/* Extending a class with a method, subject to dynamic dispatch,
   using double unsafe type cast (two wrongs make a right?) 
*/

using namespace std;
#include<iostream>
#include<string>


class A 
{
public:
  int x;
  A(int z) {x=z;}
  virtual void f() { cout << "A.f" << endl; }
};

class B : public A
{
public:
  double y;
  B(int a, double b):A(a) {y=b;}
  virtual void f() { cout << "B.f" << endl; }  
};


// Now I want to add an additional capability to classes A,B (void g()):

// adapter class that adds a new method to A, subject to dynamic dispatch
class AX   // to be used in the form ((AB*)n->g() where A* g;
{
public:
  static void gg(A *n) { cout << "AX.gg, x is " << n->x << endl; }
  void g() { gg( (A*)this ); } // don't mark as virtual
};

class BX 
{
public:
  static void gg(B *n)
  { cout << "BX.gg, x, y are " << n->x << " , " << n->y << endl; }
  void g() { gg( (B*)this ); }
};


int main()
{
  A *n = new A(5);
  A *m = new B(2,3.5);
  ((AX*)n)->g();
  ((BX*)m)->g();  // extension methods can override this way
  return 0;
}

// this is not dynamic dispatch: in fact 'virtual' will mess it up.
// It's just a trick to get C++ to call the function you want.