Re: [Haskell-beginners] Questions on data/type

2009/11/15 Matthew Wong :

If I want to express the following idea (the following won't compiler):

data TypeCon a = ValConA a | ValConB [ValConA a] | ValConC [ValConB a]

In this definition, you are confusing constructors with types. You can't have a list of `ValConB a` -- the type is actually `TypeCon a`.

The alternative is use 3 different type constructors,

data TypeConA a = ValConA a data TypeConB a = ValConB a data TypeConC a = ValConC a

This is more promising. I'd need to see the typeclass you're trying to define to say more. -- Jason Dusek