Make Applicative a superclass of Monad

[Ashley Yakeley]

Make Applicative (in Control.Applicative) a superclass of Monad (in Control.Monad). Rename members of Applicative and other functions, to avoid unnecessary duplication.

class Functor f => Applicative f where
  return :: a -> f a
  ap :: f (a -> b) -> f a -> f b

liftA2 :: Applicative f => (a -> b -> c) -> f a -> f b -> f c
liftA2 f a b = ap (fmap f a) b

(>>) :: (Applicative f) => f a -> f b -> f b
(>>) = liftA2 (const id)

-- etc.

class Applicative m => Monad m where
  (>>=) :: forall a b . m a -> (a -> m b) -> m b
  fail :: String -> m a
  fail s = error s

[Ashley Yakeley]

Will break Haskell 98.

[igloo]

Ashley says "OK. Please close it, and I'll submit it for [Haskell] Prime."