Bifoldable instance for Map

[Joseph C. Sible]

I'll admit I don't have a strong use case for this. I was just looking
at instances and noticed that these seemed to be a weird omission,
since there was an obvious definition. But I also don't think it's
confusing at all. Since (,), Set, and HashSet are Foldable, and (,)
and (,,) x are Bifoldable, it seems only logical to have Map and
HashMap be Bifoldable too. What exactly would be confusing about any
of these?

Joseph C. Sible

On Sat, May 30, 2020 at 8:33 PM David Feuer <david.feuer at gmail.com> wrote:
>
> Let me take that back. I forgot how weird Bifoldable and Bitraversable are for product types and product-like types. Is this instance actually useful for anything, or is it mostly confusing?
>
> On Mon, Apr 13, 2020, 9:46 PM David Feuer <david.feuer at gmail.com> wrote:
>>
>> I would go as far as to say we don't need to continue the proposal process here. We're doing it.
>>
>> On Mon, Apr 13, 2020, 9:44 PM David Feuer <david.feuer at gmail.com> wrote:
>>>
>>> This seems eminently reasonable to me. We must also be sure to add one to Data.HashMap if that's missing too.
>>>
>>> On Mon, Apr 13, 2020, 9:36 PM Joseph C. Sible <josephcsible at gmail.com> wrote:
>>>>
>>>> I'd like to propose a change to the containers package: adding a
>>>> Bifoldable instance to Map. I briefly mentioned this on Reddit [1] and
>>>> no obvious problems were brought up. I submitted a PR implementing it
>>>> [2]. This seems like an obvious and straightforward instance to me.
>>>> Thoughts?
>>>>
>>>> Joseph C. Sible
>>>>
>>>> [1]: https://old.reddit.com/r/haskell/comments/fsgqd6/monthly_hask_anything_april_2020/fn90d6k/
>>>> [2]: https://github.com/haskell/containers/pull/714
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