[Haskell-cafe] Proposal: Instance apartness guards

[Dmitry Olshansky]

Dear Anthony C & Richard E!

>From my side (as GHC-user) it definitely looks like the much more natural
way than OverlappedInstances (say, +1).
Unfortunately I am not an expert and can only ask with you for feedback
from experts.

Dmitry


2017-11-08 12:29 GMT+03:00 Anthony Clayden <anthony_clayden at clear.net.nz>:

> Surprisinlgy little comment on this proposal.
> Perhaps it landed when yous were busy elsewhere.
> I'd like to push it to the committee soon;
> this is an invitation for more feedback.
>
> Richard E wrote a nice brief summary
> https://github.com/ghc-proposals/ghc-proposals/pull/
> 56#issuecomment-311421457
>
> Thank you
> AntC
>
>
> ----- Original Message Follows -----
> > After years of pondering this idea (in various forms),
> > and several rounds of discussion on several forums,
> > I've written it up.
> >
> > "This proposal tackles the thorny topic of Overlapping
> > instances,
> >  for both type classes and Type Families/Associated types,
> >  by annotating instance heads with type-level apartness
> > Guards.
> >  Type-level disequality predicates appear in Sulzmann &
> > Stuckey 2002;
> >  in the type-level ‘case selection’ in HList 2004;
> >  and in various guises in Haskell cafe discussions in
> > following years.
> >  This proposal builds on the apartness testing implemented
> >  as part of the Closed Type Families work."
> >
> > All feedback welcome.
> >
> >
> https://github.com/AntC2/ghc-proposals/blob/instance-
> apartness-guards/proposals/0000-instance-apartness-guards.rst
> >
> > AntC
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/haskell-cafe/attachments/20171109/c9507323/attachment.html>