1<===> input.scss
2@function foo($value, $default: 13, $args...) {
3  $res: $value + $default;
4  @if length($args) != 0 {
5    $res: $res + nth($args, 1);
6  }
7  @return $res;
8}
9
10.test {
11  value: foo(3); // expected: 16
12  value: foo(3, 4); // expected: 7
13  value: foo(3, 4, 5, 6); // expected: 12
14}
15
16<===> output.css
17.test {
18  value: 16;
19  value: 7;
20  value: 12;
21}
22