C++虚函数、赋值兼容原则

 #include <iostream.h>
 
 class A
 {
 public:
     void f1()
     { cout << "a" << endl; }
     virtual void f2()
     { cout << "b" << endl; }
 };
 
 class B : public A
 {
 public:
     void f1()
     { cout << "c" << endl; }
     virtual void f2()
     { cout << "d" << endl; }
 };
 
 void main()
 {
     A a;
     B b;
     a.f1();
     a.f2();
     b.f1();
     cout << "--------------------" << endl;
 
     A *pa = &b;
     pa->f1();//a
     pa->f2();//d
     cout << "-------------------" << endl;
 
     A *fa = (A *)&b;
     fa->f1();//a
     fa->f2();//d
     cout << "-------------------" << endl;
 }