On Mon, Jan 19, 2009 at 01:13:37PM -0800, Jonathan Cast wrote: > (On the other hand, your hunch that lift = return is correct --- so you > get a cookie for that; it's just that return here is neither the return > of the monad for m nor the return of the monad for ReaderT m. It is, > instead, the return of the *applicative functor* --- on the category of > monads and monad homomorphisms --- associated to the monad transformer > ReaderT.)
It's also a monad in the category of monads, as are ErrorT, StateT and WriteT (see Moggi, An Abstract View of Programming Languages, 1989, s4). _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
