//Sales_item.h
#ifndef SALESITEM_H#define SALESITEM_H#include <iostream>#include<string>class Sales_item{public:	std::istream &input(std::istream & in);	std::ostream & output(std::ostream & out)const;	double avg_price() const;	bool same_isbn(Sales_item& rhs)const;	Sales_item add(Sales_item& other);	Sales_item::Sales_item() :unit_sale(0), revenue(0){}private:	std::string isbn;//isbn号	int unit_sale;//数量	double revenue;//总价};#endif

//Sales_item.cpp#include "Sales_item.h"std::istream& Sales_item::input(std::istream & in){	double price;	in >> isbn >> unit_sale >> price;	if (in)		revenue = unit_sale*price;	else	{		unit_sale = 0;		revenue = 0.0;	}	return in;}std::ostream& Sales_item::output(std::ostream & out)const{	out << isbn << "\t" << unit_sale << "\t"		<< revenue << "\t" << avg_price();	return out;}double Sales_item::avg_price() const{	if (unit_sale)		return revenue / unit_sale;	else		return 0.0;}bool Sales_item::same_isbn(Sales_item& rhs)const{	return isbn == rhs.isbn;}Sales_item Sales_item::add(Sales_item& other){		unit_sale += other.unit_sale;		revenue += other.revenue;		return *this;}

//main.cpp#include <iostream>//#include <string>//#include <vector>//#include <cctype>//#include <cstring>//#include <bitset>#include "Sales_item.h"using namespace std;int main(int argc, char **argv){	Sales_item total, trans;	cout << "Enter some transaction (ctrl + z to end)" << endl;	if (total.input(cin)){//读入第一个交易		while (trans.input(cin))		{			if (total.same_isbn(trans))				total.add(trans);			else			{				total.output(cout);				total = trans;			}		}		//输出最后一个交易		total.output(cout) << endl;	}	else	{		cout << "No data!" << endl;		return -1;	}	cout << endl;	system("pause");	return 0;}