RESET mixin

SassMeister-input.scss

// ----
// Sass (v3.3.14)
// Compass (v1.0.3)
// ----

@mixin width($span: 1 1, $options: ()) {
  @include width-helper(map-merge((span: $span), $options)...);
}

@mixin width-helper($span: 1 1, $right: null, $left: null, $cycle: null, $out: null) {

  $n: nth($span, 1); $d: nth($span, 2);
  width: $n / $d * 100%;

  @if $right { margin-right: nth($right, 1) / if(length($right) > 1, nth($right, 2), $d) * 100%; }
  @if $left { margin-left: nth($left, 1) / if(length($left) > 1, nth($left, 2), $d) * 100%; }
  @if $cycle { &:nth-child(#{$cycle}n+1) { clear: left; } }
  @else if $out { position: absolute; #{opposite($out)}: 100%; }
}

.test {
  color: blue;
  @include width(1 3, (right: 1 2, left: 2 5));
}
.test2 {
  color: blue;
  @include width(1 1, (out: right));
}

SassMeister-output.css

.test {
  color: blue;
  width: 33.33333%;
  margin-right: 50%;
  margin-left: 40%;
}

.test2 {
  color: blue;
  width: 100%;
  position: absolute;
  opposite(right): 100%;
}