Is the standard pair-with-monoid monad instance in some standard place? I see the Applicative instance in Control.Applicative, and the pair-with-monoid Functor instance in Control.Monad.Instances, and the (->) e and Either e monad instances also in Control.Monad.Instances.

I'm looking for something like

    instance Monoid o => Monad ((,) o) where
      return a    = (mempty,a)
      (o,a) >>= f = (o `mappend` o', b)
        where (o',b) = f a

Where is it hiding from me?

http://hackage.haskell.org/packages/archive/transformers/0.2.2.0/doc/html/Control-Monad-Trans-Writer-Lazy.html#t:WriterT ?

Regards,

Sean