I am having a hard time figuring out what views gain you, if anything. If you know from the start you want abstract deconstructors, then you can do that now and it has never been an issue, just mechanical and verbose:
date Term = Ap Term Term | Let Id Term Term
fromAp :: Term -> Maybe (Term,Term) fromAp (Ap a b) = Just (a,b) fromAp _ = Nothing
foo t | Just (a,b) <- fromAp t = ...
now views give you some (perhaps) nicer syntax for matching these sort of functions, but they don't make declaring them any less mechanical and verbose, but more importantly, you still have to know a priori whether you will need abstract deconstructors or not. the issue that needs to be solved is letting you extend pattern matching "after the fact", if you know you want abstract deconstructors from the beginning, then views don't make much difference, if you don't and want to seamlessly extend an existing type, then you are out of luck, views or not. John -- John Meacham - ⑆repetae.net⑆john⑈