Hi guys, I have a typeclass like that: class Signal s where type SignalData s :: * The idea is that when some signal "s" fires, it returns a data of type (SignalData s). This is all fine except when I instantiate the class with: data Input a = Input [(a, String)] instance Signal (Input a) type SignalData (Input a) = a The concrete type of Input a is not known, so its difficult to store in lists, to serialize... So I need to create a "view" for the it: class (Signal s, Signal v) => SignalView s v where view :: s -> v data InputView = InputView [(Int, String)] instance Signal InputView type SignalData InputView = Int instance SignalView (Input a) InputView view (Input as) = InputView (zip [0…] (snd <$> as)) Is this a common pattern? I'm not sure I get it right...