1   // Fig. 21.3: fig21_03.cpp
2   // Demonstrating the const_cast operator. 
3   #include <iostream.h>
4         
5   class ConstCastTest {
6   public:
7      void setNumber( int );
8      int getNumber() const;
9      void printNumber() const;
10  private:
11     int number;
12  };
13  
14  void ConstCastTest::setNumber( int num ) { number = num; }
15  
16  int ConstCastTest::getNumber() const { return number; }
17  
18  void ConstCastTest::printNumber() const
19  {
20     cout << "\nNumber after modification: ";
21  
22     // the expression number-- would generate compile error
23     // undo const-ness to allow modification
24     const_cast< ConstCastTest * >( this )->number--;
25  
26     cout << number << endl;
27  }
28  
29  int main()
30  {
31     ConstCastTest x;
32     x.setNumber( 8 );  // set private data number to 8
33     
34     cout << "Initial value of number: " << x.getNumber();
35  
36     x.printNumber();
37     return 0;
38  }
39  }