Proposal: Bring the Contravariant class to base

Bardur Arantsson spam at
Fri Sep 15 16:55:30 UTC 2017

On 2017-09-15 02:01, Edward Kmett wrote:
> Random bike shedding on module migration generally leads to a very slow
> migration process with no good user story for how to perform the move.
>  Every bad experience I've encountered due to this process has come from
> some well-intentioned change like this. Users get hung up on how to
> perform the move, then incompatible package bounds abound.
> I for one am pretty strongly -1 on bike shedding the module contents
> during the move.
> contramap has had a few years to settle into users' consciousness and it
> helps drive home the fact that a contravariant functor is not a
> "cofunctor" (cofunctor = functor!) a common mistake among newbie
> category theorists that leads to all sorts of other misconceptions, like
> why isn't a comonad a "cofunctor" which cmap leaves notationally ambiguous.

+1 for the "minimal migration" you suggested.

-1000 on bikeshedding this. Even disregarding your good argument for
"contramap" vs. "cmap": the mere dropping of 5 letters is not *ever*
going to be significant in the grand scheme of things.


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