15-27.md

#include <iostream>
using std::cin; using std::cout; using std::cerr; using std::endl;
using std::ostream;
#include <string>
using std::string;

class Quote{
public:
    Quote() = default;
    Quote(const string &book, double sales_price) :
            bookNo(book), price(sales_price) {};
    string isbn() const { return bookNo;}
    //返回给定数量的书籍的销售总额
    //派生类负责改写并使用不同的折扣计算算法
    virtual double net_price(size_t n) const { return n * price;};
    virtual ostream &debug(ostream &os) const {
        os << "Quote::bookNo : " << bookNo << "\n"
           << "Quote::price :" << price << endl;
        return os;
    }
    virtual ~Quote() { cout << "~Quote" << endl;}   //对析构函数进行动态绑定
    Quote(const Quote &rhs) : price(rhs.price), bookNo(rhs.bookNo) {
        cout << "Quote(const Quote &rhs)" << endl;
    }   //拷贝构造函数
    Quote(Quote &&rhs) noexcept : price(std::move(rhs.price)), bookNo(std::move(rhs.bookNo)){
        cout << "Quote(Quote &&rhs)" << endl;
    }   //移动构造函数
    Quote &operator=(const Quote &rhs){
        price = rhs.price;
        bookNo = rhs.bookNo;
        cout << "operator=(const Quote &rhs)" << endl;
        return *this;
    }   //拷贝赋值运算符
    Quote &operator=(Quote &&rhs) noexcept {
        price = std::move(rhs.price);
        bookNo = std::move(rhs.bookNo);
        cout << "operator=(Quote &&rhs)" << endl;
        return *this;
    }   //移动赋值运算符
private:
    string bookNo;      //书籍的ISBN编号
protected:
    double price = 0.0;     //代表普通状态下不打折的价格
};

//计算并打印销售给定数量的某种书籍所得的费用
double print_total(ostream &os, const Quote &item, size_t n){
    //根据传入item形参的对象类型调用Quote::net_price
    //或者Bulk_quote::net_price
    double ret = item.net_price(n);
    os << "ISBN: " << item.isbn()   //调用Quote::isbn()
       << " # sold: " << n << " total due: " << ret << endl;
    return ret;
}

//用于保存折扣值和购买量的类，派生类使用这些数据可以实现不同的价格策略
class Disc_quote : public Quote{
public:
    Disc_quote() = default;
    Disc_quote(const string &book, double price, size_t qty, double disc) :
            Quote(book, price), quantity(qty), discount(disc) {};
    double net_price(size_t) const = 0 ;
    ~Disc_quote() override { cout << "~Disc_quote()" << endl;}
    Disc_quote(const Disc_quote &rhs) : Quote(rhs), quantity(rhs.quantity), discount(rhs.discount){
        cout << "Disc_quote(const Disc_quote &rhs)" << endl;
    }   //拷贝构造函数
    Disc_quote(Disc_quote &&rhs) noexcept : Quote(std::move(rhs)), quantity(std::move(rhs.quantity)),
        discount(std::move(rhs.discount)) {
        cout << "Disc_quote(Disc_quote &&rhs)" << endl;
    }   //移动构造函数
    Disc_quote &operator=(const Disc_quote &rhs){
        Quote::operator=(rhs);
        quantity = rhs.quantity;
        discount = rhs.discount;
        cout << "operator=(const Disc_quote &rhs)" << endl;
        return *this;
    }   //拷贝赋值运算符
    Disc_quote &operator=(Disc_quote &&rhs) noexcept {
        Quote::operator=(std::move(rhs));
        quantity = std::move(rhs.quantity);
        discount = std::move(rhs.discount);
        cout << "operator=(Disc_quote &&rhs)" << endl;
        return *this;
    }   //移动赋值运算符
protected:
    size_t quantity = 0;    //折扣适用的购买量
    double discount = 0.0;  //表示折扣的小数值
};

//当同一书籍的销售量超过某个值时启用折扣
//折扣的值是一个小于1的正的小数值，以此来降低正常销售价格
class Bulk_quote : public Disc_quote{    //Bulk_quote直接继承自Disc_quote，间接继承自Quote
public:
    using Disc_quote::Disc_quote;
    //覆盖基类的函数版本以实现基于大量购买的折扣政策
    double net_price(size_t) const override;
};

//如果达到了购买书籍的某个最低限量值，就可以享受折扣价格了
double Bulk_quote::net_price(size_t cnt) const {
    if (cnt > quantity)
        return cnt * (1 - discount) * price;
    else
        return cnt * price;
}

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

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

int main(){
    Quote basic("978-7-121-15535-2", 128.00);
    Bulk_quote bulk("978-7-121-15535-2", 128.00, 100, 0.3);
    L_Bulk_quote l_bulk("978-7-121-15535-2", 128.00, 150, 0.3);

    print_total(cout, basic, 20);
    print_total(cout, bulk, 120);
    print_total(cout, l_bulk, 200);

    Quote basic_v1(basic);
    Quote basic_v2 = basic_v1;
    Quote basic_v3(std::move(basic_v2));

    L_Bulk_quote l_bulk_v1(l_bulk);
    L_Bulk_quote l_bulk_v2 = l_bulk_v1;
    L_Bulk_quote l_bulk_v3(std::move(l_bulk_v2));
}