静态联编

#include"iostream"
using namespace std;
class point
{
public:
    point(double x1 = 10, double y1 = 0) :x(x1), y(y1) {}
    double area() { return 0; }

private:
    double x, y;

};
class circle:public point
{
public:
    circle(double x, double y, double r1) :point(x, y), r(r1) {}
    double area() { return 3.14*r*r; }

private:
    double r;
};
int main()
{
    point a(2, 2); circle c(3,3,1);
    cout << a.area() << endl;
    cout << c.area() << endl;
    point *pc = &c, &rc = c;
    cout << pc->area() << endl;
    cout << rc.area() << endl;
    return 0;

}