$u-spacing-types: (
  margin: (
    m: margin,
    mb: margin-bottom,
    ml: margin-left,
    mr: margin-right,
    mt: margin-top,
    mv: (margin-bottom, margin-top),
    mh: (margin-left, margin-right)
  ),
  padding: (
    p: padding,
    pb: padding-bottom,
    pl: padding-left,
    pr: padding-right,
    pt: padding-top,
    pv: (padding-bottom, padding-top),
    ph: (padding-left, padding-right)
  )
) !default;

$u-spacing-mt-zero-first-child: true !default;
$u-spacing-mb-zero-last-child: true !default;

@each $spacing-name, $spacing-value in $u-spacings {
  @each $type, $map in $u-spacing-types {
    @each $class-name, $property-name in get($u-spacing-types, $type) {
      %u-spacing-#{$class-name}-#{$spacing-name},
      .u-spacing-#{$class-name}-#{$spacing-name} {
        @each $property in $property-name {
          #{$property}: $spacing-value;
        }
      }
    }
  }
}

@if ($u-spacing-mt-zero-first-child) {
  %u-spacing-mt-zero-first-child,
  .u-spacing-mt-zero-first-child {
    &:first-child {
      margin-top: 0;
    }
  }
}

@if ($u-spacing-mb-zero-last-child) {
  %u-spacing-mb-zero-last-child,
  .u-spacing-mb-zero-last-child {
    &:last-child {
      margin-bottom: 0;
    }
  }
}