@function add-gutter($gutter-definition) {
  $parsed: parse-add($gutter-definition);

  @if nth($parsed, 2) == false and length($gutters) == 0 {
    @return nth($parsed, 1);
  }
  @else {
    @return append($gutters, (nth($parsed, 1) nth($parsed, 2)), 'comma');
  }
}