Hi - I'm wondering if there is any possiblility of getting intersection types into Haskell. For example, at the moment there is no (proper) typing for: f g x y = (g x, g y) Ideally, I'd like to be able to write: f:: (a -> b & c -> d) -> a -> c -> (b,d) or f :: (a -> b a) -> c -> d -> (b c, b d) which is perhaps clearer and prevents bad types such as (Int -> String & Int -> Char) by construction. While it may be impossible (?) to infer such a type for f, would it be possible to make use of such an annotation (esp since Haskell with GHC extensions already has arbitary rank polymorphism)? Also, as a second point, could functional dependencies in type classes be written using a similar syntax eg instead of class Insert t c a | c a -> t where insert :: t -> c a -> c a we could write: class Insert (h (c a)) c a where insert :: h (c a) -> c a -> c a or class Insert t@(h (c a)) c a where -- re-using as-pattern syntax insert :: t -> c a -> c a to avoid having to have a special syntax just for functional dependencies and/or to be able to write more complicated fundeps more succinctly? Regards, Brian Hulley