-----Original Message----- From: Daniel Everett [mailto:djeinbrum@yahoo.co.uk]
OK, this now compiles thanks to (a) hacking Setup.hs to refer to odbc_config rather than odbcconf and (b) unregistering the user packages with ghc-pkg --user unregister Takusen.
Please create a darcs patch for Setup.hs and send it to me. IIRC, you were on Linux? I'm not sure if Takusen has been tested under Linux. We've receieved patches for OSX, Oleg uses BSD, and I have Windows, so it would be useful to get patches for Linux installs too.
create table dummy (id int primary key);
query1Iteratee :: (Monad m) => Int -> String -> Double -> IterAct m [(Int, String, Double)] query1Iteratee a b c accum = result' ((a, b, c):accum)
r <- doQuery (sql "select id from dummy") query1Iteratee [] liftIO(putStrLn(show r)) )
fromUTF8Ptr: zero byte found in string as position 8
Is there any thing wrong with the above code?
Yes. The iteratee function expects three columns in the result-set (with types Int, String, and Double, in that order), but your query only provides one column (dummy, of type Int). There is the beginnings of some code in a couple of the backends to validate the iteratee against the actual result-set, but it's nowhere near complete. So if you have a mismatch between iteratee and query, then you are likely to get marshaling erros and/or garbage. Note that it's OK to have a result-set return more columns than the iteratee consumes, but obviously to converse cannnot work.
Also, what does liftIO actually do?
The monad that your database session is in is a ReaderT wrapper over IO. In order to perform actions that run in the IO monad, you need to "lift" them. http://www.haskell.org/haskellwiki/Monad_Transformers_Explained Alistair ***************************************************************** Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. *****************************************************************