Getting comonad into base

chessai chessai1996 at
Fri Sep 11 19:27:06 UTC 2020

Sorry, I still have semigroupoids on my mind. There's no renaming like with
Foldable1, so yes the migration path is not more complicated than what you

I still think a proposal is worthwhile because many people (including
myself) fail to see motivation for comonads in every day programming. The
fact that Ollie, an experienced haskell programmer, also shares this
sentiment makes me more certain that people need motivating. I think a
proposal is a good way to do that.

On Fri, Sep 11, 2020, 14:16 Sandy Maguire <sandy at> wrote:

> Ollie: It's for giving my own instances. I suspect most of the reasons
> that comonads feel uninteresting is that they've been relegated to a
> second-class citizen in the ecosystem.
> chessai: I'm not proposing the whole package; just the class. I can't
> imagine the migration path is any harder than putting an ifdef into the
> comonads package.
> On Fri, Sep 11, 2020 at 12:06 PM chessai <chessai1996 at> wrote:
>> Hi Sandy,
>> I think this would be a good candidate for the new Libraries Proposal
>> process, modelled after ghc-proposals. See
>> I recommend writing a proposal there. In particular, for changes like
>> this, one of the things that needs the most thought is the story around a
>> migration path.
>> Hope this helps.
>> Thanks
>> On Fri, Sep 11, 2020, 13:55 Sandy Maguire <sandy at> wrote:
>>> Hi all,
>>> I frequently regret the lack of having the Comonad class in base. Are
>>> there any good reasons for its absence? If not, I can get started on a
>>> patch.
>>> Best,
>>> Sandy
>>> _______________________________________________
>>> Libraries mailing list
>>> Libraries at
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