of arguments that you pushed onto the stack.
+All arguments and the function value are popped from the stack
+when the function is called.
+The function results are pushed onto the stack when the function returns.
+The number of results is adjusted to nresults,
+unless nresults is LUA_MULTRET.
+In this case, all results from the function are pushed.
+Lua takes care that the returned values fit into the stack space.
+The function results are pushed onto the stack in direct order
+(the first result is pushed first),
+so that after the call the last result is on the top of the stack.
+
+
+
+Any error inside the called function is propagated upwards
+(with a longjmp).
+
+
+
+The following example shows how the host program can do the +equivalent to this Lua code: + +
+ a = f("how", t.x, 14)
++Here it is in C: + +
+ lua_getfield(L, LUA_GLOBALSINDEX, "f"); /* function to be called */ + lua_pushstring(L, "how"); /* 1st argument */ + lua_getfield(L, LUA_GLOBALSINDEX, "t"); /* table to be indexed */ + lua_getfield(L, -1, "x"); /* push result of t.x (2nd arg) */ + lua_remove(L, -2); /* remove 't' from the stack */ + lua_pushinteger(L, 14); /* 3rd argument */ + lua_call(L, 3, 1); /* call 'f' with 3 arguments and 1 result */ + lua_setfield(L, LUA_GLOBALSINDEX, "a"); /* set global 'a' */ +
+Note that the code above is "balanced": +at its end, the stack is back to its original configuration. +This is considered good programming practice. + + + + + +
lua_CFunctiontypedef int (*lua_CFunction) (lua_State *L);+ +
+Type for C functions. + + +
+In order to communicate properly with Lua,
+a C function must use the following protocol,
+which defines the way parameters and results are passed:
+a C function receives its arguments from Lua in its stack
+in direct order (the first argument is pushed first).
+So, when the function starts,
+lua_gettop(L) returns the number of arguments received by the function.
+The first argument (if any) is at index 1
+and its last argument is at index lua_gettop(L).
+To return values to Lua, a C function just pushes them onto the stack,
+in direct order (the first result is pushed first),
+and returns the number of results.
+Any other value in the stack below the results will be properly
+discarded by Lua.
+Like a Lua function, a C function called by Lua can also return
+many results.
+
+
+
+As an example, the following function receives a variable number +of numerical arguments and returns their average and sum: + +
+ static int foo (lua_State *L) {
+ int n = lua_gettop(L); /* number of arguments */
+ lua_Number sum = 0;
+ int i;
+ for (i = 1; i <= n; i++) {
+ if (!lua_isnumber(L, i)) {
+ lua_pushstring(L, "incorrect argument");
+ lua_error(L);
+ }
+ sum += lua_tonumber(L, i);
+ }
+ lua_pushnumber(L, sum/n); /* first result */
+ lua_pushnumber(L, sum); /* second result */
+ return 2; /* number of results */
+ }
+
+
+
+
+
+lua_checkstack+[-0, +0, m] +
int lua_checkstack (lua_State *L, int extra);+ +
+Ensures that there are at least extra free stack slots in the stack.
+It returns false if it cannot grow the stack to that size.
+This function never shrinks the stack;
+if the stack is already larger than the new size,
+it is left unchanged.
+
+
+
+
+
+
lua_close+[-0, +0, -] +
void lua_close (lua_State *L);+ +
+Destroys all objects in the given Lua state +(calling the corresponding garbage-collection metamethods, if any) +and frees all dynamic memory used by this state. +On several platforms, you may not need to call this function, +because all resources are naturally released when the host program ends. +On the other hand, long-running programs, +such as a daemon or a web server, +might need to release states as soon as they are not needed, +to avoid growing too large. + + + + + +
lua_concat+[-n, +1, e] +
void lua_concat (lua_State *L, int n);+ +
+Concatenates the n values at the top of the stack,
+pops them, and leaves the result at the top.
+If n is 1, the result is the single value on the stack
+(that is, the function does nothing);
+if n is 0, the result is the empty string.
+Concatenation is performed following the usual semantics of Lua
+(see §2.5.4).
+
+
+
+
+
+
lua_cpcall+[-0, +(0|1), -] +
int lua_cpcall (lua_State *L, lua_CFunction func, void *ud);+ +
+Calls the C function func in protected mode.
+func starts with only one element in its stack,
+a light userdata containing ud.
+In case of errors,
+lua_cpcall returns the same error codes as lua_pcall,
+plus the error object on the top of the stack;
+otherwise, it returns zero, and does not change the stack.
+All values returned by func are discarded.
+
+
+
+
+
+
lua_createtable+[-0, +1, m] +
void lua_createtable (lua_State *L, int narr, int nrec);+ +
+Creates a new empty table and pushes it onto the stack.
+The new table has space pre-allocated
+for narr array elements and nrec non-array elements.
+This pre-allocation is useful when you know exactly how many elements
+the table will have.
+Otherwise you can use the function lua_newtable.
+
+
+
+
+
+
lua_dump+[-0, +0, m] +
int lua_dump (lua_State *L, lua_Writer writer, void *data);+ +
+Dumps a function as a binary chunk.
+Receives a Lua function on the top of the stack
+and produces a binary chunk that,
+if loaded again,
+results in a function equivalent to the one dumped.
+As it produces parts of the chunk,
+lua_dump calls function writer (see lua_Writer)
+with the given data
+to write them.
+
+
+
+The value returned is the error code returned by the last +call to the writer; +0 means no errors. + + +
+This function does not pop the Lua function from the stack. + + + + + +
lua_equal+[-0, +0, e] +
int lua_equal (lua_State *L, int index1, int index2);+ +
+Returns 1 if the two values in acceptable indices index1 and
+index2 are equal,
+following the semantics of the Lua == operator
+(that is, may call metamethods).
+Otherwise returns 0.
+Also returns 0 if any of the indices is non valid.
+
+
+
+
+
+
lua_error+[-1, +0, v] +
int lua_error (lua_State *L);+ +
+Generates a Lua error.
+The error message (which can actually be a Lua value of any type)
+must be on the stack top.
+This function does a long jump,
+and therefore never returns.
+(see luaL_error).
+
+
+
+
+
+
lua_gc+[-0, +0, e] +
int lua_gc (lua_State *L, int what, int data);+ +
+Controls the garbage collector. + + +
+This function performs several tasks,
+according to the value of the parameter what:
+
+
LUA_GCSTOP:
+stops the garbage collector.
+LUA_GCRESTART:
+restarts the garbage collector.
+LUA_GCCOLLECT:
+performs a full garbage-collection cycle.
+LUA_GCCOUNT:
+returns the current amount of memory (in Kbytes) in use by Lua.
+LUA_GCCOUNTB:
+returns the remainder of dividing the current amount of bytes of
+memory in use by Lua by 1024.
+LUA_GCSTEP:
+performs an incremental step of garbage collection.
+The step "size" is controlled by data
+(larger values mean more steps) in a non-specified way.
+If you want to control the step size
+you must experimentally tune the value of data.
+The function returns 1 if the step finished a
+garbage-collection cycle.
+LUA_GCSETPAUSE:
+sets data as the new value
+for the pause of the collector (see §2.10).
+The function returns the previous value of the pause.
+LUA_GCSETSTEPMUL:
+sets data as the new value for the step multiplier of
+the collector (see §2.10).
+The function returns the previous value of the step multiplier.
+lua_getallocf+[-0, +0, -] +
lua_Alloc lua_getallocf (lua_State *L, void **ud);+ +
+Returns the memory-allocation function of a given state.
+If ud is not NULL, Lua stores in *ud the
+opaque pointer passed to lua_newstate.
+
+
+
+
+
+
lua_getfenv+[-0, +1, -] +
void lua_getfenv (lua_State *L, int index);+ +
+Pushes onto the stack the environment table of +the value at the given index. + + + + + +
lua_getfield+[-0, +1, e] +
void lua_getfield (lua_State *L, int index, const char *k);+ +
+Pushes onto the stack the value t[k],
+where t is the value at the given valid index.
+As in Lua, this function may trigger a metamethod
+for the "index" event (see §2.8).
+
+
+
+
+
+
lua_getglobal+[-0, +1, e] +
void lua_getglobal (lua_State *L, const char *name);+ +
+Pushes onto the stack the value of the global name.
+It is defined as a macro:
+
+
+ #define lua_getglobal(L,s) lua_getfield(L, LUA_GLOBALSINDEX, s) ++ + + + +
lua_getmetatable+[-0, +(0|1), -] +
int lua_getmetatable (lua_State *L, int index);+ +
+Pushes onto the stack the metatable of the value at the given +acceptable index. +If the index is not valid, +or if the value does not have a metatable, +the function returns 0 and pushes nothing on the stack. + + + + + +
lua_gettable+[-1, +1, e] +
void lua_gettable (lua_State *L, int index);+ +
+Pushes onto the stack the value t[k],
+where t is the value at the given valid index
+and k is the value at the top of the stack.
+
+
+
+This function pops the key from the stack +(putting the resulting value in its place). +As in Lua, this function may trigger a metamethod +for the "index" event (see §2.8). + + + + + +
lua_gettop+[-0, +0, -] +
int lua_gettop (lua_State *L);+ +
+Returns the index of the top element in the stack. +Because indices start at 1, +this result is equal to the number of elements in the stack +(and so 0 means an empty stack). + + + + + +
lua_insert+[-1, +1, -] +
void lua_insert (lua_State *L, int index);+ +
+Moves the top element into the given valid index, +shifting up the elements above this index to open space. +Cannot be called with a pseudo-index, +because a pseudo-index is not an actual stack position. + + + + + +
lua_Integertypedef ptrdiff_t lua_Integer;+ +
+The type used by the Lua API to represent integral values. + + +
+By default it is a ptrdiff_t,
+which is usually the largest signed integral type the machine handles
+"comfortably".
+
+
+
+
+
+
lua_isboolean+[-0, +0, -] +
int lua_isboolean (lua_State *L, int index);+ +
+Returns 1 if the value at the given acceptable index has type boolean, +and 0 otherwise. + + + + + +
lua_iscfunction+[-0, +0, -] +
int lua_iscfunction (lua_State *L, int index);+ +
+Returns 1 if the value at the given acceptable index is a C function, +and 0 otherwise. + + + + + +
lua_isfunction+[-0, +0, -] +
int lua_isfunction (lua_State *L, int index);+ +
+Returns 1 if the value at the given acceptable index is a function +(either C or Lua), and 0 otherwise. + + + + + +
lua_islightuserdata+[-0, +0, -] +
int lua_islightuserdata (lua_State *L, int index);+ +
+Returns 1 if the value at the given acceptable index is a light userdata, +and 0 otherwise. + + + + + +
lua_isnil+[-0, +0, -] +
int lua_isnil (lua_State *L, int index);+ +
+Returns 1 if the value at the given acceptable index is nil, +and 0 otherwise. + + + + + +
lua_isnone+[-0, +0, -] +
int lua_isnone (lua_State *L, int index);+ +
+Returns 1 if the given acceptable index is not valid +(that is, it refers to an element outside the current stack), +and 0 otherwise. + + + + + +
lua_isnoneornil+[-0, +0, -] +
int lua_isnoneornil (lua_State *L, int index);+ +
+Returns 1 if the given acceptable index is not valid +(that is, it refers to an element outside the current stack) +or if the value at this index is nil, +and 0 otherwise. + + + + + +
lua_isnumber+[-0, +0, -] +
int lua_isnumber (lua_State *L, int index);+ +
+Returns 1 if the value at the given acceptable index is a number +or a string convertible to a number, +and 0 otherwise. + + + + + +
lua_isstring+[-0, +0, -] +
int lua_isstring (lua_State *L, int index);+ +
+Returns 1 if the value at the given acceptable index is a string +or a number (which is always convertible to a string), +and 0 otherwise. + + + + + +
lua_istable+[-0, +0, -] +
int lua_istable (lua_State *L, int index);+ +
+Returns 1 if the value at the given acceptable index is a table, +and 0 otherwise. + + + + + +
lua_isthread+[-0, +0, -] +
int lua_isthread (lua_State *L, int index);+ +
+Returns 1 if the value at the given acceptable index is a thread, +and 0 otherwise. + + + + + +
lua_isuserdata+[-0, +0, -] +
int lua_isuserdata (lua_State *L, int index);+ +
+Returns 1 if the value at the given acceptable index is a userdata +(either full or light), and 0 otherwise. + + + + + +
lua_lessthan+[-0, +0, e] +
int lua_lessthan (lua_State *L, int index1, int index2);+ +
+Returns 1 if the value at acceptable index index1 is smaller
+than the value at acceptable index index2,
+following the semantics of the Lua < operator
+(that is, may call metamethods).
+Otherwise returns 0.
+Also returns 0 if any of the indices is non valid.
+
+
+
+
+
+
lua_load+[-0, +1, -] +
int lua_load (lua_State *L, + lua_Reader reader, + void *data, + const char *chunkname);+ +
+Loads a Lua chunk.
+If there are no errors,
+lua_load pushes the compiled chunk as a Lua
+function on top of the stack.
+Otherwise, it pushes an error message.
+The return values of lua_load are:
+
+
LUA_ERRSYNTAX:
+syntax error during pre-compilation;LUA_ERRMEM:
+memory allocation error.+This function only loads a chunk; +it does not run it. + + +
+lua_load automatically detects whether the chunk is text or binary,
+and loads it accordingly (see program luac).
+
+
+
+The lua_load function uses a user-supplied reader function
+to read the chunk (see lua_Reader).
+The data argument is an opaque value passed to the reader function.
+
+
+
+The chunkname argument gives a name to the chunk,
+which is used for error messages and in debug information (see §3.8).
+
+
+
+
+
+
lua_newstate+[-0, +0, -] +
lua_State *lua_newstate (lua_Alloc f, void *ud);+ +
+Creates a new, independent state.
+Returns NULL if cannot create the state
+(due to lack of memory).
+The argument f is the allocator function;
+Lua does all memory allocation for this state through this function.
+The second argument, ud, is an opaque pointer that Lua
+simply passes to the allocator in every call.
+
+
+
+
+
+
lua_newtable+[-0, +1, m] +
void lua_newtable (lua_State *L);+ +
+Creates a new empty table and pushes it onto the stack.
+It is equivalent to lua_createtable(L, 0, 0).
+
+
+
+
+
+
lua_newthread+[-0, +1, m] +
lua_State *lua_newthread (lua_State *L);+ +
+Creates a new thread, pushes it on the stack,
+and returns a pointer to a lua_State that represents this new thread.
+The new state returned by this function shares with the original state
+all global objects (such as tables),
+but has an independent execution stack.
+
+
+
+There is no explicit function to close or to destroy a thread. +Threads are subject to garbage collection, +like any Lua object. + + + + + +
lua_newuserdata+[-0, +1, m] +
void *lua_newuserdata (lua_State *L, size_t size);+ +
+This function allocates a new block of memory with the given size, +pushes onto the stack a new full userdata with the block address, +and returns this address. + + +
+Userdata represent C values in Lua. +A full userdata represents a block of memory. +It is an object (like a table): +you must create it, it can have its own metatable, +and you can detect when it is being collected. +A full userdata is only equal to itself (under raw equality). + + +
+When Lua collects a full userdata with a gc metamethod,
+Lua calls the metamethod and marks the userdata as finalized.
+When this userdata is collected again then
+Lua frees its corresponding memory.
+
+
+
+
+
+
lua_next+[-1, +(2|0), e] +
int lua_next (lua_State *L, int index);+ +
+Pops a key from the stack,
+and pushes a key-value pair from the table at the given index
+(the "next" pair after the given key).
+If there are no more elements in the table,
+then lua_next returns 0 (and pushes nothing).
+
+
+
+A typical traversal looks like this: + +
+ /* table is in the stack at index 't' */
+ lua_pushnil(L); /* first key */
+ while (lua_next(L, t) != 0) {
+ /* uses 'key' (at index -2) and 'value' (at index -1) */
+ printf("%s - %s\n",
+ lua_typename(L, lua_type(L, -2)),
+ lua_typename(L, lua_type(L, -1)));
+ /* removes 'value'; keeps 'key' for next iteration */
+ lua_pop(L, 1);
+ }
+
+
+
+While traversing a table,
+do not call lua_tolstring directly on a key,
+unless you know that the key is actually a string.
+Recall that lua_tolstring changes
+the value at the given index;
+this confuses the next call to lua_next.
+
+
+
+
+
+
lua_Numbertypedef double lua_Number;+ +
+The type of numbers in Lua.
+By default, it is double, but that can be changed in luaconf.h.
+
+
+
+Through the configuration file you can change +Lua to operate with another type for numbers (e.g., float or long). + + + + + +
lua_objlen+[-0, +0, -] +
size_t lua_objlen (lua_State *L, int index);+ +
+Returns the "length" of the value at the given acceptable index:
+for strings, this is the string length;
+for tables, this is the result of the length operator ('#');
+for userdata, this is the size of the block of memory allocated
+for the userdata;
+for other values, it is 0.
+
+
+
+
+
+
lua_pcall+[-(nargs + 1), +(nresults|1), -] +
int lua_pcall (lua_State *L, int nargs, int nresults, int errfunc);+ +
+Calls a function in protected mode. + + +
+Both nargs and nresults have the same meaning as
+in lua_call.
+If there are no errors during the call,
+lua_pcall behaves exactly like lua_call.
+However, if there is any error,
+lua_pcall catches it,
+pushes a single value on the stack (the error message),
+and returns an error code.
+Like lua_call,
+lua_pcall always removes the function
+and its arguments from the stack.
+
+
+
+If errfunc is 0,
+then the error message returned on the stack
+is exactly the original error message.
+Otherwise, errfunc is the stack index of an
+error handler function.
+(In the current implementation, this index cannot be a pseudo-index.)
+In case of runtime errors,
+this function will be called with the error message
+and its return value will be the message returned on the stack by lua_pcall.
+
+
+
+Typically, the error handler function is used to add more debug
+information to the error message, such as a stack traceback.
+Such information cannot be gathered after the return of lua_pcall,
+since by then the stack has unwound.
+
+
+
+The lua_pcall function returns 0 in case of success
+or one of the following error codes
+(defined in lua.h):
+
+
LUA_ERRRUN:
+a runtime error.
+LUA_ERRMEM:
+memory allocation error.
+For such errors, Lua does not call the error handler function.
+LUA_ERRERR:
+error while running the error handler function.
+lua_pop+[-n, +0, -] +
void lua_pop (lua_State *L, int n);+ +
+Pops n elements from the stack.
+
+
+
+
+
+
lua_pushboolean+[-0, +1, -] +
void lua_pushboolean (lua_State *L, int b);+ +
+Pushes a boolean value with value b onto the stack.
+
+
+
+
+
+
lua_pushcclosure+[-n, +1, m] +
void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n);+ +
+Pushes a new C closure onto the stack. + + +
+When a C function is created,
+it is possible to associate some values with it,
+thus creating a C closure (see §3.4);
+these values are then accessible to the function whenever it is called.
+To associate values with a C function,
+first these values should be pushed onto the stack
+(when there are multiple values, the first value is pushed first).
+Then lua_pushcclosure
+is called to create and push the C function onto the stack,
+with the argument n telling how many values should be
+associated with the function.
+lua_pushcclosure also pops these values from the stack.
+
+
+
+The maximum value for n is 255.
+
+
+
+
+
+
lua_pushcfunction+[-0, +1, m] +
void lua_pushcfunction (lua_State *L, lua_CFunction f);+ +
+Pushes a C function onto the stack.
+This function receives a pointer to a C function
+and pushes onto the stack a Lua value of type function that,
+when called, invokes the corresponding C function.
+
+
+
+Any function to be registered in Lua must
+follow the correct protocol to receive its parameters
+and return its results (see lua_CFunction).
+
+
+
+lua_pushcfunction is defined as a macro:
+
+
+ #define lua_pushcfunction(L,f) lua_pushcclosure(L,f,0) ++ + + + +
lua_pushfstring+[-0, +1, m] +
const char *lua_pushfstring (lua_State *L, const char *fmt, ...);+ +
+Pushes onto the stack a formatted string
+and returns a pointer to this string.
+It is similar to the C function sprintf,
+but has some important differences:
+
+
%%' (inserts a '%' in the string),
+'%s' (inserts a zero-terminated string, with no size restrictions),
+'%f' (inserts a lua_Number),
+'%p' (inserts a pointer as a hexadecimal numeral),
+'%d' (inserts an int), and
+'%c' (inserts an int as a character).
+lua_pushinteger+[-0, +1, -] +
void lua_pushinteger (lua_State *L, lua_Integer n);+ +
+Pushes a number with value n onto the stack.
+
+
+
+
+
+
lua_pushlightuserdata+[-0, +1, -] +
void lua_pushlightuserdata (lua_State *L, void *p);+ +
+Pushes a light userdata onto the stack. + + +
+Userdata represent C values in Lua. +A light userdata represents a pointer. +It is a value (like a number): +you do not create it, it has no individual metatable, +and it is not collected (as it was never created). +A light userdata is equal to "any" +light userdata with the same C address. + + + + + +
lua_pushliteral+[-0, +1, m] +
void lua_pushliteral (lua_State *L, const char *s);+ +
+This macro is equivalent to lua_pushlstring,
+but can be used only when s is a literal string.
+In these cases, it automatically provides the string length.
+
+
+
+
+
+
lua_pushlstring+[-0, +1, m] +
void lua_pushlstring (lua_State *L, const char *s, size_t len);+ +
+Pushes the string pointed to by s with size len
+onto the stack.
+Lua makes (or reuses) an internal copy of the given string,
+so the memory at s can be freed or reused immediately after
+the function returns.
+The string can contain embedded zeros.
+
+
+
+
+
+
lua_pushnil+[-0, +1, -] +
void lua_pushnil (lua_State *L);+ +
+Pushes a nil value onto the stack. + + + + + +
lua_pushnumber+[-0, +1, -] +
void lua_pushnumber (lua_State *L, lua_Number n);+ +
+Pushes a number with value n onto the stack.
+
+
+
+
+
+
lua_pushstring+[-0, +1, m] +
void lua_pushstring (lua_State *L, const char *s);+ +
+Pushes the zero-terminated string pointed to by s
+onto the stack.
+Lua makes (or reuses) an internal copy of the given string,
+so the memory at s can be freed or reused immediately after
+the function returns.
+The string cannot contain embedded zeros;
+it is assumed to end at the first zero.
+
+
+
+
+
+
lua_pushthread+[-0, +1, -] +
int lua_pushthread (lua_State *L);+ +
+Pushes the thread represented by L onto the stack.
+Returns 1 if this thread is the main thread of its state.
+
+
+
+
+
+
lua_pushvalue+[-0, +1, -] +
void lua_pushvalue (lua_State *L, int index);+ +
+Pushes a copy of the element at the given valid index +onto the stack. + + + + + +
lua_pushvfstring+[-0, +1, m] +
const char *lua_pushvfstring (lua_State *L, + const char *fmt, + va_list argp);+ +
+Equivalent to lua_pushfstring, except that it receives a va_list
+instead of a variable number of arguments.
+
+
+
+
+
+
lua_rawequal+[-0, +0, -] +
int lua_rawequal (lua_State *L, int index1, int index2);+ +
+Returns 1 if the two values in acceptable indices index1 and
+index2 are primitively equal
+(that is, without calling metamethods).
+Otherwise returns 0.
+Also returns 0 if any of the indices are non valid.
+
+
+
+
+
+
lua_rawget+[-1, +1, -] +
void lua_rawget (lua_State *L, int index);+ +
+Similar to lua_gettable, but does a raw access
+(i.e., without metamethods).
+
+
+
+
+
+
lua_rawgeti+[-0, +1, -] +
void lua_rawgeti (lua_State *L, int index, int n);+ +
+Pushes onto the stack the value t[n],
+where t is the value at the given valid index.
+The access is raw;
+that is, it does not invoke metamethods.
+
+
+
+
+
+
lua_rawset+[-2, +0, m] +
void lua_rawset (lua_State *L, int index);+ +
+Similar to lua_settable, but does a raw assignment
+(i.e., without metamethods).
+
+
+
+
+
+
lua_rawseti+[-1, +0, m] +
void lua_rawseti (lua_State *L, int index, int n);+ +
+Does the equivalent of t[n] = v,
+where t is the value at the given valid index
+and v is the value at the top of the stack.
+
+
+
+This function pops the value from the stack. +The assignment is raw; +that is, it does not invoke metamethods. + + + + + +
lua_Readertypedef const char * (*lua_Reader) (lua_State *L, + void *data, + size_t *size);+ +
+The reader function used by lua_load.
+Every time it needs another piece of the chunk,
+lua_load calls the reader,
+passing along its data parameter.
+The reader must return a pointer to a block of memory
+with a new piece of the chunk
+and set size to the block size.
+The block must exist until the reader function is called again.
+To signal the end of the chunk,
+the reader must return NULL or set size to zero.
+The reader function may return pieces of any size greater than zero.
+
+
+
+
+
+
lua_register+[-0, +0, e] +
void lua_register (lua_State *L, + const char *name, + lua_CFunction f);+ +
+Sets the C function f as the new value of global name.
+It is defined as a macro:
+
+
+ #define lua_register(L,n,f) \ + (lua_pushcfunction(L, f), lua_setglobal(L, n)) ++ + + + +
lua_remove+[-1, +0, -] +
void lua_remove (lua_State *L, int index);+ +
+Removes the element at the given valid index, +shifting down the elements above this index to fill the gap. +Cannot be called with a pseudo-index, +because a pseudo-index is not an actual stack position. + + + + + +
lua_replace+[-1, +0, -] +
void lua_replace (lua_State *L, int index);+ +
+Moves the top element into the given position (and pops it), +without shifting any element +(therefore replacing the value at the given position). + + + + + +
lua_resume+[-?, +?, -] +
int lua_resume (lua_State *L, int narg);+ +
+Starts and resumes a coroutine in a given thread. + + +
+To start a coroutine, you first create a new thread
+(see lua_newthread);
+then you push onto its stack the main function plus any arguments;
+then you call lua_resume,
+with narg being the number of arguments.
+This call returns when the coroutine suspends or finishes its execution.
+When it returns, the stack contains all values passed to lua_yield,
+or all values returned by the body function.
+lua_resume returns
+LUA_YIELD if the coroutine yields,
+0 if the coroutine finishes its execution
+without errors,
+or an error code in case of errors (see lua_pcall).
+In case of errors,
+the stack is not unwound,
+so you can use the debug API over it.
+The error message is on the top of the stack.
+To restart a coroutine, you put on its stack only the values to
+be passed as results from yield,
+and then call lua_resume.
+
+
+
+
+
+
lua_setallocf+[-0, +0, -] +
void lua_setallocf (lua_State *L, lua_Alloc f, void *ud);+ +
+Changes the allocator function of a given state to f
+with user data ud.
+
+
+
+
+
+
lua_setfenv+[-1, +0, -] +
int lua_setfenv (lua_State *L, int index);+ +
+Pops a table from the stack and sets it as
+the new environment for the value at the given index.
+If the value at the given index is
+neither a function nor a thread nor a userdata,
+lua_setfenv returns 0.
+Otherwise it returns 1.
+
+
+
+
+
+
lua_setfield+[-1, +0, e] +
void lua_setfield (lua_State *L, int index, const char *k);+ +
+Does the equivalent to t[k] = v,
+where t is the value at the given valid index
+and v is the value at the top of the stack.
+
+
+
+This function pops the value from the stack. +As in Lua, this function may trigger a metamethod +for the "newindex" event (see §2.8). + + + + + +
lua_setglobal+[-1, +0, e] +
void lua_setglobal (lua_State *L, const char *name);+ +
+Pops a value from the stack and
+sets it as the new value of global name.
+It is defined as a macro:
+
+
+ #define lua_setglobal(L,s) lua_setfield(L, LUA_GLOBALSINDEX, s) ++ + + + +
lua_setmetatable+[-1, +0, -] +
int lua_setmetatable (lua_State *L, int index);+ +
+Pops a table from the stack and +sets it as the new metatable for the value at the given +acceptable index. + + + + + +
lua_settable+[-2, +0, e] +
void lua_settable (lua_State *L, int index);+ +
+Does the equivalent to t[k] = v,
+where t is the value at the given valid index,
+v is the value at the top of the stack,
+and k is the value just below the top.
+
+
+
+This function pops both the key and the value from the stack. +As in Lua, this function may trigger a metamethod +for the "newindex" event (see §2.8). + + + + + +
lua_settop+[-?, +?, -] +
void lua_settop (lua_State *L, int index);+ +
+Accepts any acceptable index, or 0,
+and sets the stack top to this index.
+If the new top is larger than the old one,
+then the new elements are filled with nil.
+If index is 0, then all stack elements are removed.
+
+
+
+
+
+
lua_Statetypedef struct lua_State lua_State;+ +
+Opaque structure that keeps the whole state of a Lua interpreter. +The Lua library is fully reentrant: +it has no global variables. +All information about a state is kept in this structure. + + +
+A pointer to this state must be passed as the first argument to
+every function in the library, except to lua_newstate,
+which creates a Lua state from scratch.
+
+
+
+
+
+
lua_status+[-0, +0, -] +
int lua_status (lua_State *L);+ +
+Returns the status of the thread L.
+
+
+
+The status can be 0 for a normal thread,
+an error code if the thread finished its execution with an error,
+or LUA_YIELD if the thread is suspended.
+
+
+
+
+
+
lua_toboolean+[-0, +0, -] +
int lua_toboolean (lua_State *L, int index);+ +
+Converts the Lua value at the given acceptable index to a C boolean
+value (0 or 1).
+Like all tests in Lua,
+lua_toboolean returns 1 for any Lua value
+different from false and nil;
+otherwise it returns 0.
+It also returns 0 when called with a non-valid index.
+(If you want to accept only actual boolean values,
+use lua_isboolean to test the value's type.)
+
+
+
+
+
+
lua_tocfunction+[-0, +0, -] +
lua_CFunction lua_tocfunction (lua_State *L, int index);+ +
+Converts a value at the given acceptable index to a C function.
+That value must be a C function;
+otherwise, returns NULL.
+
+
+
+
+
+
lua_tointeger+[-0, +0, -] +
lua_Integer lua_tointeger (lua_State *L, int index);+ +
+Converts the Lua value at the given acceptable index
+to the signed integral type lua_Integer.
+The Lua value must be a number or a string convertible to a number
+(see §2.2.1);
+otherwise, lua_tointeger returns 0.
+
+
+
+If the number is not an integer, +it is truncated in some non-specified way. + + + + + +
lua_tolstring+[-0, +0, m] +
const char *lua_tolstring (lua_State *L, int index, size_t *len);+ +
+Converts the Lua value at the given acceptable index to a C string.
+If len is not NULL,
+it also sets *len with the string length.
+The Lua value must be a string or a number;
+otherwise, the function returns NULL.
+If the value is a number,
+then lua_tolstring also
+changes the actual value in the stack to a string.
+(This change confuses lua_next
+when lua_tolstring is applied to keys during a table traversal.)
+
+
+
+lua_tolstring returns a fully aligned pointer
+to a string inside the Lua state.
+This string always has a zero ('\0')
+after its last character (as in C),
+but can contain other zeros in its body.
+Because Lua has garbage collection,
+there is no guarantee that the pointer returned by lua_tolstring
+will be valid after the corresponding value is removed from the stack.
+
+
+
+
+
+
lua_tonumber+[-0, +0, -] +
lua_Number lua_tonumber (lua_State *L, int index);+ +
+Converts the Lua value at the given acceptable index
+to the C type lua_Number (see lua_Number).
+The Lua value must be a number or a string convertible to a number
+(see §2.2.1);
+otherwise, lua_tonumber returns 0.
+
+
+
+
+
+
lua_topointer+[-0, +0, -] +
const void *lua_topointer (lua_State *L, int index);+ +
+Converts the value at the given acceptable index to a generic
+C pointer (void*).
+The value can be a userdata, a table, a thread, or a function;
+otherwise, lua_topointer returns NULL.
+Different objects will give different pointers.
+There is no way to convert the pointer back to its original value.
+
+
+
+Typically this function is used only for debug information. + + + + + +
lua_tostring+[-0, +0, m] +
const char *lua_tostring (lua_State *L, int index);+ +
+Equivalent to lua_tolstring with len equal to NULL.
+
+
+
+
+
+
lua_tothread+[-0, +0, -] +
lua_State *lua_tothread (lua_State *L, int index);+ +
+Converts the value at the given acceptable index to a Lua thread
+(represented as lua_State*).
+This value must be a thread;
+otherwise, the function returns NULL.
+
+
+
+
+
+
lua_touserdata+[-0, +0, -] +
void *lua_touserdata (lua_State *L, int index);+ +
+If the value at the given acceptable index is a full userdata,
+returns its block address.
+If the value is a light userdata,
+returns its pointer.
+Otherwise, returns NULL.
+
+
+
+
+
+
lua_type+[-0, +0, -] +
int lua_type (lua_State *L, int index);+ +
+Returns the type of the value in the given acceptable index,
+or LUA_TNONE for a non-valid index
+(that is, an index to an "empty" stack position).
+The types returned by lua_type are coded by the following constants
+defined in lua.h:
+LUA_TNIL,
+LUA_TNUMBER,
+LUA_TBOOLEAN,
+LUA_TSTRING,
+LUA_TTABLE,
+LUA_TFUNCTION,
+LUA_TUSERDATA,
+LUA_TTHREAD,
+and
+LUA_TLIGHTUSERDATA.
+
+
+
+
+
+
lua_typename+[-0, +0, -] +
const char *lua_typename (lua_State *L, int tp);+ +
+Returns the name of the type encoded by the value tp,
+which must be one the values returned by lua_type.
+
+
+
+
+
+
lua_Writertypedef int (*lua_Writer) (lua_State *L, + const void* p, + size_t sz, + void* ud);+ +
+The type of the writer function used by lua_dump.
+Every time it produces another piece of chunk,
+lua_dump calls the writer,
+passing along the buffer to be written (p),
+its size (sz),
+and the data parameter supplied to lua_dump.
+
+
+
+The writer returns an error code:
+0 means no errors;
+any other value means an error and stops lua_dump from
+calling the writer again.
+
+
+
+
+
+
lua_xmove+[-?, +?, -] +
void lua_xmove (lua_State *from, lua_State *to, int n);+ +
+Exchange values between different threads of the same global state. + + +
+This function pops n values from the stack from,
+and pushes them onto the stack to.
+
+
+
+
+
+
lua_yield+[-?, +?, -] +
int lua_yield (lua_State *L, int nresults);+ +
+Yields a coroutine. + + +
+This function should only be called as the +return expression of a C function, as follows: + +
+ return lua_yield (L, nresults); +
+When a C function calls lua_yield in that way,
+the running coroutine suspends its execution,
+and the call to lua_resume that started this coroutine returns.
+The parameter nresults is the number of values from the stack
+that are passed as results to lua_resume.
+
+
+
+
+
+
+
+
+Lua has no built-in debugging facilities. +Instead, it offers a special interface +by means of functions and hooks. +This interface allows the construction of different +kinds of debuggers, profilers, and other tools +that need "inside information" from the interpreter. + + + +
lua_Debugtypedef struct lua_Debug {
+ int event;
+ const char *name; /* (n) */
+ const char *namewhat; /* (n) */
+ const char *what; /* (S) */
+ const char *source; /* (S) */
+ int currentline; /* (l) */
+ int nups; /* (u) number of upvalues */
+ int linedefined; /* (S) */
+ int lastlinedefined; /* (S) */
+ char short_src[LUA_IDSIZE]; /* (S) */
+ /* private part */
+ other fields
+} lua_Debug;
+
+
+A structure used to carry different pieces of
+information about an active function.
+lua_getstack fills only the private part
+of this structure, for later use.
+To fill the other fields of lua_Debug with useful information,
+call lua_getinfo.
+
+
+
+The fields of lua_Debug have the following meaning:
+
+
source:
+If the function was defined in a string,
+then source is that string.
+If the function was defined in a file,
+then source starts with a '@' followed by the file name.
+short_src:
+a "printable" version of source, to be used in error messages.
+linedefined:
+the line number where the definition of the function starts.
+lastlinedefined:
+the line number where the definition of the function ends.
+what:
+the string "Lua" if the function is a Lua function,
+"C" if it is a C function,
+"main" if it is the main part of a chunk,
+and "tail" if it was a function that did a tail call.
+In the latter case,
+Lua has no other information about the function.
+currentline:
+the current line where the given function is executing.
+When no line information is available,
+currentline is set to -1.
+name:
+a reasonable name for the given function.
+Because functions in Lua are first-class values,
+they do not have a fixed name:
+some functions can be the value of multiple global variables,
+while others can be stored only in a table field.
+The lua_getinfo function checks how the function was
+called to find a suitable name.
+If it cannot find a name,
+then name is set to NULL.
+namewhat:
+explains the name field.
+The value of namewhat can be
+"global", "local", "method",
+"field", "upvalue", or "" (the empty string),
+according to how the function was called.
+(Lua uses the empty string when no other option seems to apply.)
+nups:
+the number of upvalues of the function.
+lua_gethook+[-0, +0, -] +
lua_Hook lua_gethook (lua_State *L);+ +
+Returns the current hook function. + + + + + +
lua_gethookcount+[-0, +0, -] +
int lua_gethookcount (lua_State *L);+ +
+Returns the current hook count. + + + + + +
lua_gethookmask+[-0, +0, -] +
int lua_gethookmask (lua_State *L);+ +
+Returns the current hook mask. + + + + + +
lua_getinfo+[-(0|1), +(0|1|2), m] +
int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar);+ +
+Returns information about a specific function or function invocation. + + +
+To get information about a function invocation,
+the parameter ar must be a valid activation record that was
+filled by a previous call to lua_getstack or
+given as argument to a hook (see lua_Hook).
+
+
+
+To get information about a function you push it onto the stack
+and start the what string with the character '>'.
+(In that case,
+lua_getinfo pops the function in the top of the stack.)
+For instance, to know in which line a function f was defined,
+you can write the following code:
+
+
+ lua_Debug ar;
+ lua_getfield(L, LUA_GLOBALSINDEX, "f"); /* get global 'f' */
+ lua_getinfo(L, ">S", &ar);
+ printf("%d\n", ar.linedefined);
+
+
+
+Each character in the string what
+selects some fields of the structure ar to be filled or
+a value to be pushed on the stack:
+
+
n': fills in the field name and namewhat;
+S':
+fills in the fields source, short_src,
+linedefined, lastlinedefined, and what;
+l': fills in the field currentline;
+u': fills in the field nups;
+f':
+pushes onto the stack the function that is
+running at the given level;
+L':
+pushes onto the stack a table whose indices are the
+numbers of the lines that are valid on the function.
+(A valid line is a line with some associated code,
+that is, a line where you can put a break point.
+Non-valid lines include empty lines and comments.)
+
+This function returns 0 on error
+(for instance, an invalid option in what).
+
+
+
+
+
+
lua_getlocal+[-0, +(0|1), -] +
const char *lua_getlocal (lua_State *L, lua_Debug *ar, int n);+ +
+Gets information about a local variable of a given activation record.
+The parameter ar must be a valid activation record that was
+filled by a previous call to lua_getstack or
+given as argument to a hook (see lua_Hook).
+The index n selects which local variable to inspect
+(1 is the first parameter or active local variable, and so on,
+until the last active local variable).
+lua_getlocal pushes the variable's value onto the stack
+and returns its name.
+
+
+
+Variable names starting with '(' (open parentheses)
+represent internal variables
+(loop control variables, temporaries, and C function locals).
+
+
+
+Returns NULL (and pushes nothing)
+when the index is greater than
+the number of active local variables.
+
+
+
+
+
+
lua_getstack+[-0, +0, -] +
int lua_getstack (lua_State *L, int level, lua_Debug *ar);+ +
+Get information about the interpreter runtime stack. + + +
+This function fills parts of a lua_Debug structure with
+an identification of the activation record
+of the function executing at a given level.
+Level 0 is the current running function,
+whereas level n+1 is the function that has called level n.
+When there are no errors, lua_getstack returns 1;
+when called with a level greater than the stack depth,
+it returns 0.
+
+
+
+
+
+
lua_getupvalue+[-0, +(0|1), -] +
const char *lua_getupvalue (lua_State *L, int funcindex, int n);+ +
+Gets information about a closure's upvalue.
+(For Lua functions,
+upvalues are the external local variables that the function uses,
+and that are consequently included in its closure.)
+lua_getupvalue gets the index n of an upvalue,
+pushes the upvalue's value onto the stack,
+and returns its name.
+funcindex points to the closure in the stack.
+(Upvalues have no particular order,
+as they are active through the whole function.
+So, they are numbered in an arbitrary order.)
+
+
+
+Returns NULL (and pushes nothing)
+when the index is greater than the number of upvalues.
+For C functions, this function uses the empty string ""
+as a name for all upvalues.
+
+
+
+
+
+
lua_Hooktypedef void (*lua_Hook) (lua_State *L, lua_Debug *ar);+ +
+Type for debugging hook functions. + + +
+Whenever a hook is called, its ar argument has its field
+event set to the specific event that triggered the hook.
+Lua identifies these events with the following constants:
+LUA_HOOKCALL, LUA_HOOKRET,
+LUA_HOOKTAILRET, LUA_HOOKLINE,
+and LUA_HOOKCOUNT.
+Moreover, for line events, the field currentline is also set.
+To get the value of any other field in ar,
+the hook must call lua_getinfo.
+For return events, event can be LUA_HOOKRET,
+the normal value, or LUA_HOOKTAILRET.
+In the latter case, Lua is simulating a return from
+a function that did a tail call;
+in this case, it is useless to call lua_getinfo.
+
+
+
+While Lua is running a hook, it disables other calls to hooks. +Therefore, if a hook calls back Lua to execute a function or a chunk, +this execution occurs without any calls to hooks. + + + + + +
lua_sethook+[-0, +0, -] +
int lua_sethook (lua_State *L, lua_Hook f, int mask, int count);+ +
+Sets the debugging hook function. + + +
+Argument f is the hook function.
+mask specifies on which events the hook will be called:
+it is formed by a bitwise or of the constants
+LUA_MASKCALL,
+LUA_MASKRET,
+LUA_MASKLINE,
+and LUA_MASKCOUNT.
+The count argument is only meaningful when the mask
+includes LUA_MASKCOUNT.
+For each event, the hook is called as explained below:
+
+
count instructions.
+(This event only happens while Lua is executing a Lua function.)
+
+A hook is disabled by setting mask to zero.
+
+
+
+
+
+
lua_setlocal+[-(0|1), +0, -] +
const char *lua_setlocal (lua_State *L, lua_Debug *ar, int n);+ +
+Sets the value of a local variable of a given activation record.
+Parameters ar and n are as in lua_getlocal
+(see lua_getlocal).
+lua_setlocal assigns the value at the top of the stack
+to the variable and returns its name.
+It also pops the value from the stack.
+
+
+
+Returns NULL (and pops nothing)
+when the index is greater than
+the number of active local variables.
+
+
+
+
+
+
lua_setupvalue+[-(0|1), +0, -] +
const char *lua_setupvalue (lua_State *L, int funcindex, int n);+ +
+Sets the value of a closure's upvalue.
+It assigns the value at the top of the stack
+to the upvalue and returns its name.
+It also pops the value from the stack.
+Parameters funcindex and n are as in the lua_getupvalue
+(see lua_getupvalue).
+
+
+
+Returns NULL (and pops nothing)
+when the index is greater than the number of upvalues.
+
+
+
+
+
+
+
+
+ +The auxiliary library provides several convenient functions +to interface C with Lua. +While the basic API provides the primitive functions for all +interactions between C and Lua, +the auxiliary library provides higher-level functions for some +common tasks. + + +
+All functions from the auxiliary library
+are defined in header file lauxlib.h and
+have a prefix luaL_.
+
+
+
+All functions in the auxiliary library are built on +top of the basic API, +and so they provide nothing that cannot be done with this API. + + +
+Several functions in the auxiliary library are used to
+check C function arguments.
+Their names are always luaL_check* or luaL_opt*.
+All of these functions throw an error if the check is not satisfied.
+Because the error message is formatted for arguments
+(e.g., "bad argument #1"),
+you should not use these functions for other stack values.
+
+
+
+
+Here we list all functions and types from the auxiliary library +in alphabetical order. + + + +
luaL_addchar+[-0, +0, m] +
void luaL_addchar (luaL_Buffer *B, char c);+ +
+Adds the character c to the buffer B
+(see luaL_Buffer).
+
+
+
+
+
+
luaL_addlstring+[-0, +0, m] +
void luaL_addlstring (luaL_Buffer *B, const char *s, size_t l);+ +
+Adds the string pointed to by s with length l to
+the buffer B
+(see luaL_Buffer).
+The string may contain embedded zeros.
+
+
+
+
+
+
luaL_addsize+[-0, +0, m] +
void luaL_addsize (luaL_Buffer *B, size_t n);+ +
+Adds to the buffer B (see luaL_Buffer)
+a string of length n previously copied to the
+buffer area (see luaL_prepbuffer).
+
+
+
+
+
+
luaL_addstring+[-0, +0, m] +
void luaL_addstring (luaL_Buffer *B, const char *s);+ +
+Adds the zero-terminated string pointed to by s
+to the buffer B
+(see luaL_Buffer).
+The string may not contain embedded zeros.
+
+
+
+
+
+
luaL_addvalue+[-1, +0, m] +
void luaL_addvalue (luaL_Buffer *B);+ +
+Adds the value at the top of the stack
+to the buffer B
+(see luaL_Buffer).
+Pops the value.
+
+
+
+This is the only function on string buffers that can (and must) +be called with an extra element on the stack, +which is the value to be added to the buffer. + + + + + +
luaL_argcheck+[-0, +0, v] +
void luaL_argcheck (lua_State *L, + int cond, + int narg, + const char *extramsg);+ +
+Checks whether cond is true.
+If not, raises an error with the following message,
+where func is retrieved from the call stack:
+
+
+ bad argument #<narg> to <func> (<extramsg>) ++ + + + +
luaL_argerror+[-0, +0, v] +
int luaL_argerror (lua_State *L, int narg, const char *extramsg);+ +
+Raises an error with the following message,
+where func is retrieved from the call stack:
+
+
+ bad argument #<narg> to <func> (<extramsg>) ++ +
+This function never returns,
+but it is an idiom to use it in C functions
+as return luaL_argerror(args).
+
+
+
+
+
+
luaL_Buffertypedef struct luaL_Buffer luaL_Buffer;+ +
+Type for a string buffer. + + +
+A string buffer allows C code to build Lua strings piecemeal. +Its pattern of use is as follows: + +
b of type luaL_Buffer.luaL_buffinit(L, &b).luaL_add* functions.
+luaL_pushresult(&b).
+This call leaves the final string on the top of the stack.
+
+During its normal operation,
+a string buffer uses a variable number of stack slots.
+So, while using a buffer, you cannot assume that you know where
+the top of the stack is.
+You can use the stack between successive calls to buffer operations
+as long as that use is balanced;
+that is,
+when you call a buffer operation,
+the stack is at the same level
+it was immediately after the previous buffer operation.
+(The only exception to this rule is luaL_addvalue.)
+After calling luaL_pushresult the stack is back to its
+level when the buffer was initialized,
+plus the final string on its top.
+
+
+
+
+
+
luaL_buffinit+[-0, +0, -] +
void luaL_buffinit (lua_State *L, luaL_Buffer *B);+ +
+Initializes a buffer B.
+This function does not allocate any space;
+the buffer must be declared as a variable
+(see luaL_Buffer).
+
+
+
+
+
+
luaL_callmeta+[-0, +(0|1), e] +
int luaL_callmeta (lua_State *L, int obj, const char *e);+ +
+Calls a metamethod. + + +
+If the object at index obj has a metatable and this
+metatable has a field e,
+this function calls this field and passes the object as its only argument.
+In this case this function returns 1 and pushes onto the
+stack the value returned by the call.
+If there is no metatable or no metamethod,
+this function returns 0 (without pushing any value on the stack).
+
+
+
+
+
+
luaL_checkany+[-0, +0, v] +
void luaL_checkany (lua_State *L, int narg);+ +
+Checks whether the function has an argument
+of any type (including nil) at position narg.
+
+
+
+
+
+
luaL_checkint+[-0, +0, v] +
int luaL_checkint (lua_State *L, int narg);+ +
+Checks whether the function argument narg is a number
+and returns this number cast to an int.
+
+
+
+
+
+
luaL_checkinteger+[-0, +0, v] +
lua_Integer luaL_checkinteger (lua_State *L, int narg);+ +
+Checks whether the function argument narg is a number
+and returns this number cast to a lua_Integer.
+
+
+
+
+
+
luaL_checklong+[-0, +0, v] +
long luaL_checklong (lua_State *L, int narg);+ +
+Checks whether the function argument narg is a number
+and returns this number cast to a long.
+
+
+
+
+
+
luaL_checklstring+[-0, +0, v] +
const char *luaL_checklstring (lua_State *L, int narg, size_t *l);+ +
+Checks whether the function argument narg is a string
+and returns this string;
+if l is not NULL fills *l
+with the string's length.
+
+
+
+This function uses lua_tolstring to get its result,
+so all conversions and caveats of that function apply here.
+
+
+
+
+
+
luaL_checknumber+[-0, +0, v] +
lua_Number luaL_checknumber (lua_State *L, int narg);+ +
+Checks whether the function argument narg is a number
+and returns this number.
+
+
+
+
+
+
luaL_checkoption+[-0, +0, v] +
int luaL_checkoption (lua_State *L, + int narg, + const char *def, + const char *const lst[]);+ +
+Checks whether the function argument narg is a string and
+searches for this string in the array lst
+(which must be NULL-terminated).
+Returns the index in the array where the string was found.
+Raises an error if the argument is not a string or
+if the string cannot be found.
+
+
+
+If def is not NULL,
+the function uses def as a default value when
+there is no argument narg or if this argument is nil.
+
+
+
+This is a useful function for mapping strings to C enums. +(The usual convention in Lua libraries is +to use strings instead of numbers to select options.) + + + + + +
luaL_checkstack+[-0, +0, v] +
void luaL_checkstack (lua_State *L, int sz, const char *msg);+ +
+Grows the stack size to top + sz elements,
+raising an error if the stack cannot grow to that size.
+msg is an additional text to go into the error message.
+
+
+
+
+
+
luaL_checkstring+[-0, +0, v] +
const char *luaL_checkstring (lua_State *L, int narg);+ +
+Checks whether the function argument narg is a string
+and returns this string.
+
+
+
+This function uses lua_tolstring to get its result,
+so all conversions and caveats of that function apply here.
+
+
+
+
+
+
luaL_checktype+[-0, +0, v] +
void luaL_checktype (lua_State *L, int narg, int t);+ +
+Checks whether the function argument narg has type t.
+See lua_type for the encoding of types for t.
+
+
+
+
+
+
luaL_checkudata+[-0, +0, v] +
void *luaL_checkudata (lua_State *L, int narg, const char *tname);+ +
+Checks whether the function argument narg is a userdata
+of the type tname (see luaL_newmetatable).
+
+
+
+
+
+
luaL_dofile+[-0, +?, m] +
int luaL_dofile (lua_State *L, const char *filename);+ +
+Loads and runs the given file. +It is defined as the following macro: + +
+ (luaL_loadfile(L, filename) || lua_pcall(L, 0, LUA_MULTRET, 0)) +
+It returns 0 if there are no errors +or 1 in case of errors. + + + + + +
luaL_dostring+[-0, +?, m] +
int luaL_dostring (lua_State *L, const char *str);+ +
+Loads and runs the given string. +It is defined as the following macro: + +
+ (luaL_loadstring(L, str) || lua_pcall(L, 0, LUA_MULTRET, 0)) +
+It returns 0 if there are no errors +or 1 in case of errors. + + + + + +
luaL_error+[-0, +0, v] +
int luaL_error (lua_State *L, const char *fmt, ...);+ +
+Raises an error.
+The error message format is given by fmt
+plus any extra arguments,
+following the same rules of lua_pushfstring.
+It also adds at the beginning of the message the file name and
+the line number where the error occurred,
+if this information is available.
+
+
+
+This function never returns,
+but it is an idiom to use it in C functions
+as return luaL_error(args).
+
+
+
+
+
+
luaL_getmetafield+[-0, +(0|1), m] +
int luaL_getmetafield (lua_State *L, int obj, const char *e);+ +
+Pushes onto the stack the field e from the metatable
+of the object at index obj.
+If the object does not have a metatable,
+or if the metatable does not have this field,
+returns 0 and pushes nothing.
+
+
+
+
+
+
luaL_getmetatable+[-0, +1, -] +
void luaL_getmetatable (lua_State *L, const char *tname);+ +
+Pushes onto the stack the metatable associated with name tname
+in the registry (see luaL_newmetatable).
+
+
+
+
+
+
luaL_gsub+[-0, +1, m] +
const char *luaL_gsub (lua_State *L, + const char *s, + const char *p, + const char *r);+ +
+Creates a copy of string s by replacing
+any occurrence of the string p
+with the string r.
+Pushes the resulting string on the stack and returns it.
+
+
+
+
+
+
luaL_loadbuffer+[-0, +1, m] +
int luaL_loadbuffer (lua_State *L, + const char *buff, + size_t sz, + const char *name);+ +
+Loads a buffer as a Lua chunk.
+This function uses lua_load to load the chunk in the
+buffer pointed to by buff with size sz.
+
+
+
+This function returns the same results as lua_load.
+name is the chunk name,
+used for debug information and error messages.
+
+
+
+
+
+
luaL_loadfile+[-0, +1, m] +
int luaL_loadfile (lua_State *L, const char *filename);+ +
+Loads a file as a Lua chunk.
+This function uses lua_load to load the chunk in the file
+named filename.
+If filename is NULL,
+then it loads from the standard input.
+The first line in the file is ignored if it starts with a #.
+
+
+
+This function returns the same results as lua_load,
+but it has an extra error code LUA_ERRFILE
+if it cannot open/read the file.
+
+
+
+As lua_load, this function only loads the chunk;
+it does not run it.
+
+
+
+
+
+
luaL_loadstring+[-0, +1, m] +
int luaL_loadstring (lua_State *L, const char *s);+ +
+Loads a string as a Lua chunk.
+This function uses lua_load to load the chunk in
+the zero-terminated string s.
+
+
+
+This function returns the same results as lua_load.
+
+
+
+Also as lua_load, this function only loads the chunk;
+it does not run it.
+
+
+
+
+
+
luaL_newmetatable+[-0, +1, m] +
int luaL_newmetatable (lua_State *L, const char *tname);+ +
+If the registry already has the key tname,
+returns 0.
+Otherwise,
+creates a new table to be used as a metatable for userdata,
+adds it to the registry with key tname,
+and returns 1.
+
+
+
+In both cases pushes onto the stack the final value associated
+with tname in the registry.
+
+
+
+
+
+
luaL_newstate+[-0, +0, -] +
lua_State *luaL_newstate (void);+ +
+Creates a new Lua state.
+It calls lua_newstate with an
+allocator based on the standard C realloc function
+and then sets a panic function (see lua_atpanic) that prints
+an error message to the standard error output in case of fatal
+errors.
+
+
+
+Returns the new state,
+or NULL if there is a memory allocation error.
+
+
+
+
+
+
luaL_openlibs+[-0, +0, m] +
void luaL_openlibs (lua_State *L);+ +
+Opens all standard Lua libraries into the given state. + + + + + +
luaL_optint+[-0, +0, v] +
int luaL_optint (lua_State *L, int narg, int d);+ +
+If the function argument narg is a number,
+returns this number cast to an int.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
+
+
+
+
luaL_optinteger+[-0, +0, v] +
lua_Integer luaL_optinteger (lua_State *L, + int narg, + lua_Integer d);+ +
+If the function argument narg is a number,
+returns this number cast to a lua_Integer.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
+
+
+
+
luaL_optlong+[-0, +0, v] +
long luaL_optlong (lua_State *L, int narg, long d);+ +
+If the function argument narg is a number,
+returns this number cast to a long.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
+
+
+
+
luaL_optlstring+[-0, +0, v] +
const char *luaL_optlstring (lua_State *L, + int narg, + const char *d, + size_t *l);+ +
+If the function argument narg is a string,
+returns this string.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
+
+If l is not NULL,
+fills the position *l with the results's length.
+
+
+
+
+
+
luaL_optnumber+[-0, +0, v] +
lua_Number luaL_optnumber (lua_State *L, int narg, lua_Number d);+ +
+If the function argument narg is a number,
+returns this number.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
+
+
+
+
luaL_optstring+[-0, +0, v] +
const char *luaL_optstring (lua_State *L, + int narg, + const char *d);+ +
+If the function argument narg is a string,
+returns this string.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
+
+
+
+
luaL_prepbuffer+[-0, +0, -] +
char *luaL_prepbuffer (luaL_Buffer *B);+ +
+Returns an address to a space of size LUAL_BUFFERSIZE
+where you can copy a string to be added to buffer B
+(see luaL_Buffer).
+After copying the string into this space you must call
+luaL_addsize with the size of the string to actually add
+it to the buffer.
+
+
+
+
+
+
luaL_pushresult+[-?, +1, m] +
void luaL_pushresult (luaL_Buffer *B);+ +
+Finishes the use of buffer B leaving the final string on
+the top of the stack.
+
+
+
+
+
+
luaL_ref+[-1, +0, m] +
int luaL_ref (lua_State *L, int t);+ +
+Creates and returns a reference,
+in the table at index t,
+for the object at the top of the stack (and pops the object).
+
+
+
+A reference is a unique integer key.
+As long as you do not manually add integer keys into table t,
+luaL_ref ensures the uniqueness of the key it returns.
+You can retrieve an object referred by reference r
+by calling lua_rawgeti(L, t, r).
+Function luaL_unref frees a reference and its associated object.
+
+
+
+If the object at the top of the stack is nil,
+luaL_ref returns the constant LUA_REFNIL.
+The constant LUA_NOREF is guaranteed to be different
+from any reference returned by luaL_ref.
+
+
+
+
+
+
luaL_Regtypedef struct luaL_Reg {
+ const char *name;
+ lua_CFunction func;
+} luaL_Reg;
+
+
+Type for arrays of functions to be registered by
+luaL_register.
+name is the function name and func is a pointer to
+the function.
+Any array of luaL_Reg must end with an sentinel entry
+in which both name and func are NULL.
+
+
+
+
+
+
luaL_register+[-(0|1), +1, m] +
void luaL_register (lua_State *L, + const char *libname, + const luaL_Reg *l);+ +
+Opens a library. + + +
+When called with libname equal to NULL,
+it simply registers all functions in the list l
+(see luaL_Reg) into the table on the top of the stack.
+
+
+
+When called with a non-null libname,
+luaL_register creates a new table t,
+sets it as the value of the global variable libname,
+sets it as the value of package.loaded[libname],
+and registers on it all functions in the list l.
+If there is a table in package.loaded[libname] or in
+variable libname,
+reuses this table instead of creating a new one.
+
+
+
+In any case the function leaves the table +on the top of the stack. + + + + + +
luaL_typename+[-0, +0, -] +
const char *luaL_typename (lua_State *L, int index);+ +
+Returns the name of the type of the value at the given index. + + + + + +
luaL_typerror+[-0, +0, v] +
int luaL_typerror (lua_State *L, int narg, const char *tname);+ +
+Generates an error with a message like the following: + +
+ location: bad argument narg to 'func' (tname expected, got rt) +
+where location is produced by luaL_where,
+func is the name of the current function,
+and rt is the type name of the actual argument.
+
+
+
+
+
+
luaL_unref+[-0, +0, -] +
void luaL_unref (lua_State *L, int t, int ref);+ +
+Releases reference ref from the table at index t
+(see luaL_ref).
+The entry is removed from the table,
+so that the referred object can be collected.
+The reference ref is also freed to be used again.
+
+
+
+If ref is LUA_NOREF or LUA_REFNIL,
+luaL_unref does nothing.
+
+
+
+
+
+
luaL_where+[-0, +1, m] +
void luaL_where (lua_State *L, int lvl);+ +
+Pushes onto the stack a string identifying the current position
+of the control at level lvl in the call stack.
+Typically this string has the following format:
+
+
+ chunkname:currentline: +
+Level 0 is the running function, +level 1 is the function that called the running function, +etc. + + +
+This function is used to build a prefix for error messages. + + + + + + + +
+The standard Lua libraries provide useful functions
+that are implemented directly through the C API.
+Some of these functions provide essential services to the language
+(e.g., type and getmetatable);
+others provide access to "outside" services (e.g., I/O);
+and others could be implemented in Lua itself,
+but are quite useful or have critical performance requirements that
+deserve an implementation in C (e.g., table.sort).
+
+
+
+All libraries are implemented through the official C API +and are provided as separate C modules. +Currently, Lua has the following standard libraries: + +
+Except for the basic and package libraries, +each library provides all its functions as fields of a global table +or as methods of its objects. + + +
+To have access to these libraries,
+the C host program should call the luaL_openlibs function,
+which opens all standard libraries.
+Alternatively,
+it can open them individually by calling
+luaopen_base (for the basic library),
+luaopen_package (for the package library),
+luaopen_string (for the string library),
+luaopen_table (for the table library),
+luaopen_math (for the mathematical library),
+luaopen_io (for the I/O library),
+luaopen_os (for the Operating System library),
+and luaopen_debug (for the debug library).
+These functions are declared in lualib.h
+and should not be called directly:
+you must call them like any other Lua C function,
+e.g., by using lua_call.
+
+
+
+
+The basic library provides some core functions to Lua. +If you do not include this library in your application, +you should check carefully whether you need to provide +implementations for some of its facilities. + + +
+
assert (v [, message])v is false (i.e., nil or false);
+otherwise, returns all its arguments.
+message is an error message;
+when absent, it defaults to "assertion failed!"
+
+
+
+
++
collectgarbage (opt [, arg])
+This function is a generic interface to the garbage collector.
+It performs different functions according to its first argument, opt:
+
+
arg
+(larger values mean more steps) in a non-specified way.
+If you want to control the step size
+you must experimentally tune the value of arg.
+Returns true if the step finished a collection cycle.
+arg as the new value for the pause of
+the collector (see §2.10).
+Returns the previous value for pause.
+arg as the new value for the step multiplier of
+the collector (see §2.10).
+Returns the previous value for step.
++
dofile (filename)dofile executes the contents of the standard input (stdin).
+Returns all values returned by the chunk.
+In case of errors, dofile propagates the error
+to its caller (that is, dofile does not run in protected mode).
+
+
+
+
++
error (message [, level])message as the error message.
+Function error never returns.
+
+
+
+Usually, error adds some information about the error position
+at the beginning of the message.
+The level argument specifies how to get the error position.
+With level 1 (the default), the error position is where the
+error function was called.
+Level 2 points the error to where the function
+that called error was called; and so on.
+Passing a level 0 avoids the addition of error position information
+to the message.
+
+
+
+
+
+
_G_G._G = _G).
+Lua itself does not use this variable;
+changing its value does not affect any environment,
+nor vice-versa.
+(Use setfenv to change environments.)
+
+
+
+
++
getfenv ([f])f can be a Lua function or a number
+that specifies the function at that stack level:
+Level 1 is the function calling getfenv.
+If the given function is not a Lua function,
+or if f is 0,
+getfenv returns the global environment.
+The default for f is 1.
+
+
+
+
++
getmetatable (object)
+If object does not have a metatable, returns nil.
+Otherwise,
+if the object's metatable has a "__metatable" field,
+returns the associated value.
+Otherwise, returns the metatable of the given object.
+
+
+
+
+
+
ipairs (t)
+Returns three values: an iterator function, the table t, and 0,
+so that the construction
+
+
+ for i,v in ipairs(t) do body end +
+will iterate over the pairs (1,t[1]), (2,t[2]), ···,
+up to the first integer key absent from the table.
+
+
+
+
+
+
load (func [, chunkname])
+Loads a chunk using function func to get its pieces.
+Each call to func must return a string that concatenates
+with previous results.
+A return of an empty string, nil, or no value signals the end of the chunk.
+
+
+
+If there are no errors, +returns the compiled chunk as a function; +otherwise, returns nil plus the error message. +The environment of the returned function is the global environment. + + +
+chunkname is used as the chunk name for error messages
+and debug information.
+When absent,
+it defaults to "=(load)".
+
+
+
+
+
+
loadfile ([filename])
+Similar to load,
+but gets the chunk from file filename
+or from the standard input,
+if no file name is given.
+
+
+
+
+
+
loadstring (string [, chunkname])
+Similar to load,
+but gets the chunk from the given string.
+
+
+
+To load and run a given string, use the idiom + +
+ assert(loadstring(s))() ++ +
+When absent,
+chunkname defaults to the given string.
+
+
+
+
+
+
next (table [, index])
+Allows a program to traverse all fields of a table.
+Its first argument is a table and its second argument
+is an index in this table.
+next returns the next index of the table
+and its associated value.
+When called with nil as its second argument,
+next returns an initial index
+and its associated value.
+When called with the last index,
+or with nil in an empty table,
+next returns nil.
+If the second argument is absent, then it is interpreted as nil.
+In particular,
+you can use next(t) to check whether a table is empty.
+
+
+
+The order in which the indices are enumerated is not specified,
+even for numeric indices.
+(To traverse a table in numeric order,
+use a numerical for or the ipairs function.)
+
+
+
+The behavior of next is undefined if,
+during the traversal,
+you assign any value to a non-existent field in the table.
+You may however modify existing fields.
+In particular, you may clear existing fields.
+
+
+
+
+
+
pairs (t)
+Returns three values: the next function, the table t, and nil,
+so that the construction
+
+
+ for k,v in pairs(t) do body end +
+will iterate over all key–value pairs of table t.
+
+
+
+See function next for the caveats of modifying
+the table during its traversal.
+
+
+
+
+
+
pcall (f, arg1, ···)
+Calls function f with
+the given arguments in protected mode.
+This means that any error inside f is not propagated;
+instead, pcall catches the error
+and returns a status code.
+Its first result is the status code (a boolean),
+which is true if the call succeeds without errors.
+In such case, pcall also returns all results from the call,
+after this first result.
+In case of any error, pcall returns false plus the error message.
+
+
+
+
+
+
print (···)stdout,
+using the tostring function to convert them to strings.
+print is not intended for formatted output,
+but only as a quick way to show a value,
+typically for debugging.
+For formatted output, use string.format.
+
+
+
+
++
rawequal (v1, v2)v1 is equal to v2,
+without invoking any metamethod.
+Returns a boolean.
+
+
+
+
++
rawget (table, index)table[index],
+without invoking any metamethod.
+table must be a table;
+index may be any value.
+
+
+
+
++
rawset (table, index, value)table[index] to value,
+without invoking any metamethod.
+table must be a table,
+index any value different from nil,
+and value any Lua value.
+
+
+
+This function returns table.
+
+
+
+
+
+
select (index, ···)
+If index is a number,
+returns all arguments after argument number index.
+Otherwise, index must be the string "#",
+and select returns the total number of extra arguments it received.
+
+
+
+
+
+
setfenv (f, table)
+Sets the environment to be used by the given function.
+f can be a Lua function or a number
+that specifies the function at that stack level:
+Level 1 is the function calling setfenv.
+setfenv returns the given function.
+
+
+
+As a special case, when f is 0 setfenv changes
+the environment of the running thread.
+In this case, setfenv returns no values.
+
+
+
+
+
+
setmetatable (table, metatable)
+Sets the metatable for the given table.
+(You cannot change the metatable of other types from Lua, only from C.)
+If metatable is nil,
+removes the metatable of the given table.
+If the original metatable has a "__metatable" field,
+raises an error.
+
+
+
+This function returns table.
+
+
+
+
+
+
tonumber (e [, base])tonumber returns this number;
+otherwise, it returns nil.
+
+
+
+An optional argument specifies the base to interpret the numeral.
+The base may be any integer between 2 and 36, inclusive.
+In bases above 10, the letter 'A' (in either upper or lower case)
+represents 10, 'B' represents 11, and so forth,
+with 'Z' representing 35.
+In base 10 (the default), the number can have a decimal part,
+as well as an optional exponent part (see §2.1).
+In other bases, only unsigned integers are accepted.
+
+
+
+
+
+
tostring (e)string.format.
+
+
+
+If the metatable of e has a "__tostring" field,
+then tostring calls the corresponding value
+with e as argument,
+and uses the result of the call as its result.
+
+
+
+
+
+
type (v)nil" (a string, not the value nil),
+"number",
+"string",
+"boolean",
+"table",
+"function",
+"thread",
+and "userdata".
+
+
+
+
++
unpack (list [, i [, j]])+ return list[i], list[i+1], ···, list[j] +
+except that the above code can be written only for a fixed number
+of elements.
+By default, i is 1 and j is the length of the list,
+as defined by the length operator (see §2.5.5).
+
+
+
+
+
+
_VERSIONLua 5.1".
+
+
+
+
++
xpcall (f, err)
+This function is similar to pcall,
+except that you can set a new error handler.
+
+
+
+xpcall calls function f in protected mode,
+using err as the error handler.
+Any error inside f is not propagated;
+instead, xpcall catches the error,
+calls the err function with the original error object,
+and returns a status code.
+Its first result is the status code (a boolean),
+which is true if the call succeeds without errors.
+In this case, xpcall also returns all results from the call,
+after this first result.
+In case of any error,
+xpcall returns false plus the result from err.
+
+
+
+
+
+
+
+
+The operations related to coroutines comprise a sub-library of
+the basic library and come inside the table coroutine.
+See §2.11 for a general description of coroutines.
+
+
+
+
coroutine.create (f)
+Creates a new coroutine, with body f.
+f must be a Lua function.
+Returns this new coroutine,
+an object with type "thread".
+
+
+
+
+
+
coroutine.resume (co [, val1, ···])
+Starts or continues the execution of coroutine co.
+The first time you resume a coroutine,
+it starts running its body.
+The values val1, ··· are passed
+as the arguments to the body function.
+If the coroutine has yielded,
+resume restarts it;
+the values val1, ··· are passed
+as the results from the yield.
+
+
+
+If the coroutine runs without any errors,
+resume returns true plus any values passed to yield
+(if the coroutine yields) or any values returned by the body function
+(if the coroutine terminates).
+If there is any error,
+resume returns false plus the error message.
+
+
+
+
+
+
coroutine.running ()+Returns the running coroutine, +or nil when called by the main thread. + + + + +
+
coroutine.status (co)
+Returns the status of coroutine co, as a string:
+"running",
+if the coroutine is running (that is, it called status);
+"suspended", if the coroutine is suspended in a call to yield,
+or if it has not started running yet;
+"normal" if the coroutine is active but not running
+(that is, it has resumed another coroutine);
+and "dead" if the coroutine has finished its body function,
+or if it has stopped with an error.
+
+
+
+
+
+
coroutine.wrap (f)
+Creates a new coroutine, with body f.
+f must be a Lua function.
+Returns a function that resumes the coroutine each time it is called.
+Any arguments passed to the function behave as the
+extra arguments to resume.
+Returns the same values returned by resume,
+except the first boolean.
+In case of error, propagates the error.
+
+
+
+
+
+
coroutine.yield (···)
+Suspends the execution of the calling coroutine.
+The coroutine cannot be running a C function,
+a metamethod, or an iterator.
+Any arguments to yield are passed as extra results to resume.
+
+
+
+
+
+
+
+
+The package library provides basic
+facilities for loading and building modules in Lua.
+It exports two of its functions directly in the global environment:
+require and module.
+Everything else is exported in a table package.
+
+
+
+
module (name [, ···])
+Creates a module.
+If there is a table in package.loaded[name],
+this table is the module.
+Otherwise, if there is a global table t with the given name,
+this table is the module.
+Otherwise creates a new table t and
+sets it as the value of the global name and
+the value of package.loaded[name].
+This function also initializes t._NAME with the given name,
+t._M with the module (t itself),
+and t._PACKAGE with the package name
+(the full module name minus last component; see below).
+Finally, module sets t as the new environment
+of the current function and the new value of package.loaded[name],
+so that require returns t.
+
+
+
+If name is a compound name
+(that is, one with components separated by dots),
+module creates (or reuses, if they already exist)
+tables for each component.
+For instance, if name is a.b.c,
+then module stores the module table in field c of
+field b of global a.
+
+
+
+This function can receive optional options after +the module name, +where each option is a function to be applied over the module. + + + + +
+
require (modname)
+Loads the given module.
+The function starts by looking into the package.loaded table
+to determine whether modname is already loaded.
+If it is, then require returns the value stored
+at package.loaded[modname].
+Otherwise, it tries to find a loader for the module.
+
+
+
+To find a loader,
+require is guided by the package.loaders array.
+By changing this array,
+we can change how require looks for a module.
+The following explanation is based on the default configuration
+for package.loaders.
+
+
+
+First require queries package.preload[modname].
+If it has a value,
+this value (which should be a function) is the loader.
+Otherwise require searches for a Lua loader using the
+path stored in package.path.
+If that also fails, it searches for a C loader using the
+path stored in package.cpath.
+If that also fails,
+it tries an all-in-one loader (see package.loaders).
+
+
+
+Once a loader is found,
+require calls the loader with a single argument, modname.
+If the loader returns any value,
+require assigns the returned value to package.loaded[modname].
+If the loader returns no value and
+has not assigned any value to package.loaded[modname],
+then require assigns true to this entry.
+In any case, require returns the
+final value of package.loaded[modname].
+
+
+
+If there is any error loading or running the module,
+or if it cannot find any loader for the module,
+then require signals an error.
+
+
+
+
+
+
package.cpath
+The path used by require to search for a C loader.
+
+
+
+Lua initializes the C path package.cpath in the same way
+it initializes the Lua path package.path,
+using the environment variable LUA_CPATH
+or a default path defined in luaconf.h.
+
+
+
+
+
+ +
package.loaded
+A table used by require to control which
+modules are already loaded.
+When you require a module modname and
+package.loaded[modname] is not false,
+require simply returns the value stored there.
+
+
+
+
+
+
package.loaders
+A table used by require to control how to load modules.
+
+
+
+Each entry in this table is a searcher function.
+When looking for a module,
+require calls each of these searchers in ascending order,
+with the module name (the argument given to require) as its
+sole parameter.
+The function can return another function (the module loader)
+or a string explaining why it did not find that module
+(or nil if it has nothing to say).
+Lua initializes this table with four functions.
+
+
+
+The first searcher simply looks for a loader in the
+package.preload table.
+
+
+
+The second searcher looks for a loader as a Lua library,
+using the path stored at package.path.
+A path is a sequence of templates separated by semicolons.
+For each template,
+the searcher will change each interrogation
+mark in the template by filename,
+which is the module name with each dot replaced by a
+"directory separator" (such as "/" in Unix);
+then it will try to open the resulting file name.
+So, for instance, if the Lua path is the string
+
+
+ "./?.lua;./?.lc;/usr/local/?/init.lua" +
+the search for a Lua file for module foo
+will try to open the files
+./foo.lua, ./foo.lc, and
+/usr/local/foo/init.lua, in that order.
+
+
+
+The third searcher looks for a loader as a C library,
+using the path given by the variable package.cpath.
+For instance,
+if the C path is the string
+
+
+ "./?.so;./?.dll;/usr/local/?/init.so" +
+the searcher for module foo
+will try to open the files ./foo.so, ./foo.dll,
+and /usr/local/foo/init.so, in that order.
+Once it finds a C library,
+this searcher first uses a dynamic link facility to link the
+application with the library.
+Then it tries to find a C function inside the library to
+be used as the loader.
+The name of this C function is the string "luaopen_"
+concatenated with a copy of the module name where each dot
+is replaced by an underscore.
+Moreover, if the module name has a hyphen,
+its prefix up to (and including) the first hyphen is removed.
+For instance, if the module name is a.v1-b.c,
+the function name will be luaopen_b_c.
+
+
+
+The fourth searcher tries an all-in-one loader.
+It searches the C path for a library for
+the root name of the given module.
+For instance, when requiring a.b.c,
+it will search for a C library for a.
+If found, it looks into it for an open function for
+the submodule;
+in our example, that would be luaopen_a_b_c.
+With this facility, a package can pack several C submodules
+into one single library,
+with each submodule keeping its original open function.
+
+
+
+
+
+
package.loadlib (libname, funcname)
+Dynamically links the host program with the C library libname.
+Inside this library, looks for a function funcname
+and returns this function as a C function.
+(So, funcname must follow the protocol (see lua_CFunction)).
+
+
+
+This is a low-level function.
+It completely bypasses the package and module system.
+Unlike require,
+it does not perform any path searching and
+does not automatically adds extensions.
+libname must be the complete file name of the C library,
+including if necessary a path and extension.
+funcname must be the exact name exported by the C library
+(which may depend on the C compiler and linker used).
+
+
+
+This function is not supported by ANSI C.
+As such, it is only available on some platforms
+(Windows, Linux, Mac OS X, Solaris, BSD,
+plus other Unix systems that support the dlfcn standard).
+
+
+
+
+
+
package.path
+The path used by require to search for a Lua loader.
+
+
+
+At start-up, Lua initializes this variable with
+the value of the environment variable LUA_PATH or
+with a default path defined in luaconf.h,
+if the environment variable is not defined.
+Any ";;" in the value of the environment variable
+is replaced by the default path.
+
+
+
+
+
+
package.preload
+A table to store loaders for specific modules
+(see require).
+
+
+
+
+
+
package.seeall (module)
+Sets a metatable for module with
+its __index field referring to the global environment,
+so that this module inherits values
+from the global environment.
+To be used as an option to function module.
+
+
+
+
+
+
+
+
+This library provides generic functions for string manipulation, +such as finding and extracting substrings, and pattern matching. +When indexing a string in Lua, the first character is at position 1 +(not at 0, as in C). +Indices are allowed to be negative and are interpreted as indexing backwards, +from the end of the string. +Thus, the last character is at position -1, and so on. + + +
+The string library provides all its functions inside the table
+string.
+It also sets a metatable for strings
+where the __index field points to the string table.
+Therefore, you can use the string functions in object-oriented style.
+For instance, string.byte(s, i)
+can be written as s:byte(i).
+
+
+
+The string library assumes one-byte character encodings. + + +
+
string.byte (s [, i [, j]])s[i],
+s[i+1], ···, s[j].
+The default value for i is 1;
+the default value for j is i.
+
+
++Note that numerical codes are not necessarily portable across platforms. + + + + +
+
string.char (···)+Note that numerical codes are not necessarily portable across platforms. + + + + +
+
string.dump (function)
+Returns a string containing a binary representation of the given function,
+so that a later loadstring on this string returns
+a copy of the function.
+function must be a Lua function without upvalues.
+
+
+
+
+
+
string.find (s, pattern [, init [, plain]])pattern in the string s.
+If it finds a match, then find returns the indices of s
+where this occurrence starts and ends;
+otherwise, it returns nil.
+A third, optional numerical argument init specifies
+where to start the search;
+its default value is 1 and can be negative.
+A value of true as a fourth, optional argument plain
+turns off the pattern matching facilities,
+so the function does a plain "find substring" operation,
+with no characters in pattern being considered "magic".
+Note that if plain is given, then init must be given as well.
+
+
++If the pattern has captures, +then in a successful match +the captured values are also returned, +after the two indices. + + + + +
+
string.format (formatstring, ···)printf family of
+standard C functions.
+The only differences are that the options/modifiers
+*, l, L, n, p,
+and h are not supported
+and that there is an extra option, q.
+The q option formats a string in a form suitable to be safely read
+back by the Lua interpreter:
+the string is written between double quotes,
+and all double quotes, newlines, embedded zeros,
+and backslashes in the string
+are correctly escaped when written.
+For instance, the call
+
+
+ string.format('%q', 'a string with "quotes" and \n new line')
++will produce the string: + +
+ "a string with \"quotes\" and \ + new line" ++ +
+The options c, d, E, e, f,
+g, G, i, o, u, X, and x all
+expect a number as argument,
+whereas q and s expect a string.
+
+
+
+This function does not accept string values
+containing embedded zeros,
+except as arguments to the q option.
+
+
+
+
+
+
string.gmatch (s, pattern)pattern over string s.
+If pattern specifies no captures,
+then the whole match is produced in each call.
+
+
++As an example, the following loop + +
+ s = "hello world from Lua" + for w in string.gmatch(s, "%a+") do + print(w) + end +
+will iterate over all the words from string s,
+printing one per line.
+The next example collects all pairs key=value from the
+given string into a table:
+
+
+ t = {}
+ s = "from=world, to=Lua"
+ for k, v in string.gmatch(s, "(%w+)=(%w+)") do
+ t[k] = v
+ end
+
+
+
+For this function, a '^' at the start of a pattern does not
+work as an anchor, as this would prevent the iteration.
+
+
+
+
+
+
string.gsub (s, pattern, repl [, n])s
+in which all (or the first n, if given)
+occurrences of the pattern have been
+replaced by a replacement string specified by repl,
+which can be a string, a table, or a function.
+gsub also returns, as its second value,
+the total number of matches that occurred.
+
+
+
+If repl is a string, then its value is used for replacement.
+The character % works as an escape character:
+any sequence in repl of the form %n,
+with n between 1 and 9,
+stands for the value of the n-th captured substring (see below).
+The sequence %0 stands for the whole match.
+The sequence %% stands for a single %.
+
+
+
+If repl is a table, then the table is queried for every match,
+using the first capture as the key;
+if the pattern specifies no captures,
+then the whole match is used as the key.
+
+
+
+If repl is a function, then this function is called every time a
+match occurs, with all captured substrings passed as arguments,
+in order;
+if the pattern specifies no captures,
+then the whole match is passed as a sole argument.
+
+
+
+If the value returned by the table query or by the function call +is a string or a number, +then it is used as the replacement string; +otherwise, if it is false or nil, +then there is no replacement +(that is, the original match is kept in the string). + + +
+Here are some examples: + +
+ x = string.gsub("hello world", "(%w+)", "%1 %1")
+ --> x="hello hello world world"
+
+ x = string.gsub("hello world", "%w+", "%0 %0", 1)
+ --> x="hello hello world"
+
+ x = string.gsub("hello world from Lua", "(%w+)%s*(%w+)", "%2 %1")
+ --> x="world hello Lua from"
+
+ x = string.gsub("home = $HOME, user = $USER", "%$(%w+)", os.getenv)
+ --> x="home = /home/roberto, user = roberto"
+
+ x = string.gsub("4+5 = $return 4+5$", "%$(.-)%$", function (s)
+ return loadstring(s)()
+ end)
+ --> x="4+5 = 9"
+
+ local t = {name="lua", version="5.1"}
+ x = string.gsub("$name-$version.tar.gz", "%$(%w+)", t)
+ --> x="lua-5.1.tar.gz"
+
+
+
+
++
string.len (s)"" has length 0.
+Embedded zeros are counted,
+so "a\000bc\000" has length 5.
+
+
+
+
++
string.lower (s)+
string.match (s, pattern [, init])pattern in the string s.
+If it finds one, then match returns
+the captures from the pattern;
+otherwise it returns nil.
+If pattern specifies no captures,
+then the whole match is returned.
+A third, optional numerical argument init specifies
+where to start the search;
+its default value is 1 and can be negative.
+
+
+
+
++
string.rep (s, n)n copies of
+the string s.
+
+
+
+
++
string.reverse (s)s reversed.
+
+
+
+
++
string.sub (s, i [, j])s that
+starts at i and continues until j;
+i and j can be negative.
+If j is absent, then it is assumed to be equal to -1
+(which is the same as the string length).
+In particular,
+the call string.sub(s,1,j) returns a prefix of s
+with length j,
+and string.sub(s, -i) returns a suffix of s
+with length i.
+
+
+
+
++
string.upper (s)+A character class is used to represent a set of characters. +The following combinations are allowed in describing a character class: + +
^$()%.[]*+-?)
+represents the character x itself.
+.: (a dot) represents all characters.%a: represents all letters.%c: represents all control characters.%d: represents all digits.%l: represents all lowercase letters.%p: represents all punctuation characters.%s: represents all space characters.%u: represents all uppercase letters.%w: represents all alphanumeric characters.%x: represents all hexadecimal digits.%z: represents the character with representation 0.%x: (where x is any non-alphanumeric character)
+represents the character x.
+This is the standard way to escape the magic characters.
+Any punctuation character (even the non magic)
+can be preceded by a '%'
+when used to represent itself in a pattern.
+[set]:
+represents the class which is the union of all
+characters in set.
+A range of characters can be specified by
+separating the end characters of the range with a '-'.
+All classes %x described above can also be used as
+components in set.
+All other characters in set represent themselves.
+For example, [%w_] (or [_%w])
+represents all alphanumeric characters plus the underscore,
+[0-7] represents the octal digits,
+and [0-7%l%-] represents the octal digits plus
+the lowercase letters plus the '-' character.
+
+
+
+The interaction between ranges and classes is not defined.
+Therefore, patterns like [%a-z] or [a-%%]
+have no meaning.
+
[^set]:
+represents the complement of set,
+where set is interpreted as above.
+
+For all classes represented by single letters (%a, %c, etc.),
+the corresponding uppercase letter represents the complement of the class.
+For instance, %S represents all non-space characters.
+
+
+
+The definitions of letter, space, and other character groups
+depend on the current locale.
+In particular, the class [a-z] may not be equivalent to %l.
+
+
+
+
+
+
+A pattern item can be + +
*',
+which matches 0 or more repetitions of characters in the class.
+These repetition items will always match the longest possible sequence;
++',
+which matches 1 or more repetitions of characters in the class.
+These repetition items will always match the longest possible sequence;
+-',
+which also matches 0 or more repetitions of characters in the class.
+Unlike '*',
+these repetition items will always match the shortest possible sequence;
+?',
+which matches 0 or 1 occurrence of a character in the class;
+%n, for n between 1 and 9;
+such item matches a substring equal to the n-th captured string
+(see below);
+%bxy, where x and y are two distinct characters;
+such item matches strings that start with x, end with y,
+and where the x and y are balanced.
+This means that, if one reads the string from left to right,
+counting +1 for an x and -1 for a y,
+the ending y is the first y where the count reaches 0.
+For instance, the item %b() matches expressions with
+balanced parentheses.
+
+A pattern is a sequence of pattern items.
+A '^' at the beginning of a pattern anchors the match at the
+beginning of the subject string.
+A '$' at the end of a pattern anchors the match at the
+end of the subject string.
+At other positions,
+'^' and '$' have no special meaning and represent themselves.
+
+
+
+
+
+
+A pattern can contain sub-patterns enclosed in parentheses;
+they describe captures.
+When a match succeeds, the substrings of the subject string
+that match captures are stored (captured) for future use.
+Captures are numbered according to their left parentheses.
+For instance, in the pattern "(a*(.)%w(%s*))",
+the part of the string matching "a*(.)%w(%s*)" is
+stored as the first capture (and therefore has number 1);
+the character matching "." is captured with number 2,
+and the part matching "%s*" has number 3.
+
+
+
+As a special case, the empty capture () captures
+the current string position (a number).
+For instance, if we apply the pattern "()aa()" on the
+string "flaaap", there will be two captures: 3 and 5.
+
+
+
+A pattern cannot contain embedded zeros. Use %z instead.
+
+
+
+
+
+
+
+
+
+
+
+
+This library provides generic functions for table manipulation.
+It provides all its functions inside the table table.
+
+
+
+Most functions in the table library assume that the table +represents an array or a list. +For these functions, when we talk about the "length" of a table +we mean the result of the length operator. + + +
+
table.concat (table [, sep [, i [, j]]])table[i]..sep..table[i+1] ··· sep..table[j].
+The default value for sep is the empty string,
+the default for i is 1,
+and the default for j is the length of the table.
+If i is greater than j, returns the empty string.
+
+
+
+
++
table.insert (table, [pos,] value)
+Inserts element value at position pos in table,
+shifting up other elements to open space, if necessary.
+The default value for pos is n+1,
+where n is the length of the table (see §2.5.5),
+so that a call table.insert(t,x) inserts x at the end
+of table t.
+
+
+
+
+
+
table.maxn (table)+Returns the largest positive numerical index of the given table, +or zero if the table has no positive numerical indices. +(To do its job this function does a linear traversal of +the whole table.) + + + + +
+
table.remove (table [, pos])
+Removes from table the element at position pos,
+shifting down other elements to close the space, if necessary.
+Returns the value of the removed element.
+The default value for pos is n,
+where n is the length of the table,
+so that a call table.remove(t) removes the last element
+of table t.
+
+
+
+
+
+
table.sort (table [, comp])table[1] to table[n],
+where n is the length of the table.
+If comp is given,
+then it must be a function that receives two table elements,
+and returns true
+when the first is less than the second
+(so that not comp(a[i+1],a[i]) will be true after the sort).
+If comp is not given,
+then the standard Lua operator < is used instead.
+
+
++The sort algorithm is not stable; +that is, elements considered equal by the given order +may have their relative positions changed by the sort. + + + + + + + +
+This library is an interface to the standard C math library.
+It provides all its functions inside the table math.
+
+
+
+
math.abs (x)
+Returns the absolute value of x.
+
+
+
+
+
+
math.acos (x)
+Returns the arc cosine of x (in radians).
+
+
+
+
+
+
math.asin (x)
+Returns the arc sine of x (in radians).
+
+
+
+
+
+
math.atan (x)
+Returns the arc tangent of x (in radians).
+
+
+
+
+
+
math.atan2 (y, x)
+Returns the arc tangent of y/x (in radians),
+but uses the signs of both parameters to find the
+quadrant of the result.
+(It also handles correctly the case of x being zero.)
+
+
+
+
+
+
math.ceil (x)
+Returns the smallest integer larger than or equal to x.
+
+
+
+
+
+
math.cos (x)
+Returns the cosine of x (assumed to be in radians).
+
+
+
+
+
+
math.cosh (x)
+Returns the hyperbolic cosine of x.
+
+
+
+
+
+
math.deg (x)
+Returns the angle x (given in radians) in degrees.
+
+
+
+
+
+
math.exp (x)+Returns the value ex. + + + + +
+
math.floor (x)
+Returns the largest integer smaller than or equal to x.
+
+
+
+
+
+
math.fmod (x, y)
+Returns the remainder of the division of x by y
+that rounds the quotient towards zero.
+
+
+
+
+
+
math.frexp (x)
+Returns m and e such that x = m2e,
+e is an integer and the absolute value of m is
+in the range [0.5, 1)
+(or zero when x is zero).
+
+
+
+
+
+
math.huge
+The value HUGE_VAL,
+a value larger than or equal to any other numerical value.
+
+
+
+
+
+
math.ldexp (m, e)
+Returns m2e (e should be an integer).
+
+
+
+
+
+
math.log (x)
+Returns the natural logarithm of x.
+
+
+
+
+
+
math.log10 (x)
+Returns the base-10 logarithm of x.
+
+
+
+
+
+
math.max (x, ···)+Returns the maximum value among its arguments. + + + + +
+
math.min (x, ···)+Returns the minimum value among its arguments. + + + + +
+
math.modf (x)
+Returns two numbers,
+the integral part of x and the fractional part of x.
+
+
+
+
+
+
math.pi+The value of pi. + + + + +
+
math.pow (x, y)
+Returns xy.
+(You can also use the expression x^y to compute this value.)
+
+
+
+
+
+
math.rad (x)
+Returns the angle x (given in degrees) in radians.
+
+
+
+
+
+
math.random ([m [, n]])
+This function is an interface to the simple
+pseudo-random generator function rand provided by ANSI C.
+(No guarantees can be given for its statistical properties.)
+
+
+
+When called without arguments,
+returns a uniform pseudo-random real number
+in the range [0,1).
+When called with an integer number m,
+math.random returns
+a uniform pseudo-random integer in the range [1, m].
+When called with two integer numbers m and n,
+math.random returns a uniform pseudo-random
+integer in the range [m, n].
+
+
+
+
+
+
math.randomseed (x)
+Sets x as the "seed"
+for the pseudo-random generator:
+equal seeds produce equal sequences of numbers.
+
+
+
+
+
+
math.sin (x)
+Returns the sine of x (assumed to be in radians).
+
+
+
+
+
+
math.sinh (x)
+Returns the hyperbolic sine of x.
+
+
+
+
+
+
math.sqrt (x)
+Returns the square root of x.
+(You can also use the expression x^0.5 to compute this value.)
+
+
+
+
+
+
math.tan (x)
+Returns the tangent of x (assumed to be in radians).
+
+
+
+
+
+
math.tanh (x)
+Returns the hyperbolic tangent of x.
+
+
+
+
+
+
+
+
+The I/O library provides two different styles for file manipulation. +The first one uses implicit file descriptors; +that is, there are operations to set a default input file and a +default output file, +and all input/output operations are over these default files. +The second style uses explicit file descriptors. + + +
+When using implicit file descriptors,
+all operations are supplied by table io.
+When using explicit file descriptors,
+the operation io.open returns a file descriptor
+and then all operations are supplied as methods of the file descriptor.
+
+
+
+The table io also provides
+three predefined file descriptors with their usual meanings from C:
+io.stdin, io.stdout, and io.stderr.
+The I/O library never closes these files.
+
+
+
+Unless otherwise stated, +all I/O functions return nil on failure +(plus an error message as a second result and +a system-dependent error code as a third result) +and some value different from nil on success. + + +
+
io.close ([file])
+Equivalent to file:close().
+Without a file, closes the default output file.
+
+
+
+
+
+
io.flush ()
+Equivalent to file:flush over the default output file.
+
+
+
+
+
+
io.input ([file])+When called with a file name, it opens the named file (in text mode), +and sets its handle as the default input file. +When called with a file handle, +it simply sets this file handle as the default input file. +When called without parameters, +it returns the current default input file. + + +
+In case of errors this function raises the error, +instead of returning an error code. + + + + +
+
io.lines ([filename])+Opens the given file name in read mode +and returns an iterator function that, +each time it is called, +returns a new line from the file. +Therefore, the construction + +
+ for line in io.lines(filename) do body end +
+will iterate over all lines of the file. +When the iterator function detects the end of file, +it returns nil (to finish the loop) and automatically closes the file. + + +
+The call io.lines() (with no file name) is equivalent
+to io.input():lines();
+that is, it iterates over the lines of the default input file.
+In this case it does not close the file when the loop ends.
+
+
+
+
+
+
io.open (filename [, mode])
+This function opens a file,
+in the mode specified in the string mode.
+It returns a new file handle,
+or, in case of errors, nil plus an error message.
+
+
+
+The mode string can be any of the following:
+
+
+The mode string can also have a 'b' at the end,
+which is needed in some systems to open the file in binary mode.
+This string is exactly what is used in the
+standard C function fopen.
+
+
+
+
+
+
io.output ([file])
+Similar to io.input, but operates over the default output file.
+
+
+
+
+
+
io.popen (prog [, mode])
+Starts program prog in a separated process and returns
+a file handle that you can use to read data from this program
+(if mode is "r", the default)
+or to write data to this program
+(if mode is "w").
+
+
+
+This function is system dependent and is not available +on all platforms. + + + + +
+
io.read (···)
+Equivalent to io.input():read.
+
+
+
+
+
+
io.tmpfile ()+Returns a handle for a temporary file. +This file is opened in update mode +and it is automatically removed when the program ends. + + + + +
+
io.type (obj)
+Checks whether obj is a valid file handle.
+Returns the string "file" if obj is an open file handle,
+"closed file" if obj is a closed file handle,
+or nil if obj is not a file handle.
+
+
+
+
+
+
io.write (···)
+Equivalent to io.output():write.
+
+
+
+
+
+
file:close ()
+Closes file.
+Note that files are automatically closed when
+their handles are garbage collected,
+but that takes an unpredictable amount of time to happen.
+
+
+
+
+
+
file:flush ()
+Saves any written data to file.
+
+
+
+
+
+
file:lines ()+Returns an iterator function that, +each time it is called, +returns a new line from the file. +Therefore, the construction + +
+ for line in file:lines() do body end +
+will iterate over all lines of the file.
+(Unlike io.lines, this function does not close the file
+when the loop ends.)
+
+
+
+
+
+
file:read (···)
+Reads the file file,
+according to the given formats, which specify what to read.
+For each format,
+the function returns a string (or a number) with the characters read,
+or nil if it cannot read data with the specified format.
+When called without formats,
+it uses a default format that reads the entire next line
+(see below).
+
+
+
+The available formats are + +
+
file:seek ([whence] [, offset])
+Sets and gets the file position,
+measured from the beginning of the file,
+to the position given by offset plus a base
+specified by the string whence, as follows:
+
+
+In case of success, function seek returns the final file position,
+measured in bytes from the beginning of the file.
+If this function fails, it returns nil,
+plus a string describing the error.
+
+
+
+The default value for whence is "cur",
+and for offset is 0.
+Therefore, the call file:seek() returns the current
+file position, without changing it;
+the call file:seek("set") sets the position to the
+beginning of the file (and returns 0);
+and the call file:seek("end") sets the position to the
+end of the file, and returns its size.
+
+
+
+
+
+
file:setvbuf (mode [, size])+Sets the buffering mode for an output file. +There are three available modes: + +
flush the file
+(see io.flush)).
+
+For the last two cases, size
+specifies the size of the buffer, in bytes.
+The default is an appropriate size.
+
+
+
+
+
+
file:write (···)
+Writes the value of each of its arguments to
+the file.
+The arguments must be strings or numbers.
+To write other values,
+use tostring or string.format before write.
+
+
+
+
+
+
+
+
+This library is implemented through table os.
+
+
+
+
os.clock ()+Returns an approximation of the amount in seconds of CPU time +used by the program. + + + + +
+
os.date ([format [, time]])
+Returns a string or a table containing date and time,
+formatted according to the given string format.
+
+
+
+If the time argument is present,
+this is the time to be formatted
+(see the os.time function for a description of this value).
+Otherwise, date formats the current time.
+
+
+
+If format starts with '!',
+then the date is formatted in Coordinated Universal Time.
+After this optional character,
+if format is the string "*t",
+then date returns a table with the following fields:
+year (four digits), month (1--12), day (1--31),
+hour (0--23), min (0--59), sec (0--61),
+wday (weekday, Sunday is 1),
+yday (day of the year),
+and isdst (daylight saving flag, a boolean).
+
+
+
+If format is not "*t",
+then date returns the date as a string,
+formatted according to the same rules as the C function strftime.
+
+
+
+When called without arguments,
+date returns a reasonable date and time representation that depends on
+the host system and on the current locale
+(that is, os.date() is equivalent to os.date("%c")).
+
+
+
+
+
+
os.difftime (t2, t1)
+Returns the number of seconds from time t1 to time t2.
+In POSIX, Windows, and some other systems,
+this value is exactly t2-t1.
+
+
+
+
+
+
os.execute ([command])
+This function is equivalent to the C function system.
+It passes command to be executed by an operating system shell.
+It returns a status code, which is system-dependent.
+If command is absent, then it returns nonzero if a shell is available
+and zero otherwise.
+
+
+
+
+
+
os.exit ([code])
+Calls the C function exit,
+with an optional code,
+to terminate the host program.
+The default value for code is the success code.
+
+
+
+
+
+
os.getenv (varname)
+Returns the value of the process environment variable varname,
+or nil if the variable is not defined.
+
+
+
+
+
+
os.remove (filename)+Deletes the file or directory with the given name. +Directories must be empty to be removed. +If this function fails, it returns nil, +plus a string describing the error. + + + + +
+
os.rename (oldname, newname)
+Renames file or directory named oldname to newname.
+If this function fails, it returns nil,
+plus a string describing the error.
+
+
+
+
+
+
os.setlocale (locale [, category])
+Sets the current locale of the program.
+locale is a string specifying a locale;
+category is an optional string describing which category to change:
+"all", "collate", "ctype",
+"monetary", "numeric", or "time";
+the default category is "all".
+The function returns the name of the new locale,
+or nil if the request cannot be honored.
+
+
+
+If locale is the empty string,
+the current locale is set to an implementation-defined native locale.
+If locale is the string "C",
+the current locale is set to the standard C locale.
+
+
+
+When called with nil as the first argument, +this function only returns the name of the current locale +for the given category. + + + + +
+
os.time ([table])
+Returns the current time when called without arguments,
+or a time representing the date and time specified by the given table.
+This table must have fields year, month, and day,
+and may have fields hour, min, sec, and isdst
+(for a description of these fields, see the os.date function).
+
+
+
+The returned value is a number, whose meaning depends on your system.
+In POSIX, Windows, and some other systems, this number counts the number
+of seconds since some given start time (the "epoch").
+In other systems, the meaning is not specified,
+and the number returned by time can be used only as an argument to
+date and difftime.
+
+
+
+
+
+
os.tmpname ()+Returns a string with a file name that can +be used for a temporary file. +The file must be explicitly opened before its use +and explicitly removed when no longer needed. + + +
+On some systems (POSIX), +this function also creates a file with that name, +to avoid security risks. +(Someone else might create the file with wrong permissions +in the time between getting the name and creating the file.) +You still have to open the file to use it +and to remove it (even if you do not use it). + + +
+When possible,
+you may prefer to use io.tmpfile,
+which automatically removes the file when the program ends.
+
+
+
+
+
+
+
+
+This library provides +the functionality of the debug interface to Lua programs. +You should exert care when using this library. +The functions provided here should be used exclusively for debugging +and similar tasks, such as profiling. +Please resist the temptation to use them as a +usual programming tool: +they can be very slow. +Moreover, several of these functions +violate some assumptions about Lua code +(e.g., that variables local to a function +cannot be accessed from outside or +that userdata metatables cannot be changed by Lua code) +and therefore can compromise otherwise secure code. + + +
+All functions in this library are provided
+inside the debug table.
+All functions that operate over a thread
+have an optional first argument which is the
+thread to operate over.
+The default is always the current thread.
+
+
+
+
debug.debug ()
+Enters an interactive mode with the user,
+running each string that the user enters.
+Using simple commands and other debug facilities,
+the user can inspect global and local variables,
+change their values, evaluate expressions, and so on.
+A line containing only the word cont finishes this function,
+so that the caller continues its execution.
+
+
+
+Note that commands for debug.debug are not lexically nested
+within any function, and so have no direct access to local variables.
+
+
+
+
+
+
debug.getfenv (o)o.
+
+
+
+
++
debug.gethook ([thread])
+Returns the current hook settings of the thread, as three values:
+the current hook function, the current hook mask,
+and the current hook count
+(as set by the debug.sethook function).
+
+
+
+
+
+
debug.getinfo ([thread,] function [, what])
+Returns a table with information about a function.
+You can give the function directly,
+or you can give a number as the value of function,
+which means the function running at level function of the call stack
+of the given thread:
+level 0 is the current function (getinfo itself);
+level 1 is the function that called getinfo;
+and so on.
+If function is a number larger than the number of active functions,
+then getinfo returns nil.
+
+
+
+The returned table can contain all the fields returned by lua_getinfo,
+with the string what describing which fields to fill in.
+The default for what is to get all information available,
+except the table of valid lines.
+If present,
+the option 'f'
+adds a field named func with the function itself.
+If present,
+the option 'L'
+adds a field named activelines with the table of
+valid lines.
+
+
+
+For instance, the expression debug.getinfo(1,"n").name returns
+a table with a name for the current function,
+if a reasonable name can be found,
+and the expression debug.getinfo(print)
+returns a table with all available information
+about the print function.
+
+
+
+
+
+
debug.getlocal ([thread,] level, local)
+This function returns the name and the value of the local variable
+with index local of the function at level level of the stack.
+(The first parameter or local variable has index 1, and so on,
+until the last active local variable.)
+The function returns nil if there is no local
+variable with the given index,
+and raises an error when called with a level out of range.
+(You can call debug.getinfo to check whether the level is valid.)
+
+
+
+Variable names starting with '(' (open parentheses)
+represent internal variables
+(loop control variables, temporaries, and C function locals).
+
+
+
+
+
+
debug.getmetatable (object)
+Returns the metatable of the given object
+or nil if it does not have a metatable.
+
+
+
+
+
+
debug.getregistry ()+Returns the registry table (see §3.5). + + + + +
+
debug.getupvalue (func, up)
+This function returns the name and the value of the upvalue
+with index up of the function func.
+The function returns nil if there is no upvalue with the given index.
+
+
+
+
+
+
debug.setfenv (object, table)
+Sets the environment of the given object to the given table.
+Returns object.
+
+
+
+
+
+
debug.sethook ([thread,] hook, mask [, count])
+Sets the given function as a hook.
+The string mask and the number count describe
+when the hook will be called.
+The string mask may have the following characters,
+with the given meaning:
+
+
"c": the hook is called every time Lua calls a function;"r": the hook is called every time Lua returns from a function;"l": the hook is called every time Lua enters a new line of code.
+With a count different from zero,
+the hook is called after every count instructions.
+
+
+
+When called without arguments,
+debug.sethook turns off the hook.
+
+
+
+When the hook is called, its first parameter is a string
+describing the event that has triggered its call:
+"call", "return" (or "tail return",
+when simulating a return from a tail call),
+"line", and "count".
+For line events,
+the hook also gets the new line number as its second parameter.
+Inside a hook,
+you can call getinfo with level 2 to get more information about
+the running function
+(level 0 is the getinfo function,
+and level 1 is the hook function),
+unless the event is "tail return".
+In this case, Lua is only simulating the return,
+and a call to getinfo will return invalid data.
+
+
+
+
+
+
debug.setlocal ([thread,] level, local, value)
+This function assigns the value value to the local variable
+with index local of the function at level level of the stack.
+The function returns nil if there is no local
+variable with the given index,
+and raises an error when called with a level out of range.
+(You can call getinfo to check whether the level is valid.)
+Otherwise, it returns the name of the local variable.
+
+
+
+
+
+
debug.setmetatable (object, table)
+Sets the metatable for the given object to the given table
+(which can be nil).
+
+
+
+
+
+
debug.setupvalue (func, up, value)
+This function assigns the value value to the upvalue
+with index up of the function func.
+The function returns nil if there is no upvalue
+with the given index.
+Otherwise, it returns the name of the upvalue.
+
+
+
+
+
+
debug.traceback ([thread,] [message] [, level])
+Returns a string with a traceback of the call stack.
+An optional message string is appended
+at the beginning of the traceback.
+An optional level number tells at which level
+to start the traceback
+(default is 1, the function calling traceback).
+
+
+
+
+
+
+
+
+Although Lua has been designed as an extension language,
+to be embedded in a host C program,
+it is also frequently used as a stand-alone language.
+An interpreter for Lua as a stand-alone language,
+called simply lua,
+is provided with the standard distribution.
+The stand-alone interpreter includes
+all standard libraries, including the debug library.
+Its usage is:
+
+
+ lua [options] [script [args]] +
+The options are: + +
-e stat: executes string stat;-l mod: "requires" mod;-i: enters interactive mode after running script;-v: prints version information;--: stops handling options;-: executes stdin as a file and stops handling options.
+After handling its options, lua runs the given script,
+passing to it the given args as string arguments.
+When called without arguments,
+lua behaves as lua -v -i
+when the standard input (stdin) is a terminal,
+and as lua - otherwise.
+
+
+
+Before running any argument,
+the interpreter checks for an environment variable LUA_INIT.
+If its format is @filename,
+then lua executes the file.
+Otherwise, lua executes the string itself.
+
+
+
+All options are handled in order, except -i.
+For instance, an invocation like
+
+
+ $ lua -e'a=1' -e 'print(a)' script.lua +
+will first set a to 1, then print the value of a (which is '1'),
+and finally run the file script.lua with no arguments.
+(Here $ is the shell prompt. Your prompt may be different.)
+
+
+
+Before starting to run the script,
+lua collects all arguments in the command line
+in a global table called arg.
+The script name is stored at index 0,
+the first argument after the script name goes to index 1,
+and so on.
+Any arguments before the script name
+(that is, the interpreter name plus the options)
+go to negative indices.
+For instance, in the call
+
+
+ $ lua -la b.lua t1 t2 +
+the interpreter first runs the file a.lua,
+then creates a table
+
+
+ arg = { [-2] = "lua", [-1] = "-la",
+ [0] = "b.lua",
+ [1] = "t1", [2] = "t2" }
+
+and finally runs the file b.lua.
+The script is called with arg[1], arg[2], ···
+as arguments;
+it can also access these arguments with the vararg expression '...'.
+
+
+
+In interactive mode, +if you write an incomplete statement, +the interpreter waits for its completion +by issuing a different prompt. + + +
+If the global variable _PROMPT contains a string,
+then its value is used as the prompt.
+Similarly, if the global variable _PROMPT2 contains a string,
+its value is used as the secondary prompt
+(issued during incomplete statements).
+Therefore, both prompts can be changed directly on the command line
+or in any Lua programs by assigning to _PROMPT.
+See the next example:
+
+
+ $ lua -e"_PROMPT='myprompt> '" -i +
+(The outer pair of quotes is for the shell,
+the inner pair is for Lua.)
+Note the use of -i to enter interactive mode;
+otherwise,
+the program would just end silently
+right after the assignment to _PROMPT.
+
+
+
+To allow the use of Lua as a
+script interpreter in Unix systems,
+the stand-alone interpreter skips
+the first line of a chunk if it starts with #.
+Therefore, Lua scripts can be made into executable programs
+by using chmod +x and the #! form,
+as in
+
+
+ #!/usr/local/bin/lua +
+(Of course,
+the location of the Lua interpreter may be different in your machine.
+If lua is in your PATH,
+then
+
+
+ #!/usr/bin/env lua +
+is a more portable solution.) + + + +
+Here we list the incompatibilities that you may find when moving a program
+from Lua 5.0 to Lua 5.1.
+You can avoid most of the incompatibilities compiling Lua with
+appropriate options (see file luaconf.h).
+However,
+all these compatibility options will be removed in the next version of Lua.
+
+
+
+
arg with a
+table with the extra arguments to the vararg expression.
+(See compile-time option LUA_COMPAT_VARARG in luaconf.h.)
+[[string]])
+does not allow nesting.
+You can use the new syntax ([=[string]=]) in these cases.
+(See compile-time option LUA_COMPAT_LSTR in luaconf.h.)
+string.gfind was renamed string.gmatch.
+(See compile-time option LUA_COMPAT_GFIND in luaconf.h.)
+string.gsub is called with a function as its
+third argument,
+whenever this function returns nil or false the
+replacement string is the whole match,
+instead of the empty string.
+table.setn was deprecated.
+Function table.getn corresponds
+to the new length operator (#);
+use the operator instead of the function.
+(See compile-time option LUA_COMPAT_GETN in luaconf.h.)
+loadlib was renamed package.loadlib.
+(See compile-time option LUA_COMPAT_LOADLIB in luaconf.h.)
+math.mod was renamed math.fmod.
+(See compile-time option LUA_COMPAT_MOD in luaconf.h.)
+table.foreach and table.foreachi are deprecated.
+You can use a for loop with pairs or ipairs instead.
+require due to
+the new module system.
+However, the new behavior is mostly compatible with the old,
+but require gets the path from package.path instead
+of from LUA_PATH.
+collectgarbage has different arguments.
+Function gcinfo is deprecated;
+use collectgarbage("count") instead.
+luaopen_* functions (to open libraries)
+cannot be called directly,
+like a regular C function.
+They must be called through Lua,
+like a Lua function.
+lua_open was replaced by lua_newstate to
+allow the user to set a memory-allocation function.
+You can use luaL_newstate from the standard library to
+create a state with a standard allocation function
+(based on realloc).
+luaL_getn and luaL_setn
+(from the auxiliary library) are deprecated.
+Use lua_objlen instead of luaL_getn
+and nothing instead of luaL_setn.
+luaL_openlib was replaced by luaL_register.
+luaL_checkudata now throws an error when the given value
+is not a userdata of the expected type.
+(In Lua 5.0 it returned NULL.)
++Here is the complete syntax of Lua in extended BNF. +(It does not describe operator precedences.) + + + + +
+
+ chunk ::= {stat [`;´]} [laststat [`;´]]
+
+ block ::= chunk
+
+ stat ::= varlist `=´ explist |
+ functioncall |
+ do block end |
+ while exp do block end |
+ repeat block until exp |
+ if exp then block {elseif exp then block} [else block] end |
+ for Name `=´ exp `,´ exp [`,´ exp] do block end |
+ for namelist in explist do block end |
+ function funcname funcbody |
+ local function Name funcbody |
+ local namelist [`=´ explist]
+
+ laststat ::= return [explist] | break
+
+ funcname ::= Name {`.´ Name} [`:´ Name]
+
+ varlist ::= var {`,´ var}
+
+ var ::= Name | prefixexp `[´ exp `]´ | prefixexp `.´ Name
+
+ namelist ::= Name {`,´ Name}
+
+ explist ::= {exp `,´} exp
+
+ exp ::= nil | false | true | Number | String | `...´ | function |
+ prefixexp | tableconstructor | exp binop exp | unop exp
+
+ prefixexp ::= var | functioncall | `(´ exp `)´
+
+ functioncall ::= prefixexp args | prefixexp `:´ Name args
+
+ args ::= `(´ [explist] `)´ | tableconstructor | String
+
+ function ::= function funcbody
+
+ funcbody ::= `(´ [parlist] `)´ block end
+
+ parlist ::= namelist [`,´ `...´] | `...´
+
+ tableconstructor ::= `{´ [fieldlist] `}´
+
+ fieldlist ::= field {fieldsep field} [fieldsep]
+
+ field ::= `[´ exp `]´ `=´ exp | Name `=´ exp | exp
+
+ fieldsep ::= `,´ | `;´
+
+ binop ::= `+´ | `-´ | `*´ | `/´ | `^´ | `%´ | `..´ |
+ `<´ | `<=´ | `>´ | `>=´ | `==´ | `~=´ |
+ and | or
+
+ unop ::= `-´ | not | `#´
+
+
+
++ + + + + + + +
+Documentation
++ +