[Haskell-cafe] Monad transformer, liftIO

[Andrew Wagner]

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 at 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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