[Proposal] Renaming (:=:) to (==)

Edward Kmett ekmett at gmail.com
Sun Sep 29 15:21:24 UTC 2013


I can appreciate the objections to (==) and I'm absolutely open to other
names.

I just rather dislike (:=:).

Lets throwing this open to bikeshedding. Alternatives?

-Edward


On Sun, Sep 29, 2013 at 8:33 AM, Roman Cheplyaka <roma at ro-che.info> wrote:

> I agree with Richard here — this overloading of == doesn't seem
> intuitive to me. Using it for type-level boolean equality would be much
> more natural.
>
> That said, :=: could probably benefit from the relaxed rules for type
> operators; I just don't think == is a good choice.
>
> Roman
>
> * Richard Eisenberg <eir at cis.upenn.edu> [2013-09-29 00:10:46-0400]
> > -1 from me.
> >
> > Shachaf stated my argument correctly -- I think that the (:=:) operator
> means something quite different from the term-level (==) operator, and the
> name should reflect this. I do like thinking about a better name, though,
> and I'm happy enough if I'm outvoted here.
> >
> > Richard
> >
> > On Sep 28, 2013, at 10:08 PM, Shachaf Ben-Kiki wrote:
> >
> > > On Sat, Sep 28, 2013 at 6:57 PM, Edward Kmett <ekmett at gmail.com>
> wrote:
> > >> As part of the discussion about Typeable, GHC 7.8 is going to include
> a
> > >> Data.Type.Equality module that provides a polykinded type equality
> data
> > >> type.
> > >>
> > >> I'd like to propose that we rename this type to (==) rather than the
> (:=:)
> > >> it was developed under.
> > >>
> > >> We are already using (+), (-), (*), etc. at the type level in
> type-nats, so
> > >> it would seem to fit the surrounding convention.
> > >>
> > >> I've done the work of preparing a patch, visible here:
> > >>
> > >>
> https://github.com/ekmett/packages-base/commit/fb47f8368ad3d40fdd79bdeec334c0554fb17110
> > >>
> > >> Thoughts?
> > >>
> > >> Normally, I'd let this run the usual 2 week course, but we're getting
> down
> > >> to the wire for 7.8's release. Once 7.8 ships, we'd basically be
> stuck with
> > >> the current name forever.
> > >>
> > >> Discussion Period: 1 week
> > >>
> > >> -Edward Kmett
> > >>
> > >
> > > +1. For what it's worth, I suggested that name before, and Richard
> > > Eisenberg suggested that == should be for type-level Boolean equality:
> > > <http://markmail.org/message/3yifytgt2k3cfwws>. I'm not convinced,
> > > though -- this seems fundamental enough to deserve the simplest name
> > > possible.
> > >
> > > (I'm using that link because the haskell.org mailing list archive
> > > seems to be gone... Hopefully that comes back, eventually.)
> > >
> > >    Shachaf
> > > _______________________________________________
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> >
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