Re: [Haskell-cafe] Generalizing unionWithKey, unionWith, ...

Jose A. Lopes writes:

unionWith :: Ord k => (a -> b -> c) -> Map k a -> Map k b -> Map k c

what should be the result of unionWith undefined (M.singleton False 42) (M.singleton True "bar") ? perhaps you mean intersectionWith, which already has the type you want. - J.W.