a test program for polymophism in c++

 

#include<iostream>

using namespace std;

 

class B

{

public:

       virtual void f1() const

       {

              cout<<"B::f1"<<endl;

       }

       virtual void f2() const

       {

              cout<<"B::f2"<<endl;

       }

};

class D: public B

{

public:

       void f1() const

       {

              cout<<"D::f1"<<endl;

       }

       virtual void f3() const

       {

              cout<<"D::f3"<<endl;

       }

};

 

void main()

{

       D d;

 

       //pointer and reference both can achieve polymophism

       B& rb=d;

       rb.f1();     //output: D::f1

       rb.B::f1(); //output: B::f1

 

       B* pb = &d;

       pb->f1();    //output: D::f1

       pb->B::f1(); //output: B::f1

 

       char ch;//pause

       cin>>ch;

}

Output:

 

 If  D::f1 changed to

       void f1()

       {

              cout<<"D::f1"<<endl;

       }

That is delete the const, then the result is:

This is because Constness is a part of function signature.