github.com/hugorut/terraform@v1.1.3/website/docs/language/expressions/operators.mdx (about)

     1  ---
     2  page_title: Operators - Configuration Language
     3  description: >-
     4    Operators transform or combine expressions. Learn about arithmetic, logical,
     5    equality, and comparison operators.
     6  ---
     7  
     8  # Arithmetic and Logical Operators
     9  
    10  An _operator_ is a type of expression that transforms or combines one or more
    11  other expressions. Operators either combine two values in some way to
    12  produce a third result value, or transform a single given value to
    13  produce a single result.
    14  
    15  Operators that work on two values place an operator symbol between the two
    16  values, similar to mathematical notation: `1 + 2`. Operators that work on
    17  only one value place an operator symbol before that value, like
    18  `!true`.
    19  
    20  The Terraform language has a set of operators for both arithmetic and logic,
    21  which are similar to operators in programming languages such as JavaScript
    22  or Ruby.
    23  
    24  When multiple operators are used together in an expression, they are evaluated
    25  in the following order of operations:
    26  
    27  1. `!`, `-` (multiplication by `-1`)
    28  1. `*`, `/`, `%`
    29  1. `+`, `-` (subtraction)
    30  1. `>`, `>=`, `<`, `<=`
    31  1. `==`, `!=`
    32  1. `&&`
    33  1. `||`
    34  
    35  Use parentheses to override the default order of operations. Without
    36  parentheses, higher levels will be evaluated first, so Terraform will interpret
    37  `1 + 2 * 3` as `1 + (2 * 3)` and _not_ as `(1 + 2) * 3`.
    38  
    39  The different operators can be gathered into a few different groups with
    40  similar behavior, as described below. Each group of operators expects its
    41  given values to be of a particular type. Terraform will attempt to convert
    42  values to the required type automatically, or will produce an error message
    43  if automatic conversion is impossible.
    44  
    45  ## Arithmetic Operators
    46  
    47  The arithmetic operators all expect number values and produce number values
    48  as results:
    49  
    50  * `a + b` returns the result of adding `a` and `b` together.
    51  * `a - b` returns the result of subtracting `b` from `a`.
    52  * `a * b` returns the result of multiplying `a` and `b`.
    53  * `a / b` returns the result of dividing `a` by `b`.
    54  * `a % b` returns the remainder of dividing `a` by `b`. This operator is
    55    generally useful only when used with whole numbers.
    56  * `-a` returns the result of multiplying `a` by `-1`.
    57  
    58  Terraform supports some other less-common numeric operations as
    59  [functions](/language/expressions/function-calls). For example, you can calculate exponents
    60  using
    61  [the `pow` function](/language/functions/pow).
    62  
    63  ## Equality Operators
    64  
    65  The equality operators both take two values of any type and produce boolean
    66  values as results.
    67  
    68  * `a == b` returns `true` if `a` and `b` both have the same type and the same
    69    value, or `false` otherwise.
    70  * `a != b` is the opposite of `a == b`.
    71  
    72  Because the equality operators require both arguments to be of exactly the
    73  same type in order to decide equality, we recommend using these operators only
    74  with values of primitive types or using explicit type conversion functions
    75  to indicate which type you are intending to use for comparison.
    76  
    77  Comparisons between structural types may produce surprising results if you
    78  are not sure about the types of each of the arguments. For example,
    79  `var.list == []` may seem like it would return `true` if `var.list` were an
    80  empty list, but `[]` actually builds a value of type `tuple([])` and so the
    81  two values can never match. In this situation it's often clearer to write
    82  `length(var.list) == 0` instead.
    83  
    84  ## Comparison Operators
    85  
    86  The comparison operators all expect number values and produce boolean values
    87  as results.
    88  
    89  * `a < b` returns `true` if `a` is less than `b`, or `false` otherwise.
    90  * `a <= b` returns `true` if `a` is less than or equal to `b`, or `false`
    91    otherwise.
    92  * `a > b` returns `true` if `a` is greater than `b`, or `false` otherwise.
    93  * `a >= b` returns `true` if `a` is greater than or equal to `b`, or `false` otherwise.
    94  
    95  ## Logical Operators
    96  
    97  The logical operators all expect bool values and produce bool values as results.
    98  
    99  * `a || b` returns `true` if either `a` or `b` is `true`, or `false` if both are `false`.
   100  * `a && b` returns `true` if both `a` and `b` are `true`, or `false` if either one is `false`.
   101  * `!a` returns `true` if `a` is `false`, and `false` if `a` is `true`.
   102  
   103  Terraform does not have an operator for the "exclusive OR" operation. If you
   104  know that both operators are boolean values then exclusive OR is equivalent
   105  to the `!=` ("not equal") operator.