STM would complicate things too much for me. At least I think so. I would love to use STM but I would need to fit it into "type ScriptState = ErrorT String (StateT World IO)" just to use the logger. I'm not THAT comfortable with monads. Let me see if I understand you correctly... Are you saying that I should be using getChanContents in the code below? logger :: Handle -> MVar () -> IO () logger h die = do empty <- isEmptyChan parent unless empty $ do x <- readChan parent putStrLn x hPutStrLn h x alive <- isEmptyMVar die when (alive || not empty) $ logger h die I think using Maybe is a great trick but I'm curious why so few messages actually get taken out of the channel in the code above? Are you saing that with all the checking it does not get to pull messages out? I see clearly how using Maybe with getChanContents will work out perfectly. I don't understand why the above code is inefficient to the point of printing just a few messages (out of hundreds) out on Windows. I would like to understand it to avoid such mistakes in the future. Thanks, Joel On Nov 21, 2005, at 9:56 PM, Tomasz Zielonka wrote:
You seem to be busy waiting. I can see two ways of solving the problem: 1. use STM and non-deterministic choice 2. use a (Chan (Maybe String)), where (Just s) means the next log entry, and Nothing means "break the logger loop"