/* Code for exercise 12.1. |  | "C++ Solutions--Companion to The C++ Programming Language, Third Edition" | by David Vandevoorde; Addison-Wesley 1998; ISBN 0-201-30965-3. | | Permission to use, copy, modify, distribute and sell this software | and its documentation for any purpose is hereby granted without fee. | The author makes no representations about the suitability of this | software for any purpose.  It is provided "as is" without express or | implied warranty. `----------------------------------------------------------------------*/#include <iostream>class base {public:   virtual void iam() { std::cout << "base\n"; }};struct Northpole: public base {   virtual void iam() { std::cout << "Northpole.\n"; }};struct Southpole: public base {   virtual void iam() { std::cout << "Southpole.\n"; }};int main() {   Northpole NP;   Southpole SP;   NP.iam();   SP.iam();   base *pole1= &NP, *pole2 = &SP;   pole1->iam(); // or (*pole1).iam()   (*pole2).iam(); // or pole2->iam()   return 0;}