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
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