Re: Overlapping and incoherent instances

Hello, I have no strong feelings about what words we use, but I wanted to point out that while we are thinking of names, we may want to consider 3 (and not just 2). Currently we have: * OVERLAPPING: This instances may overlap existing instances * OVERLAPPABLE: This instance may be overlapped by existing instances * OVERLAPS: This instance is both OVERLAPPING and OVERLAPPABLE Of course, the 3rd one (OVERLAPS) could be replaced by a comma separated list of the first two, but I could not see how to make this work easily with GHC's pragmas. It would not be hard to simply allow 2 pragmas after the `instance` keyword, but both of those seem rather long. Either way, I'll keep an eye on the discussion, and would be happy to change the names if a consesus is reached. -Iavor On Tue, Jul 29, 2014 at 9:57 AM, David Thomas wrote:

Honestly, I think "OVERLAPS" and "OVERLAPPED" are perfectly clear.

...

CAN-OVERLAP and CAN-BE-OVERLAPPED are nice and clear. A little long,

On Tue, Jul 29, 2014 at 9:52 AM, David Feuer wrote: perhaps.

...

On Tue, Jul 29, 2014 at 12:29 PM, Simon Peyton Jones wrote:

...

CAN_OVERLAP and CAN_BE_OVERLAPPED?

(instead of OVERLAPPING and OVERLAPPABLE)

Or CAN-OVERLAP, CAN-BE-OVERLAPPED

That’s ok with me if that’s what you all want!

Simon

From: Glasgow-haskell-users [mailto:glasgow-haskell-users-bounces@haskell.org] On Behalf Of

Krzysztof

...

...

Skrzetnicki Sent: 29 July 2014 16:56 To: Brandon Allbery Cc: Simon Peyton Jones; Andreas Abel; GHC users; Haskell Libraries (libraries@haskell.org); ghc-devs

Subject: Re: Overlapping and incoherent instances

How about CAN_OVERLAP?

-- Krzysztof

29-07-2014 15:40, "Brandon Allbery" napisał(a):

On Tue, Jul 29, 2014 at 8:33 AM, Andreas Abel wrote:

+1. I like Niklas' syntax better. Also OVERLAPPABLE is a horrible word, OVERLAPPING sound less formidable (even though it might be slightly less accurrate).

We already get "overlap ok" in instance-related type errors, so OVERLAP_OK wouldn't be particularly alien even if it doesn't quite fit in with existing pragmas.

--

brandon s allbery kf8nh sine nomine associates

allbery.b@gmail.com ballbery@sinenomine.net

unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

_______________________________________________ Libraries mailing list Libraries@haskell.org http://www.haskell.org/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://www.haskell.org/mailman/listinfo/libraries

_______________________________________________ Libraries mailing list Libraries@haskell.org http://www.haskell.org/mailman/listinfo/libraries

---

Libraries mailing list Libraries@haskell.org http://www.haskell.org/mailman/listinfo/libraries