// 声明块
@mixin b($block) {
  $B: $namespace + '-' + $block !global;

  .#{$B} {
    @content;
  }
}

// 声明元素
@mixin e($element) {
  $E: $element !global;
  $selector: &;
  $currentSelector: '';

  @each $unit in $element {
    $currentSelector: #{$currentSelector + '.' + $B + $element-separator + $unit + ','}
  }

  @if hitAllSpecialNestRule($selector) {
    @at-root {
      #{$selector} {
        #{$currentSelector} {
          @content;
        }
      }
    }
  } @else {
    @at-root {
      #{$currentSelector} {
        @content;
      }
    }
  }
}

// 声明修饰符
@mixin m($modifier) {
  $selector: &;
  $currentSelector: '';
  
  @each $unit in $modifier {
    $currentSelector: #{$currentSelector + $selector + $modifier-separator + $unit + ','}
  }

  @at-root {
    #{$currentSelector} {
      @content;
    }
  }
}