private class PointXCompare
	super Comparator

	redef type COMPARED: Point[Float]

	redef fun compare(a,b) do
		if a.x == b.x then
			if a.y == b.y then return 0
			if a.y > b.y then return - 1
			return 1
		else
			if a.x > b.x then return -1
			return 1
		end
	end
end