José Miguel Vilaça wrote:

Hi

If I understand your problem than the following is a solution:

--------------------------------------------------

{-# OPTIONS -fglasgow-exts #-}

class Foo a b where g :: a -> b

type A = {- change the following -} Int type B = {- change the following -} Char

instance Foo A B where g a = {- change the following -} ' '

type C = {- change the following -} Float type D = {- change the following -} String

instance Foo C D where g c = {- change the following -} ""

f :: (Foo a b, Foo c d) => a -> c -> (b, d) f x y = (g x, g y)

Thanks for the workaround. However this does not seem to be quite so general as intersection types, because it would only allow me to define f for some specific g ie the g of Foo, rather than for any general function... Regards, Brian Hulley