RULE traverse = traverse_?

[Edward Kmett]

On an instance by instance basis I have zero objection and it can
definitely work fine.

-Edward

On Tue, Mar 31, 2015 at 7:56 AM, Joachim Breitner <mail at joachim-breitner.de>
wrote:

> Hi,
>
>
> Am Dienstag, den 31.03.2015, 07:04 -0400 schrieb Edward Kmett:
>
> > Your proposed optimization breaks at least the (2a) approach above.
> >
> > The key is don't get to know that `foldMap f` and `getConst . traverse
> > (Const . f)` for a given container build the exact same tree. One
> > might associate differently than the other, and in fact if you
> > supplied a definition of the Foldable in terms of foldr and the
> > Traversable in terms of traverse, this is precisely what happens, so
> > it isn't even an academic exercise. =/
>
> This argues against a generic "traverse = traverse_" rule. But how about
> per-instances rules, for instances where we know that they build the
> applicative result in the same way?
>
> Greetings,
> Joachim
>
> --
> Joachim “nomeata” Breitner
>   mail at joachim-breitner.de • http://www.joachim-breitner.de/
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>   Debian Developer: nomeata at debian.org
>
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