On Mon, 2009-01-19 at 21:31 +0000, Ross Paterson wrote: > 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).
Nice! I really haven't studied monad transformers nearly as much as I should have. (I also really need to read more Moggi :) jcc _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
