[Haskell-cafe] Extending GHCi

[Steffen Schuldenzucker]

Ok, so someFunction should modify the server's configuration? Maybe you 
can model it with an IORef like this (untested!):

 > import Data.IORef
 >
 > type Config = String  -- String to be prepended to every answer
 >
 > someFunction :: String -> IORef Config -> IORef Config
 > someFunction s r = modifyIORef s (++ s)
 >
 > startMyServer :: IO (IORef Config)
 > startMyServer = do
 >     r <- newIORef ""
 >     forkIO $ runServer r
 >     return r
 >
 > runServer :: IORef -> IO ()
 > runServer r = do
 >     client <- waitForAndAcceptConnection
 >     request <- getSomeData client
 >     prep <- readIORef r
 >     sendSomeAnswer client $ prep ++ request
 >     runServer r

And then:

*MyModule> r <- startMyServer
(plain echo server running)
*MyModule> someFunction "hello" r
(now echo server with prepend "hello")
*MyModule> someFunction "world" r
(now echo server with prepend "helloworld")

-- Steffen

On 02/04/2011 03:41 PM, C K Kashyap wrote:
> Thanks Steffen,
>
>     Prelude> :l MyModule.hs
>     *MyModule> conn <- waitForAndAcceptConnection
>     *MyModule> someData <- getSomeData conn
>     *MyModule> sendSomeAnswer conn $ processSomeData someData
>     ...
>
>
> So this cycle of getting data from the connection and writing answer 
> on the connection should happen concurrently with the ghci interaction 
> ... so lets say that when the "thread" is forked that listens on 
> socket behaves like an echo server ... as in, it reads data from the 
> client till "\n" and echoes it back ... All this would happen without 
> the intervention of the user using GHCI ... However, using GHCI, the 
> user should be able to modify the code such that the server returns 
> "hello" prepended to the input. ..
>
> > startMyServer -- at this point the the echo server gets spawned
> >                       -- echo server continues to run
> > someFunction "hello" --- now onwards  hello gets prepended
> >                       --- echo server continues to run returning 
> "hello" prepended
> > someFunction "world" --- now onwards "helloworld" get
>
> I hope this is possible without having to modify ghci itself.
>
> Regards,
> Kashyap

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.haskell.org/pipermail/haskell-cafe/attachments/20110204/5a69a247/attachment.htm>