Hello, I want to make a Monad which is almost exactly like the Writer monad, except instead of using mappend to glue Monoids together, it uses <*> to glue applicative functors together. Here is the code: import Control.Applicative import Data.Monoid -- * Sample Implementation of the Writer Monad data Writer w a = Writer { runWriter :: (w, a) } instance (Monoid w) => Monad (Writer w) where return a = Writer (mempty, a) (>>=) = bindWriter bindWriter :: (Monoid w) => Writer w a -> (a -> Writer w b) -> Writer w b bindWriter (Writer (w,a)) f = let (Writer (w', b)) = f a in Writer (w `mappend` w', b) -- * Sample Implementation of the Applicative Functor Monad data AF af a = AF { runAF :: (af, a) } bindAF :: (Applicative f) => AF (f (a -> b)) x -> (x -> AF (f a) y) -> AF (f b) y bindAF (AF (f, x)) g = let (AF (a, y)) = g x in AF (f <*> a, y) -- instance (Applicative f) => Monad (AF (f ... As you can see, the similarity is striking. Alas, AF and bindAF do not quite have the right type signatures to be used for an instance of the Monad class. Is there some clever work-around I missing? (Aside from, -fno-implicit-prelude). Thanks! - jeremy