main :: IO () main = do withSession (connect "USER" "PASSWORD" "DB") $ do -- simple query, returning reversed list of rows. r <- doQuery (sql "select username from all_users") query1Iteratee [] liftIO $ putStrLn $ show r
The error I'm getting is
db.hs:10:64: Couldn't match expected type `forall mark. DBM mark Session a' against inferred type `a1 b' In the second argument of `($)', namely `do r <- doQuery (sql "select username from all_users") ...
This is a fault in the example. Try this:
-- ($) replaced here with () withSession (connect "USER" "PASSWORD" "DB") ( do r <- doQuery (sql ... liftIO $ putStrLn $ show r --- here should be OK )
($) doesn't handle higher-ranked types, and overusing it can lead to these kinds of errors. 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. *****************************************************************