[Haskell-beginners] getChar and keyboard reading

[Magnus Therning]

On 24/01/10 20:49, Matthias Güdemann wrote:
> 
> Hi,
> 
> I wrote a program which should read the number of key presses in a
> given time. It forks a thread which calls getChar and increases a MVar
> each time getChar suceeds. After a delay (here 2s) the MVar is read,
> its value is printed and the program exits.
> 
> 
> import Control.Concurrent
> 
> increaseEveryPush mVCount = do
>   _ <- getChar
>   inh <- takeMVar mVCount
>   putMVar mVCount (inh + 1)
>   increaseEveryPush mVCount
>   
> main = do
>   x <- newMVar 0
>   forkIO (increaseEveryPush x)
>   threadDelay 2000000
>   inh <- takeMVar x
>   putStr $ "\n" ++ (show inh) ++ " times button pushed\n"
> 
> 
> But this does not work, as getChar does not succeed if there is no EOF
> given (^D). It normally just exits with 0 as value in the MVar. Is
> there a way toread the keyboard without having to terminate with EOF? 

In the past I've done this sort of thing by turning of buffering on stdin:

hSetBuffering stdin NoBuffering

/M

-- 
Magnus Therning                        (OpenPGP: 0xAB4DFBA4)
magnus＠therning．org          Jabber: magnus＠therning．org
http://therning.org/magnus         identi.ca|twitter: magthe

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 198 bytes
Desc: OpenPGP digital signature
Url : http://www.haskell.org/pipermail/beginners/attachments/20100124/2ea9b110/signature.bin