On Wed, Jul 09, 2008 at 11:05:47PM -0400, Ronald Guida wrote: > Question: If I can't change my function f (in this case, accumulator), > then is it possible to get the effect I want without having to resort > to "unsafeInterleaveIO"?
Here's a possibility; you may or may not like it. module Main where import Control.Concurrent import Control.Concurrent.Chan import Control.Concurrent.MVar import Control.Monad {- promptInt, accumulator, makeAccPrompt as before -} main :: IO () main = do inChan <- newChan outMVar <- newEmptyMVar forkIO $ (getChanContents inChan) >>= (mapM_ (putMVar outMVar) . accumulator) let go = do p <- takeMVar outMVar m <- promptInt (makeAccPrompt p) case m of Just n -> do writeChan inChan n ns <- go return $ n:ns Nothing -> return [] xs <- go print xs The unsafeInterleaveIO is now hidden inside getChanContents. (I have an outMVar rather than an outChan just in case accumulator could produce lots of output before consuming much of its input.) Regards, Reid Barton _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe