Enumerable#chunk from rubinius

lib-topaz/enumerable.rb

@@ -437,4 +437,37 @@ def grep(pattern, &block)
     end
     ret
   end
+
+  def chunk(initial_state = nil, &original_block)
+    raise ArgumentError.new("no block given") unless original_block
+    ::Enumerator.new do |yielder|
+      previous = nil
+      accumulate = []
+      block = initial_state.nil? ? original_block : Proc.new{ |val| original_block.yield(val, initial_state.clone)}
+      each do |val|
+        key = block.yield(val)
+        if key.nil? || (key.is_a?(Symbol) && key.to_s[0, 1] == "_")
+          yielder.yield [previous, accumulate] unless accumulate.empty?
+          accumulate = []
+          previous = nil
+          case key
+          when nil, :_separator
+          when :_alone
+            yielder.yield [key, [val]]
+          else
+            raise RuntimeError.new("symbols beginning with an underscore are reserved")
+          end
+        else
+          if previous.nil? || previous == key
+            accumulate << val
+          else
+            yielder.yield [previous, accumulate] unless accumulate.empty?
+            accumulate = [val]
+          end
+          previous = key
+        end
+      end
+      yielder.yield [previous, accumulate] unless accumulate.empty?
+    end
+  end
 end