main :: IO ()
main = do args <- getArgs
          case head args of
            "-h" -> (new :: IO HDB) >>= main' 
            "-b" -> (new :: IO BDB) >>= main' 
            "-f" -> (new :: IO FDB) >>= main' 
            _ -> putStrLn "./myapp1 [-h|-b|-f]"
main :: IO ()
main = do args <- getArgs
          case head args of
            "-h" -> (new :: IO HDB) >>= main' 
            "-b" -> (new :: IO BDB) >>= main' 
            "-f" -> (new :: IO FDB) >>= main' 
            _ -> putStrLn "./myapp1 [-h|-b|-f]"
main = do args <- getArgs
          case head args of
            "-h" -> (new :: IO HDB) >>= main' 
            "-b" -> (new :: IO BDB) >>= main' 
            "-f" -> (new :: IO FDB) >>= main' 
            _ -> putStrLn "./myapp1 [-h|-b|-f]"