You haven't really said what happens when you try this, but I would bet that things would be clarified greatly if you put type signatures on your two definitions. 

On Fri, Apr 3, 2009 at 12:49 PM, Michael Roth <mroth@nessie.de> wrote:
Hello list,

maybe I'm just stupid, I'm trying to do something like this:


       import Control.Monad
       import Control.Monad.Trans
       import Control.Monad.List

       foobar = do
               a <- [1,2,3]
               b <- [4,5,6]
               liftIO $ putStrLn $ (show a) ++ " " ++ (show b)
               return (a+b)

       main = do
               sums <- foobar
               print sums


But this apparently doesn't work... I'm total clueless how
to achieve the correct solution. Maybe my mental image
on the monad transformer thing is totally wrong?


Michael
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