Re: [Haskell-cafe] Idiomatic ways to make all instances of a certain class also instances of another?

For: instance (Ord a) => Max a where maximum = max The same could more simply be achieved with a function: maximum :: Ord a => a maximum = max Now, you probably wanted both a base-case using max and type specific, special cases: instance Max Int where maximum = 2^16 If you have both instances defined in the same module, GHC should always pick the special case for Int if overlapping instances is turned on. However, I've never found a description of how it resolves instance selection if you have the specialized cases in different modules. Unspecified [*] behaviour is not something I'd want to rely on, so I always avoid Overlapping Instances. [*] Of course, the multiple module behaviour might be specified somewhere...