Hi Tom,
I played a bit with your suggestion, and it is running now :-)
But instead of IO [Int] I think we need IO [Only Int] because of
the 1-element-tupel problem?
With IO [Only Int] it looks like this:
-------------------------------------------------------------------------------------------
{-# LANGUAGE OverloadedStrings #-}
import Database.PostgreSQL.Simple
myconn :: ConnectInfo
myconn = defaultConnectInfo {
connectUser = "test",
connectPassword = "test",
connectDatabase = "test"}
main :: IO ()
main = do
c <- connect myconn :: IO Connection
rs <- query_ c "select 2 + 2" :: IO [Only Int]
putStrLn $ "Result from database " ++ show (fromOnly $ head rs)
return ()
-------------------------------------------------------------------------------------------
Best regards
Hartmut
On 08/18/2013 12:11 AM, Tom Ellis wrote:
On Sat, Aug 17, 2013 at 11:59:24PM +0200, Hartmut Pfarr wrote:
{-# LANGUAGE OverloadedStrings #-}
import Database.PostgreSQL.Simple
import Database.PostgreSQL.Simple.FromRow
hello :: (FromRow a) => IO [a]
hello = do
conn <- connect defaultConnectInfo
query_ conn "select 2 + 2"
Either
main = print =<< (hello :: IO [Int])
or give hello a monomorphic type signature, such as
hello :: IO [Int]
Tom
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