#include <iostream>

 class A

 {

 public:

     A(){}

     ~A(){}

     virtual int data(){return ;}

 };

 class B:public A

 {

 public:

     B(){}

     ~B(){}

     int data(){return ;}

 };

 class C:public A

 {

 public:

     C(){}

     ~C(){}

     int data(){return ;}

 };

 class D:public C

 {

 public:

     D(){}

     ~D(){}

     int data(){return ;}

 };

 int main()

 {

     std::cout<<"dynamic_cast begin \n";

     A *a=new A;

     B *b=new B;

     C *c=new C;

     D *d=new D;

     if(dynamic_cast<B*> (a))   //this will fail  派生类不能指向基类

     {

         std::cout<<"A *a convert B class ok\n";

     }

     if(dynamic_cast<A*> (b))    // this will be ok   基类指向派生类 ok

     {

         std::cout<<"B *b convert A class ok\n";

     }

     if(dynamic_cast<C*> (a))     // 派生类不能指向基类

     {

         std::cout<<"A *a convert C class ok\n";

     }

     if(dynamic_cast<A*> (c))    //c派生类 所以可以被A指向

     {

         std::cout<<"A *a convert C class ok\n";

     }

     if(dynamic_cast<A*> (d))    //  A <- C <- D   基类可以指向派生类 ok

     {

         std::cout<<"D *d convert A class ok\n";

     }

     if(dynamic_cast<D*> (c))    // 派生类不能指向基类

     {

         std::cout<<"C *c convert D class ok\n";

     }

     if(dynamic_cast<C*> (d))    // C基类可以指向派生类D ok

     {

         std::cout<<"D *d convert C class ok\n";

     }

     if(dynamic_cast<D*> (d))    // ok

     {

         std::cout<<"d *d convert D class ok\n";

     }

     std::cin.get();

     return ;

 }