Speed up compilation a bit.

doc-src/lib/stylesheets.rb

@@ -128,11 +128,20 @@ def mixin_signature(mixin)
   mixin.sass_signature(:include)
 end
 
-def mixin_examples(item, mixin)
+def example_items
-  @items.select do |i|
+  @example_items ||= @items.select{|i| i[:example]}
-    i[:example] &&
+end
+
+def examples_for_item(item)
+  @examples ||= {}
+  @examples[item] ||= example_items.select do |i|
     i[:framework] == item[:framework] &&
-    i[:stylesheet] == item[:stylesheet] &&
+    i[:stylesheet] == item[:stylesheet]
+  end
+end
+
+def mixin_examples(item, mixin)
+  examples_for_item(item).select do |i|
     i[:mixin] == mixin.name
   end.map{|i| i.reps.find{|r| r.name == :default}}
 end