_functions.scss

// Strip the unit from the given value and return the value
@function strip-unit($value) {
    @return $value / ($value * 0 + 1);
}

// Return an em unit based on the pixel value and context
@function rem($px, $context: $base-font-size) {
    @return #{strip-unit($px / strip-unit($context))}rem;
}

// Returns the opposite direction of each direction in a list
// @param {List} $directions - List of initial directions
// @return {List} - List of opposite directions
@function opposite-direction($directions) {
    $opposite-directions: ();
    $direction-map: (
        'top':    'bottom',
        'right':  'left',
        'bottom': 'top',
        'left':   'right',
        'center': 'center',
        'ltr':    'rtl',
        'rtl':    'ltr'
    );

    @each $direction in $directions {
        $direction: to-lower-case($direction);

        @if map-has-key($direction-map, $direction) {
            $opposite-directions: append($opposite-directions, unquote(map-get($direction-map, $direction)));
        }
        @else {
            @warn 'No opposite direction can be found for `#{$direction}`. Direction omitted.';
        }
    }
    @return $opposite-directions;
}