areComposable :: Eq a => SizeChangeGraph a b -> SizeChangeGraph a b -> Bool
areComposable (_, _, y) (y', _, _) = y == y'
areComposable :: Eq a => SizeChangeGraph a b -> SizeChangeGraph a b -> Bool
areComposable (_, _, y) (y', _, _) = y == y'
areComposable (_, _, y) (y', _, _) = y == y'