1<===> input.scss
2
3@mixin flex($grow: 1, $shrink: null, $basis: null) {
4  -webkit-box-flex: $grow;
5  -webkit-flex: $grow $shrink $basis;
6  -moz-box-flex: $grow;
7  -moz-flex: $grow $shrink $basis;
8  -ms-flex: $grow $shrink $basis;
9  flex: $grow $shrink $basis;
10}
11
12[flex] {
13  @include flex;
14}
15
16<===> output.css
17[flex] {
18  -webkit-box-flex: 1;
19  -webkit-flex: 1;
20  -moz-box-flex: 1;
21  -moz-flex: 1;
22  -ms-flex: 1;
23  flex: 1;
24}
25