On 28 June 2011 18:32, Erik de Castro Lopo <mle+hs@mega-nerd.com> wrote:

The hlint program would have flagged both of those and possibly
others. See:

It didn't flag either for me, but it recommended replacing ++ (show port) with ++ show port, if then else with unless, putStrLn (show x) with print x, and do stuff with stuff.

On 28 June 2011 18:16, Ivan Lazar Miljenovic <ivan.miljenovic@gmail.com> wrote:

I don't think you need all those return () everywhere...

You're right. At some point I added it in to (try to) make the compiler happy, but it must have been or become unnecessary.

I still need two though because forkIO (and therefore my processLine function) returns IO ThreadId, but the last line for do notation must be return () (see below).

On 28 June 2011 18:16, Ivan Lazar Miljenovic <ivan.miljenovic@gmail.com> wrote:

And at the end, why do you do "line <- getLine" when you don't use the result?

Oh that. I was trying to figure out a way to terminate by program. I've now changed it to exit on EOF.

Here is my second attempt. Is it much better?:

import Control.Concurrent

import Control.Exception

import Control.Monad

import Network

import System.IO

import System.IO.Error (isEOFError)

main = withSocketsDo $ do

sListen <- listenOn (PortNumber 8000)

putStrLn "Listening on Port 8000"

forkIO $ forever $ do

(sSession, hostname, port) <- accept sListen

putStrLn ("Connected to " ++ hostname ++ ":" ++ show port)

let processLine = forkIO $ do

lineResult <- try (hGetLine sSession)

case lineResult of

Right line -> do

putStrLn line

processLine

return ()

Left e -> if isEOFError e

then print e

else ioError e

processLine

return()

putStrLn "Press <CTRL-D> to quit."

let processStdIn = do

lineResult <- try getLine

case lineResult of

Right line -> processStdIn

Left e -> unless (isEOFError e) $ ioError e

processStdIn

Thanks for the suggestions.

Cheers,