Re: [Haskell-cafe] Intersection types for Haskell?

On 1/10/06, Brian Hulley wrote:

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)

I have no idea what kind of function would have type (a -> b & c -> d). Can you give an example?

f :: (a -> b a) -> c -> d -> (b c, b d)

f :: (forall a. a -> b a) -> c -> d -> (b c, b d) -- Taral "Computer science is no more about computers than astronomy is about telescopes." -- Edsger Dijkstra