Re: [Haskell-cafe] deriving instances of Enum for tuples of bounded, enumerable types (useful for generating QuickCheck.Arbitrary instances for collection of collection types)

On Sat, Mar 8, 2008 at 9:23 PM, Brandon S. Allbery KF8NH

I think you might be able to do this as a typeclass instead, at the expense of having to insert an instance declaration for each type. (You will have to use an extension if you want to declare instances for types such as Int. I think.)

class (Bounded a, Enum a) => BoundedEnum a where -- empty

instance BoundedEnum MyType a where instance BoundedEnum Int where -- requires FlexibleInstances?

I've had good luck with things like: class (Bounded a, Enum a) => BoundedEnum a instance (Bounded a, Enum a) => BoundedEnum a which picks up everything that can inhabit the new class. -Antoine