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@@ -46,25 +46,40 @@ module Sass
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   # It keeps the semantics and most of the efficiency of normal hashes
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   # while also keeping track of the order in which elements were set.
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   class OrderedHash
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-    Node = Struct.new('Node', :key, :value, :next)
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+    Node = Struct.new(:key, :value, :next, :prev)
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     include Enumerable
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     def initialize
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       @hash = {}
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     end
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+    def initialize_copy(other)
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+      @hash = other.instance_variable_get('@hash').clone
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+    end
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+
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     def [](key)
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       @hash[key] && @hash[key].value
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     end
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     def []=(key, value)
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-      node = Node.new(key, value, nil)
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+      node = Node.new(key, value)
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+
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+      if old = @hash[key]
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+        if old.prev
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+          old.prev.next = old.next
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+        else # old is @first and @last
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+          @first = @last = nil
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+        end
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+      end
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+
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       if @first.nil?
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         @first = @last = node
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       else
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+        node.prev = @last
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         @last.next = node
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         @last = node
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       end
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+
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       @hash[key] = node
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       value
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     end