Position mixin

@mixin pos-a($top,$right,$bottom,$left,$width,$height,$zindex){
  position: absolute;
  @if($top != ''){
    top: rem($top)
  }
  @if($left != ''){
    left: rem($left)
  }
  @if($bottom != ''){
    bottom: rem($bottom)
  }
  @if($right != ''){
    right: rem($right)
  }
  @if($width != ''){
    width: rem($width)
  } @else {
    width: auto
  }
  @if($height != ''){
    height: rem($height)
  }
  @if($zindex != ''){
    z-index: $zindex;
  }
}

@mixin pos-f($top,$right,$bottom,$left,$width,$height,$zindex){
  position: fixed;
  @if($top != ''){
    top: rem($top)
  }
  @if($left != ''){
    left: rem($left)
  }
  @if($bottom != ''){
    bottom: rem($bottom)
  }
  @if($right != ''){
    right: rem($right)
  }
  @if($width != ''){
    width: rem($width)
  } @else {
    width: auto
  }
  @if($height != ''){
    height: rem($height)
  }
  @if($zindex != ''){
    z-index: $zindex;
  }
}

// example
div { @include pos-a(0,0,'','',100px,100px,5) }