[Haskell-cafe] A Question of Restriction

Hello all. I would like to define a data type that is the super-set of several types and then each of the proper subset types. For example: data Foo = One | Two | Three | Four data Odd = One | Three data Even = Two | Four This, of course, does not work. It seems that such a thing should possible to express entirely in the type system, but I cannot think of how. Would someone be so kind as to explain how this sort of thing can be accomplished? Thanks, Brian