On 23 November 2005 13:29, Joel Reymont wrote:
On Nov 23, 2005, at 1:18 PM, Simon Marlow wrote:
After subsequent dicsussion, do you still think something strange was going on here?
Yes, but in a different thread. The "Postmortem" one.
so this basically loops until there are no messages in the channel, and then exits. Is that what you wanted, or did you want it to keep reading from the channel until told to die?
I probably made a mistake someplace as I wanted to read until told to die but ONLY if the channel was empty. I replaced that code with Tomasz's elegant solution so now I read until Nothing is read from the channel.
logger :: Handle -> IO () logger h = do ss <- getChanContents parent logger' ss where logger' [] = return () logger' (Nothing:_) = return () logger' ((Just x):xs) = do putStrLn x hPutStrLn h x logger' xs yield
The yield is unnecessary. Also, getChanContents is considered by some (me included) to be poor style, because it relies on lazy I/O. This should work just as well: logger h = do m <- readChan parent case m of Nothing -> return () Just x -> do hPutStrLn h x; logger h Cheers, Simon