Using WrappedApplicative with DerivingVia
Topsii opened this issue · comments
Wouldn't it make sense to define WrappedApplicative's fmap via liftA instead of <$> to support the following use case?
{-# language DerivingVia #-}
import Data.Functor.Apply
data Vec3 a = MkVec3 a a a
deriving stock Show
deriving Functor via WrappedApplicative Vec3
instance Applicative Vec3 where
pure x = MkVec3 x x x
(MkVec3 f g h) <*> (MkVec3 x y z) = MkVec3 (f x) (g y) (h z)
This would be a breaking change since the instance would change from
instance Functor f => Functor (WrappedApplicative f) where
fmap f (WrapApplicative a) = WrapApplicative (f <$> a)
to
instance Applicative f => Functor (WrappedApplicative f) where
fmap f (WrapApplicative a) = WrapApplicative (liftA f a)
However due to the name WrappedApplicative it seems reasonable to require an Applicative instance.
The same approach does not work for WrappedMonad. Notably it is in conflict with the Monad of no return proposal.