Re: Local evidence and type class instances

On Sat, Oct 16, 2010 at 7:11 AM, Max Bolingbroke wrote:

Hi GHC users,

Now that the Glorious New type checker can handle local evidence seamlessly, is it a big implementation burden to extend it to deal with local *type class instances* in addition to local *equality constraints*?

For example, you could write this:

""" f :: Bool f = id < id  where   instance Ord (a -> b) where     _ `compare` _ = LT """

Along similar lines as my last post, would I be able to write the following type signature: myFunct :: Ord Int => Int -> (...) and have it always use the local instance for Ord Int? Is this the type that the type checker would infer for my function? Antoine