@function strip($number) { ... }@function strip($number) { 
  @if meta.type-of($number) == 'number' and not math.is-unitless($number) {
    @return math.div($number, $number * 0 + 1);
  }

  @return $number;
 }

@function convert($values, $unit: rem, $base: $baseline-font-size) { ... }@function convert($values, $unit: rem, $base: $baseline-font-size) { 
  $result: ();

  @each $raw-value in $values {
    $unitless: math.is-unitless($raw-value);
    $compatible: math.compatible($raw-value, if($unit == 'em', 1em, 1rem));

    // If number is already the unit, just return it as is
    @if (not $unitless and $compatible) or $raw-value == 0 {
      $result: list.append($result, $raw-value);
    } @else {
      $base: strip($base);
      $value: strip($raw-value);
      $new-unit: if($unit == 'em', 1em, 1rem);
      $rem-value: math.div($value, $base) * $new-unit;
      $result: list.append($result, $rem-value);
    }
  }

  // Return the plain value if it's just one. If a list with just one
  // value is returned, math functions might not work as expected.
  @if list.length($result) == 1 {
    @return list.nth($result, 1);
  }

  @return $result;
 }

@function rem($values) { ... }@function rem($values) { 
  @return convert($values);
 }

@function em($values, $parent-font-size: $baseline-font-size) { ... }@function em($values, $parent-font-size: $baseline-font-size) { 
  @return convert($values, 'em', $parent-font-size);
 }

@function negative($args...) { ... }@function negative($args...) { 
  $negatives: ();

  @if list.length($args) == 1 and meta.type-of(list.nth($args, 1)) == 'list' {
    @each $arg in list.nth($args, 1) {
      $negatives: list.append($negatives, calc(#{$arg} * -1));
    }

    @return $negatives;
  }

  @each $arg in $args {
    $negatives: list.append($negatives, calc(#{$arg} * -1));
  }

  @return $negatives;
 }