/* 范例：13-6 */
#include <iostream.h>
class A
{
  public:
    A():a(7){}
    int a;
    int get_a() const;
};
int A::get_a() const
{
  (const_cast<A*>(this))->a = 2*a;  // #1
  return (this->a);
}
void main()
{
  const A *pa = new A;

  (const_cast<A*>(pa))->a = 11; // #2
  cout << pa->a << endl;
  //  pa->a = 5; // #3 error

  A *pa2 = new A;
  cout << pa2->a << endl;
  cout << pa2->get_a() << endl;
  delete pa;
  delete pa2;

  getchar();
}

程序執行結果：
11
7
14