Lua reference manual/Standard libraries
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The standard Lua libraries provide essential services and performancecritical functions to Lua. Only those portions of the standard libraries that are available in Scribunto are documented here.
Basic functions
_G
This variable holds a reference to the current global variable table; the global variable foo
may also be accessed as _G.foo
. Note, however, that there is nothing special about _G itself; it may be reassigned in the same manner as any other variable:
foo = 1 mw.log( foo )  logs "1" _G.foo = 2 mw.log( foo )  logs "2" _G = {}  _G no longer points to the global variable table _G.foo = 3 mw.log( foo )  still logs "2"
The global variable table may be used just like any other table. For example,
 Call a function whose name is stored in a variable _G[var]()
 Log the names and stringified values of all global variables for k, v in pairs( _G ) do mw.log( k, v ) end
 Log the creation of new global variables setmetatable( _G, { __newindex = function ( t, k, v ) mw.log( "Creation of new global variable '" .. k .. "'" ) rawset( t, k, v ) end } )
_VERSION
A string containing the running version of Lua, e.g. "Lua 5.1".
assert
assert( v, message, ... )
If v
is nil or false, issues an error. In this case, message
is used as the text of the error: if nil (or unspecified), the text is "assertion failed!"; if a string or number, the text is that value; otherwise assert itself will raise an error.
If v
is any other value, assert returns all arguments including v
and message
.
A somewhat common idiom in Lua is for a function to return a "true" value in normal operation, and on failure return nil or false as the first value and an error message as the second value. Easy error checking can then be implemented by wrapping the call in a call to assert
:
 This doesn't check for errors local result1, result2, etc = func( ... )  This works the same, but does check for errors local result1, result2, etc = assert( func( ... ) )
error
error( message, level )
Issues an error, with text message
.
error
normally adds some information about the location of the error. If level
is 1 or omitted, that information is the location of the call to error
itself; 2 uses the location of the call of the function that called error; and so on. Passing 0 omits inclusion of the location information.
getfenv
getfenv( f )
Note this function may not be available, depending on allowEnvFuncs
in the engine configuration.
Returns an environment (global variable table), as specified by f
:
 If 1, nil, or omitted, returns the environment of the function calling
getfenv
. Often this will be the same as_G
.  Integers 2–10 return the environment of functions higher in the call stack. For example, 2 returns the environment for the function that called the current function, 3 returns the environment for the function calling that function, and so on. An error will be raised if the value is higher than the number of function calls in the stack, or if the targeted stack level returned with a tail call.
 Passing a function returns the environment that will be used when that function is called.
The environments used by all standard library functions and Scribunto library functions are protected. Attempting to access these environments using getfenv
will return nil instead.
getmetatable
getmetatable( table )
Returns the metatable of a table. Any other type will return nil.
If the metatable has a __metatable
field, that value will be returned instead of the actual metatable.
ipairs
ipairs( t )
Returns three values: an iterator function, the table t
, and 0. This is intended for use in the iterator form of for
:
for i, v in ipairs( t ) do  block end
This will iterate over the pairs ( 1, t[1] ), ( 2, t[2] ), and so on, stopping when t[i] would be nil.
The standard behavior may be overridden by providing an __ipairs
metamethod. If that metamethod exists, the call to ipairs will return the three values returned by __ipairs( t )
instead.
next
next( table, key )
This allows for iterating over the keys in a table. If key
is nil or unspecified, returns the "first" key in the table and its value; otherwise, it returns the "next" key and its value. When no more keys are available, returns nil. It is possible to check whether a table is empty using the expression next( t ) == nil
.
Note that the order in which the keys are returned is not specified, even for tables with numeric indexes. To traverse a table in numerical order, use a numerical for or ipairs.
Behavior is undefined if, when using next for traversal, any nonexisting key is assigned a value. Assigning a new value (including nil) to an existing field is allowed.
pairs
pairs( t )
Returns three values: an iterator function (next
or a workalike), the table t
, and nil
. This is intended for use in the iterator form of for
:
for k, v in pairs( t ) do  block end
This will iterate over the keyvalue pairs in t
just as next
would; see the documentation for next
for restrictions on modifying the table during traversal.
The standard behavior may be overridden by providing a __pairs
metamethod. If that metamethod exists, the call to pairs will return the three values returned by __pairs( t )
instead.
pcall
pcall( f, ... )
Calls the function f
with the given arguments in protected mode. This means that if an error is raised during the call to f
, pcall will return false and the error message raised. If no error occurs, pcall will return true and all values returned by the call.
In pseudocode, pcall
might be defined something like this:
function pcall( f, ... ) try return true, f( ... ) catch ( message ) return false, message end end
rawequal
rawequal( a, b )
This is equivalent to a == b
except that it ignores any __eq
metamethod.
rawget
rawget( table, k )
This is equivalent to table[k]
except that it ignores any __index
metamethod.
rawset
rawset( table, k, v )
This is equivalent to table[k] = v
except that it ignores any __newindex
metamethod.
select
select( index, ... )
If index
is a number, returns all arguments in ...
after that index. If index
is the string '#'
, returns the count of arguments in ...
.
In other words, select
is something roughly like the following except that it will work correctly even when ...
contains nil values (see documentation for #
and unpack
for the problem with nil
s).
function select( index, ... ) local t = { ... } if index == '#' then return #t else return unpack( t, index ) end end
Negative numbers count from the end of the table, e.g.:
local secondToLast, last = select(2, "one", "two", "three", "four") mw.log(secondToLast) > "two" mw.log(last) > "three"
local secondToLast, last = select(2, "one", "two", "three", "four") mw.log(secondToLast) > "three" mw.log(last) > "four"
setmetatable
setmetatable( table, metatable )
Sets the metatable of a table. metatable
may be nil, but must be explicitly provided.
If the current metatable has a __metatable
field, setmetatable
will throw an error.
tonumber
tonumber( value, base )
Tries to convert value
to a number. If it is already a number or a string convertible to a number, then tonumber
returns this number; otherwise, it returns nil
.
The optional base
(default 10) 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 value may have a decimal part, be expressed in E notation, and may have a leading "0x" to indicate base 16. In other bases, only unsigned integers are accepted.
tostring
tostring( value )
Converts value
to a string. See Data types above for details on how each type is converted.
The standard behavior for tables may be overridden by providing a __tostring
metamethod. If that metamethod exists, the call to tostring will return the single value returned by __tostring( value )
instead.
type
type( value )
Returns the type of value
as a string: "nil"
, "number"
, "string"
, "boolean"
, "table"
, or "function"
.
unpack
unpack( table, i, j )
Returns values from the given table, something like table[i], table[i+1], ···, table[j]
would do if written out manually. If nil
or not given, i
defaults to 1 and j
defaults to #table
.
Note that results are not deterministic if table
is not a sequence and j
is nil
or unspecified; see Length operator for details.
xpcall
xpcall( f, errhandler )
This is much like pcall
, except that the error message is passed to the function errhandler
before being returned.
In pseudocode, xpcall
might be defined something like this:
function xpcall( f, errhandler ) try return true, f() catch ( message ) message = errhandler( message ) return false, message end end
Debug library
debug.traceback
debug.traceback( 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 stack level to start the traceback.
Math library
math.abs
math.abs( x )
Returns the absolute value of x
.
math.acos
math.acos( x )
Returns the arc cosine of x
(given in radians).
math.asin
math.asin( x )
Returns the arc sine of x
(given in radians).
math.atan
math.atan( x )
Returns the arc tangent of x
(given in radians).
math.atan2
math.atan2( y, x )
Returns the arc tangent of y/x
(given in radians), using the signs of both parameters to find the
quadrant of the result.
math.ceil
math.ceil( x )
Returns the smallest integer larger than or equal to x
.
math.cos
math.cos( x )
Returns the cosine of x
(given in radians).
math.cosh
math.cosh( x )
Returns the hyperbolic cosine of x
.
math.deg
math.deg( x )
Returns the angle x
(given in radians) in degrees.
math.exp
math.exp( x )
Returns the value .
math.floor
math.floor( x )
Returns the largest integer smaller than or equal to x
.
math.fmod
math.fmod( x, y )
Returns the remainder of the division of x
by y
that rounds the quotient towards zero.
math.frexp
math.frexp( x )
Returns two values m
and e
such that:
 If
x
is finite and nonzero: ,e
is an integer, and the absolute value ofm
is in the range  If
x
is zero:m
ande
are 0  If
x
is NaN or infinite:m
isx
ande
is not specified
math.huge
The value representing positive infinity; larger than or equal to any other numerical value.
math.ldexp
math.ldexp( m, e )
Returns (e
should be an integer).
math.log
math.log( x )
Returns the natural logarithm of x
.
math.log10
math.log10( x )
Returns the base10 logarithm of x
.
math.max
math.max( x, ... )
Returns the maximum value among its arguments.
Behavior with NaNs is not specified. With the current implementation, NaN will be returned if x
is NaN, but any other NaNs will be ignored.
math.min
math.min( x, ... )
Returns the minimum value among its arguments.
Behavior with NaNs is not specified. With the current implementation, NaN will be returned if x
is NaN, but any other NaNs will be ignored.
math.modf
math.modf( x )
Returns two numbers, the integral part of x
and the fractional part of x
.
math.pi
The value of .
math.pow
math.pow( x, y )
Equivalent to x^y
.
math.rad
math.rad( x )
Returns the angle x
(given in degrees) in radians.
math.random
math.random( m, n )
Returns a pseudorandom number.
The arguments m
and n
may be omitted, but if specified must be convertible to integers.
 With no arguments, returns a real number in the range
 With one argument, returns an integer in the range
 With two arguments, returns an integer in the range
math.randomseed
math.randomseed( x )
Sets x
as the seed for the pseudorandom generator.
Note that using the same seed will cause math.random
to output the same sequence of numbers.
math.sin
math.sin( x )
Returns the sine of x
(given in radians).
math.sinh
math.sinh( x )
Returns the hyperbolic sine of x
.
math.sqrt
math.sqrt( x )
Returns the square root of x
. Equivalent to x^0.5
.
math.tan
math.tan( x )
Returns the tangent of x
(given in radians).
math.tanh
math.tanh( x )
Returns the hyperbolic tangent of x
.
Operating system library
os.clock
os.clock()
Returns an approximation of the amount in seconds of CPU time used by the program.
os.date
os.date( format, time )
 Language library's formatDate may be used for more comprehensive date formatting
Returns a string or a table containing date and time, formatted according to format
. If the format is omitted or nil, "%c" is used.
If time
is given, it is the time to be formatted (see os.time()
). Otherwise the current time is used.
If format
starts with '!', then the date is formatted in UTC rather than the server's local time. After this optional character, if format is the string "*t", then date returns a table with the following fields:
 year (full)
 month (1–12)
 day (1–31)
 hour (0–23)
 min (0–59)
 sec (0–60)
 wday (weekday, Sunday is 1)
 yday (day of the year)
 isdst (daylight saving flag, a boolean; may be absent if the information is not available)
If format is not "*t", then date returns the date as a string, formatted according to the same rules as the C function strftime.
os.difftime
os.difftime( t2, t1 )
Returns the number of seconds from t1
to t2
.
os.time
os.time( table )
Returns a number representing the current time.
When called without arguments, returns the current time. If passed a table, the time encoded in the table will be parsed. The table must have the fields "year", "month", and "day", and may also include "hour" (default 12), "min" (default 0), "sec" (default 0), and "isdst".
Package library
require
require( modulename )
Loads the specified module.
First, it looks in package.loaded[modulename]
to see if the module is already loaded. If so, returns package.loaded[modulename]
.
Otherwise, it calls each loader in the package.loaders
sequence to attempt to find a loader for the module. If a loader is found, that loader is called. The value returned by the loader is stored into package.loaded[modulename]
and is returned.
See the documentation for package.loaders
for information on the loaders available.
Note that every required module is loaded in its own sandboxed environment, so it cannot export global variables as is sometimes done in Lua 5.1. Instead, everything that the module wishes to export should be included in the table returned by the module.
For example, if you have a module "Module:Giving" containing the following:
local p = {} p.someDataValue = 'Hello!' return p
You can load this in another module with code such as this:
local giving = require( "Module:Giving" ) local value = giving.someDataValue  value is now 'Hello!'
Global modules
Modules hosted in dev.wikia.com are called global modules because they can be loaded by other modules using a similar syntax to loading local modules.^{[1]} The correct syntax to use is require("Dev:ModuleName")
. This is case sensitive. It should also be added to all modules hosted on dev.wikia or else it'll attempt to use a module in a local wikia (e.g. crocodile.wikia.com).
You can load this in another module from another wiki with code such as this:
local giving = require( "Dev:Giving" ) local value = giving.someDataValue  value is now 'Hello!'
package.loaded
This table holds the loaded modules. The keys are the module names, and the values are the values returned when the module was loaded.
package.loaders
This table holds the sequence of searcher functions to use when loading modules. Each searcher function is called with a single argument, the name of the module to load. If the module is found, the searcher must return a function that will actually load the module and return the value to be returned by require
. Otherwise, it must return nil.
Scribunto provides two searchers:
 Look in
package.preload[modulename]
for the loader function  Look in the modules provided with Scribunto for the module name, and if that fails look in the Module: namespace. The "Module:" prefix must be provided.
Note that the standard Lua loaders are not included.
package.preload
This table holds loader functions, used by the first searcher Scribunto includes in package.loaders
.
package.seeall
package.seeall( table )
Sets the __index
metamethod for table
to _G
.
String library
In all string functions, the first character is at position 1, not position 0 as in C, PHP, and JavaScript. Indexes may be negative, in which case they count from the end of the string: position 1 is the last character in the string, 2 is the secondlast, and so on.
Warning: The string library assumes onebyte character encodings. It cannot handle Unicode characters. To operate on Unicode strings, use the corresponding methods in the Scribunto Ustring library.
string.byte
string.byte( s, i, j )
If the string is considered as an array of bytes, returns the byte values for s[i]
, s[i+1]
, ···, s[j]
.
The default value for i
is 1;
the default value for j
is i
.
Identical to mw.ustring.byte()
.
string.char
string.char( ... )
Receives zero or more integers. Returns a string with length equal to the number of arguments, in which each character has the byte value equal to its corresponding argument. See mw.ustring.char()
for a similar function that uses Unicode codepoints rather than byte values.
string.find
string.find( s, pattern, init, plain )
Looks for the first match of pattern
in the string s
. If it finds a match, then find
returns the offsets in s
where this occurrence starts and ends; otherwise, it returns nil. If the pattern has captures, then in a successful match the captured values are also returned after the two indices.
A third, optional numerical argument init
specifies where to start the search; its default value is 1 and can be negative. A value of true as a fourth, optional argument plain
turns off the pattern matching facilities, so the function does a plain "find substring" operation, with no characters in pattern
being considered "magic".
Note that if plain
is given, then init
must be given as well.
See mw.ustring.find()
for a similar function extended as described in Ustring patterns and where the init
offset is in characters rather than bytes.
string.format
string.format( formatstring, ... )
Returns a formatted version of its variable number of arguments following the description given in its first argument (which must be a string).
The format string uses a limited subset of the printf
format specifiers:
 Recognized flags are '', '+', ' ', '#', and '0'.
 Integer field widths up to 99 are supported. '*' is not supported.
 Integer precisions up to 99 are supported. '*' is not supported.
 Length modifiers are not supported.
 Recognized conversion specifiers are 'c', 'd', 'i', 'o', 'u', 'x', 'X', 'e', 'E', 'f', 'g', 'G', 's', '%', and the nonstandard 'q'.
 Positional specifiers (e.g. "%2$s") are not supported.
The conversion specifier 'q' is like 's', but formats the 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.
Conversion between strings and numbers is performed as specified in Data types; other types are not automatically converted to strings. Strings containing NUL characters (byte value 0) are not properly handled.
Identical to mw.ustring.format()
.
string.gmatch
string.gmatch( s, pattern )
Returns an iterator function that, each time it is called, returns the next captures from pattern
over string s
. If pattern
specifies no captures, then the whole match is produced in each call.
For this function, a '^
' at the start of a pattern is not magic, as this would prevent the iteration. It is treated as a literal character.
See mw.ustring.gmatch()
for a similar function for which the pattern is extended as described in Ustring patterns.
string.gsub
string.gsub( s, pattern, repl, n )
Returns a copy of s
in which all (or the first n
, if given) occurrences of the pattern
have been replaced by a replacement string specified by repl
, which can be a string, a table, or a function. gsub
also returns, as its second value, the total number of matches that occurred.
If repl
is a string, then its value is used for replacement. The character %
works as an escape character: any sequence in repl
of the form %n
,
with n between 1 and 9, stands for the value of the nth captured substring. The sequence %0
stands for the whole match, and 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).
See mw.ustring.gsub()
for a similar function in which the pattern is extended as described in Ustring patterns.
string.len
string.len( s )
Returns the length of the string, in bytes. Is not confused by ASCII NUL characters. Equivalent to #s
.
See mw.ustring.len()
for a similar function using Unicode codepoints rather than bytes.
string.lower
string.lower( s )
Returns a copy of this string with all ASCII uppercase letters changed to lowercase. All other characters are left unchanged.
See mw.ustring.lower()
for a similar function in which all characters with uppercase to lowercase definitions in Unicode are converted.
string.match
string.match( s, pattern, init )
Looks for the first match of pattern
in the string. If it finds one, then match
returns the captures from the pattern; otherwise it returns nil. If pattern
specifies no captures, then the whole match is returned.
A third, optional numerical argument init
specifies where to start the search; its default value is 1 and can be negative.
See mw.ustring.match()
for a similar function in which the pattern is extended as described in Ustring patterns and the init
offset is in characters rather than bytes.
string.rep
string.rep( s, n )
Returns a string that is the concatenation of n
copies of the string s
. Identical to mw.ustring.rep()
.
string.reverse
string.reverse( s )
Returns a string that is the string s
reversed (bytewise).
string.sub
string.sub( s, i, j )
Returns the substring of s
that starts at i
and continues until j
; i
and j
can be negative. If j
is nil or omitted, 1 is used.
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
.
See mw.ustring.sub()
for a similar function in which the offsets are characters rather than bytes.
string.upper
string.upper( s )
Returns a copy of this string with all ASCII lowercase letters changed to uppercase. All other characters are left unchanged.
See mw.ustring.upper()
for a similar function in which all characters with uppercase to lowercase definitions in Unicode are converted.
Patterns
Note that Lua's patterns are similar to regular expressions, but are not identical. In particular, note the following differences from regular expressions and PCRE:
 The quoting character is percent (
%
), not backslash (\
).  Dot (
.
) always matches all characters, including newlines.  No caseinsensitive mode.
 No alternation (the

operator).  Quantifiers (
*
,+
,?
, and
) may only be applied to individual characters or character classes, not to capture groups.  The only nongreedy quantifier is

, which is equivalent to PCRE's*?
quantifier.  No generalized finite quantifier (e.g. the
{n,m}
quantifier in PCRE).  The only zerowidth assertions are
^
,$
, and the%f[set]
"frontier" pattern; assertions such as PCRE's\b
or(?=···)
are not present.  Patterns themselves do not recognize character escapes such as '\ddd'. However, since patterns are strings these sort of escapes may be used in the string literals used to create the patternstring.
Also note that a pattern cannot contain embedded zero bytes (ASCII NUL, "\0"
). Use %z
instead.
Also see Ustring patterns for a similar patternmatching scheme using Unicode characters.
Character class
A character class is used to represent a set of characters. The following combinations are allowed in describing a character class:
 x: (where x is not one of the magic characters
^$()%.[]*+?
) represents the character x itself. 
.
: (a dot) represents all characters. 
%a
: represents all ASCII letters. 
%c
: represents all ASCII control characters. 
%d
: represents all digits. 
%l
: represents all ASCII lowercase letters. 
%p
: represents all punctuation characters. 
%s
: represents all ASCII space characters. 
%u
: represents all ASCII uppercase letters. 
%w
: represents all ASCII alphanumeric characters. 
%x
: represents all hexadecimal digits. 
%z
: represents ASCII NUL, the zero byte. 
%A
: All characters not in%a
. 
%C
: All characters not in%c
. 
%D
: All characters not in%d
. 
%L
: All characters not in%l
. 
%P
: All characters not in%p
. 
%S
: All characters not in%s
. 
%U
: All characters not in%u
. 
%W
: All characters not in%w
. 
%X
: All characters not in%x
. 
%Z
: All characters not in%z
. 
%x
: (where x is any nonalphanumeric character) represents the character x. This is the standard way to escape the magic characters. Any punctuation character (even the non magic) can be preceded by a '%
' when used to represent itself in a pattern. 
[set]
: represents the class which is the union of all characters in set. A range of characters can be specified by separating the end characters of the range with a '
'. All classes%x
described above can also be used as components in set. All other characters in set represent themselves. For example,[%w_]
(or[_%w]
) represents all alphanumeric characters plus the underscore,[07]
represents the octal digits, and[07%l%]
represents the octal digits plus the lowercase letters plus the '
' character.The interaction between ranges and classes is not defined. Therefore, patterns like
[%az]
or[a%%]
have no meaning. 
[^set]
: represents the complement of set, where set is interpreted as above.
Pattern items
A pattern item can be
 a single character class, which matches any single character in the class;
 a single character class followed by '
*
', which matches 0 or more repetitions of characters in the class. These repetition items will always match the longest possible sequence;  a single character class followed by '
+
', which matches 1 or more repetitions of characters in the class. These repetition items will always match the longest possible sequence;  a single character class followed by '

', which also matches 0 or more repetitions of characters in the class. Unlike '*
', these repetition items will always match the shortest possible sequence;  a single character class followed by '
?
', 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 nth 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. 
%f[set]
, a frontier pattern; such item matches an empty string at any position such that the next character belongs to set and the previous character does not belong to set. The set set is interpreted as previously described. The beginning and the end of the subject are handled as if they were the character '\0'.
Note that frontier patterns were present but undocumented in Lua 5.1, and officially added to Lua in 5.2. The implementation in Lua 5.2.1 is unchanged from that in 5.1.0.
Pattern
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.
Captures
A pattern can contain subpatterns 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.
Table library
Most functions in the table library assume that the table represents a sequence.
The functions table.foreach()
, table.foreachi()
, and table.getn()
may be available but are deprecated. Use a for loop with pairs()
, a for loop with ipairs()
, and the length operator instead.
table.concat
table.concat( table, sep, i, j )
Given an array where all elements are strings or numbers, returns 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.insert( table, value )
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 the length of the table plus 1, so that a call table.insert(t, x)
inserts x
at the end of table t
.
Elements up to #table
are shifted; see Length operator for caveats if the table is not a sequence.
table.maxn
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 this, it iterates over the whole table. This is roughly equivalent to
function table.maxn( table ) local maxn, k = 0, nil repeat k = next( table, k ) if type( k ) == 'number' and k > maxn then maxn = k end until not k return maxn end
table.remove
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 the length of the table, so that a call table.remove( t )
removes the last element of table t
.
Elements up to #table
are shifted; see Length operator for caveats if the table is not a sequence.
table.sort
table.sort( table, comp )
Sorts table elements in a given order, inplace, from table[1]
to table[#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.
Optimization (Garbage Collector)
Methods for collecting and flushing garbage^{[2]} are unavailable in Scribunto^{[3]}.