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2018-10-30 01:49:10

•   /*
   * This file contains code from "C   Primer, Fourth Edition", by Stanley B。
   * Lippman, Jose Lajoie, and Barbara E。
     Moo, and is covered under the
   * copyright and warranty notices given in that book:
   * 
   * "Copyright (c) 2005 by Objectwrite, Inc。
    , Jose 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 Contracts Department
   * 75 Arlington Street, Suite 300
   * Boston, MA 02216
   * Fax: (617) 848-7047
  */ #ifndef SALESITEM_H
  #define SALESITEM_H// Definition of Sales_item class and related functions goes here
  #include 
  #include class Sales_item {
  friend bool operator==(const Sales_item&, const Sales_item&);
  // other members as before
  public:
   // added constructors to initialize from a string or an istream
   Sales_item(const std::string &book):
   isbn(book), units_sold(0), revenue(0。
    0) { }
   Sales_item(std::istream &is) { is >> *this; }
   friend std::istream& operator>>(std::istream&, Sales_item&);
   friend std::ostream& operator>(istream& in, Sales_item& s)
  {
   double price;
   in >> s。
    isbn >> s。units_sold >> price;
   // check that the inputs succeeded
   if (in)
   s。revenue = s。
    units_sold * price;
   else 
   s = Sales_item(); // input failed: reset object to default state
   return in;
  }inline
  ostream& 
  operator<<(ostream& out, const Sales_item& s)
  {
   out << s。
    isbn << "	" << s。units_sold << "	" 
   << s。revenue << "	" << s。
    avg_price();
   return out;
  }inline
  double Sales_item::avg_price() const
  {
   if (units_sold) 
   return revenue/units_sold; 
   else 
   return 0;
  }
  #endif。

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  2018-10-30 01:49:10

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