instance Functor Set, was: Re: Export lists in modules

Malcolm Wallace wrote:

But if contexts-on-datatypes worked correctly,

data Set a = Ord a => ....

then even the "real" map from Data.Set:

map :: (Ord a, Ord b) => (a -> b) -> Set a -> Set b

could be an instance method of Functor.

I'd love that. But I don't quite understand: do you think this is/should be possible with: current Haskell? Haskell-Prime? Current ghc (what extensions)? -- -- Johannes Waldmann -- Tel/Fax (0341) 3076 6479/80 -- ---- http://www.imn.htwk-leipzig.de/~waldmann/ -------