text: /*
   * This file contains code from "C++ Primer, Fifth Edition", by Stanley B.
   * Lippman, Josee Lajoie, and Barbara E. Moo, and is covered under the
   * copyright and warranty notices given in that book:
   * 
   * "Copyright (c) 2013 by Objectwrite, Inc., Josee Lajoie, and Barbara E. Moo."
   * 
   * 
   * "The authors and publisher have taken care in the preparation of this book,
   * but make no expressed or implied warranty of any kind and assume no
   * responsibility for errors or omissions. No liability is assumed for
   * incidental or consequential damages in connection with or arising out of the
   * use of the information or programs contained herein."
   * 
   * Permission is granted for this code to be used for educational purposes in
   * association with the book, given proper citation if and when posted or
   * reproduced.Any commercial use of this code requires the explicit written
   * permission of the publisher, Addison-Wesley Professional, a division of
   * Pearson Education, Inc. Send your request for permission, stating clearly
   * what code you would like to use, and in what specific way, to the following
   * address: 
   * 
   * 	Pearson Education, Inc.
   * 	Rights and Permissions Department
   * 	One Lake Street
   * 	Upper Saddle River, NJ  07458
   * 	Fax: (201) 236-3290
  */ 
  
  #include <iostream>
  #include "Sales_item.h"
  
  int main() 
  {
      Sales_item item1, item2;
  
      std::cin >> item1 >> item2;
  	// first check that item1 and item2 represent the same book
  	if (item1.isbn() == item2.isbn()) {
      	std::cout << item1 + item2 << std::endl;
      	return 0;   // indicate success
  	} else {
      	std::cerr << "Data must refer to same ISBN" 
  		          << std::endl;
      	return -1;  // indicate failure
  	}
  }
  