Sass: mixins

mixins.scss

@mixin box-emboss($opacity, $opacity2){
    box-shadow:white($opacity) 0 1px 0, inset black($opacity2) 0 1px 0;
}

/*
.box { @include box-emboss(0.8, 0.05); }
*/

@mixin letterpress($opacity){
    text-shadow:white($opacity) 0 1px 0;
}

@mixin box-shadow($top, $left, $blur, $color, $inset:"") {
  -webkit-box-shadow:$top $left $blur $color #{$inset};
  -moz-box-shadow:$top $left $blur $color #{$inset};
  box-shadow:$top $left $blur $color #{$inset};
}


/*
|--------------------------------------------------------------------------
| Functions
|--------------------------------------------------------------------------
*/
@function rem($pxval, $base:16) {
  @return ($pxval / $base) * 1rem;
}


/*
|--------------------------------------------------------------------------
| Mixins
|--------------------------------------------------------------------------
*/
// #selector { @include rgba-background-fallback(#333, 0.5); }
@mixin rgba-background-fallback($color, $opacity: 1.0) {
  background-color: $color; /* The Fallback */
  background-color: rgba($color, $opacity);
}
@mixin rgba-color-fallback($color, $opacity: 1.0) {
  color: $color; /* The Fallback */
  color: rgba($color, $opacity);
}

@mixin rem-font-size($pxval, $base:16) {
  font-size: $pxval * 1px;
  font-size: rem($pxval, $base);
}

@mixin opacity($opacity){
  opacity: $opacity;
  $opacity-ie: $opacity * 100;
  filter: alpha(opacity=$opacity-ie); // ie8
}



// Taken from Compass framework
// Usage: http://compass-style.org/reference/compass/layout/sticky_footer/
@mixin sticky-footer($footer-height, $root-selector: unquote("#root"), $root-footer-selector: unquote("#root_footer"), $footer-selector: unquote("#footer")) {
  html, body {
    height: 100%; }
  #{$root-selector} {
    clear: both;
    min-height: 100%;
    height: auto !important;
    height: 100%;
    margin-bottom: -$footer-height;
    #{$root-footer-selector} {
      height: $footer-height; } }
  #{$footer-selector} {
    clear: both;
    position: relative;
    height: $footer-height; } }

modifier-mixin.scss

@mixin modifier($modifier) {
  @if (str-index(#{$modifier}, 'shadow')){
    color: red;
  }
}

.test--shadow {
  color: blue;
  @include modifier(&);
}