[Haskell-cafe] How to expose if a constraint is satisfiable

[Brandon Allbery]

On Mon, May 7, 2018 at 7:50 AM, Clinton Mead <clintonmead at gmail.com> wrote:

> class Num t => MyNum t where
>   type IsNum t
> instance Num t => MyNum t where
>   type IsNum t = Satisfied
>

This looks wrong to me: given how instance resolution works, I'd expect
this to match every type and produce Satisfied, and later rejection based
on the context wouldn't affect it. But I could well be thinking about it
incorrectly.

-- 
brandon s allbery kf8nh                               sine nomine associates
allbery.b at gmail.com                                  ballbery at sinenomine.net
unix, openafs, kerberos, infrastructure, xmonad        http://sinenomine.net
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