C++ Primer, Fifth Edition

15.2.1. Defining a Base Class

We’ll start by completing the definition of our Quote class:

class Quote {public:    Quote() = default;  // = default see § 7.1.4 (p. 264)    Quote(const std::string &book, double sales_price):                     bookNo(book), price(sales_price) { }    std::string isbn() const { return bookNo; }    // returns the total sales price for the specified number of items    // derived classes will override and apply different discount algorithms    virtual double net_price(std::size_t n) const               { return n * price; }    virtual ~Quote() = default; // dynamic binding for the destructorprivate:    std::string ...