---
title: Flow Control Rules
introduction: >
  Sass provides a number of at-rules that make it possible to control whether
  styles get emitted, or to emit them multiple times with small variations. They
  can also be used in [mixins](mixin) and [functions](function) to write small
  algorithms to make writing your Sass easier.
---

Sass supports four flow control rules:

* [`@if`](control/if) controls whether or not a block is evaluated.
* [`@each`](control/each) evaluates a block for each element in a [list][] or
  each pair in a [map][].
* [`@for`](control/for) evaluates a block a certain number of times.
* [`@while`](control/while) evaluates a block until a certain condition is met.

[list]: ../values/lists
[map]: ../values/maps