Dear HC, Does AFunctor below have a standard name? It's a generalization of the Functor class in terms of Arrow instead of (->):
fmap :: Functor f => (i -> o) -> f i -> f o afmap :: Arrow a, AFunctor f => a i o -> a (f i) (f o) It pops up in less general form (AFunctor = []) in iterated functions (difference equations / state space models), where the arrow is the update function parameterized by state type: data Iter s i o = Iter ((s,i) -> (s,o)) instance Arrow (Iter s) More concretely: > afmap :: ((s,i) -> (s, o)) -> (s,[i]) -> (s,[o]) > afmap f (s,[]) = (s,[]) > afmap f (s0, i:is) = (sn, o:os) where > (s1, o) = f (s0,i) > (sn, os) = afmap f (s1, is) > f (s,i) = (s', s') where s' = s + i > is = [1,1,1,1,1] > os = afmap f (0,is) -- (5,[1,2,3,4,5]) Cheers, Tom _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe