83 lines
3.1 KiB
Markdown
83 lines
3.1 KiB
Markdown
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---
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layout: "language"
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page_title: "Operators - Configuration Language"
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---
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# Arithmetic and Logical Operators
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An _operator_ is a type of expression that transforms or combines one or more
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other expressions. Operators either combine two values in some way to
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produce a third result value, or transform a single given value to
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produce a single result.
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Operators that work on two values place an operator symbol between the two
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values, similar to mathematical notation: `1 + 2`. Operators that work on
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only one value place an operator symbol before that value, like
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`!true`.
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The Terraform language has a set of operators for both arithmetic and logic,
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which are similar to operators in programming languages such as JavaScript
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or Ruby.
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When multiple operators are used together in an expression, they are evaluated
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in the following order of operations:
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1. `!`, `-` (multiplication by `-1`)
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1. `*`, `/`, `%`
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1. `+`, `-` (subtraction)
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1. `>`, `>=`, `<`, `<=`
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1. `==`, `!=`
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1. `&&`
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1. `||`
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Parentheses can be used to override the default order of operations. Without
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parentheses, higher levels are evaluated first, so `1 + 2 * 3` is interpreted
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as `1 + (2 * 3)` and _not_ as `(1 + 2) * 3`.
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The different operators can be gathered into a few different groups with
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similar behavior, as described below. Each group of operators expects its
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given values to be of a particular type. Terraform will attempt to convert
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values to the required type automatically, or will produce an error message
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if this automatic conversion is not possible.
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## Arithmetic Operators
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The arithmetic operators all expect number values and produce number values
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as results:
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* `a + b` returns the result of adding `a` and `b` together.
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* `a - b` returns the result of subtracting `b` from `a`.
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* `a * b` returns the result of multiplying `a` and `b`.
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* `a / b` returns the result of dividing `a` by `b`.
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* `a % b` returns the remainder of dividing `a` by `b`. This operator is
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generally useful only when used with whole numbers.
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* `-a` returns the result of multiplying `a` by `-1`.
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## Equality Operators
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The equality operators both take two values of any type and produce boolean
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values as results.
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* `a == b` returns `true` if `a` and `b` both have the same type and the same
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value, or `false` otherwise.
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* `a != b` is the opposite of `a == b`.
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## Comparison Operators
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The comparison operators all expect number values and produce boolean values
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as results.
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* `a < b` returns `true` if `a` is less than `b`, or `false` otherwise.
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* `a <= b` returns `true` if `a` is less than or equal to `b`, or `false`
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otherwise.
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* `a > b` returns `true` if `a` is greater than `b`, or `false` otherwise.
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* `a >= b` returns `true` if `a` is greater than or equal to `b`, or `false` otherwise.
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## Logical Operators
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The logical operators all expect bool values and produce bool values as results.
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* `a || b` returns `true` if either `a` or `b` is `true`, or `false` if both are `false`.
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* `a && b` returns `true` if both `a` and `b` are `true`, or `false` if either one is `false`.
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* `!a` returns `true` if `a` is `false`, and `false` if `a` is `true`.
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