gistfile1.hsc

f :: Monad m => m Int -> m Bool
f a = do
    b <- a
    return $ b == 0

main :: IO ()
main = do
    dump $ Just 10
    dump $ Just 0
    dump Nothing
    dump []
    dump [-2, -1 .. 2]

    where
        dump :: (Monad m, Show (m Bool), Show (m Int)) => m Int -> IO ()
        dump a = putStrLn ("f(" ++ show a ++ "): " ++ show (f a))