sass-site/source/documentation/breaking-changes/slash-div.html.md.erb

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---
title: "Breaking Change: Slash as Division"
introduction: >
Sass currently treats `/` as a division operation in some contexts and a
separator in others. This makes it difficult for Sass users to tell what any
given `/` will mean, and makes it hard to work with new CSS features that use
`/` as a separator.
---
<% impl_status dart: false, libsass: false, ruby: false %>
Today, Sass uses [complex heuristics][] to figure out whether a `/` should be
treated as division or a separator. Even then, as a separator it just produces
an unquoted string that's difficult to inspect from within Sass. As more and
more CSS features like [CSS Grid][] and the [new `rgb()` and `hsl()` syntax][]
use `/` as a separator, this is becoming more and more painful to Sass users.
[complex heuristics]: ../operators/numeric#slash-separated-values
[CSS Grid]: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-row
[new `rgb()` and `hsl()` syntax]: https://drafts.csswg.org/css-color/#rgb-functions
Because Sass is a CSS superset, we're matching CSS's syntax by redefining `/` to
be *only* a separator. `/` will be treated as a new type of list separator,
similar to how `,` works today. Division will instead be written using the new
`math.div()` function. This function will behave exactly the same as `/` does
today.
<% example do %>
@use "sass:math";
// Future Sass, doesn't work yet!
.item3 {
$row: span math.div(6, 2) / 7; // A two-element slash-separated list.
grid-row: $row;
}
===
@use "sass:math"
// Future Sass, doesn't work yet!
.item3
$row: span math.div(6, 2) / 7 // A two-element slash-separated list.
grid-row: $row
===
.item3 {
grid-row: span 3 / 7;
}
<% end %>
## Transition Period
<% impl_status dart: "1.33.0", libsass: false, ruby: false,
feature: "math.div() and list.slash()" %>
To ease the transition, we've begun by adding the `math.div()` function. The `/`
operator still does division for now, but it also prints a deprecation warning
when it does so. Users should switch all division to use `math.div()` instead.
<% example(autogen_css: false) do %>
@use "sass:math";
// WRONG, will not work in future Sass versions.
@debug (12px/4px); // 3
// RIGHT, will work in future Sass versions.
@debug math.div(12px, 4px); // 3
===
@use "sass:math"
// WRONG, will not work in future Sass versions.
@debug (12px/4px) // 3
// RIGHT, will work in future Sass versions.
@debug math.div(12px, 4px) // 3
<% end %>
Slash-separated lists will also be available in the transition period. Because
they can't be created with `/` yet, the `list.slash()` function will be added to
create them. You will also be able to pass `"slash"` as the `$separator` to the
[`list.join()` function][] and the [`list.append()` function][].
[`list.join()` function]: ../modules/list#join
[`list.append()` function]: ../modules/list#append
<% example do %>
@use "sass:list";
.item3 {
$row: list.slash(span divide(6, 2), 7);
grid-row: $row;
}
===
@use "sass:list";
.item3
$row: list.slash(span divide(6, 2), 7)
grid-row: $row
===
.item3 {
grid-row: span 3 / 7;
}
<% end %>
## Automatic Migration
You can use [the Sass migrator][] to automatically update your stylesheets to
use `math.div()` and `list.slash()`.
[the Sass migrator]: https://github.com/sass/migrator#readme
```shellsession
$ npm install -g sass-migrator
$ sass-migrator division **/*
```