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                <h1>This requires sassy-maps</h1>
<p>The error is caused by the lack of sassy-maps</p>



                @import "compass/css3";

// some placeholder values
$z-indexs: (
  floor_1: 1,
  floor_2: 50,
  floor_3: 100,
  floor_4: 150,
  floor_5: 200,
  floor_6: 300,
  floor_7: 350,
  floor_8: 400,
  floor_9: 450,
  floor_10: 500

// create a hidden extend class for each of the items in teh z-indexs object
@mixin z-ex($map: $z-indexs) {
	$values: map-keys($map);
	@each $item in $values {
		@at-root {
			%#{$item} {
				z-index: map-get($map, $item);
// call it
@include z-ex();

// usage
// first argument is the named position, the named positions are set in the z-indexs object
// if you are creating a new position then you must provide some context for the position,
// this is where the above or below arguments come in.
// you must set which position the position should go above or below
// for example, my new position called slide needs to go above floor_1
// you can also pass in a tolerance, the default is 5.  This is the value that is added or subtracted 
// from the existing position
// Using extend will funnily enough create a silent placeholder than can be used again and again.
// if the new z-index value produced already exists in the object a new name will not be created 
// instead the existing on extended. keen!

// example
// .slide { @include z(slide, $above: floor_10); }
// .slide__pagination { @include z(slide_pagination, $above: slide)}

@mixin z($position: 1, $above: false, $below: false, $tolerance: 5, $extend: true) {

	$save_new_position: null;
	$results: null;
	$val: null;
	$new_map: null;
	$keys: null;
	$extended: null;

	// if the position already exists
	@if map-has-key($z-indexs, $position) {

		@debug 'key exists';
		// get the position value
		$result: map-get($z-indexs, $position);
		// if extend is true, 
		// extend the class created by z-ex
		@if $extend == true {
			@extend %#{$position};
		} @else {
			// or don't extend
			z-index: $result;

	// if the position does not yet exist
	@else {
		// set the direction, this is a little flaky
		$direction: null;
		@if $above != false {
			$direction: $above;

		@if $below != false {
			$direction: $below;

		@if $direction != null {
			// check to see if the direction exists, i.e a previously created position
			@if map-has-key($z-indexs, $direction) {
				// get the z-index value of the given position
				$val: map-get($z-indexs, $direction);
				// if its above need to add
				@if $direction == $above {
					$val: $val + $tolerance;
				// below minus
				@if $direction == $below {
					$val: $val - $tolerance;
				// update the map with the new position and value
				// this is a global variable
				$z-indexs: map-set($z-indexs, $position, $val) !global;
				// if we're extending
				@if $extend == true {

						// check to see if $val already exists
						// so assign each of the values to a var (list)
						$keys: map-values($z-indexs);
						// loop through each item in the list
						@each $value in $keys {
							// if the value matches the val, get the name of the key
							@if $val == $value {
								// get the index of the item
								$index: index($keys, $value);
								// return the resulting object
								$list: nth($z-indexs, $index);
								// the above returns both the key and the value, so now we just want the key
								// set this to the $extend var
								$extended: nth($list, 1);
						// so if floor_7 == 10 and new_position == 10, we don't need to create a new extend class
						@if $extended != $position {
							@extend %#{$extended};
						} @else {
							// it's a totally new position so let's create the extend.
							@at-root {
								%#{$position} {
									z-index: $val;
							// and now extend it.
							@extend %#{$position};
				} @else {
					// not extending, fair enough
					z-index: $val;

			} @else {
				@warn "above map position does not exist";

.a1 {
	@include z('floor_2');

.a2 {
	@include z('slide', $above: 'floor_2');

.a3 {
	@include z('slider', $above: 'slide');

.a4 {
	@include z('slide_item', $below: slider);

// output

.a1 {
  z-index: 50;
.a2, .a4 {
  z-index: 55;

.a3 {
  z-index: 60;