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SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

// all credits to bootstrap

//
//
// I want to generate something like this:
// http://sassmeister.com/gist/1d3659803d5833e75709
//
//
$grid-columns: 12;

@mixin float-grid-columns($class, $i: 1, $list: ".col-#{$class}-#{$i}") {
  @for $i from (1 + 1) through $grid-columns {
    $list: "#{$list}, .col-#{$class}-#{$i}";
  }

  #{$list} {
    float: left;
  }
}

@mixin calc-grid-column($index, $class, $type) {
  @if ($type == width) and ($index > 0) {
    .col-#{$class}-#{$index} {
      width: percentage(($index / $grid-columns));
    }
  }
}

@mixin loop-grid-columns($columns, $class, $type) {
  @for $i from 0 through $columns {
    @include calc-grid-column($i, $class, $type);
  }
}

@mixin make-grid($class) {
  @include float-grid-columns($class);
  @include loop-grid-columns($grid-columns, $class, width);
}

@include make-grid(xs);

SassMeister-output.css

.col-xs-1, .col-xs-2, .col-xs-3, .col-xs-4, .col-xs-5, .col-xs-6, .col-xs-7, .col-xs-8, .col-xs-9, .col-xs-10, .col-xs-11, .col-xs-12 {
  float: left;
}

.col-xs-1 {
  width: 8.33333%;
}

.col-xs-2 {
  width: 16.66667%;
}

.col-xs-3 {
  width: 25%;
}

.col-xs-4 {
  width: 33.33333%;
}

.col-xs-5 {
  width: 41.66667%;
}

.col-xs-6 {
  width: 50%;
}

.col-xs-7 {
  width: 58.33333%;
}

.col-xs-8 {
  width: 66.66667%;
}

.col-xs-9 {
  width: 75%;
}

.col-xs-10 {
  width: 83.33333%;
}

.col-xs-11 {
  width: 91.66667%;
}

.col-xs-12 {
  width: 100%;
}