[ghc-steering-committee] Please review #303: Constraint based arrow notation, Shepherd: Alejandro

Alejandro Serrano Mena trupill at gmail.com
Sun May 24 19:19:59 UTC 2020

Hi everybody,
The discussion in the GitHub thread seems to have come to a conclusion, and
I encourage you to look at the proposal and give your opinion. The author
of the proposal has written a very good introduction to the general idea of
arrows that is quite useful (or at least has been for me!) to understand
the context ->

Everybody that has discussed there seems to be willing to break
backwards-compatibility, as the scenario where it breaks is quite rare in
practice. In fact, the goal of the proposal is to make those scenarios
simpler, so that "control operators" can be more easily used and defined.

Note that the proposal also mentions some alternatives or points in the
design space:
- Should the proposal be under a different extension or under `Arrows`?
- Should a flattened or nested tuple representation be used? This comments [
may give you some additional information.
- Should the type families described there be wired-in?

Looking forward to hearing from everyone. This is a complex proposal, with
possible future ramifications. If there's no discussion in one week, I'll
write again to the list.

El mar., 19 may. 2020 a las 9:02, Joachim Breitner (<
mail at joachim-breitner.de>) escribió:

> If there is active discussion, we usually put it back to the previous
> state, and wait for discussion to come to conclusions.
> 19.05.2020 08:36:42 Alejandro Serrano Mena <trupill at gmail.com>:
> Dear Committee,
> When I took care of this proposal, the GitHub thread was quite dormant.
> However, it seems that right now there's quite some activity, and even
> proposals to completely redesign arrows. What is the right approach: let
> the discussion cool off, and then ask all of you to review the text (which
> I don't think is going to change substantially in any case) or move the
> proposal back to the previous state?
> Alejandro
> El vie., 15 may. 2020 a las 11:03, Richard Eisenberg (<rae at richarde.dev>)
> escribió:
>> I have some concerns -- mostly: is the improvement worth the
>> implementation complexity? I've posted on GitHub.
>> Richard
>> On May 15, 2020, at 8:01 AM, Alejandro Serrano Mena <trupill at gmail.com>
>> wrote:
>> Dear Committee,
>> This proposal looks good to me. The author has done a lot of work to
>> formalize the new rules, and has done a check that no packages using arrow
>> syntax would be broken by this modification. Thus, I recommend we accept
>> this proposal.
>> Apart from the general discussion, I think it might be worth focusing on
>> a specific part of the design: the use of a couple of type families to
>> express "arrow stacks". I am not aware of other GHC extensions depending on
>> particular type families.
>> - As the author discusses, these type families ought to be wired-in, so
>> they can benefit from improvement during type checking. Is this a good
>> choice? It looks to be, but other may have a different opinion.
>> - Would this type family pose a problem for optimization / specialization
>> / ...?
>> Kind regards,
>> Alejandro
>> El lun., 4 may. 2020 a las 23:08, Joachim Breitner (<
>> mail at joachim-breitner.de>) escribió:
>>> Dear Committee
>>> I took the liberty to re-asssign #303 to Alejandro; the authors
>>> rightfully asked for progress in the discussion thread.
>>> Cheers,
>>> Joachim
>>> Am Freitag, den 03.01.2020, 15:20 +0100 schrieb Joachim Breitner:
>>> > Dear Committee,
>>> >
>>> > this is your secretary speaking:
>>> >
>>> > Constraint based arrow notation
>>> > has been proposed by Aleix King
>>> > https://github.com/ghc-proposals/ghc-proposals/pull/303
>>> >
>>> https://github.com/lexi-lambda/ghc-proposals/blob/constraint-based-arrow-notation/proposals/0000-constraint-based-arrow-notation.md
>>> >
>>> > I propose Chris Done as the shepherd.
>>> >
>>> > Please guide us to a conclusion as outlined in
>>> > https://github.com/ghc-proposals/ghc-proposals#committee-process
>>> >
>>> > Thanks,
>>> > Joachim
>>> --
>>> Joachim Breitner
>>>   mail at joachim-breitner.de
>>>   http://www.joachim-breitner.de/
>>> _______________________________________________
>>> ghc-steering-committee mailing list
>>> ghc-steering-committee at haskell.org
>>> https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee
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