142 lines
2.7 KiB
Plaintext
142 lines
2.7 KiB
Plaintext
---
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layout: docs
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page_title: range - Functions - Configuration Language
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sidebar_title: range
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description: The range function generates sequences of numbers.
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---
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# `range` Function
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`range` generates a list of numbers using a start value, a limit value,
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and a step value.
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```hcl
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range(max)
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range(start, limit)
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range(start, limit, step)
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```
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The `start` and `step` arguments can be omitted, in which case `start` defaults
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to zero and `step` defaults to either one or negative one depending on whether
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`limit` is greater than or less than `start`.
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The resulting list is created by starting with the given `start` value and
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repeatedly adding `step` to it until the result is equal to or beyond `limit`.
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The interpretation of `limit` depends on the direction of `step`: for a positive
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step, the sequence is complete when the next number is greater than or equal
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to `limit`. For a negative step, it's complete when less than or equal.
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The sequence-building algorithm follows the following pseudocode:
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```text
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let num = start
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while num < limit: (or, for negative step, num >= limit)
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append num to the sequence
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num = num + step
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return the sequence
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```
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Because the sequence is created as a physical list in memory, Packer imposes
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an artificial limit of 1024 numbers in the resulting sequence in order to avoid
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unbounded memory usage if, for example, a very large value were accidentally
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passed as the limit or a very small value as the step. If the algorithm above
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would append the 1025th number to the sequence, the function immediately exits
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with an error.
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We recommend iterating over existing collections where possible, rather than
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creating ranges. However, creating small numerical sequences can sometimes
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be useful when combined with other collections in collection-manipulation
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functions or `for` expressions.
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## Examples
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```shell-session
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> range(3)
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[
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0,
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1,
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2,
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]
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> range(1, 4)
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[
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1,
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2,
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3,
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]
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> range(1, 8, 2)
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[
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1,
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3,
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5,
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7,
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]
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> range(1, 4, 0.5)
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[
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1,
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1.5,
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2,
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2.5,
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3,
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3.5,
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]
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> range(4, 1)
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[
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4,
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3,
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2,
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]
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> range(10, 5, -2)
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[
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10,
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8,
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6,
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]
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```
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The `range` function is primarily useful when working with other collections
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to produce a certain number of instances of something. For example:
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```hcl
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variable "name_counts" {
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type = map(number)
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default = {
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"foo" = 2
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"bar" = 4
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}
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}
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locals {
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expanded_names = {
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for name, count in var.name_counts : name => [
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for i in range(count) : format("%s%02d", name, i)
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]
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}
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}
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output "expanded_names" {
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value = local.expanded_names
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}
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# Produces the following expanded_names value when run with the default
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# "name_counts":
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#
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# {
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# "bar" = [
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# "bar00",
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# "bar01",
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# "bar02",
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# "bar03",
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# ]
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# "foo" = [
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# "foo00",
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# "foo01",
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# ]
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# }
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```
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