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
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