Re: [Haskell-cafe] Context for type parameters of type constructors

My question was why he doesn't believe that. My definition data (Num a) => VList a = VList [a] clearly states that VLists will ever get types of class Num as parameters.

Ah. Constraints on datatype declarations are a misfeature of Haskell, and have no useful effect. You shouldn't use them. --KW 8-) -- Keith Wansbrough http://www.cl.cam.ac.uk/users/kw217/ University of Cambridge Computer Laboratory.