text: //!@Yue Wang
  //!
  //! Exercise 6.12:
  //! Rewrite the program from exercise 6.10 in § 6.2.1 (p. 210) to use
  //! references instead of pointers to swap the value of two ints. Which
  //! version do you think would be easier to use and why?
  //  The version using reference is easier.
  //!
  #include <iostream>
  #include <string>
  
  void swap(int& lhs, int& rhs)
  {
      int temp = lhs;
      lhs = rhs;
      rhs = temp;
  }
  
  int main()
  {
      for (int left, right;
           std::cout << "Please Enter:\n", std::cin >> left >> right;) {
          swap(left, right);
          std::cout << left << " " << right << std::endl;
      }
  
      return 0;
  }
  