private class PipeAlternate[E]
	super Iterator[E]

	var source: Iterator[E]
	var odd_item: E
	var odd = true

	redef fun is_ok do return source.is_ok

	redef fun item
	do
		if odd then
			return source.item
		else
			return odd_item
		end
	end

	redef fun next
	do
		if odd then
			source.next
		end
		odd = not odd
	end
end