Re: ConstraintKinds and default associated empty constraints

On 23 December 2011 17:44, Simon Peyton-Jones wrote:

My attempt at forming a new understanding was driven by your example.

class Functor f where    type C f :: * -> Constraint    type C f = ()

sorry -- that was simply type incorrect.  () does not have kind *  -> Constraint

So am I correct that the `class Empty a; instance Empty a` trick is currently the only way to get default associated empty constraints? Will this change in GHC-7.4.1? (For example by having an overloaded `()`) The reason I ask is I would like to know if it's already feasible to start proposing adding these associated constraints to Functor, Applicative and Monad. Cheers, Bas