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.cursor/rules/roblox/en-us/luau/operators.md
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350
.cursor/rules/roblox/en-us/luau/operators.md
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---
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title: Operators
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description: Operators are symbols for performing an operation or conditional evaluation.
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---
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An **operator** is a symbol for performing an operation or conditional evaluation.
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## Logical
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Logical operators return values depending on the boolean values of the given arguments. If an argument isn't `false` or `nil`, then the operator evaluates it as `true`. Unlike many other languages, Luau considers both zero and the empty string as `true`. The following table summarizes how logical operators behave in [conditionals](./control-structures.md#if-statements).
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<table>
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<thead>
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<tr>
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<th>Operator</th>
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<th>Descriptions</th>
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</tr>
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</thead>
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<tr>
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<td>`and`</td>
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<td>Evaluates as `true` only if both conditions are true</td>
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</tr>
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<tr>
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<td>`or`</td>
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<td>Evaluates as `true` if either condition is true</td>
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</tr>
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<tr>
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<td>`not`</td>
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<td>Evaluates as the opposite of the condition</td>
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</tr>
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</table>
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### and
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The binary operator `and` returns one of the two arguments. If the first argument evaluates to `true`, then it returns the second argument. Otherwise, it returns the first argument.
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```lua
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print(4 and 5) -- 5
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print(nil and 12) -- nil
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print(false and 12) -- false
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print(false and true) -- false
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print(false and false) -- false
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print(true and false) -- false
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print(true and true) -- true
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```
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You can use `and` to test multiple conditions in [control structures](./control-structures.md) such as [`if` statements](./control-structures.md#if-statements) and [`while` loops](./control-structures.md#while-loops). For example, the following `if`‑`then` statement tests that two conditions are both true:
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```lua
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local pasta = true
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local tomatoSauce = true
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if pasta == true and tomatoSauce == true then
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print("We have spaghetti dinner")
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else
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print("Something is missing...")
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end
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-- Output: We have spaghetti dinner
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```
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### or
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The binary operator `or` returns one of the two arguments. If the first argument evaluates to `true`, then it returns the first argument. Otherwise, it returns the second argument.
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```lua
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local y = x or 1
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print(y) -- 1 because x doesn't exist and is therefore nil
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local d = false
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local e = d or 1
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print(e) -- 1 because d is false
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print(4 or 5) -- 4
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print(nil or 12) -- 12
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print(false or 12) -- 12
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print(false or true) -- true
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print(false or false) -- false
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print(true or false) -- true
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print(true or true) -- true
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```
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You can use `or` to perform complex logical tests in [control structures](./control-structures.md). For example, the following `if`‑`then` statement tests whether two conditions are true **or** a third condition is true:
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```lua
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local pasta = false
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local tomatoSauce = true
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local garlicBread = true
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if (pasta == true and tomatoSauce == true) or garlicBread == true then
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print("We have either spaghetti dinner OR garlic bread")
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else
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print("Something is missing...")
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end
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-- Output: We have either spaghetti dinner OR garlic bread
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```
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### not
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The unary operator `not` returns the opposite boolean value of the argument. If the argument is `false` or `nil`, then it returns `true`. Otherwise, it returns `false`.
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```lua
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print(not true) -- false
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print(not false) -- true
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print(not nil) -- true
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print(not "text") -- false
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print(not 0) -- false
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```
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You can use the `not` operator to trigger a conditional or loop if a variable is `false` or `nil`.
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```lua
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local nilVariable -- Variable is declared but has no value, so it's nil
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local falseVariable = false -- Variable is declared with value of false
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if not nilVariable then
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print(nilVariable) -- Outputs "nil" because nil isn't true
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end
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if not falseVariable then
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print(falseVariable) -- Outputs "false" because false isn't true
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end
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```
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You can also use the `not` operator to test for the opposite of an entire multi-condition statement. In the following code sample, the `if`‑`then` conditional tests that it's neither true that three is greater than four nor is it true that five is greater than four.
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```lua
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local three = 3
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local four = 4
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local five = 5
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if not (three > four or five < four) then
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print("Three is less than 4 and five is greater than 4.")
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end
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-- Output: Three is less than 4 and five is greater than 4.
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```
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## Relational
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Relational operators compare two parameters and return a [`boolean`](./booleans.md): `true` or `false`.
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<table>
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<thead>
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<tr>
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<th>Operator</th>
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<th>Description</th>
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<th>Example</th>
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<th>Associated metamethod</th>
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</tr>
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</thead>
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<tr>
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<td>`==`</td>
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<td>Equal to</td>
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<td>`3 == 5` → `false`</td>
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<td>`__eq`</td>
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</tr>
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<tr>
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<td>`~=`</td>
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<td>Not equal to</td>
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<td>`3 ~= 5` → `true`</td>
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<td></td>
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</tr>
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<tr>
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<td>`>`</td>
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<td>Greater than</td>
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<td>`3 > 5` → `false`</td>
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<td></td>
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</tr>
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<tr>
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<td>`<`</td>
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<td>Less than</td>
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<td>`3 < 5` → `true`</td>
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<td>`__lt`</td>
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</tr>
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<tr>
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<td>`>=`</td>
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<td>Greater than or equal to</td>
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<td>`3 >= 5` → `false`</td>
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<td></td>
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</tr>
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<tr>
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<td>`<=`</td>
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<td>Less than or equal to</td>
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<td>`3 <= 5` → `true`</td>
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<td>`__le`</td>
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</tr>
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</table>
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## Arithmetic
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Luau supports the usual binary operators along with exponentiation, modulus, and unary negation.
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<table>
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<thead>
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<tr>
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<th>Operator</th>
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<th>Description</th>
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<th>Example</th>
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<th>Associated metamethod</th>
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</tr>
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</thead>
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<tr>
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<td>`+`</td>
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<td>Addition</td>
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<td>`1 + 1 = 2`</td>
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<td>`__add`</td>
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</tr>
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<tr>
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<td>`-`</td>
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<td>Subtraction</td>
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<td>`1 - 1 = 0`</td>
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<td>`__sub`</td>
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</tr>
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<tr>
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<td>`*`</td>
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<td>Multiplication</td>
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<td>`5 * 5 = 25`</td>
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<td>`__mul`</td>
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</tr>
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<tr>
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<td>`/`</td>
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<td>Division</td>
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<td>`10 / 5 = 2`</td>
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<td>`__div`</td>
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</tr>
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<tr>
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<td>`//`</td>
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<td>Floor Division</td>
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<td>
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`10 // 4 = 2`<br />
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`-10 // 4 = -3`
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</td>
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<td>`__idiv`</td>
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</tr>
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<tr>
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<td>`^`</td>
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<td>Exponentiation</td>
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<td>`2 ^ 4 = 16`</td>
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<td>`__pow`</td>
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</tr>
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<tr>
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<td>`%`</td>
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<td>Modulus</td>
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<td>`13 % 7 = 6`</td>
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<td>`__mod`</td>
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</tr>
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<tr>
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<td>`-`</td>
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<td>Unary negation</td>
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<td>`-2 = 0 - 2`</td>
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<td>`__unm`</td>
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</tr>
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</table>
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## Compound assignment
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You can use compound assignment operators to set a variable equal to the result of an operation where the first parameter is the variable's current value.
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The operation in a compound assignment occurs once. For example, if an expression generates a random index in a table, Luau uses the same index for both the operation and the assignment.
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In the following examples, suppose `local x = 3`.
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<table>
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<thead>
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<tr>
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<th>Operator</th>
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<th>Operation</th>
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<th>Example</th>
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<th>New Value of `x`</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td>`+=`</td>
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<td>Addition</td>
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<td>`x += 2`</td>
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<td>`5`</td>
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</tr>
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<tr>
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<td>`-=`</td>
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<td>Subtraction</td>
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<td>`x -= 2`</td>
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<td>`1`</td>
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</tr>
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<tr>
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<td>`*=`</td>
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<td>Multiplication</td>
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<td>`x *= 2`</td>
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<td>`6`</td>
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</tr>
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<tr>
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<td>`/=`</td>
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<td>Division</td>
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<td>`x /= 2`</td>
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<td>`1.5`</td>
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</tr>
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<tr>
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<td>`//=`</td>
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<td>Floor Division</td>
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<td>`x //= 2`</td>
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<td>`1`</td>
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</tr>
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<tr>
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<td>`%=`</td>
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<td>Modulus</td>
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<td>`x %= 2`</td>
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<td>`1`</td>
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</tr>
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<tr>
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<td>`^=`</td>
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<td>Exponentiation</td>
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<td>`x ^= 2`</td>
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<td>`9`</td>
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</tr>
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<tr>
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<td>`..=`</td>
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<td>Concatenation</td>
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<td>`x ..= " World!" `</td>
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<td>`"3 World!"`</td>
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</tr>
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</tbody>
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</table>
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## Miscellaneous
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Miscellaneous operators include **concatenation** and **length**.
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<table>
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<thead>
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<tr>
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<th>Operator</th>
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<th>Description</th>
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<th>Example</th>
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<th>Associated metamethod</th>
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</tr>
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</thead>
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<tr>
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<td>`..`</td>
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<td>Concatenates two strings</td>
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<td>`print("Hello " .. "World!")`</td>
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<td>`__concat`</td>
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</tr>
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<tr>
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<td>`#`</td>
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<td>Length of table</td>
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<td>If `tableVar = {1, 2, 3}`, then `#tableVar == 3`.</td>
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<td>`__len`</td>
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</tr>
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</table>
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