Common Functions

Basic Functions

Function Name	Function Description & Example
type(v)	Used to judge the type of v, returning the string "nil", "number", "string", "boolean", "table", "function", "thread", or "userdata".
tonumber(e [,base])	Converts a string to a number. Converts e (must be a number or a string convertible to a number) to a decimal number. base specifies the base (2-36), defaulting to 10. Example: tonumber('10') → Result: 10
tostring(var)	Converts a variable to a string. Converts any type of e to a string in an appropriate format. If the metatable of e has a __tostring function, it will be called with e as the parameter, and the return value will be the result. Example: tostring(math.asin(0.5)) → Result: "0.52359877"
isboolean(var)	Checks if the variable is of boolean type.
isnil(var)	Checks if the variable is nil.
isstring(var)	Checks if the variable is of string type.
isinteger(var)	Checks if the variable is of integer type.

Mathematical Functions

Function Name	Function Description	Example	Example Result
abs	Returns the absolute value of a number	math.abs(-15)	15
acos	Returns the arccosine value (in radians)	math.acos(0.5)	1.04719755
asin	Returns the arcsine value (in radians)	math.asin(0.5)	0.52359877
atan2	Returns the arctangent value of x/y (in radians)	math.atan2(90.0, 45.0)	1.10714871
atan	Returns the arctangent value (in radians)	math.atan(0.5)	0.4636476095
ceil	Returns the smallest integer greater than or equal to x	math.ceil(5.8)	6
cosh	Returns the hyperbolic cosine value	math.cosh(0.5)	1.276259652
cos	Returns the cosine value (in radians)	math.cos(0.5)	0.87758256
deg	Converts radians to degrees	math.deg(math.pi)	180
exp	Calculates e raised to the power of x (where e is the base of natural logarithm)	math.exp(2)	7.389056096 (Note: The original example result was incorrect; e²≈7.389)
floor	Returns the largest integer less than or equal to x	math.floor(5.6)	5
fmod (mod)	Performs modulo operation (returns the remainder of x/y)	math.mod(14, 5)	4
frexp	Decomposes the double-precision number val into a mantissa (x) and an exponent n (base 2), i.e., val = x * 2ⁿ	math.frexp(10.0)	0.625, 4 (Since 10 = 0.625 × 2⁴)
ldexp	Calculates value * 2ⁿ	math.ldexp(10.0, 3)	80 (10 × 2³ = 80)
log10	Calculates the base-10 logarithm of a number	math.log10(100)	2
log	Calculates the natural logarithm (base e) of a number	math.log(2.71)	0.9969
max	Returns the maximum value among the parameters	math.max(2.71, 100, -98, 23)	100
min	Returns the minimum value among the parameters	math.min(2.71, 100, -98, 23)	-98
modf	Splits a number into its integer and fractional parts	math.modf(15.98)	15, 0.98 (Note: The original example result "15 98" was incorrect; it should be the fractional part 0.98)
pow	Calculates x raised to the power of y	math.pow(2, 5)	32 (2⁵ = 32)
rad	Converts degrees to radians	math.rad(180)	3.141592654 (≈ π)
random	Generates a random number. To use it, you must first set a random seed with math.randomseed(). - math.random(): Returns a float between 0 and 1. - math.random(n): Returns an integer between 1 and n. - math.random(m, n): Returns an integer between m and n.	math.random(1, 100)	A random integer between 1 and 100
randomseed	Sets the random number seed (to ensure different random sequences)	math.randomseed(os.time())	(Sets the seed based on the current time; no direct return value)
sinh	Returns the hyperbolic sine value	math.sinh(0.5)	0.521095305 (Note: The original example result "0.5" was approximate; the precise value is ~0.5211)
sin	Returns the sine value (in radians)	math.sin(math.rad(30))	0.5 (Note: The original example result "15" was incorrect; sin(30°) = 0.5)
sqrt	Calculates the square root of a number	math.sqrt(16)	4
tanh	Returns the hyperbolic tangent value	math.tanh(0.5)	0.46211715
tan	Returns the tangent value (in radians)	math.tan(0.5)	0.5463024

String Functions

Serial Number	Method & Description
1	string.upper(argument): Converts all characters in the string to uppercase.
2	string.lower(argument): Converts all characters in the string to lowercase.
3	string.sub(s, i [, j]): Extracts a substring from s. i is the start position, j is the end position (defaults to -1, meaning the last character).
4	string.gsub(mainString, findString, replaceString, num): Replaces substrings in a string. - mainString: The target string to process. - findString: The substring to be replaced. - replaceString: The substring to use for replacement. - num: The number of replacements (optional; defaults to replacing all occurrences). Example: string.gsub("aaaa","a","z",3) → Result: "zzza", 3 (returns the new string and the number of replacements)
5	string.find(str, substr, [init, [plain]]): Searches for substr in the target string str. - Returns the start and end indices of the matched substring if found; returns nil otherwise. - init: The start position of the search (defaults to 1; can be negative, meaning counting from the end). - plain: Whether to use simple mode (defaults to false; true for exact substring search, false for regex matching). Example: string.find("Hello Lua user", "Lua", 1) → Result: 7, 9
6	string.reverse(arg): Reverses the string. Example: string.reverse("Lua") → Result: "auL"
7	string.format(...): Returns a formatted string (similar to printf in C). Example: string.format("the value is:%d",4) → Result: "the value is:4"
8	string.char(arg) and string.byte(arg[, int]): - string.char: Converts integer values to characters and concatenates them. - string.byte: Converts a character to its integer ASCII value (specify the character index with int; defaults to the first character). Examples: string.char(97,98,99,100) → Result: "abcd" string.byte("ABCD",4) → Result: 68 (ASCII value of 'D') string.byte("ABCD") → Result: 65 (ASCII value of 'A')
9	string.len(arg): Calculates the length of the string. Example: string.len("abc") → Result: 3
10	string.rep(string, n): Returns n copies of the string concatenated together. Example: string.rep("abcd",2) → Result: "abcdabcd"
11	.. (Concatenation Operator): Concatenates two strings. Example: print("www.ai-v".."ision.com") → Result: "www.ai-vision.com"
12	string.gmatch(str, pattern): Returns an iterator function. Each call to this function returns the next substring in str that matches pattern. Returns nil if no matches are found. Example: for word in string.gmatch("Hello ai vision", "%a+") do print(word) end → Result: "Hello" "ai" "vision" (Note: %a+ matches one or more letters)
13	string.match(str, pattern, init): Searches for the first match of pattern in str. - init: Optional start position (defaults to 1). - Returns all capture results if capture markers are set; returns the entire matched string if no captures are set; returns nil if no match is found. Examples: string.match("I have 2 questions for you.", "%d+ %a+") → Result: "2 questions" string.format("%d, %q", string.match("I have 2 questions for you.", "(%d+) (%a+)")) → Result: "2, "questions"" (captures the number and the word separately)