proj :: (Functor f) => (f:*:f') (a,b) -> f a proj (Pair x _) = fmap fst x
Yes I think that was what I needed. ;-) It seems I also need
fsplit :: (Functor f, Functor f') => (f a, f' b) -> (f :*: f') (a,b)
for same data (f:*:f') o = Pair (f o) (f' o)
Which takes (FA, F'B) into FxF' (A,B). I am confused by the fact of having two instances of F and somehow I need to map on both of them simultaneously.
Med vänliga hälsningar / Yours Sincerely, Johan Glimming _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
