[C++知识库]机械祭天法力无边：C++primer之书店程序包含Sales_item.h源码

好吧，作为一个老菜鸟，还有第一章几道题实在写不下去了，直接写书店程序，这个书店程序只能满足2 2? 2 3 3 这种连续的情况，无法满足2 3 2 3这种情况。

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首先上Sales_item.h头文件源码在哪找，这个文件在书本给出网站中，底部有个download，如图

下载那个GCC pre-C++ 11 compiler 2012文件。?

Sales_item.h源码如下：

#ifndef SALESITEM_H
#define SALESITEM_H
#include <iostream>
#include <string>

class Sales_item
{
public:
	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:
	Sales_item & operator+=(const Sales_item&);
public:
	double avg_price() const;
	bool same_isbn(const Sales_item &rhs)const
	{
		return isbn == rhs.isbn;
	}
	Sales_item() :units_sold(0), revenue(0.0) {}
public:
	std::string isbn;
	unsigned units_sold;
	double revenue;
};

using std::istream;
using std::ostream;
Sales_item operator+(const Sales_item &, const Sales_item &);
inline bool operator==(const Sales_item &lhs, const Sales_item &rhs)
{
	return lhs.units_sold == rhs.units_sold && lhs.revenue == rhs.revenue && lhs.same_isbn(rhs);
}
inline bool operator!=(const Sales_item &lhs, const Sales_item &rhs)
{
	return !(lhs == rhs);
}

inline Sales_item & Sales_item::operator +=(const Sales_item &rhs)
{
	units_sold += rhs.units_sold;
	revenue += rhs.revenue;
	return *this;
}
inline Sales_item operator+(const Sales_item &lhs, const Sales_item &rhs)
{
	Sales_item ret(lhs);
	ret += rhs;
	return ret;
}
inline istream& operator>>(istream &in, Sales_item &s)
{
	double price;
	in >> s.isbn >> s.units_sold >> price;
	if (in)
		s.revenue = s.units_sold * price;
	else
		s = Sales_item();
	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

书店程序.cpp

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

int main()
{
	Sales_item total;//保存下一条交易的变量
	if(std::cin >> total){
		Sales_item trans;//保存和的变量
		//读取并处理剩余交易记录
		while (std::cin >> trans) {
			//如果我们任处理相同的书
			if (total.isbn() == trans.isbn()) {
				total += trans;//更新销售额
			}
			else {
				//打印前一本书的结果
				std::cout << total << endl;
				total = trans;//total现在表示下一本书的销售额
			
			}
			
		}
		cout << total << endl;//打印最后一本书的结果
}
	else {
		//没有输入!警告
		cerr << "No data?!" << endl;
		return -1;
	}
}

上面的程序运行会出现这种错误：

不知道怎么解决。?