f1208.cpp

it is a usefull thing

//=====================================
// f1208.cpp
// Virtual Function Problem
//=====================================
#include<iostream>
using namespace std;
//-------------------------------------
class Base{
public:
  virtual Base* afn(){
    cout<<"In Base class\n";
    return this;
  }
};//-----------------------------------
class Sub : public Base{
public:
  Sub* afn(){
    cout<<"In Sub class\n";
    return this;
  }
};//-----------------------------------
void test(Base& x){
  Base* b;
  b = x.afn();
}//------------------------------------
int main(){
  test(Base());
  test(Sub());
}//====================================