operator 重载找不到重载函数

/*

 * 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:


 *


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*/


/* This file defines the Sales_item class used in chapter 1.

 * The code used in this file will be explained in

 * Chapter 7 (Classes) and Chapter 14 (Overloaded Operators)

 * Readers shouldn't try to understand the code in this file

 * until they have read those chapters.
*/

#ifndef SALESITEM_H
// we're here only if SALESITEM_H has not yet been defined

#define SALESITEM_H

// Definition of Sales_item class and related functions goes here
#include <iostream>
#include <string>

class Sales_item {
// these declarations are explained section 7.2.1, p. 270

// and in chapter 14, pages 557, 558, 561
friend std::istream& operator>>(std::istream&, Sales_item&);
friend std::ostream& operator<<(std::ostream&, const Sales_item&);
friend bool operator<(const Sales_item&, const Sales_item&);
friend bool operator==(const Sales_item&, const Sales_item&);
public:
    // constructors are explained in section 7.1.4, pages 262 - 265
    // default constructor needed to initialize members of built-in type
    Sales_item() = default;
    Sales_item(const std::string &book): bookNo(book) { }
    Sales_item(std::istream &is) { is >> *this; }
public:
    // operations on Sales_item objects
    // member binary operator: left-hand operand bound to implicit this pointer
    Sales_item& operator+=(const Sales_item&);
   

    // operations on Sales_item objects
    std::string isbn() const { return bookNo; }
    double avg_price() const;
// private members as before
private:
    std::string bookNo;      // implicitly initialized to the empty string
    unsigned units_sold = 0; // explicitly initialized
    double revenue = 0.0;
};

// used in chapter 10
inline bool compareIsbn(const Sales_item &lhs, const Sales_item &rhs)

{ return lhs.isbn() == rhs.isbn(); }

// 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.isbn() == rhs.isbn();
}

inline bool operator!=(const Sales_item &lhs, const Sales_item &rhs)
{
    return !(lhs == rhs); // != defined in terms of operator==
}

// assumes that both objects refer to the same ISBN
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
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
}

std::istream& operator>>(std::istream& in, Sales_item& s)
{
    double price;
    in >> s.bookNo >> 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;
}

std::ostream& operator<<(std::ostream& out, const Sales_item& s)
{
    out << s.isbn() << " " << s.units_sold << " "
        << s.revenue << " " << s.avg_price();
    return out;
}

double Sales_item::avg_price() const
{
    if (units_sold)

        return revenue/units_sold;

    else

        return 0;
}
#endif

#include <iostream>
//using namespace std;
#include"sales.h"

int main(int argc, char *argv[])
{
    Sales Total;
    if(std::cin>>Total){
        Sales temp;
        while(std::cin>>temp){
            if(temp==Total){
                Total+=temp;
            }else{
                std::cout<<Total;
                Total=temp;
            }
        }
        std::cout<<Total;
    }else std::cout<<"No data!";

    return 0;
}