c++primer第七章函数7.31

清疚 2022-08-07 09:35 175阅读 0赞

习题7.31

编写你自己的Sales\_item类，添加两个公用(public)成员用于读和写Sales\_item对象。这两个成员函数的功能应类似于第1章介绍的输入输出操作符。交易也应类似于那一章所定义的。利用这个类读入并交易输出一组交易。  
习题7.33 在Sales\_item类中加入一个成员，用于将两个Sales\_item对象相加。使用修改后的类重新解决第1章给出的平均价格问题。

#ifndef SALESITEM_H
    #define SALESITEM_H
    
    #include <iostream>
    #include <string>
    
    class Sales_item {
    public:
        //构造函数
        Sales_item() :units_sold(0), revenue(0.0){}
        Sales_item(const std::string &book) :isbn(book), units_sold(0), revenue(0.0){}
        //成员函数
        inline std::istream& In(std::istream&);
        inline std::ostream& Out(std::ostream&) const;
        bool same_isbn(const Sales_item &rhs){ return isbn == rhs.isbn; }
        double avg_price() const;
        //喵
        Sales_item plus(Sales_item &it1, Sales_item &it2);
    private:
        std::string isbn;
        unsigned units_sold;
        double revenue;
    };
    
    double Sales_item::avg_price() const
    {
        if (units_sold)
            return revenue / units_sold;
        else
            return 0;
    }
    std::istream& Sales_item::In(std::istream &in)
    {
        double price;
        std::cin >> isbn >> units_sold >> price;
        revenue = units_sold * price;
        return in;
    }
    std::ostream& Sales_item::Out(std::ostream &out) const
    {
        std::cout << isbn << " " << units_sold << '\t'
            << revenue << '\t' << avg_price() << std::endl;
        return out;
    }
    Sales_item Sales_item::plus(Sales_item &it1, Sales_item &it2)
    {
        isbn = it1.isbn;
        revenue = it1.revenue + it2.revenue;
        units_sold = it1.units_sold + it2.units_sold;
        return *this;
    }
    #endif
    
    
    
    
    #include <iostream>
    #include <string>
    #include
    #include "Sales_item.h"
    using namespace std;
    int main()
    {
        Sales_item item1, item2, item3;
        item1.In(cin);
        item2.In(cin);
        cout << endl;
        item1.Out(cout);
        item2.Out(cout);
        cout << endl;
        item3.plus(item1, item2);
        item3.Out(cout);
        system("pause");
        return 0;
    }