ConstraintKinds and default associated empty constraints

[Edward Kmett]

On Sun, Jan 8, 2012 at 8:32 AM, Bas van Dijk <v.dijk.bas at gmail.com> wrote:

> On 23 December 2011 17:44, Simon Peyton-Jones <simonpj at 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?
>

Yes.
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