private class MatrixIndexIterator
	super MapIterator[MatrixCoordinate, Float]

	var matrix: Matrix

	redef var key = new MatrixCoordinate(0, 0)

	redef fun is_ok do return key.y < matrix.height

	redef fun item
	do
		assert is_ok
		return matrix[key.y, key.x]
	end

	redef fun next
	do
		assert is_ok
		var key = key
		if key.x == matrix.width - 1 then
			key.x = 0
			key.y += 1
		else
			key.x += 1
		end
	end
end