_sass/vendor/neat/grid/_span-columns.scss

@mixin span-columns($span: $columns of $container-columns, $display: block) {
  $columns: nth($span, 1);
  $container-columns: container-span($span);

  // Set nesting context (used by shift())
  $parent-columns: get-parent-columns($container-columns) !global;

  $direction: get-direction($layout-direction, $default-layout-direction);
  $opposite-direction: get-opposite-direction($direction);

  $display-table: is-display-table($container-display-table, $display);

  @if $display-table  {
    display: table-cell;
    width: percentage($columns / $container-columns);
  } @else {
    float: #{$opposite-direction};

    @if $display != no-display {
      display: block;
    }

    @if $display == collapse {
      @warn "The 'collapse' argument will be deprecated. Use 'block-collapse' instead."
    }

    @if $display == collapse or $display == block-collapse {
      width: flex-grid($columns, $container-columns) + flex-gutter($container-columns);

      &:last-child {
        width: flex-grid($columns, $container-columns);
      }

    } @else {
      margin-#{$direction}: flex-gutter($container-columns);
      width: flex-grid($columns, $container-columns);

      &:last-child {
        margin-#{$direction}: 0;
      }
    }
  }
}