// mixins

@mixin hello($a: one, $b:two, $c:three, $d: four) {
    out: $a $b $c $d;
}

pre {
    @include hello(alpha, $d: palace, $b: fort);
}


// functions

@function cool($a, $b) {
    @return $a - $b;
}

div {
    hello: cool($b: 5, $a: 10);
    world: cool(5, 10);
}