On 2015-08-03, Mario Blažević wrote:

Date: Mon, 3 Aug 2015 10:22:56 From: Mario Blažević To: libraries@haskell.org Subject: Re: Proposal: newtype for applicatives of monoids

On 07/26/2015 11:34 PM, David Feuer wrote:

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Sorry for the terrible title, but I think we should add something like the following to Data.Monoid (I already mentioned this in the discussion of a Monoid instance for ZipList).

newtype Appl f m = Appl (f m)

instance (Applicative f, Monoid m) => Monoid (Appl f m) where mempty = Appl $ pure mempty mplus (Appl x) (Appl y) = Appl $ liftA2 mplus x y

The method is called mappend, not mplus. Otherwise +1.

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It may be possible to use coercions to improve mplus; I haven't tried it.

This type is the same as WrappedApplicative from semigroupoids, do it might be best just to give it that name.

+1, with mappend. (I just tripped over the Monad instance of the same thing. It's very nice to be able to use (<>) on something like Monad m => Control.Monad.Trans.Exception m () .) Cheers, David -- David Casperson, PhD, R.P., | David.Casperson@unbc.ca Associate Professor and Chair, | (250) 960-6672 Fax 960-5544 Computer Science | 3333 University Way University of Northern British Columbia | Prince George, BC V2N 4Z9 | CANADA

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Christopher Allen writes:

Might as well capture all of 'em in one go. +1 w/ aforementioned mappend/mplus fix.

+1 John

On 08/03/2015 09:14 PM, Edward Kmett wrote:

To offer a couple more colors for the bikeshed:

In my old monoids package, this exists as App:

http://hackage.haskell.org/package/monoids-0.3.2/docs/Data-Monoid-Applicativ...

In the newer reducers package, it has been shortened to Ap:

http://hackage.haskell.org/package/reducers-3.10.3.2/docs/Data-Semigroup-App...

It *must* be App because apps are cool! ... I think? Regards,

Ap seems a good name, and it's already used for that, so I'd support that bike shed color. On Aug 3, 2015 3:14 PM, "Edward Kmett" wrote:

To offer a couple more colors for the bikeshed:

In my old monoids package, this exists as App:

http://hackage.haskell.org/package/monoids-0.3.2/docs/Data-Monoid-Applicativ...

In the newer reducers package, it has been shortened to Ap:

http://hackage.haskell.org/package/reducers-3.10.3.2/docs/Data-Semigroup-App...

-Edward

On Mon, Aug 3, 2015 at 1:58 PM, John Wiegley wrote:

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> Christopher Allen writes:

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Might as well capture all of 'em in one go. +1 w/ aforementioned mappend/mplus fix.

+1

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

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There is also http://hackage.haskell.org/package/free-4.12.1/docs/Control-Applicative-Free... http://hackage.haskell.org/package/free-4.12.1/docs/Control-Applicative-Free..., which is totally different thing, yet related to Applicative. reducers Ap has getApp field name, which is probably copy&paste mistake: http://hackage.haskell.org/package/reducers-3.10.3.2/docs/Data-Semigroup-App... http://hackage.haskell.org/package/reducers-3.10.3.2/docs/Data-Semigroup-App... In that light I’d prefer - Appl with getAppl, - Ap unchanged in free package - App left free

On 05 Aug 2015, at 12:15, Andreas Abel wrote:

+1 to Ap.

On 04.08.2015 05:21, David Feuer wrote:

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Ap seems a good name, and it's already used for that, so I'd support that bike shed color.

On Aug 3, 2015 3:14 PM, "Edward Kmett" mailto:ekmett@gmail.com> wrote:

To offer a couple more colors for the bikeshed:

In my old monoids package, this exists as App:

http://hackage.haskell.org/package/monoids-0.3.2/docs/Data-Monoid-Applicativ...

In the newer reducers package, it has been shortened to Ap:

http://hackage.haskell.org/package/reducers-3.10.3.2/docs/Data-Semigroup-App...

-Edward

On Mon, Aug 3, 2015 at 1:58 PM, John Wiegley mailto:johnw@newartisans.com> wrote:

>>>>> Christopher Allen mailto:cma@bitemyapp.com> writes:

> Might as well capture all of 'em in one go. > +1 w/ aforementioned mappend/mplus fix.

+1

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-- Andreas Abel <>< Du bist der geliebte Mensch.

Department of Computer Science and Engineering Chalmers and Gothenburg University, Sweden

andreas.abel@gu.se http://www2.tcs.ifi.lmu.de/~abel/ _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

It was fixed in HEAD for a while. I've now shipped that fix as part of 3.11. -Edward On Wed, Aug 12, 2015 at 4:09 AM, Petr Pudlák wrote:

IIRC the accessor is still called getApp in reducers, which is slightly inconsistent. Perhaps it'd be worth fixing on some future release that will bring other incompatible changes.

Thanks Petr

Dne po 3. 8. 2015 21:14 uživatel Edward Kmett napsal:

To offer a couple more colors for the bikeshed:

In my old monoids package, this exists as App:

http://hackage.haskell.org/package/monoids-0.3.2/docs/Data-Monoid-Applicativ...

In the newer reducers package, it has been shortened to Ap:

http://hackage.haskell.org/package/reducers-3.10.3.2/docs/Data-Semigroup-App...

-Edward

On Mon, Aug 3, 2015 at 1:58 PM, John Wiegley wrote:

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Christopher Allen writes:

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Might as well capture all of 'em in one go. +1 w/ aforementioned mappend/mplus fix.

+1

John

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