open monad io

loop m n | n < m = do
            loop' n 0
            putStrLn ""
            loop m (n + 1)
         | else = do return ()
          where loop' m n | n <= m = do
                              putStr "*"
                              loop' m (n + 1)
                          | else = do return ()

_ = loop 10 1 ::: IO