In writing up part 2 of my Scala Comonad Tutorial, and coming up with my talk for Scala World, I idly pondered this question:

If all monads are given by composing adjoint pairs of functors, what adjoint pair of functors forms the `Reader` monad? And if we compose those functors the other way, which comonad do we get?

Following leads from Shachaf Ben-Kiki on IRC, I thought about whether there was a free-forgetful adjunction given by an isomorphism between Kleisli arrows in the Reader monad on...