A loop to generate util classes for paddings and margins

_spacings.scss

// ----
// Sass (v3.4.25)
// Compass (v1.0.3)
// ----

$spaceamounts: (auto, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 80, 100);
$sides: (
  t: top,
  b: bottom,
  l: left,
  r: right,
  a: all,
  s: sides
);

@each $prefix, $side in $sides {
  @each $space in $spaceamounts {
    $unit: if($space == 0 or $space == auto, $space, #{$space}px);
    $property: if($prefix == '', '', -#{$side});
    
    @if $prefix == a {
      .m-#{$space} {
        margin: $unit;
      }

      @if $unit != auto {
        .p-#{$space} {
          padding: $unit;
        }
      }
    } @else if $prefix == s {
      .m-#{$prefix}-#{$space} {
        margin-left: $unit;
        margin-right: $unit;
      }
      @if $unit != auto {
        .p-#{$prefix}-#{$space} {
          padding-left: $unit;
          padding-right: $unit;
        }
      }
    } @else {
      @if $space == auto {
        .m-#{$prefix}-a {
          margin-#{$side}: auto;
        }
      } @else if $unit != auto {
        .m-#{$prefix}-#{$space} {
          margin-#{$side}: $unit;
        }
        .p-#{$prefix}-#{$space} {
          padding-#{$side}: $unit;
        }
      }
    }
  }
}

// Create classes to break out of wrapper gutters via negative margins
.nm {
  @for $i from 1 through 4 {
    $level: #{$i * 10};
    $unit: -#{$level}px;
    @each $prefix, $side in $sides {

      @if $prefix == a {
        &-#{$level} {
          margin: $unit;
        }
      } @else if $prefix == s {
        &-#{$prefix}-#{$level} {
          margin-left: $unit;
          margin-right: $unit;
        }
      } @else {
        &-#{$prefix}-#{$level} {
          margin-#{$side}: $unit;
        }
      }
    }
  }
}