+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
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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