Re: [Haskell-cafe] Where is the pairing-with-monoid monad instance?

On Wed, Jan 11, 2012 at 03:23, Conal Elliott wrote:

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/Co... Regards, Sean