Re: Overlapping and incoherent instances

Iavor, I am a bit surprised by the distinction you outline below. This is maybe because I am native German, not English. The German equivalent of "overlap", "überschneiden/überlappen", is used exclusively in a symmetrical fashion. It's like in English, if I say "our interests overlap", then it is pointless to ask whether my interest are overlapping yours or are overlapped by yours. I want to alert you to the fact that non-native English speaker might have little understanding for a distinction between "OVERLAPPING" and "OVERLAPPABLE". Let's try to guess what it meant: Given A) instance Bla Char B) instance Bla a => Bla [a] C) instance Bla String you will in context A,B write C as OVERLAPPING, and in context A,C write B as OVERLAPPABLE? Is this correct? Is it important to distinguish between OVERLAPPING and OVERLAPPABLE? Why? -- Andreas On 29.07.2014 19:28, Iavor Diatchki wrote:

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 mailto:davidleothomas@gmail.com> wrote:

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

On Tue, Jul 29, 2014 at 9:52 AM, David Feuer mailto:david.feuer@gmail.com> wrote: > CAN-OVERLAP and CAN-BE-OVERLAPPED are nice and clear. A little long, perhaps. > > On Tue, Jul 29, 2014 at 12:29 PM, Simon Peyton Jones > mailto:simonpj@microsoft.com> 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 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 mailto:libraries@haskell.org); ghc-devs >> >> >> Subject: Re: Overlapping and incoherent instances >> >> >> >> How about CAN_OVERLAP? >> >> -- >> Krzysztof >> >> 29-07-2014 15:40, "Brandon Allbery" mailto:allbery.b@gmail.com> napisał(a): >> >> On Tue, Jul 29, 2014 at 8:33 AM, Andreas Abel mailto:andreas.abel@ifi.lmu.de> >> 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 mailto:allbery.b@gmail.com ballbery@sinenomine.net mailto:ballbery@sinenomine.net >> >> unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net >> >> >> _______________________________________________ >> Libraries mailing list >> Libraries@haskell.org mailto:Libraries@haskell.org >> http://www.haskell.org/mailman/listinfo/libraries >> >> >> _______________________________________________ >> Libraries mailing list >> Libraries@haskell.org mailto:Libraries@haskell.org >> http://www.haskell.org/mailman/listinfo/libraries >> > _______________________________________________ > Libraries mailing list > Libraries@haskell.org mailto:Libraries@haskell.org > http://www.haskell.org/mailman/listinfo/libraries _______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org http://www.haskell.org/mailman/listinfo/libraries

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