[Haskell-cafe] Cleaner way to write code and handle errors?

[Ivan Lazar Miljenovic]

On 28 June 2011 18:08, John Ky <newhoggy at gmail.com> wrote:
> Hi all,
> I'm practising my Haskell by writing a simple TCP echo server and finding
> that getting my program control to be succinct is rather tricky.  In
> particular, I have return () everywhere, my error handling is verbose and
> I'm not entirely sure my recursion is the cleanest way syntactically to get
> my loops going and terminating.
> I must be doing something obviously un-Haskell-like.
> Any suggestions on how I can improve my code?  Code below.
> Cheers,
> -John
>
> 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 putStrLn (show e)
>                 else do
>                   ioError e
>                   return ()
>         return ()
>     processLine
>     return()
>   line <- getLine
>   return ()

I don't think you need all those return () everywhere... And at the
end, why do you do "line <- getLine" when you don't use the result?

-- 
Ivan Lazar Miljenovic
Ivan.Miljenovic at gmail.com
IvanMiljenovic.wordpress.com