---
title: Functions
---

<% impl_status dart: true, libsass: '3.5.0', ruby: '3.5.0' do %>
  In older versions of LibSass and Ruby Sass, the [`call()` function][] took a
  string representing a function's name. This was changed to take a function
  value instead in preparation for a new module system where functions are no
  longer global and so a given name may not always refer to the same function.

  [`call()` function]: ../functions/meta#call
<% end %>

[Functions][] can be values too! You can't directly write a function as a value,
but you can pass a function's name to the [`get-function()` function][] to get
it as a value. Once you have a function value, you can pass it to the [`call()`
function][] to call it. This is useful for writing *higher-order functions* that
call other functions.

[Functions]: ../at-rules/function
[`get-function` function]: ../functions/meta#get-function
[`call()` function]: ../functions/meta#call

<%# TODO(nweiz): auto-generate this CSS once we're compiling with Dart Sass %>

<% example do %>
  /// Return a copy of $list with all elements for which $condition returns `true`
  /// removed.
  @function remove-where($list, $condition) {
    $new-list: ();
    $separator: list-separator($list);
    @each $element in $list {
      @if not call($condition, $element) {
        $new-list: append($new-list, $element, $separator: $separator);
      }
    }
    @return $new-list;
  }

  $fonts: Tahoma, Geneva, "Helvetica Neue", Helvetica, Arial, sans-serif;

  content {
    @function contains-helvetica($string) {
      @return str-index($string, "Helvetica");
    }
    font-family: remove-where($fonts, get-function("contains-helvetica"));
  }
  ===
  /// Return a copy of $list with all elements for which $condition returns `true`
  /// removed.
  @function remove-where($list, $condition)
    $new-list: ()
    $separator: list-separator($list)
    @each $element in $list
      @if not call($condition, $element)
        $new-list: append($new-list, $element, $separator: $separator)


    @return $new-list


  $fonts: Tahoma, Geneva, "Helvetica Neue", Helvetica, Arial, sans-serif

  content
    @function contains-helvetica($string)
      @return str-index($string, "Helvetica")

    font-family: remove-where($fonts, get-function("contains-helvetica"))
  ===
  content {
    font-family: Tahoma, Geneva, Arial, sans-serif;
  }
<% end %>