Hi list, to further my haskell skills I decided to produce my own raw MySQL connection. So far I can connect to the server and extract the handshake initialisation packet (HIP) and create the client authentication packet. Once I've figured out how to implement the salting and hashing I have a chance of starting a session. Not a problem, just got to do it. I want a module that I can use for simple DBMS I/O that doesn't use libmysql or odbc as sometimes these things just refuse to install on certain platform / architecture combinations! So, here's my problem: I kind of understand monads, I can use them and appreciate what/why they are useful etc. but my current implementation of reading the HIP into the type I created (shown next) appears to me at least to be plain clunky, ugly and inelegant compared to ninja haskell code I've read and one day hope to match, here's my code... apologies for the length of the post but I hope it's interesting to some! data PktHIP = PktHIP { hipProtoVer :: Int , hipSvrVer :: String , hipThreadId :: Int , hipScramble :: BS.ByteString , hipSvrCaps :: Integer , hipSvrLang :: Int , hipSvrStat :: Int , hipScramLen :: Int , hipPlugin :: String } deriving(Show) and reading it... getHIP :: Handle -> IO PktHIP getHIP h = do ver <- streamInt h 1 str <- getNTS h tid <- streamInt h 4 buf <- BS.hGet h 8 BS.hGet h 1 -- filler scap1 <- streamInt h 2 slang <- streamInt h 1 sstat <- streamInt h 2 scap2 <- streamInt h 2 scrln <- streamInt h 1 BS.hGet h 10 -- filler scram <- getNTS h -- todo: there *has* to be a more concise way of doing this? return $ PktHIP { hipProtoVer = ver , hipSvrVer = str , hipThreadId = tid , hipScramble = buf , hipSvrCaps = fromIntegral scap1 -- scap2 << 2 ? TODO! , hipSvrLang = slang , hipSvrStat = sstat , hipScramLen = scrln , hipPlugin = scram } -- Extract an N byte Int value from the input stream streamInt :: Handle -> Int -> IO Int streamInt h len = liftM bsVal $ BS.hGet h len bsVal :: BS.ByteString -> Int bsVal = BS.foldr' (\byte total -> fromEnum byte + (shiftL total 8)) 0 -- Get a Null-Terminated String getNTS :: Handle -> IO String getNTS h = streamInt h 1 >>= \b -> getString h "" b where getString :: Handle -> String -> Int -> IO String getString h acc c | c == 0 = return $ reverse acc | otherwise = streamInt h 1 >>= getString h ((chr c):acc) Then I read about the Data.Binary package and the Get monad and got this far... readHIP :: Get (Maybe PktHIP) readHIP = do return (Nothing) I looked at the example on this page: http://www.haskell.org/haskellwiki/DealingWithBinaryData , I stopped because I realised that the Get monad was only going to mean I ended up with very similarly structured code and probably a lot of it. I know the PktHIP has lots of fields but even so I am convinced it can be reduced and re-factored into much more beautiful code that I know how to write so far. I've tried to reason about it and I can "see" that there is a function out there that takes a Handle and "a record modifier function" and I can see also that it might be time for me to create my first Monad type ever IIUC, by implementing >>=, >> and return and I make use of the many monad centric modules that exist but I also am under the impression that I can add as many other functions to my Monad class as I need to do what I need to do, is that correct? I would therefore like some way to create an initial "thing" that contains the handle passed in to the function so that the >>= invocations can be as clean as possible because somewhere in my mind I can feel code resembling something like this: getHIP :: Handle -> MyMonad PktHIP getHIP h = do -- science fiction code starts now! let rs = ... --- record state monad thing with "h" and "PktHIP" getInt 1 rs hipProtoVer >> getNTS rs hipSvrVer >> getInt 4 rs hipThreadId >> getBS 8 rs hipScramble >> skip 1 >> : : ...etc return $ theHIP getInt :: Int -> ST ? -> (PktHIP -> PktHIP) -> MyMonad PktHIP getInt len state fmod = do val <- readStream ("h from state") len let state' = modify state by setting field "fmod" to "val" return state' Problems / things I am clueless about how to do here |1| how to create "something" that each >>= can modify (state monad instance?) |2| how to put the Handle "h" somewhere it can be read on each read action |3| everything else!!! So, any ideas, examples etc. would be most enlightening and gratefully absorbed! Sean Charles. :)