-Lua 5.1 Reference Manual
-
-Lua 5.1 Reference Manual
-- -Copyright © 2006-2007 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 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 may 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 may contain any 8-bit value, including embedded zeros,
-which can be specified as '\0'.
-
-
-
-To put a double (single) quote, a newline, a backslash, -or an embedded zero -inside a literal string enclosed by double (single) quotes -you must use an escape sequence. -Any other character may be directly inserted into the literal. -(Some control characters may cause problems for the file system, -but Lua has no problem with them.) - - -
-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 may run for several lines,
-do not interpret any escape sequences,
-and ignore long brackets of any other level.
-They may 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 literals below denote the same string:
-
-
- a = 'alo\n123"' - a = "alo\n123\"" - a = '\97lo\10\04923"' - a = [[alo - 123"]] - a = [==[ - alo - 123"]==] -- -
-A numerical constant may 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 may 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 may 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 may contain functions. -Thus tables may 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 -assignment, 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 may be stored in a file or in a string inside the host program. -When a chunk is executed, first it is pre-compiled into instructions for -a virtual machine, -and then the compiled code is executed -by an interpreter for the virtual machine. - - -
-Chunks may 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 may 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 assignment. -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 ::= varlist1 `=´ explist1
- varlist1 ::= var {`,´ var}
- explist1 ::= 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 this call enter in 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.
-
-
-
-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 may 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 may return more than one value, -so the syntax for the return statement is - -
- stat ::= return [explist1] -- -
-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 are here 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 explist1 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 may be declared anywhere inside a block. -The declaration may include an initial assignment: - -
- stat ::= local namelist [`=´ explist1] -
-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 may result in multiple values. -If the expression is used as a statement (see §2.4.6) -(only possible for function calls), -then its return list is adjusted to zero elements, -thus discarding all returned values. -If the 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 may 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
-
-
-
-An 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). - - - - - -
-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 may 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 may 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. -Constructors can be used to create empty tables, -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 may 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 ::= `(´ [explist1] `)´ - 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 ::= `(´ [parlist1] `)´ 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 -may refer to different external local variables -and may have different environment tables. - - -
-Parameters act as local variables that are -initialized with the argument values: - -
- parlist1 ::= 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 the call 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 may 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 using the debug library);
-you must use the C API for that.
-
-
-
-Tables and userdata have individual metatables -(although multiple tables and userdata can share their metatables); -values of all other types share one single metatable per type. -So, there is one single metatable for all numbers, -and for all strings, etc. - - -
-A metatable may control how an object behaves in arithmetic operations, -order comparisons, concatenation, length operation, and indexing. -A metatable can also 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 - return 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. - - -
-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 their threads and
-non-nested functions created by the thread
-(through loadfile, loadstring or load)
-and can be directly accessed by C code (see §3.3).
-
-
-
-Environments associated with C functions can be directly -accessed by C code (see §3.3). -They are used as the default environment for other C functions -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 other 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, these objects that are no longer accessible from Lua). -All objects in Lua are subject to automatic management: -tables, userdata, functions, threads, and strings. - - -
-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. - - -
-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 1 mean the collector will not wait to -start a new cycle. -A value of 2 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 1 make the collector too slow and -may result in the collector never finishing a cycle. -The default, 2, 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.
-Both get percentage points as arguments
-(so an argument of 100 means a real value of 1).
-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. - - - - - -
-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 field __mode.
-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
-the 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,
-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.
-
-
-
-Almost any function in the API may raise an error,
-for instance due to a memory allocation error.
-The following functions run in protected mode
-(that is, they create a protected environment to run),
-so they never raise an error:
-lua_newstate, lua_close, lua_load,
-lua_pcall, and lua_cpcall.
-
-
-
-Inside a C function you can raise an error by calling lua_error.
-
-
-
-
-
-
-Here we list all functions and types from the C API in -alphabetical order. - - - -
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_atpaniclua_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 may 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_callvoid 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 may 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_checkstackint 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_closevoid 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_concatvoid 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 string on the stack
-(that is, the function does nothing);
-if n is 0, the result is the empty string.
-Concatenation is done following the usual semantics of Lua
-(see §2.5.4).
-
-
-
-
-
-
lua_cpcallint 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_createtablevoid 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_dumpint 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_equalint 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_errorint 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_gcint 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/100 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/100 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_getallocflua_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_getfenvvoid lua_getfenv (lua_State *L, int index);- -
-Pushes onto the stack the environment table of -the value at the given index. - - - - - -
lua_getfieldvoid 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 index.
-As in Lua, this function may trigger a metamethod
-for the "index" event (see §2.8).
-
-
-
-
-
-
lua_getglobalvoid 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_getmetatableint 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_gettablevoid 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 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_gettopint 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_insertvoid 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_isbooleanint lua_isboolean (lua_State *L, int index);- -
-Returns 1 if the value at the given acceptable index has type boolean, -and 0 otherwise. - - - - - -
lua_iscfunctionint 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_isfunctionint 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_islightuserdataint 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_isnilint lua_isnil (lua_State *L, int index);- -
-Returns 1 if the value at the given acceptable index is nil, -and 0 otherwise. - - - - - -
lua_isnoneint lua_isnone (lua_State *L, int index);- -
-Returns 1 if the the given acceptable index is not valid -(that is, it refers to an element outside the current stack), -and 0 otherwise. - - - - - -
lua_isnoneornilint lua_isnoneornil (lua_State *L, int index);- -
-Returns 1 if the 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_isnumberint 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_isstringint 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_istableint lua_istable (lua_State *L, int index);- -
-Returns 1 if the value at the given acceptable index is a table, -and 0 otherwise. - - - - - -
lua_isthreadint lua_isthread (lua_State *L, int index);- -
-Returns 1 if the value at the given acceptable index is a thread, -and 0 otherwise. - - - - - -
lua_isuserdataint 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_lessthanint 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_loadint 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_newstatelua_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_newtablevoid 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_newthreadlua_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_newuserdatavoid *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_nextint 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_objlensize_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_pcallint 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_popvoid lua_pop (lua_State *L, int n);- -
-Pops n elements from the stack.
-
-
-
-
-
-
lua_pushbooleanvoid lua_pushboolean (lua_State *L, int b);- -
-Pushes a boolean value with value b onto the stack.
-
-
-
-
-
-
lua_pushcclosurevoid 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.
-
-
-
-
-
-
lua_pushcfunctionvoid 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_pushfstringconst 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_pushintegervoid lua_pushinteger (lua_State *L, lua_Integer n);- -
-Pushes a number with value n onto the stack.
-
-
-
-
-
-
lua_pushlightuserdatavoid 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_pushlstringvoid 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_pushnilvoid lua_pushnil (lua_State *L);- -
-Pushes a nil value onto the stack. - - - - - -
lua_pushnumbervoid lua_pushnumber (lua_State *L, lua_Number n);- -
-Pushes a number with value n onto the stack.
-
-
-
-
-
-
lua_pushstringvoid 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_pushthreadint 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_pushvaluevoid lua_pushvalue (lua_State *L, int index);- -
-Pushes a copy of the element at the given valid index -onto the stack. - - - - - -
lua_pushvfstringconst 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_rawequalint 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_rawgetvoid lua_rawget (lua_State *L, int index);- -
-Similar to lua_gettable, but does a raw access
-(i.e., without metamethods).
-
-
-
-
-
-
lua_rawgetivoid 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 index.
-The access is raw;
-that is, it does not invoke metamethods.
-
-
-
-
-
-
lua_rawsetvoid lua_rawset (lua_State *L, int index);- -
-Similar to lua_settable, but does a raw assignment
-(i.e., without metamethods).
-
-
-
-
-
-
lua_rawsetivoid 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 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.
-The reader function may return pieces of any size greater than zero.
-
-
-
-
-
-
lua_registervoid 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_removevoid 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_replacevoid 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_resumeint 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_setallocfvoid 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_setfenvint 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_setfieldvoid 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 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_setglobalvoid 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_setmetatableint 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_settablevoid lua_settable (lua_State *L, int index);- -
-Does the equivalent to t[k] = v,
-where t is the value at the given valid index 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_settopvoid 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_statusint 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_tobooleanint 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_tocfunctionlua_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_tointegerlua_Integer lua_tointeger (lua_State *L, int idx);- -
-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_tolstringconst 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 may 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_tonumberlua_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_topointerconst void *lua_topointer (lua_State *L, int index);- -
-Converts the value at the given acceptable index to a generic
-C pointer (void*).
-The value may 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_tostringconst char *lua_tostring (lua_State *L, int index);- -
-Equivalent to lua_tolstring with len equal to NULL.
-
-
-
-
-
-
lua_tothreadlua_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_touserdatavoid *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_typeint 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_typenameconst 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 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_xmovevoid 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_yieldint 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 may be the value of multiple global variables,
-while others may 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_gethooklua_Hook lua_gethook (lua_State *L);- -
-Returns the current hook function. - - - - - -
lua_gethookcountint lua_gethookcount (lua_State *L);- -
-Returns the current hook count. - - - - - -
lua_gethookmaskint lua_gethookmask (lua_State *L);- -
-Returns the current hook mask. - - - - - -
lua_getinfoint 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_getlocalconst 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_getstackint 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_getupvalueconst 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 may 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_sethookint 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_setlocalconst 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_setupvalueconst 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 raise 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_addcharvoid luaL_addchar (luaL_Buffer *B, char c);- -
-Adds the character c to the buffer B
-(see luaL_Buffer).
-
-
-
-
-
-
luaL_addlstringvoid 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_addsizevoid 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_addstringvoid 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_addvaluevoid 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_argcheckvoid 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_argerrorint 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_buffinitvoid 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_callmetaint 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_checkanyvoid luaL_checkany (lua_State *L, int narg);- -
-Checks whether the function has an argument
-of any type (including nil) at position narg.
-
-
-
-
-
-
luaL_checkintint 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_checkintegerlua_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_checklonglong 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_checklstringconst 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.
-
-
-
-
-
-
luaL_checknumberlua_Number luaL_checknumber (lua_State *L, int narg);- -
-Checks whether the function argument narg is a number
-and returns this number.
-
-
-
-
-
-
luaL_checkoptionint 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_checkstackvoid 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_checkstringconst char *luaL_checkstring (lua_State *L, int narg);- -
-Checks whether the function argument narg is a string
-and returns this string.
-
-
-
-
-
-
luaL_checktypevoid luaL_checktype (lua_State *L, int narg, int t);- -
-Checks whether the function argument narg has type t.
-
-
-
-
-
-
luaL_checkudatavoid *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_dofileint 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_dostringint 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_errorint 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_getmetafieldint 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_getmetatablevoid 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_gsubconst 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_loadbufferint 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_loadfileint 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_loadstringint 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_newmetatableint 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_newstatelua_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_openlibsvoid luaL_openlibs (lua_State *L);- -
-Opens all standard Lua libraries into the given state. - - - - - -
luaL_optintint 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_optintegerlua_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_optlonglong 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_optlstringconst 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_optnumberlua_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_optstringconst 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_prepbufferchar *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_pushresultvoid luaL_pushresult (luaL_Buffer *B);- -
-Finishes the use of buffer B leaving the final string on
-the top of the stack.
-
-
-
-
-
-
luaL_refint 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_registervoid 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_typenameconst char *luaL_typename (lua_State *L, int idx);- -
-Returns the name of the type of the value at index idx.
-
-
-
-
-
-
luaL_typerrorint 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_unrefvoid 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_wherevoid 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., 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 and the Operating System libraries),
-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/100 as the new value for the pause of
-the collector (see §2.10).
-arg/100 as the new value for the step multiplier of
-the collector (see §2.10).
--
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 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.
-
-
-
-
-
-
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))() -- - - -
-
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 may 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 may 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,
-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 below).
-
-
-
-When loading a C library,
-require first uses a dynamic link facility to link the
-application with the library.
-Then it tries to find a C function inside this 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.
-
-
-
-If require finds neither a Lua library nor a
-C library for a module,
-it calls the all-in-one loader.
-This loader 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.
-
-
-
-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
-(plus another 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.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.
-
-
-
-A path is a sequence of templates separated by semicolons.
-For each template, require will change each interrogation
-mark in the template by filename,
-which is modname with each dot replaced by a
-"directory separator" (such as "/" in Unix);
-then it will try to load the resulting file name.
-So, for instance, if the Lua path is
-
-
- "./?.lua;./?.lc;/usr/local/?/init.lua" -
-the search for a Lua loader for module foo
-will try to load the files
-./foo.lua, ./foo.lc, and
-/usr/local/foo/init.lua, in that order.
-
-
-
-
-
-
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).
-
-
-
-
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 may 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 occurrences of the pattern have been
-replaced by a replacement string specified by repl,
-which may be a string, a table, or a function.
-gsub also returns, as its second value,
-the total number of substitutions made.
-
-
-
-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). - - -
-The optional last parameter n limits
-the maximum number of substitutions to occur.
-For instance, when n is 1 only the first occurrence of
-pattern is replaced.
-
-
-
-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", "%$(%w+)", t)
- --> x="lua-5.1.tar.gz"
-
-
-
-
--
string.len (s)"" has length 0.
-Embedded zeros are counted,
-so "a\000bc\000" has length 5.
-
-
-
-
--
string.lower (s)-
string.match (s, pattern [, init])pattern in the string s.
-If it finds one, then match returns
-the captures from the pattern;
-otherwise it returns nil.
-If pattern specifies no captures,
-then the whole match is returned.
-A third, optional numerical argument init specifies
-where to start the search;
-its default value is 1 and may be negative.
-
-
-
-
--
string.rep (s, n)n copies of
-the string s.
-
-
-
-
--
string.reverse (s)s reversed.
-
-
-
-
--
string.sub (s, i [, j])s that
-starts at i and continues until j;
-i and j may be negative.
-If j is absent, then it is assumed to be equal to -1
-(which is the same as the string length).
-In particular,
-the call string.sub(s,1,j) returns a prefix of s
-with length j,
-and string.sub(s, -i) returns a suffix of s
-with length i.
-
-
-
-
--
string.upper (s)-A character class is used to represent a set of characters. -The following combinations are allowed in describing a character class: - -
^$()%.[]*+-?)
-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 may be specified by
-separating the end characters of the range with a '-'.
-All classes %x described above may 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 may 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 may 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 (x, y)
-Returns the arc tangent of x/y (in radians),
-but uses the signs of both parameters to find the
-quadrant of the result.
-(It also handles correctly the case of y 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 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.
-
-
-
-
-
-
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 pseudo-random real number
-in the range [0,1).
-When called with a number m,
-math.random returns
-a pseudo-random integer in the range [1, m].
-When called with two numbers m and n,
-math.random returns a 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.
-
-
-
-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 may 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 locate is set to an implementation-defined native locale.
-If locate is the string "C",
-the current locate 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. - - - - - - - -
-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 its 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 may 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 name of 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"),
-"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.
-For instance,
-
-
- $ lua -e"_PROMPT='myprompt> '" -i -
-(the outer pair of quotes is for the shell,
-the inner pair is for Lua),
-or in any Lua programs by assigning to _PROMPT.
-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 found 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 ::= varlist1 `=´ explist1 |
- 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 explist1 do block end |
- function funcname funcbody |
- local function Name funcbody |
- local namelist [`=´ explist1]
-
- laststat ::= return [explist1] | break
-
- funcname ::= Name {`.´ Name} [`:´ Name]
-
- varlist1 ::= var {`,´ var}
-
- var ::= Name | prefixexp `[´ exp `]´ | prefixexp `.´ Name
-
- namelist ::= Name {`,´ Name}
-
- explist1 ::= {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 ::= `(´ [explist1] `)´ | tableconstructor | String
-
- function ::= function funcbody
-
- funcbody ::= `(´ [parlist1] `)´ block end
-
- parlist1 ::= namelist [`,´ `...´] | `...´
-
- tableconstructor ::= `{´ [fieldlist] `}´
-
- fieldlist ::= field {fieldsep field} [fieldsep]
-
- field ::= `[´ exp `]´ `=´ exp | Name `=´ exp | exp
-
- fieldsep ::= `,´ | `;´
-
- binop ::= `+´ | `-´ | `*´ | `/´ | `^´ | `%´ | `..´ |
- `<´ | `<=´ | `>´ | `>=´ | `==´ | `~=´ |
- and | or
-
- unop ::= `-´ | not | `#´
-
-
-
-- - - - - - -