Proposal: Adding on

[Cale Gibbard]

I agree with Duncan here, and I'd prefer to keep all three.

On 03/11/06, Duncan Coutts <duncan.coutts at worc.ox.ac.uk> wrote:
> On Fri, 2006-11-03 at 18:05 +0100, Nils Anders Danielsson wrote:
> > On Fri, 03 Nov 2006, Duncan Coutts <duncan.coutts at worc.ox.ac.uk> wrote:
> >
> > >    groupBy ((==) `on` fst)
> >
> > Read it as "group by equality on first".
> >
> > > vs groupBy (equating fst)
> >
> > > So do you suggest that we deprecate and remove comparing?
> >
> > Yes, this seems like a good idea. (I had forgotten that comparing was
> > added before 6.6 was released.) I can add a deprecation pragma to my
> > patch. Any objections?
>
> As I've said before, I think there is room for both the general and
> special cases. We're not talking about polluting the namespace here,
> Data.Ord and Data.Eq are pretty new and have to be imported explicitly.
> It's not like adding something to Data.List which many existing programs
> import without qualification.
>
> But mainly I think it should be consistent. We should either have all
> three or just `on`. Keeping comparing but not adding equating doesn't
> seem to make a lot of sense. We should either agree to deprecate
> comparing or add equating too.
>
> So now that we have `on`, is there any desire for comparing and
> equating. I think there is, but lets see what other people think.
>
> Duncan
>
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