add map back to Functor

[Carter Schonwald]

You make a good point, we should cook up this desired magic pragma!

Could you sketch out 1-2 examples of what you’d want this pragma to do?

Something like
{-# method_synonym_of fmap map #-}
?
This would sort of be like a sort of duplicate record field for how names
are mapped to definitions?
This example would be “fmap is an alias of map”


On Fri, Feb 8, 2019 at 1:46 PM Edward Kmett <ekmett at gmail.com> wrote:

> The real problem with this sketch of a proposal is the lack of a nice
> migration plan.
>
> If it is top level and just calls fmap, then the distinction requires
> random rote memorization of which one you can define.
>
> On the other hand, say you put it in Functor today as an extra member.
> Currently everybody has definitions in terms of `fmap`, so you'd need to
> make the two definitions mutual. This would mean enlarging the dictionaries
> for one of the most common structures in Haskell for a rather far flung
> removal that breaks everyone.
>
> If we had a way (say a pragma or other syntactic form) to say that fmap
> and map were somehow the 'same name' or something and so that defining one
> was the same as defining the other, so that this tax didn't exist, I could
> see how we might get there.
>
> That sort of "magic" might be useful for making migration plans to get
> sequenceA to be sequence and mapM and traverse without requiring folks to
> memorize which one is in the class and which is a top level definition.
>
> Without something like that, I'd remain somewhat inclined against
> concocting a complicated migration plan to save one letter.
>
> -Edward
>
> On Fri, Feb 8, 2019 at 12:07 PM Carter Schonwald <
> carter.schonwald at gmail.com> wrote:
>
>> harkening back to the old Haskell 1.5 days, Lets have map back in
>> functor. it "F"-  strange to not have our lovely maps be functorial by
>> default.
>>
>> I think it would be a genuine boon for old and new haskellers alike, and
>> those who disagree with this change already use alt-preludes for pedagogy
>> reasons anyways
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>
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