@function test ($value) {
  $delta: $value + 1;
  @if($value == 0)
  {
    @return 0;
  }@else if($value == 1) {
    @return 10;
  }
  @else{@return $delta;}
}

@mixin test-each ($items) {
  @each $i in $items
  {
    .item-#{$i} {
      width: 2em * $i;
    }
  }
}

@for $i from 1 through 3
{
  .item-#{$i} {
    width: 2em * $i;
  }
}