On 23 December 2011 17:44, Simon Peyton-Jones <simonpj@microsoft.com> 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?