/* Return index of matched value in list */
@function -index($list, $value) {

  @for $i from 1 through length($list) {
    @if nth($list, $i) == $value {
      @return $i;
    }
  }

  @return null;
}

@function -z($key, $mod: 0) {

  $index: -index($layers, $key) * 10;

  @if $mod {
    @return $index + $mod;
  }

  @return $index;
}

@function -color($key) {
  @if map-has-key($colors, $key) {
    @return map-get($colors, $key);
  }

  @warn "Unknown `#{$key}` in $colors.";
  @return null;
}

@function -weight($key) {
  @if map-has-key($font-weights, $key) {
    @return map-get($font-weights, $key);
  }

  @warn "Unknown `#{$key}` in $font-weights.";
  @return null;
}

@function -bp($key) {
  @if map-has-key($breakpoints, $key) {
    @return map-get($breakpoints, $key);
  }

  @warn "Unknown `#{$key}` in $breakpoints.";
  @return null;
}