Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.9)
// Compass (v1.0.0.alpha.20)
// ----

$elements: project-covers, user-tooltip, sorting-bar, modals, navigation;
$modal-elements: modal__header, modal__content, modal__footer;

@mixin make-z( $class, $value) {
  .#{$class} {
    z-index: #{$value};
  }
}

@mixin for-z($properties) {
  @for $i from 1 through length($properties) {
    .#{nth($properties, $i)} {
      z-index: index($properties, nth($properties, $i));
    }
  }
}

@mixin nested-z($parent, $children){
  .#{$parent} {
    @include for-z($children)
  }
}

@include for-z($elements);

@include nested-z(modal, $modal-elements);

// @each $val in $elements {
//   @include make-z($val, index($elements, $val));
// }

SassMeister-output.css

.project-covers {
  z-index: 1;
}

.user-tooltip {
  z-index: 2;
}

.sorting-bar {
  z-index: 3;
}

.modals {
  z-index: 4;
}

.navigation {
  z-index: 5;
}

.modal .modal__header {
  z-index: 1;
}
.modal .modal__content {
  z-index: 2;
}
.modal .modal__footer {
  z-index: 3;
}