ex8_07.cpp

Beginning Visual C++ 6源码。Wrox。

// EX8_07.CPP
// Creating a friend function of a class
#include <iostream>
using namespace std;

class CBox                              // Class definition at global scope
{
   public:

      // Constructor definition
   CBox(double lv = 1.0, double bv = 1.0, double hv = 1.0): m_Length(lv),
                                                            m_Breadth(bv),
                                                            m_Height(hv)
      {
         cout << endl << "Constructor called.";
      }

      // Function to calculate the volume of a box
      double Volume()
      {
         return m_Length*m_Breadth*m_Height;
      }

   private:
      double m_Length;                       // Length of a box in inches
      double m_Breadth;                      // Breadth of a box in inches
      double m_Height;                       // Height of a box in inches

   //Friend function
   friend double BoxSurface(CBox aBox);

};

// friend function to calculate the surface area of a Box object
double BoxSurface(CBox aBox)
{
   return 2.0*(aBox.m_Length*aBox.m_Breadth +
               aBox.m_Length*aBox.m_Height +
               aBox.m_Height*aBox.m_Breadth);
}

int main()
{
   CBox match(2.2, 1.1, 0.5);           // Declare match box
   CBox box2;                           // Declare box2 - no initial values

   cout << endl
        << "Volume of match = "
        << match.Volume();

   cout << endl
        << "Surface area of match = "
        << BoxSurface(match);

   cout << endl
        << "Volume of box2 = "
        << box2.Volume();

   cout << endl
        << "Surface area of box2 = "
        << BoxSurface(box2);

   cout << endl;
   return 0;
}