Re: [Haskell] Wanted: tricks for conflicting instances

Hello,

Is it plausible to improve instance selection to use contexts? I imagine doing so would require some kind of backtracking search.

Sometimes you can explicitly program instance selection by using type level bools. Oleg has written several examples of this; here is one which implements Prolog style proof-search: http://okmij.org/ftp/Haskell/types.html#de-typechecker If you can implement IsFunctor and IsCofunctor as type level functions (which might be very tedious or even impossible), then you could re-implement Functor and Cofunctor with the desired functionality. hth, Jeff