[Haskell-beginners] Re: Talking betwean the parsers.

17 Jul 2009

      On Sat, 2009-07-18 at 00:40 +0200, Maciej Piechotka wrote:
...
I have a data structure of 
data Monad m => NntpConnection m = NntpConnection {
  input :: ByteString,
  output :: ByteString -> m ()
    }
I'd like to create echo structure such that the goes to output is going
to (lazy) input. For sure it is possible to use network and IO monad -
is is possible to do it purely?
Regards
I come up to with:

createEcho :: IO (NntpConnection IO)
createEcho = do (r, w) <- runKleisli (Kleisli fdToHandle ***
                                      Kleisli fdToHandle) =<< createPipe
                hSetBuffering r LineBuffering
                hSetBuffering w LineBuffering
                c <- hGetContents r
                return $ NntpConnection c $ hPut w

Which have advantage of not involving network stack but is
POSIX-specific.

Regards