private class PipeUniq[E]
	super Iterator[E]

	var source: Iterator[E]

	var seen = new HashSet[Object] # FIXME HashSet[E]

	redef fun is_ok do return source.is_ok

	redef fun item do return source.item

	redef fun next
	do
		self.seen.add(self.item.as(Object))
		source.next
		while source.is_ok and self.seen.has(source.item.as(Object)) do
			source.next
		end
	end
end