Adding Backwards to base, re-export from Control.Applicative

[Baldur Blöndal]

Is it time to move Control.Applicative.Backwards module from transformers to base, and maybe re-export it from Control.Applicative.

It's an interesting, important, simple property of Applicative that they can be run backwards.

[chessai .]

I support this. +1

Should we copy in the libraries mailing list?

On Tue, Nov 12, 2019, 5:56 AM Baldur Blöndal <bald...@gmail.com> wrote:

Is it time to move Control.Applicative.Backwards module from transformers to base, and maybe re-export it from Control.Applicative.

It's an interesting, important, simple property of Applicative that they can be run backwards.

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[Ryan Scott]

This discussion definitely belongs on the mailing list, yes.

Ryan

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[George Wilson]

I support this.
It would require coordinating with Ross Paterson, the maintainer of
transformers.

On Tue, 26 Nov 2019 at 09:58, Baldur Blöndal <bald...@gmail.com> wrote:
>
> I'll CC Haskell Libraries

> _______________________________________________
> Libraries mailing list
> Libr...@haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

[David Feuer]

If Backwards moves, then Reverse probably should too.

On Mon, Nov 25, 2019, 6:58 PM Baldur Blöndal <bald...@gmail.com> wrote:

I'll CC Haskell Libraries

þri., 12. nóv. 2019 kl. 22:14 skrifaði Ryan Scott <ryan.g...@gmail.com>:

_______________________________________________

[chessai .]

I think that makes sense. It wouldn't be disruptive, both changes are small but useful.

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[Edward Kmett]

I’m a strong +1 on moving Backwards and Reverse to base. This is basically free for everybody for a nice consistency win.

I’m -1 on exporting them from Control.Applicative. That module is imported unqualified by a significant cross section of the Haskell ecosystem, so this just gratuitously introduces risk of name conflicts for little tangible benefit. In the presence of possible conflicts there I’d err on the side of the status quo over change for change’s sake.

The only real precedent for doing so is that Control.Applicative also gratuitously exports Const, which is more historical accident than precedent to follow.

-Edward

On Nov 27, 2019, at 1:36 PM, chessai . <chess...@gmail.com> wrote:



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[Fumiaki Kinoshita]

Same as Edward; like Compose and Identity, I'm +1 to adding them into base but -1 to reexporting.

2019年12月6日(金) 2:43 Edward Kmett <ekm...@gmail.com>: