ex9_04.cpp

来自「Beginning Visual C++ 6源码。Wrox。」· C++ 代码 · 共 79 行

//EX9_04.CPP
// Implementing a complete overloaded 'greater than' operator
#include <iostream>                    // For stream I/O
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() const
      {
         return m_Length*m_Breadth*m_Height;
      }

      // Operator function for 'greater than' that
      // compares volumes of CBox objects.
      bool operator>(const CBox& aBox) const
      {
         return this->Volume() > aBox.Volume();
      }

      // Function to compare a CBox object with a constant
      bool operator>(const double& value) const
      {
         return this->Volume() > value;
      }

      // Destructor definition
      ~CBox()
      { cout << "Destructor called." << endl;}

   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
};

int operator>(const double& value, const CBox& aBox); // Function prototype

int main()
{
   CBox smallBox(4.0, 2.0, 1.0);
   CBox mediumBox(10.0, 4.0, 2.0);

   if(mediumBox > smallBox)
      cout << endl
           << "mediumBox is bigger than smallBox";

   if(mediumBox > 50.0)
      cout << endl
           << "mediumBox capacity is more than 50";
   else
      cout << endl
           << "mediumBox capacity is not more than 50";

   if(10.0 > smallBox)
      cout << endl
           << "smallBox capacity is less than 10";
   else
      cout << endl
           << "smallBox capacity is not less than 10";

   cout << endl;
   return 0;
}

// Function comparing a constant with a CBox object
int operator>(const double& value, const CBox& aBox)
{
   return value > aBox.Volume();
}