An operator is a symbol that tells the interpreter to perform
specific mathematical or logical manipulations. Lua language is rich in
built-in operators and provides the following type of operators −
- Arithmetic Operators
- Relational Operators
- Logical Operators
- Misc Operators
This tutorial will explain the arithmetic, relational, logical, and other miscellaneous operators one by one.
Arithmetic Operators
Following table shows all the arithmetic operators supported by Lua language. Assume variable
A holds 10 and variable
B holds 20 then −
Show Examples
Operator |
Description |
Example |
+ |
Adds two operands |
A + B will give 30 |
- |
Subtracts second operand from the first |
A - B will give -10 |
* |
Multiply both operands |
A * B will give 200 |
/ |
Divide numerator by de-numerator |
B / A will give 2 |
% |
Modulus Operator and remainder of after an integer division |
B % A will give 0 |
^ |
Exponent Operator takes the exponents |
A^2 will give 100 |
- |
Unary - operator acts as negation |
-A will give -10 |
Relational Operators
Following table shows all the relational operators supported by Lua language. Assume variable
A holds 10 and variable
B holds 20 then −
Show Examples
Operator |
Description |
Example |
== |
Checks if the value of two operands are equal or not, if yes then condition becomes true. |
(A == B) is not true. |
~= |
Checks if the value of two operands are equal or not, if values are not equal then condition becomes true. |
(A ~= B) is true. |
> |
Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true. |
(A > B) is not true. |
< |
Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true. |
(A < B) is true. |
>= |
Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true. |
(A >= B) is not true. |
<= |
Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true. |
(A <= B) is true. |
Logical Operators
Following table shows all the logical operators supported by Lua language. Assume variable
A holds true and variable
B holds false then −
Show Examples
Operator |
Description |
Example |
and |
Called Logical AND operator. If both the operands are non zero then condition becomes true. |
(A and B) is false. |
or |
Called Logical OR Operator. If any of the two operands is non zero then condition becomes true. |
(A or B) is true. |
not |
Called Logical NOT Operator. Use to reverses the logical state of
its operand. If a condition is true then Logical NOT operator will make
false. |
!(A and B) is true. |
Misc Operators
Miscellaneous operators supported by Lua Language include
concatenation and
length.
Show Examples
Operator |
Description |
Example |
.. |
Concatenates two strings. |
a..b where a is "Hello " and b is "World", will return "Hello World". |
# |
An unary operator that return the length of the a string or a table. |
#"Hello" will return 5 |
Operators Precedence in Lua
Operator precedence determines the grouping of terms in an
expression. This affects how an expression is evaluated. Certain
operators have higher precedence than others; for example, the
multiplication operator has higher precedence than the addition operator
−
For example, x = 7 + 3 * 2; Here x is assigned 13, not 20 because
operator * has higher precedence than + so it first get multiplied with
3*2 and then adds into 7.
Here, operators with the highest precedence appear at the top of the
table, those with the lowest appear at the bottom. Within an expression,
higher precedence operators will be evaluated first.
Show Examples
Category |
Operator |
Associativity |
Unary |
not # - |
Right to left |
Concatenation |
.. |
Right to left |
Multiplicative |
* / % |
Left to right |
Additive |
+ - |
Left to right |
Relational |
< > <= >= == ~= |
Left to right |
Equality |
== ~= |
Left to right |
Logical AND |
and |
Left to right |
Logical OR |
or |
Left to right |
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