Superclass defaults

[Alexey Khudyakov]

On 15.08.2011 14:36, Simon Peyton-Jones wrote:
> With help from Conor we have made some progress on this: we have a draft design:
> 	http://hackage.haskell.org/trac/ghc/wiki/DefaultSuperclassInstances
>
> If you care about the issue, maybe you can help resolve the above questions. In particular, to give
> concrete evidence for (b), working out some case studies would be a Good Thing. The examples given in other proposals using the extension proposed here would be one starting point.
>
I don't completely understant how does it work. Does client need to 
enable language extension to get default instances?

Also proposal cannot fix Functor/Applicative/Monad problem without 
breaking client code. It requires explicit opt-out but client may define 
Applicative instance. And unless "hiding" is added it will result in 
compile error.