At 2002-02-22 01:36, Richard Uhtenwoldt wrote:

So, congratulations, you've written call/cc in Haskell. I think.

Yes. test2 :: CPS (IO ()) (); test2 = do { liftM (putStr "aa\n"); ref <- liftM (newIORef Nothing); liftM (putStr "bb\n"); flag <- peirceM (\c -> do { liftM (putStr "cc\n"); liftM (writeIORef ref (Just c)); liftM (putStr "dd\n"); c True; liftM (putStr "ee\n"); return False; }); liftM (putStr "ff\n"); if (flag) then do { liftM (putStr "gg\n"); Just c' <- liftM (readIORef ref); liftM (putStr "hh\n"); c' False; liftM (putStr "ii\n"); } else do { liftM (putStr "jj\n"); } }; ContMonad> doMonadCPS test2 aa bb cc dd ff gg hh ff jj ...which shows that the continuation passed in by peirceM works both inside and outside the call. Changing "c' False" to "c' True" gave this endless iteration: ContMonad> doMonadCPS test2 aa bb cc dd ff gg hh ff gg hh ff gg hh ... I assume by the magic of Haskell's tail recursion, this won't eat up space. -- Ashley Yakeley, Seattle WA