terraform/website/docs/configuration/expressions/operators.html.md

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language	Operators - Configuration Language

Arithmetic and Logical Operators

An operator is a type of expression that transforms or combines one or more other expressions. Operators either combine two values in some way to produce a third result value, or transform a single given value to produce a single result.

Operators that work on two values place an operator symbol between the two values, similar to mathematical notation: 1 + 2. Operators that work on only one value place an operator symbol before that value, like !true.

The Terraform language has a set of operators for both arithmetic and logic, which are similar to operators in programming languages such as JavaScript or Ruby.

When multiple operators are used together in an expression, they are evaluated in the following order of operations:

1. !, - (multiplication by -1)
2. *, /, %
3. +, - (subtraction)
4. >, >=, <, <=
5. ==, !=
6. &&
7. ||

Parentheses can be used to override the default order of operations. Without parentheses, higher levels are evaluated first, so 1 + 2 * 3 is interpreted as 1 + (2 * 3) and not as (1 + 2) * 3.

The different operators can be gathered into a few different groups with similar behavior, as described below. Each group of operators expects its given values to be of a particular type. Terraform will attempt to convert values to the required type automatically, or will produce an error message if this automatic conversion is not possible.

Arithmetic Operators

The arithmetic operators all expect number values and produce number values as results:

• a + b returns the result of adding a and b together.
• a - b returns the result of subtracting b from a.
• a * b returns the result of multiplying a and b.
• a / b returns the result of dividing a by b.
• a % b returns the remainder of dividing a by b. This operator is generally useful only when used with whole numbers.
• -a returns the result of multiplying a by -1.

Equality Operators

The equality operators both take two values of any type and produce boolean values as results.

• a == b returns true if a and b both have the same type and the same value, or false otherwise.
• a != b is the opposite of a == b.

Comparison Operators

The comparison operators all expect number values and produce boolean values as results.

• a < b returns true if a is less than b, or false otherwise.
• a <= b returns true if a is less than or equal to b, or false otherwise.
• a > b returns true if a is greater than b, or false otherwise.
• a >= b returns true if a is greater than or equal to b, or false otherwise.

Logical Operators

The logical operators all expect bool values and produce bool values as results.

• a || b returns true if either a or b is true, or false if both are false.
• a && b returns true if both a and b are true, or false if either one is false.
• !a returns true if a is false, and false if a is true.