Operators

Published Sep 23, 2023Updated May 15, 2024

Operators perform broadly logical or mathematical computations. An operator takes in one or more arguments, performs some computations based on those arguments, and returns a value.

Logical Operators

Logical operators mirror the behavior of logical concepts like conjunction, disjunction, and negation. Because Luau is not a strongly-typed language, logical operators in Luau will accept arguments other than true and false. Note also that Luau treats a value of nil as equivalent to false in the context of a logical operator.

Logical Operator	Behavior
`and`	Returns the first argument if the first argument is `false`; otherwise returns the second argument
`or`	Returns the first argument if the first argument is not `false`; otherwise returns the second argument
`not`	Returns `true` if and only if the argument is `false`; otherwise returns `false`

Examples

print(true and false) -- false
print(false and false) -- false
print(true and true) -- true
print(1 and 2) -- 2
print("Hello" and "World") -- World
print(true or false) -- true
print(false or false) -- false
print(true or true) -- true
print(1 or 2) -- 1
print("Hello" or "World) -- Hello
print(not false) -- true
print(not nil) -- true
print(not true) -- false
print(not 1) -- false
print(not "Hello World") -- false

Mathematical Operators

Mathematical operators include arithmetic and relational (comparative) operators.

Relational Operators

Relational operators compare two arguments numerically (greater than, equal to, etc.) and return a boolean value of true or false.

Relational Operator	Behavior
`==`	Returns `true` if the two arguments are equal; otherwise returns `false`
`~=`	Returns `true` if the two arguments are not equal; otherwise returns `false`
`>`	Returns `true` if the first argument is greater than the second argument; otherwise returns `false`
`<`	Returns `true` if the first argument is less than the second argument; otherwise returns `false`
`>=`	Returns `true` if the first argument is greater than or equal to the second argument; otherwise returns `false`
`<=`	Returns `true` if the first argument is less than or equal to the second argument; otherwise returns `false`

Examples

print(5 == 5) -- true
print("arts" = "sciences") -- false
print(0 ~= 9) -- true
print(true ~= true) -- false
print(15 > 2) -- true
print(6 > 9) -- false
print("apple" >= "apple") -- true
print(7 >= 8)  -- false
print(false <= false) -- true
print(3 <= 0) -- false

Arithmetic Operators

Arithmetic operators perform the basic operations of arithmetic (addition, subtraction, etc.) on the supplied arguments.

Arithmetic Operator	Behavior
`+`	Returns the sum of two arguments
`-`	Returns the value of the second argument subtracted from the first argument
`*`	Returns the product of two arguments
`/`	Returns the value of the first argument divided by the second argument
`^`	Returns the value of the first argument to the power of the second argument
`%`	Returns the remainder of the first argument divided by the second argument

Examples

print(3 + 4) -- 7
print(2.3 - 7.8) -- -5.5
print(0 * 4.2) -- 0.0
print(8 / 3) -- 2.6666666666667
print(4 ^ 6) -- 4096.0
print(8 % 2) -- 0

Other Operators

There are a couple of operators that do not fit into the categories above.

Operator	Behavior
`..`	Returns a concatenation of two string arguments
`#`	Returns the number of elements in a table

Examples

print("Finally " .. "together") -- "Finally together"
print(#{"#", "goes", "crazy"}) -- 3

Compound Assignment

Several operators can be combined with = to form a compound operator that updates the value of a variable by performing an operation on it.

Compound Operator	Behavior
`+=`	Adds argument to initial variable value
`-=`	Subtracts argument from initial value
`*=`	Multiplies argument by initial value
`/=`	Divides initial value by argument
`%=`	Variable updated to remainder of initial value divided by argument
`^=`	Variable updated to initial value to the power of the argument
`..=`	Concatenates initial value with argument

Examples

initial_value = 8
print(initial_value += 10) -- 18
print(initial_value -= 4) -- 4
print(initial_value *= 3) -- 24
print(initial_value /= 2) -- 4
print(initial_value % = 3) -- 2
print(initial_value ^= 0) -- 1.0

initial_value = "8"
print(initial_value ..= " ball") -- 8 ball