@function el($name, $extensions...) {
  @if length($extensions) == 0 {
    @return el-#{$name};
  } @else {
    $sub: nth($extensions, 1);
    @if length($extensions) == 1 {
      @return el-#{$name}__#{$sub};
    } @else {
      $modifier: nth($extensions, 2);
      @if $sub == false {
        @return el-#{$name}--#{$modifier};
      } @else {
        @return el-#{$name}__#{$sub}--#{$modifier};
      }
    }
  }
}

@function is($state) {
  @return is-#{$state};
}