C++ Primer（第5版） 练习 15.30

练习 15.30 编写你自己的Basket类，用它计算上一个练习中交易记录的总价格。

环境：Linux Ubuntu（云服务器）

工具：vim

代码块：

/*************************************************************************
	> File Name: ex15.30.cpp
	> Author: 
	> Mail: 
	> Created Time: Tus 25 Jul 2024 09:13:44 AM CST
 ************************************************************************/

#include<iostream>
#include<vector>
#include<memory>
#include<set>
using namespace std;

class Quote{
    public:
    Quote() = default;
    Quote(const std::string &book, double sales_price): bookNo(book), price(sales_price) {}
    std::string isbn() const { return bookNo; }
    
    virtual double net_price(std::size_t n) const { return n * price; }
    virtual ~Quote() = default;

    virtual Quote* clone() const &{ return new Quote(*this); }
    virtual Quote* clone() && { return new Quote(std::move(*this)); }


    private:
    std::string bookNo;
    
    protected:
    double price = 0.0;
};

class Disc_quote: public Quote{
    public:
    Disc_quote() = default;
    Disc_quote(const std::string &book, double price, std::size_t qty, double disc): Quote(book, price), quantity(qty), discount(disc) {}
    double net_price(std::size_t) const = 0;

    protected:
    std::size_t quantity = 0;
    double discount = 0.0;
};

class Bulk_quote: public Disc_quote{
    public:
    Bulk_quote() = default;
    Bulk_quote(const std::string& book, double price, std::size_t qty, double disc): Disc_quote(book, price, qty, disc) {}
    double net_price(std::size_t) const override;

    Bulk_quote* clone() const & { return new Bulk_quote(*this); }
    Bulk_quote* clone() && { return new Bulk_quote(std::move(*this)); }
};

double Bulk_quote::net_price(size_t cnt) const{
    if (cnt >= quantity){
        return cnt * (1 - discount) * price;
    }
    else{
        return cnt * price;
    }
}

double print_total(ostream &os, const Quote &item, size_t n){
    double ret = item.net_price(n);
    os<<"ISBN: "<<item.isbn()<<" # sold: "<<n<<" total due: "<<ret<<endl;
    return ret;
}

class Basket {
    public:
    void add_item(const Quote& sale){
        items.insert(std::shared_ptr<Quote>(sale.clone()));
    }
    void add_item(Quote&& sale){
        items.insert(std::shared_ptr<Quote>(std::move(sale).clone()));
    }
    double total_receipt(std::ostream&) const;

    private:
    static bool compare(const std::shared_ptr<Quote> &lhs, const std::shared_ptr<Quote> &rhs){
        return lhs->isbn() < rhs->isbn();
    }
    std::multiset<std::shared_ptr<Quote>, decltype(compare)*> items{compare};
};

double Basket::total_receipt(ostream &os) const{
    double sum = 0.0;
    for(auto iter = items.cbegin(); iter != items.cend(); iter = items.upper_bound(*iter)){
        sum += print_total(os, **iter, items.count(*iter));
    }
    os<<"Total Sales: "<<sum<<endl;
    return sum;
}

int main(){
    Basket obj;
    obj.add_item(Quote("0-101-13456-X", 10));
    obj.add_item(Bulk_quote("0-102-34567-Y", 15, 20, 0.5));
    obj.add_item(Bulk_quote("0-103-32467-X", 5, 30, 0.5));
    obj.total_receipt(cout);

    return 0;
}

运行结果显示如下：