// Returns a list of values from $lists minus duplicates
// -------------------------------------------------------------------------------
// @documentation http://sassylists.com/documentation/#union
// -------------------------------------------------------------------------------
// @alias `merge()`
// -------------------------------------------------------------------------------
// @dependence `flatten()`
// @dependence `remove-duplicates()`
// -------------------------------------------------------------------------------
// @example union((a b), (b c), (a b c d)) => a b c d
// -------------------------------------------------------------------------------
// @param $lists [ArgList] : lists
// -------------------------------------------------------------------------------
// @return [List]

@function union($lists...) {
    @return remove-duplicates(flatten($lists));
}

// Alias
@function merge($lists...) {
    @return union($lists...);
}