Proposal: Add a wrapped applicative type to Data.Monoid

[Edward Kmett]

+1 to add it.

I don't care one way or the other about the name. =)

-Edward

On Tue, Mar 27, 2018 at 11:06 AM, Daniel Cartwright <chessai1996 at gmail.com>
wrote:

> One thing that I would like to respectfully point out - is that the
> members' of this library mailing list end up derailing otherwise useful
> conversations over the choice of a name, which is frankly a silly
> bottleneck. I would much rather roll a die or flip a coin to choose a name,
> and just get on to implementing the proposed thing, provided it is the case
> that it is seen as generally useful.
>
> On Tue, Mar 27, 2018 at 10:59 AM, Daniel Cartwright <chessai1996 at gmail.com
> > wrote:
>
>> I can definitely see "App" as being overloaded (Application).
>> Good names that I see are "Ap" and "Apply".
>>
>> I think "Ap" is fine.
>> On Tue, Mar 27, 2018, 10:28 AM David Feuer <david.feuer at gmail.com> wrote:
>>
>>> I proposed same thing some time ago. The main point of contention was
>>> the name. I hope you have better luck!
>>>
>>> On Tue, Mar 27, 2018, 10:23 AM Daniel Cartwright <chessai1996 at gmail.com>
>>> wrote:
>>>
>>>> I see this as being generally (as in, to the users of Haskell as a
>>>> whole) useful:
>>>>
>>>> newtype Ap f a = Ap { getAp :: f a }
>>>>   deriving (Applicative, Eq, Foldable, Functor, Generic, Generic1
>>>>                 ,Monad, Ord, Read, Show, Traversable)
>>>>
>>>> Some hand-written instances:
>>>> instance (Applicative f, Semigroup a) => Semigroup (Ap f a) where
>>>>   (Ap x) <> (Ap y) = Ap $ liftA2 (<>) x y
>>>>
>>>> instance (Applicative f, Monoid a) => Monoid (Ap f a) where
>>>>   mempty = Ap $ pure mempty
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>>>>
>>>
>
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