Dear Sumit, You are right that there's something's fishy about the free monadic modeling of accept. The following parallel construction will prove instructive: The native effect: send :: chan -> ByteString -> IO Bool is modeled in the free monad by the constructor for the base functor Send :: chan -> ByteString -> (Bool -> next) -> NetworkActivity chan next which is the data wrapping used in the value level sendit :: chan -> ByteString -> Free (NetworkActivity chan) Bool sendit chan buf = liftF (Send chan buf identity) Analogously, the native accept :: chan -> IO chan is modeled by Accept :: chan -> (chan -> next) -> NetworkActivity chan next used in acc :: chan -> Free (NetworkActivity chan) chan acc chan = liftF (Accept chan identity) Except that you used a different constructor for the base functor. Not Accept :: chan -> (chan -> next) -> NetworkActivity chan next but Accept :: chan -> next -> (chan -> next) -> NetworkActivity chan next which is equivalent to Accept :: chan -> (Maybe chan -> next) -> NetworkActivity chan next The new free monadic term that substitutes for the native accept is the same like before acc chan = liftF (Accept chan identity) only with a different type acc :: chan -> Free (NetworkActivity chan) (Maybe chan) modeling a native accept :: chan -> IO (Maybe chan) Given a native API, its free monad encoding is entirely boilerplate. I wrote about the boilerplate process here (skip the sections that don't concern you): http://www.atamo.com/articles/free-monads-wont-detox-your-colon/ Best, Kim-Ee -- Kim-Ee On Fri, Oct 14, 2016 at 6:44 AM, Sumit Raja wrote:

...

I would really like to help you, but without your imports, packages, etc, it is really hard to interpret your program. Like where does decodeUtf8 come from, or receive, or TCPSocket? If they are functions you wrote, I don't need their code, the types would be sufficient.

Imports are:

import Protolude import Control.Monad.Free import System.Socket import System.Socket.Family.Inet import System.Socket.Type.Stream import System.Socket.Protocol.TCP import Control.Exception ( bracket, catch ) import Data.ByteString as BS (uncons)

decodeUtf8 :: ByteString -> Text encodeUtf8 :: Text -> ByteString

I'm using the socket library for the actual networking (https://hackage.haskell.org/package/socket-0.6.0.1)

type TCPSocket = Socket Inet Stream TCP receive :: Socket f t p -> Int -> MessageFlags -> IO ByteString Source send :: Socket f t p -> ByteString -> MessageFlags -> IO Int accept :: (Family f, Storable (SocketAddress f)) => Socket f t p -> IO (Socket f t p, SocketAddress f)

If it helps the full source is at https://bitbucket.org/sumitraja/network-free/src/ a4fcbc74c9e178e81d8b10b60d912b32c542b661/src/Lib.hs.

Looking forward to your assistance.

Thanks

Sumit _______________________________________________ Beginners mailing list Beginners@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/beginners