scale Sass mixin to convert pixels to EMs

scale.scss

@mixin scale($props, $sizes, $base: 16) {
    $values: ();
    $sublists: false;
    @each $s in $sizes {
        /* unwrap lists for values that have multiple list of values such as text-shadow */
        @if type-of($s) == list {
            $sublists: true;
            $vv: ();
            @each $ss in $s {
                $vv: append($vv, if(type-of($ss) == number, #{$ss / $base}em, $ss));
            }
            $values: append($values, join((), $vv));
        } @else {
            $values: append($values, if(type-of($s) == number, #{$s / $base}em, $s));
            /*$values: append($values, #{$s}px); */
        }
    }
    $value: join((), $values, if($sublists, comma, space));
    @each $prop in $props { #{$prop}: $value }
}

usage.scss

/* the simplest version */
@include scale(line-height, 30)

/* overrides the default 16px with a different base font size */
@include scale(line-height, 30, 25)

/* short-hand specifying 2 properties with the same value */
@include scale(width height, 125);

/* a property taking multiple values. output: padding: 0em 1.5625em; */
@include scale(padding, 0 25, 16);

/* A property allowing non-size values (passed through unchanged) accepting multiple properties
output: text-shadow: #0d6e28 0.0625em 0.0625em, #777 0em 0em 0.125em;
*/
@include scale(text-shadow, (#0d6e28 1 1) (#777 0 0 2), 16);