Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v2.0.0)
// ----

@import "sass-list-maps";

@function equivalent_fractions($numerator,$denominator){
    
    $fractions: ();
    @for $i from -$numerator through -1{
        @if($numerator % abs($i) == 0 and $denominator % abs($i) == 0){
            $fractions: map-merge($fractions, abs($i) #{$numerator/abs($i)}-#{$denominator/abs($i)});
        }     
    }
    // return map of all fractions
    @return $fractions;
}


/**
 * Grid Columns
 * 
 * Set the grid column widths based on the number of 
 * columns divided by the total number of columns.
 */
@mixin grid_columns($prefix: null, $suffix: null, $columns: null){
    @for $i from 1 through $columns{
        $css_classes: equivalent_fractions($i,$columns);
        $column_class: null;
        
        @each $css_class in $css_classes{
          $column_class: $column_class, 
          #{ $prefix }#{ value($css_class) }#{ $suffix };
        }
        
        #{$column_class}{
            color: red;
        }
    }
}

@include grid_columns('.col--',null,12);

SassMeister-output.css

/**
 * Grid Columns
 * 
 * Set the grid column widths based on the number of 
 * columns divided by the total number of columns.
 */
.col--1-12 {
  color: red; }

.col--1-6, .col--2-12 {
  color: red; }

.col--1-4, .col--3-12 {
  color: red; }

.col--1-3, .col--2-6, .col--4-12 {
  color: red; }

.col--5-12 {
  color: red; }

.col--1-2, .col--2-4, .col--3-6, .col--6-12 {
  color: red; }

.col--7-12 {
  color: red; }

.col--2-3, .col--4-6, .col--8-12 {
  color: red; }

.col--3-4, .col--9-12 {
  color: red; }

.col--5-6, .col--10-12 {
  color: red; }

.col--11-12 {
  color: red; }

.col--1-1, .col--2-2, .col--3-3, .col--4-4, .col--6-6, .col--12-12 {
  color: red; }