public static void main(String[] args)
  {
    Scanner console = new Scanner(System.in);
    Unicalc unicalc = new Unicalc();

    Map<String,Quantity> env = QuantityDB.getDB();

    while (true)
    {
      System.out.print("input>  ");
      String input = console.nextLine();
      
      if (input.equals("")) break;  // Quit if no input
      
      unicalc.tokenize(input);
      
      AST ast = unicalc.parse();
      
      System.out.println("Result: " + ast.eval(env) + "\n");

    }
  }