Hi Tom, There is probably more than one way to do this. Did you try using the package hint-server? [1] It has a very simple interface: you start a "server" and obtain a handle; then you can run an interpreter action using the handle. Something like this:

runIn handle (interpret msg (as :: MyType))

This expression has type IO (Either InterpreterError MyType). You can also run an interpreter action in the background. Keep in mind that the ghc-api is not thread safe, though, so you should start only one server and put the handle in an MVar.... Hope that helps Daniel [1] http://hackage.haskell.org/package/hint-server On Jun 17, 2010, at 6:35 PM, Tom Jordan wrote:

I'm trying to receive small segments of Haskell code over a socket, and be able to evaluate them in real time in GHCI. I've already downloaded Hint and have run the test code, and it's working great. I'm also using the socket server code from Ch.27 of "Real World Haskell" and that is working well also.

directly below is the function from the socket server code that handles the incoming messages. Instead of doing this: "putStrLn msg"... I want to send whatever is captured in "msg" to the GHC interpreter that is used in the Hint code, something like this: "eval msg". I'm not sure how to combine both of these functionalities to get them to work with each other..

-- A simple handler that prints incoming packets plainHandler :: HandlerFunc plainHandler addr msg = putStrLn msg

Below is the full code for the socket server, then below that is "SomeModule" used in the Hint example test below that.

-- file: ch27/syslogserver.hs import Data.Bits import Network.Socket import Network.BSD import Data.List

type HandlerFunc = SockAddr -> String -> IO ()

serveLog :: String -- ^ Port number or name; 514 is default -> HandlerFunc -- ^ Function to handle incoming messages -> IO () serveLog port handlerfunc = withSocketsDo $ do -- Look up the port. Either raises an exception or returns -- a nonempty list. addrinfos <- getAddrInfo (Just (defaultHints {addrFlags = [AI_PASSIVE]})) Nothing (Just port) let serveraddr = head addrinfos

-- Create a socket sock <- socket (addrFamily serveraddr) Datagram defaultProtocol

-- Bind it to the address we're listening to bindSocket sock (addrAddress serveraddr)

-- Loop forever processing incoming data. Ctrl-C to abort. procMessages sock where procMessages sock = do -- Receive one UDP packet, maximum length 1024 bytes, -- and save its content into msg and its source -- IP and port into addr (msg, _, addr) <- recvFrom sock 1024 -- Handle it handlerfunc addr msg -- And process more messages procMessages sock

-- A simple handler that prints incoming packets plainHandler :: HandlerFunc plainHandler addr msg = putStrLn msg

-- main = serveLog "8008" plainHandler ----------------------------------------------------------------------------------------------------------------

module SomeModule(g, h) where

f = head

g = f [f]

h = f

----------------------------------------------------------------------------------------------------------------

import Control.Monad import Language.Haskell.Interpreter

main :: IO () main = do r <- runInterpreter testHint case r of Left err -> printInterpreterError err Right () -> putStrLn "that's all folks"

-- observe that Interpreter () is an alias for InterpreterT IO () testHint :: Interpreter () testHint = do say "Load SomeModule.hs" loadModules ["SomeModule.hs"] -- say "Put the Prelude, Data.Map and *SomeModule in scope" say "Data.Map is qualified as M!" setTopLevelModules ["SomeModule"] setImportsQ [("Prelude", Nothing), ("Data.Map", Just "M")] -- say "Now we can query the type of an expression" let expr1 = "M.singleton (f, g, h, 42)" say $ "e.g. typeOf " ++ expr1 say =<< typeOf expr1 -- say $ "Observe that f, g and h are defined in SomeModule.hs, " ++ "but f is not exported. Let's check it..." exports <- getModuleExports "SomeModule" say (show exports) -- say "We can also evaluate an expression; the result will be a string" let expr2 = "length $ concat [[f,g],[h]]" say $ concat ["e.g. eval ", show expr1] a <- eval expr2 say (show a) -- say "Or we can interpret it as a proper, say, int value!" a_int <- interpret expr2 (as :: Int) say (show a_int) -- say "This works for any monomorphic type, even for function types" let expr3 = "\\(Just x) -> succ x" say $ "e.g. we interpret " ++ expr3 ++ " with type Maybe Int -> Int and apply it on Just 7" fun <- interpret expr3 (as :: Maybe Int -> Int) say . show $ fun (Just 7) -- say "And sometimes we can even use the type system to infer the expected type (eg Maybe Bool -> Bool)!" bool_val <- (interpret expr3 infer `ap` (return $ Just False)) say (show $ not bool_val) -- say "Here we evaluate an expression of type string, that when evaluated (again) leads to a string" res <- interpret "head $ map show [\"Worked!\", \"Didn't work \"]" infer >>= flip interpret infer say res

say :: String -> Interpreter () say = liftIO . putStrLn

printInterpreterError :: InterpreterError -> IO () printInterpreterError e = putStrLn $ "Ups... " ++ (show e) _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe