Defining a new monad in haskell raises no instance for Applicative

Question

I am trying to define a new monad and I am getting a strange error

newmonad.hs

newtype Wrapped a = Wrap {unwrap :: a}
instance Monad Wrap         


        

Answer 1

The most normalized and unobtrusive answer is :-

as Monad is dependent upon Applicative

class Applicative m => Monad m where ...

and Applicative is dependent upon Functor

class Functor f => Applicative f where ...

we need the instance definitions

> instance Functor Wrapped where
>     fmap = liftM

and

> instance Applicative Wrapped where
>     pure = return
>     (<*>) = ap