Proxy, new Typeable, and type-level equality

[Bas van Dijk]

On 3 April 2013 18:08, Richard Eisenberg <eir at cis.upenn.edu> wrote:
> What other instances should there be for (:~:)?

Maybe:

instance Category (:~:) where
    id = Refl
    Refl . Refl = Refl

Bas