[Haskell-cafe] fmap for lists of lists of lists of ...

15 Mar 2006


      Is it possible to make a typeclass like Functor, that has a function
(say "f_map"), which would work for the infinite hierarchy of types:
([],[[]],[[[]]],...)?  Does that make sense?  This doesn't work...
...
class Funct f where
   f_map :: (a -> b) -> f a -> f b
instance Funct [] where
   f_map = map
instance Funct a => Funct [a] where
   f_map f = map (f_map f)
main = print $ fmap (+1) [[[1,2,3]]]
...but maybe it gets the idea across?


Thanks,

Greg Buchholz