第十五章 面向对象程序设计 习题

15.3

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


double print_total(ostream &os,const Quote &item,size_t n)
{
    double ret=item.net_price(n);
    os<<"ISBN: "<<item.isbn<<" #slod: "<<n<<"total due"<<ret<<end1;
    return ret;
}

15.5

//定义Bulk_Quote类
classBulk_quote:public Quote
{
    public net_price(size_t cnt) const override
    {
        if(cnt>=min_qty)
            return cnt*(1-discount)*price;
        else
            return  cnt*price;
    }
    
    private:
    size_t cnt;
    double discount;
}