An operator is a special set of symbols used to perform an operation or conditional evaluation.
The logical operators for conditional statements are and, or, and not. These operators consider both false and nil as “false” and anything else as “true.”
| Operator | Description |
|---|---|
and |
Evaluates as true only if both conditions are true |
or |
Evaluates as true if either condition is true |
not |
Evaluates as the opposite of the condition |
Relational operators compare two parameters and return a boolean true or false.
| Operator | Description | Associated metamethod |
|---|---|---|
== |
Equal to | __eq |
~= |
Not equal to | |
> |
Greater than | |
< |
Less than | __lt |
>= |
Greater than or equal to | |
<= |
Less than or equal to | __le |
Lua supports the usual binary operators along with exponentiation, modulus, and unary negation.
| Operator | Description | Example | Associated metamethod |
|---|---|---|---|
+ |
Addition | 1 + 1 = 2 | __add |
- |
Subtraction | 1 - 1 = 0 | __sub |
* |
Multiplication | 5 * 5 = 25 | __mul |
/ |
Division | 10 / 5 = 2 | __div |
^ |
Exponentiation | 2 ^ 4 = 16 | __pow |
% |
Modulus | 13 % 7 = 6 | __mod |
- |
Unary negation | -2 = 0 - 2 | __unm |
Miscellaneous operators include concatenation and length.
| Operator | Description | Associated metamethod |
|---|---|---|
.. |
Concatenates two strings | __concat |
# |
Length of table | __len |
Compound assignment operators are used to set a variable equal to the result of an operation where the first parameter is the variable’s current value.
{% hint style="info" %} The expression on the left side of a compound assignment is only evaluated once. For example, if an expression generates a random index in a table, the same index is used for both the operation and the assignment. {% endhint %}
| Operator | Operation |
|---|---|
+= |
Addition |
-= |
Subtraction |
*= |
Multiplication |
/= |
Division |
%= |
Modulus |
^= |
Exponentiation |
..= |
Concatenation |