Re: [Haskell-cafe] Strange typing?

Hi,

Only think I can think of is having the constructors, as seperate data types, introducing new type classes to group every possible subset of [X,Y,Z] and [A,B,C,D] and use those type classes when defining the functions.

Wouldn't it be possible to use Either? You make the constructors seperate data types and then have something like

func1 :: Either X Y -> Either B C

When you need more then two alternatives you could define similar datatypes like

OneOfThree x y z = OOTFirst x | OOTSecond y | OOTThird z

or something like

{-# LANGUAGE TypeOperators #-} data Or x y = First x | Second y deriving (Show) infixl 5 `Or`

func :: Int `Or` String `Or` Integer -> String `Or` Integer

but then pattern matching becomes ugly. Christoph