On Mon, 19 Mar 2001, Simon Peyton-Jones wrote:
Lazy evaluation *is* coroutines, in a way.
What I had in mind was something like the following (pseudocode), which could easily be implemented on top of coroutines: class Channel c t where send :: t -> c -> IO () receive :: c -> IO t sender :: Int -> Channel -> ... sender n receiver = do send n receiver return (sender (n+1) receiver) receiver :: Channel -> ... receiver sender = do i <- receive sender return (receiver sender) c :: Channel Int c = ... main = run_them [ sender 1 c, receiver c ] Maybe there is also a way to achieve something similar using higher order functions---I just don't see how.
Or you may be interested in Concurrent Haskell See section 4 of "Tackling the awkward squad" http://research.microsoft.com/~simonpj/papers/marktoberdorf.htm
Thanks, I'm chewing on this paper of yours since a couple of days already. I particularly like the introduction to monads---it's the best I have seen so far. --Andreas.