[Haskell-cafe] deriving instances of Enum for tuples of bounded,
enumerable types (useful for generating QuickCheck.Arbitrary
instances for collection of collection types)
aslatter at gmail.com
Sun Mar 9 04:03:08 EDT 2008
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.
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