Proposal: Add a wrapped applicative type to Data.Monoid

[Andrew Martin]

+1 from me. I've written this type at least a dozen times in various
projects.

On Tue, Mar 27, 2018 at 10:22 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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>


-- 
-Andrew Thaddeus Martin
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