[Haskell-cafe] Using Hint with a socket server
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)
___
Re: [Haskell-cafe] Using Hint with a socket server
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
