Proposal: Add Semigroup and Monoid instances for (:~:)

[Oliver Charles]

Refl, I believe.

On Thu, Jan 14, 2016 at 1:56 PM Andreas Abel <andreas.abel at ifi.lmu.de>
wrote:

> What does this smiley :~: stand for?
>
> On 13.01.2016 06:58, David Feuer wrote:
> > These are not likely to be *useful*, but they fall easily into the
> > general bucket of "exactly one sensible instance exists".
> >
> > instance Semigroup (a :~: b) where
> >    r <> _ = r
> >
> > instance a ~ b => Monoid (a :~: b) where
> >    mempty = Refl
> >    mappend r _ = r
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>
> --
> Andreas Abel  <><      Du bist der geliebte Mensch.
>
> Department of Computer Science and Engineering
> Chalmers and Gothenburg University, Sweden
>
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