concurrentN_ :: Int -> [IO a] -> IO ()
concurrentN_ n =
  -- we could probably be more memory efficient here.
  void . concurrentN n
concurrentN_ :: Int -> [IO a] -> IO ()
concurrentN_ n =
  -- we could probably be more memory efficient here.
  void . concurrentN n
concurrentN_ n =
  -- we could probably be more memory efficient here.
  void . concurrentN n