Nicolas Frisby
I did come across that. They only call this particular lifting "not natural," which doesn't seem much of a justification - unless they mean natural in a more formal sense that isn't immediately obvious to me.
I agree it's not much of a justification. Maybe what they meant by "natural" is that the same code (using "ask" and "local") should work in the reader monad as in the continuation monad transformer applied to the reader monad. Here's an example to illustrate: import Control.Monad.Cont import Control.Monad.Reader example local = do x <- ask y <- local (1+) ask z <- ask return (x,y,z) local' f m = ContT $ \c -> do r <- ask local f (runContT m c) In ghci 6.8.2, I get *Main> runReader (runContT (example local) return) 1 (1,2,1) *Main> runReader (runContT (example local') return) 1 (1,2,2)
I revisited that paper upon finding the reference in your Delimited Dynamic Binding, the examples of which finally lent some clarity to the differences in the computational behaviors I was dealing with.
Thanks for the encouragement. (: -- Edit this signature at http://www.digitas.harvard.edu/cgi-bin/ken/sig 100 Days to close Guantanamo and end torture http://100dayscampaign.org/