Create sprite map for each subdirectory with SASS

config.rb

require 'sass'

module Sass::Script::Functions
  include Sass::Script::Value::Helpers
  
  # returns list of subdirectories to iterate
  def subdirs(dir)
    assert_type dir, :String

    dirs = []
    path = dir.value
	
    Dir.foreach(path) do |item|
      if File.directory?(path + '/' + item) and not item.start_with? '.'
        dirs.push identifier item
      end
    end

    list dirs, :space
	
  end

  declare :subdirs, [:string]

end

sprites.sass

@mixin spritez($path, $prefix, $base-class) {
	$sprite-map: sprite-map($path, $layout: smart);
	$sprite-names: sprite-names($sprite-map);

	#{$base-class} {
		background-image: sprite-url($sprite-map);
		background-repeat: no-repeat;
		display: inline-block;
	}
	
	@each $name in $sprite-names {

		.#{$prefix}-#{$name} {
			background-position: sprite-position($sprite-map, $name);
			@include sprite-dimensions($sprite-map, $name);
		}
	}
}

$subdirs: subdirs('images/icons');

// creating sprite map for each subdir in $subdirs
@each $dir in $subdirs {
	@include spritez("icons/#{$dir}/*.png", "icon-#{$dir}", '.icon-#{$dir}');
}