Proposal: Adding on

Christian Maeder maeder at
Fri Nov 3 12:33:34 EST 2006

Nils Anders Danielsson schrieb:
> On Fri, 03 Nov 2006, Duncan Coutts <duncan.coutts at> 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?

Yes, "comparing" is mentioned in "ThingsToAvoid". Adding "equating" does
do no harm. Style choices should be left to the user.


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