#include <iostream.h>

class node {
public: enum Tag { I, P };
private: 
 union { int i; node * p; };
 Tag tag;
  void check(Tag t){ if (tag!=t) {cout << "Bad access of node\n"; exit(1);}}
public:
 Tag get_tag() { return tag; }
 int & ival() { check(I); return i; }
 node * & pval() { check(P); return p; }
public:
 // Creating a new node
 node(int ii) { i=ii; tag=I; }
 node(node * pp) { p=pp; tag=P; }
 // Changing the value in a node
 void set(int ii) { i=ii; tag=I; }
 void set(node * pp) { p=pp; tag=P; }
};

int main(){

  node n(33);
  
  node * np;

  np = new node(&n);

  cout << "Should print 33: " << (np->pval())->ival() << endl;

  if (np->get_tag() == node::P) { cout << "Yes, *np is a pointer\n"; }

  np->set(45);

  if (np->get_tag() == node::I) { cout << "Now *np is the integer " << np->ival() << endl; }

  cout << "Next should be an error!\n";

  (void) (np->pval());

  return 0;

}