Advanced nth-child mixins

nth-child-quantity-mixins.scss

@mixin valid-quantity($quantity) {
  @if type-of($quantity) != 'number' {
    @error 'The "quantity" parameter must be a number!';
  }
  @if not(unitless($quantity)) {
    @error 'The "quantity" parameter must not have a unit!';
  }
  @if $quantity < 0 {
    @error 'The "quantity" parameter must be at least 0!';
  }
}

@mixin has-nth($expression, $element: '*') {
  &:nth-last-child(#{$expression}):first-child,
  &:nth-last-child(#{$expression}):first-child ~ #{$element} {
    @content;
  }
}

@mixin at-least($quantity, $element: '*') {
  @include valid-quantity($quantity);
  @include has-nth('n + #{$quantity}', $element) {
    @content;
  }
}

@mixin at-most($quantity, $element: '*') {
  @include valid-quantity($quantity);
  @include has-nth('-n + #{$quantity}', $element) {
    @content;
  }
}

@mixin divisible-by($quantity, $offset: 0, $element: '*') {
  @include valid-quantity($quantity);
  @include has-nth('#{$quantity}n + #{$offset}', $element) {
    @content;
  }
}

@mixin has-exactly($quantity, $element: '*') {
  @include valid-quantity($quantity);
  @include has-nth('#{$quantity}', $element) {
    @content;
  }
}

@mixin has-odd($element: '*') {
  @include has-nth('odd', $element) {
    @content;
  }
}

@mixin has-even($element: '*') {
  @include has-nth('even', $element) {
    @content;
  }
}