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/*
* 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<<(std::ostream&, const Sales_item&);
public:
// operations on Sales_item objects
// member binary operator: left-hand operand bound to implicit this pointer
Sales_item& operator+=(const Sales_item&);
// other members as before

public:
// operations on Sales_item objects
double avg_price() const;
bool same_isbn(const Sales_item &rhs) const
{ return isbn == rhs.isbn; }
// default constructor needed to initialize members of built-in type
Sales_item(): units_sold(0), revenue(0.0) { }
// private members as before
private:
std::string isbn;
unsigned units_sold;
double revenue;

};


// nonmember binary operator: must declare a parameter for each operand
Sales_item operator+(const Sales_item&, const Sales_item&);

inline bool
operator==(const Sales_item &lhs, const Sales_item &rhs)
{
// must be made a friend of Sales_item
return lhs.units_sold == rhs.units_sold &&
lhs.revenue == rhs.revenue &&
lhs.same_isbn(rhs);
}

inline bool
operator!=(const Sales_item &lhs, c

onst Sales_item &rhs)
{
return !(lhs == rhs); // != defined in terms of operator==
}

using std::istream; using std::ostream;

// assumes that both objects refer to the same isbn
inline
Sales_item& Sales_item::operator+=(const Sales_item& rhs)
{
units_sold += rhs.units_sold;
revenue += rhs.revenue;
return *this;
}

// assumes that both objects refer to the same isbn
inline
Sales_item
operator+(const Sales_item& lhs, const Sales_item& rhs)
{
Sales_item ret(lhs); // copy lhs into a local object that we'll return
ret += rhs; // add in the contents of rhs
return ret; // return ret by value
}

inline
istream&
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 << "\t" << s.units_sold << "\t"
<< s.revenue << "\t" << s.avg_price();
return out;
}

inline
double Sales_item::avg_price() const
{
if (units_sold)
return revenue/units_sold;
else
return 0;
}


#endif