sass-site/source/documentation/at-rules/control/index.md

title	introduction
Flow Control Rules	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](/documentation/at-rules/mixin) and [functions](/documentation/at-rules/function) to write small algorithms to make writing your Sass easier. Sass supports four flow control rules.

• @if controls whether or not a block is evaluated.

• @each evaluates a block for each element in a list or each pair in a map.

• @for evaluates a block a certain number of times.

• @while evaluates a block until a certain condition is met.