Class Circle

examples/src/json_traits_polymorphic_examples.cpp:87–113

    };                 

    class Circle : public Shape
    { 
        double radius_;

    public:
        Circle(double radius)
            : radius_(radius)
        {
        }

        const std::string& type() const
        {
            static const std::string type_ = "circle"; 
            return type_;
        }

        double radius() const
        {
            return radius_;
        }

        double area() const override
        {
            constexpr double pi = 3.14159265358979323846;
            return pi*radius_*radius_;
        }
    };                 

} // namespace ns
} // namespace