// Ascending
// Used to evaluate Sass maps like our grid breakpoints.
@mixin assert-ascending($map, $map-name) {
  $prev-key: null;
  $prev-num: null;

  @each $key, $num in $map {
    @if $prev-num == null {
      // Do nothing
    }

    @else if not comparable($prev-num, $num) {
      @warn "Potentially invalid value for #{$map-name}: This map must be in ascending order, but key '#{$key}' has value #{$num} whose unit makes it incomparable to #{$prev-num}, the value of the previous key '#{$prev-key}' !";
    }

    @else if $prev-num >= $num {
      @warn "Invalid value for #{$map-name}: This map must be in ascending order, but key '#{$key}' has value #{$num} which isn't greater than #{$prev-num}, the value of the previous key '#{$prev-key}' !";
    }
    $prev-key: $key;
    $prev-num: $num;
  }
}

// Starts at zero
// Another grid mixin that ensures the min-width of the lowest breakpoint starts at 0.
@mixin assert-starts-at-zero($map) {
  $values: map-values($map);
  $first-value: nth($values, 1);

  @if $first-value != 0 {
    @warn "First breakpoint in `$grid-breakpoints` must start at 0, but starts at #{$first-value}.";
  }
}