lua

Overview

For Loops Overview

You can use for loops in Lua to iterate over arrays and tables, performing tasks for each element.

This example simply iterates i over the values 1 to 10

-- Iterate from 1 to 10
for i = 1, 10 do
  print( i )
end

This example uses the ipairs function to sequentially iterate over a table. Note that ipairs only works on tables that have sequential elements beginning at 1.

-- Iterate over an array named 'arr'
arr = { 3, 2, 1 }

for i,v in ipairs(arr) do
  print( "arr["..i.."] = "..v )
end

-- Prints:
--  arr[1] = 3
--  arr[2] = 2
--  arr[3] = 1

This example uses pairs to iterate over all the key/value pairs in a table, unlike ipairs the keys do not have to be integral values, and can be anything.

-- Iterate over a table named 'tab'
tab = { x = 3, y = "string", z = 1 }

for key,value in pairs(tab) do
  print( "tab."..key.." = "..value )
end

-- Prints:
--  tab.y = string
--  tab.x = 3
--  tab.z = 1

Conditionals Overview

Use conditionals to test for a particular circumstance and then branch your code appropriately. See the examples below.

-- Check if x is equal to 10
if x == 10 then
  print( "x equals 10" )
end

-- else and elseif
if x == 10 then
  print( "x is 10" )
elseif x == 5 then
  print( "x is 5" )
else
  print( "x is something else: "..x )
end

-- Checking multiple values
if x == 10 and y < 5 then
  print( "x is 10 and y is less than 5" )
elseif x == 5 or y == 3 then
  print( "x is 5 or y is 3" )
else
  print( "x is "..x.." and y is "..y )
end

While Loops Overview

Use while and repeat loops to repeat code until a condition is true. While loops are used when you can’t predict the number of times a loop will iterate, such as when reading input from a file or testing for a key press.

-- simple while loop. The condition is evaluated at the beginning of the loop. The loop will never get executed if the condition is false at the beginning of the loop.
while i<=5 do
  print(i)
  i=i+1
end

-- repeat loop. The condition is evaluated at the end of the loop, so the code always gets executed at least once
repeat
  print(i)
  i=i+1
until i>5

-- break statement: break exits a loop and continues program flow with the statement immediately following the end or until condition
while true do
  print(i)
  i=i+1
  if i>5 then
      break
  end
end

Annotations Overview

Annotations can be used to indicate the type of a variable to Codea, giving you better auto-completion support.

To write a code annotation, start a comment with three dashes (—). Codea will look at the next line of code to try and auto-complete your comment if it is an assignement or function definition. You can also manually write annotations anywhere in your code following the format — variableName: variableType.

When using annotations for Objective-C types, this will add Objective-C properties and methods auto-completion to your variables.

-- method annotation
--- makeBox Creates a box body
--- pos: vec2, bottom-left position of the box
--- size: vec2, size of the box
function createBoxBody(pos, size)

-- variable annotation
--- textView: objc.UITextView
textView = objc.UITextView()

Language

print(...)

Prints values to the output console.

Parameters:

... – values to print

Syntax:

print( ... )

ipairs(table)

ipairs can be used to iterate over a table sequentially, starting from the index 1 and continuing until the first integer key absent from the table. Returns three values: an iterator function, the table, and 0.

Parameters:

table – table to iterate over

Returns:

Returns three values: an iterator function, the table, and 0

Return type:

table

Syntax:

for i,v in ipairs( t ) do body end

-- This will iterate over the pairs:
--   (1,t[1]), (2,t[2]), ...

pairs(table)

pairs can be used to iterate over a tables key-value pairs. Returns three values: the next function, the table t, and nil.

Parameters:

table – table to iterate over

Returns:

Returns three values: the next function, the table t, and nil

Return type:

table

Syntax:

for k,v in pairs( t ) do body end

-- This will iterate over all key-value
-- pairs in table t

Tables

table.concat(table, sep)

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.

Parameters:

• table – table to concatenate

• sep – separator string

• i – int, starting index to concatenate from

• j – int, ending index

Returns:

A string of the elements in table concatenated with each other, separated by sep

Return type:

string

Syntax:

table.concat( table )
table.concat( table, sep )
table.concat( table, sep, i )
table.concat( table, sep, i, j )

table.move(a1, f, e, t, a2)

Moves elements from table a1 into table a2. This function performs the equivalent to the multiple assignment: a2[t], … = a1[f], …, a1[e]. The default value for a2 is a1. The destination range can overlap with the source range. Index f must be positive.

Parameters:

• a1 – table to move elements from

• f (integer) – starting index in table to move from

• e (integer) – ending index in table to move from

• t (integer) – starting index in table to move into

• a2 – table to move elements into (defaults to a1)

Syntax:

table.move( a1, f, e, t )
table.move( a1, f, e, t, a2 )

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, so that a call table.insert(t,x) inserts x at the end of table t.

Parameters:

• table – table to insert into

• pos – int, position to inset

• value – value to insert

Syntax:

table.insert( table, value )
table.insert( table, pos, value )

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.

Parameters:

• table – table to insert into

• pos – int, position of value to remove

Returns:

Value of the removed element

Syntax:

table.remove( table )
table.remove( table, pos )

table.pack(...)

Returns a new table with all parameters stored into keys 1, 2, etc. and with a field “n” with the total number of parameters. Note that the resulting table may not be a sequence.

Parameters:

... – arguments to pack into table

Returns:

table with all parameters packed

Return type:

table

Syntax:

table.pack( ... )

table.unpack(list)

Returns the elements from the given list.

Parameters:

list – list to unpack

Returns:

elements unpacked from list

Syntax:

table.unpack( list )

table.sort(table)

Sorts table elements in a given order, in-place, from 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.

Parameters:

• table – the table to sort

• comp – a function that receives two table elements and returns true when the first is less than the second

Syntax:

table.sort( table )
table.sort( table, comp )

Strings

string.byte(s, i, j)

Returns the internal numerical codes of the characters s[i], s[i+1], …, s[j]. The default value for i is 1; the default value for j is i. These indices are corrected following the same rules of string.sub.

Parameters:

• s – string to use

• i – first index, defaults to 1

• j – last index, defaults to i

Returns:

The internal numerical codes for characters s[i] up to s[j]

Syntax:

string.byte( s )
string.byte( s, i )
string.byte( s, i, j )

string.char(...)

Returns a string with length equal to the number of arguments, in which each character has the internal numerical code equal to its corresponding argument.

Parameters:

... – a variable number of numerical codes

Returns:

String composed of characters equal to the numerical codes used as arguments

Return type:

string

Syntax:

string.char( ... )

string.dump(function)

Returns a string containing a binary representation (a binary chunk) of the given function, so that a later load on this string returns a copy of the function (with new upvalues). If strip is a true value, the binary representation is created without debug information about the function (local variable names, lines, etc).

Parameters:

• function – a function to convert to binary string

• strip (boolean) – whether to strip debug information

Returns:

Binary string representation of the specified function

Return type:

string

Syntax:

string.dump( function )
string.dump( function, strip )

string.find(s, pattern)

Looks for the first match of pattern in the string s. If it finds a match, then string.find() returns the indices of s where the occurrence starts and ends; otherwise, it returns nil. A third, optional numerical argument init specifies where to start the search, its default value is 1 and can be negative. A value of true as the fourth optional argument plain turns off the pattern matching facilities so the function performs 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.

Parameters:

• s – string to search in

• pattern – pattern to look for

• init – starting character in string to search from, default is 1

• plain (boolean) – perform a plain substring search

Returns:

The start and end indices of the match, or nil if no match. If the pattern has captures then captured values are also returned after the indices

Syntax:

string.find( s, pattern )
string.find( s, pattern, init )
string.find( s, pattern, init, plain )

string.format(formatstring, ...)

Returns a formatted version of its variable arguments following the description given in the first argument, which must be a string. The format string follows the same rules as the printf family of standard C functions. The only difference are that the options/modifiers *, 1, 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, for example all double quotes, newlines, embedded zeros and backslashes will be escaped when written.

Parameters:

formatstring – string defining the format

Returns:

A formatted string

Return type:

string

Syntax:

string.format( formatstring, ... )

string.len(s)

Receives a string and returns its length. The empty string “” has length 0.

Parameters:

s – get the length of this string

Returns:

Length of string s

Return type:

string

Syntax:

string.len( s )

string.gmatch(s, pattern)

Returns an iterator function that, each time it is called, returns the next captures from pattern (see Patterns Overview) over the string s. If pattern specifies no captures, then the whole match is produced in each call.

Parameters:

• s – string to search

• pattern – pattern to match

Returns:

Iterator function over matches of pattern within the string

Return type:

string

Syntax:

string.gmatch( s, pattern )

string.gsub(s, pattern, repl)

Returns a copy of s in which all (or the first n, if given) occurrences of the pattern (see Patterns Overview) 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. The name gsub comes from Global SUBstitution.

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 %d, with d between 1 and 9, stands for the value of the d-th captured substring. 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 repl is a function, then this function is called every time a match occurs, with all captured substrings passed as arguments, in order.

In any case, if the pattern specifies no captures, then it behaves as if the whole pattern was inside a capture.

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).

Parameters:

• s – string to substitute

• pattern – pattern to match

• repl (string) – table or function, replacement parameter

• n (integer) – number of occurrences to match (all if not specified)

Returns:

Returns a copy of s with substitutions made, as well as the number of matches

Return type:

number

Syntax:

string.gsub( s, pattern, repl )
string.gsub( s, pattern, repl, n )

string.lower(s)

Receives a string and returns a copy of this string with all uppercase letters changed to lowercase. All other characters are left unchanged.

Parameters:

s – get a lowercase version of this string

Returns:

Lowercase version of string s

Return type:

string

Syntax:

string.lower( s )

string.upper(s)

Receives a string and returns a copy of this string with all lowercase letters changed to uppercase. All other characters are left unchanged.

Parameters:

s – get an uppercase version of this string

Returns:

Uppercase version of string s

Return type:

string

Syntax:

string.upper( s )

string.match(s, pattern)

Looks for the first match of pattern in the string s. If it finds one then string.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 is 1 and can be negative.

Parameters:

• s – string to search

• pattern – pattern to match

• init – starting location in string

Returns:

Captures from the first match of pattern in string s, or nil if none were found

Return type:

string

Syntax:

string.match( s, pattern )
string.match( s, pattern, init )

string.rep(s, n)

Returns a string that is the concatenation of n copies of the string s.

Parameters:

• s – string to replicate

• n – int, number of times to replicate the string

Returns:

n concatenations of string s

Return type:

string

Syntax:

string.rep( s, n )

string.reverse(s)

This function returns the string s reversed.

Parameters:

s – string to reverse

Returns:

s reversed

Syntax:

string.reverse( s )

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 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.

Parameters:

• s – find substring of this string

• i – int, starting index

• j – int, ending index

Returns:

Substring of string s

Return type:

string

Syntax:

string.sub( s, i )
string.sub( s, i, j )

string.pack(fmt, v1, v2, ...)

Returns a binary string containing the values v1, v2, etc. packed (that is, serialized in binary form) according to the format string fmt.

Parameters:

• fmt – format string specifying binary format

• ... – arguments to pack

Returns:

Values packed into binary string

Return type:

string

Syntax:

string.pack( fmt, v1, v2, ... )

string.packsize(fmt)

Returns the size of a string resulting from string.pack with the given format. The format string cannot have the variable-length options ‘s’ or ‘z’

Parameters:

fmt – format string specifying binary format

Returns:

Size of string packed with the given format

Return type:

string

Syntax:

string.packsize( fmt )

string.unpack(fmt, s)

Returns the values packed in string s according to the format string fmt. An optional pos marks where to start reading in s (default is 1). After the read values, this function also returns the index of the first unread byte in s.

Parameters:

• fmt – format string specifying binary format

• s – string to unpack

Returns:

The values packed in s

Syntax:

string.unpack( fmt, s )
string.unpack( fmt, s, pos )

Patterns Overview

Patterns in Lua are described by regular strings, which are interpreted as patterns by the pattern-matching functions string.find, string.gmatch, string.gsub, and string.match. This section describes the syntax and the meaning (that is, what they match) of these strings.

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 letters.
%c: represents all control characters.
%d: represents all digits.
%g: represents all printable characters except space.
%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.
%x: (where x is any non-alphanumeric character)
  represents the character x.
  This is the standard way to escape
  the magic characters. Any non-alphanumeric
  character (including all punctuations, even
  the non-magical) 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, in ascending order, with a '-'.
  All classes %x described above can
  also be used as components in set.
  All other characters in set represent
  themselves. For example, [%w_] (or [_%w])
  represents all alphanumeric characters
  plus the underscore, [0-7] represents
  the octal digits, and [0-7%l%-] represents
  the octal digits plus the lowercase letters
  plus the '-' character.
[^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.

Pattern Item

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 zero 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 one 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 zero 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 zero or one occurrence of
a character in the class. It always
matches one occurrence if possible;
- %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.
- %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'.

Pattern

A pattern is a sequence of pattern items. A caret ‘^’ 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 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.

Math

math.abs(value)

This function returns the absolute value of value. For example, math.abs(-5) returns 5.

Parameters:

value – int or float, the number to get the absolute value of

Returns:

The absolute value of value

Syntax:

math.abs( value )

math.acos(value)

This function returns the arc cosine of value in radians

Parameters:

value – int or float, compute the arc cosine of this number

Returns:

The arc cosine of value in radians

Syntax:

math.acos( value )

math.asin(value)

This function returns the arc sine of value in radians

Parameters:

value – int or float, compute the arc sine of this number

Returns:

The arc sine of value in radians

Syntax:

math.asin( value )

math.atan(y, x)

Returns the arc tangent of y/x (in radians), using the signs of both arguments to find the quadrant of the result. It also handles correctly the case of x being zero

The default value for x is 1, so that the call math.atan(y) returns the arc tangent of y

Parameters:

• y (number) – numerator for arc tangent

• x (number) – denominator for arc tangent (defaults to 1)

Returns:

The arc tangent of y/x in radians

Syntax:

math.atan( y )
math.atan( y, x )

math.ceil(value)

This function returns the smallest integer larger than or equal to value. This rounds a number up to the nearest integer. For example, math.ceil(5.2) returns 6.

Parameters:

value – int or float, compute the smallest integer larger than or equal to this number

Returns:

The smallest integer larger than or equal to value

Return type:

integer

Syntax:

math.ceil( value )

math.cos(value)

This function returns the cosine of value (assumed to be in radians).

Parameters:

value – int or float, compute the cosine of this number

Returns:

Cosine of value

Syntax:

math.cos( value )

math.cosh(value)

This function returns hyperbolic cosine of value.

Parameters:

value – int or float, compute the hyperbolic cosine of this number

Returns:

Hyperbolic cosine of value

Syntax:

math.cosh( value )

math.deg(value)

This function returns the angle specified by value (given in radians) in degrees.

Parameters:

value – int or float, angle in radians to convert to degrees

Returns:

Angle specified by value (in radians) in degrees

Syntax:

math.deg( value )

math.rad(value)

This function returns the angle specified by value (given in degrees) in radians.

Parameters:

value – int or float, angle in degrees to convert to radians

Returns:

Angle specified by value (in degrees) in radians

Syntax:

math.rad( value )

math.exp(value)

This function returns e raised to value

Parameters:

value – int or float, exponent of e

Returns:

e raised to the power of value

Syntax:

math.exp( value )

math.floor(value)

This function returns the largest integer smaller than or equal to value. This rounds a number down to the nearest integer. For example, math.floorTh(5.7) returns 5.

Parameters:

value – int or float, compute the largest integer smaller than or equal to this number

Returns:

The largest integer smaller than or equal to value

Return type:

integer

Syntax:

math.floor( value )

math.fmod(x, y)

This function returns the remainder of the division of x by y that rounds the quotient towards zero.

Parameters:

• x – int or float

• y – int or float

Returns:

The remainder of the division of x by y

Syntax:

math.fmod( x, y )

math.frexp(value)

This function returns m and e such that value = m2^e, e is an integer and the absolute value of m is in the range [0.5, 1) (or zero when x is zero).

Parameters:

value – int or float

Returns:

m and e such that value = m2^e, e is an integer and the absolute value of m is in the range [0.5, 1) (or zero when x is zero).

Return type:

integer

Syntax:

math.frexp( value )

math.ldexp(m, e)

This function returns m2^e (e should be an integer)

Parameters:

• m – int or float

• e – int

Returns:

m2^e

Syntax:

math.ldexp( m, e )

math.log(value)

This function returns the natural logarithm of value

Parameters:

value – int or float, compute the natural logarithm of this value

Returns:

The natural logarithm of value

Syntax:

math.log( value )

math.log10(value)

This function returns the base-10 logarithm of value

Parameters:

value – int or float, compute the base-10 logarithm of this value

Returns:

The base-10 logarithm of value

Syntax:

math.log10( value )

math.max(value, ...)

This function returns maximum value among its arguments.

Parameters:

value – any comparable value

Returns:

The maximum value among its arguments

Syntax:

math.max( value, ... )

math.min(value, ...)

This function returns minimum value among its arguments.

Parameters:

value – any comparable value

Returns:

The minimum value among its arguments

Syntax:

math.min( value, ... )

math.modf(value)

This function returns two numbers, the integral part of value and the fractional part of value.

Parameters:

value – int or float

Returns:

Two numbers, the integral part of value and the fractional part of value

Syntax:

math.modf( value )

math.random()

When called without arguments, math.random() returns a uniform pseudo-random real number in the range [0, 1). When called with an integer number maximum, math.random() returns a uniform pseudo-random integer in the range [1, maximum]. When called with two integer numbers, minimum and maximum, math.random() returns a uniform pseudo-random integer in the range [minimum, maximum].

Parameters:

• minimum – int, minimum value of returned pseudo-random number

• maximum – int, maximum value of returned pseudo-random number

Returns:

A uniform pseudo-random real number or integer (depending on parameters)

Return type:

integer

Syntax:

math.random()
math.random( maximum )
math.random( minimum, maximum )

math.randomseed(value)

Sets value as the “seed” for the pseudo-random number generator. Equal seeds produce equal sequences of numbers.

Parameters:

value – int, seed of the pseudo-random number generator

Returns:

A uniform pseudo-random real number or integer (depending on parameters)

Return type:

integer

Syntax:

math.randomseed( value )

math.sin(value)

This function returns the sine of value (assumed to be in radians).

Parameters:

value – int or float, compute the sine of this number

Returns:

Sine of value

Syntax:

math.sin( value )

math.sinh(value)

This function returns hyperbolic sine of value.

Parameters:

value – int or float, compute the hyperbolic sine of this number

Returns:

Hyperbolic sine of value

Syntax:

math.sinh( value )

math.tan(value)

This function returns the tangent of value (assumed to be in radians).

Parameters:

value – int or float, compute the tangent of this number

Returns:

Tangent of value

Syntax:

math.tan( value )

math.tanh(value)

This function returns hyperbolic tangent of value.

Parameters:

value – int or float, compute the hyperbolic tangent of this number

Returns:

Hyperbolic tangent of value

Syntax:

math.tanh( value )

math.sqrt(value)

This function computes the square root of value. You can also use the expression value^0.5 to compute this value.

Parameters:

value – int or float, compute the square root of this number

Returns:

Square root of value

Syntax:

math.sqrt( value )

math.tointeger(value)

If value is convertible to an integer, returns that integer. Otherwise returns nil.

Parameters:

value – float, value to convert to integer

Returns:

value converted to an integer, or nil

Return type:

integer

Syntax:

math.tointeger( value )

math.type(value)

This function returns “integer” if value is an integer, “float” if it is a float, or nil if value is not a number.

Parameters:

value – int or float, get the type of this value

Returns:

“integer” or “float”

Return type:

integer

Syntax:

math.type( value )

math.ult(m, n)

This function returns a boolean, true if integer m is below integer n when they are compared as unsigned integers.

Parameters:

• m (integer) – value for m

• n (integer) – value for n

Returns:

true if m is below integer n when compared as unsigned

Return type:

boolean

Syntax:

math.ult( m, n )

math.huge: const

A value larger than or equal to any other numerical value.

Returns:

A value larger than or equal to any other numerical value

Syntax:

math.huge

math.pi: const

The value of pi.

Returns:

Value of pi

Syntax:

math.pi

math.maxinteger: const

Specifies an integer with the maximum value for an integer

Returns:

Maximum value for an integer

Return type:

integer

Syntax:

math.maxinteger

math.mininteger: const

Specifies an integer with the minimum value for an integer

Returns:

Minimum value for an integer

Return type:

integer

Syntax:

math.mininteger

Date and Time

os.clock()

Returns an approximation of the amount in seconds of CPU time used by the program.

Returns:

Approximation of the amount in seconds of CPU time used by the program.

Return type:

number

Syntax:

os.clock()

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.

Parameters:

• t2 – Ending time

• t1 – Starting time

Returns:

Number of seconds from time t1 to time t2.

Return type:

number

Syntax:

os.difftime( t2, t1 )

os.date(format)

Returns a string or a table containing the 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’)).

Parameters:

• format – String used to format the returned date

• time – If the time argument is present, this is the time to be formatted (see the os.time function for a description of this value).

Returns:

A string or a table containing the date and time.

Return type:

string

Syntax:

os.date()
os.date( format )
os.date( format, time )

os.setlocale(locale)

Sets the current locale of the program. locale is a string specifying a locale; category is an optional string describing which category to change: “all”, “collate”, “ctype”, “monetary”, “numeric”, or “time”; the default category is “all”. The function returns the name of the new locale, or nil if the request cannot be honored.

If locale is the empty string, the current locale is set to an implementation-defined native locale. If locale is the string “C”, the current locale is set to the standard C locale.

When called with nil as the first argument, this function only returns the name of the current locale for the given category.

Parameters:

• locale – String specifying a locale, can be nil or the empty string.

• category – String specifying a category to set, can be “all”, “collate”, “ctype”, “monetary”, “numeric”, or “time”

Returns:

When called with nil for the first argument, returns the name of the current locale for the given category.

Syntax:

os.setlocale( locale )
os.setlocale( locale, category )

os.time()

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.

Parameters:

table – This table must have fields year, month, and day, and may have fields hour, min, sec, and isdst

Returns:

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.

Return type:

number

Syntax:

os.time()
os.time( table )