/**********************************************************************
 * virtual.cc
 * Tom Kelliher
 *
 * This program demonstrates several advanced features of classes:
 *    o Public inheritance and the IS-A relationship.
 *    o Static re-definition of class methods.
 *    o Virtual functions and run-time re-definition of class methods.
 *      (Polymorphism)  ("Turn the way you want to turn.")
 **********************************************************************/


#include <iostream.h>


/**********************************************************************
 * class base
 **********************************************************************/

class base
{
 public:

   // Compile-time binding.
   void print1(void) { cout << "print1() of base class\n"; }

   // Run-time binding.
   virtual void print2(void) { cout << "print2() of base class\n"; }

   // Demonstrate "default" method feature of a base class.
   virtual void print3(void) { cout << "print3() of base class\n"; }
};


/**********************************************************************
 * class derived1
 **********************************************************************/

class derived1 : public base   // derived1 IS-A base.
                              // Try AS-A inheritance.
{
 public:
   void print1(void) { cout << "print1() of derived1 class\n"; }
   void print2(void) { cout << "print2() of derived1 class\n"; }

   // Note lack of re-definition of print3().
};


/**********************************************************************
 * class derived2
 **********************************************************************/

class derived2 : public base   // derived2 IS-A base.
{
 public:
   void print1(void) { cout << "print1() of derived2 class\n"; }
   void print2(void) { cout << "print2() of derived2 class\n"; }
   void print3(void) { cout << "print3() of derived2 class\n"; }
};


/**********************************************************************
 * main()
 **********************************************************************/

int main()
{
   base b;
   base *p = &b;
   derived1 d1;

   // Question: can q point to b or d2?
   derived1 *q = &d1;

   derived2 d2;

   cout << "The \"normal\" calls:\n";
   b.print1();
   b.print2();
   b.print3();
   d1.print1();
   d1.print2();
   d1.print3();
   d2.print1();
   d2.print2();
   d2.print3();

   cout << "\nWorking on instance b of base class through base*:\n";
   p->print1();
   p->print2();
   p->print3();

   cout << "\nWorking on instance d1 of derived1 class through base*:\n";
   p = &d1;
   p->print1();

   // Can I "fix" things this way?
//   p->derived1::print1();
   p->print2();
   p->print3();

   cout << "\nWorking on instance d1 of derived1 class through derived1*:\n";
   q->print1();
   q->print2();
   q->print3();

   // Will these work?
//   q = &b;
//   q = &d2;

   cout << "\nWorking on instance d2 of derived2 class through base*:\n";
   p = &d2;
   p->print1();
   p->print2();
   p->print3();

   return 0;
}