fig10_10.cpp

《c＋＋大学教程》源码

// Fig. 10.10: fig10_10.cpp
// Introducing polymorphism, virtual functions and dynamic
// binding.
#include <iostream>

using std::cout;
using std::endl;
using std::fixed;

#include <iomanip>

using std::setprecision;

#include "point.h"   // Point class definition
#include "circle.h"  // Circle class definition

int main()
{
   Point point( 30, 50 );
   Point *pointPtr = 0;

   Circle circle( 120, 89, 2.7 );
   Circle *circlePtr = 0; 

   // set floating-point numeric formatting
   cout << fixed << setprecision( 2 );

   // output objects point and circle using static binding
   cout << "Invoking print function on point and circle "
        << "\nobjects with static binding "
        << "\n\nPoint: ";
   point.print();         // static binding
   cout << "\nCircle: ";
   circle.print();        // static binding

   // output objects point and circle using dynamic binding
   cout << "\n\nInvoking print function on point and circle "
        << "\nobjects with dynamic binding";

   // aim base-class pointer at base-class object and print
   pointPtr = &point;
   cout << "\n\nCalling virtual function print with base-class"
        << "\npointer to base-class object"
        << "\ninvokes base-class print function:\n";
   pointPtr->print();

   // aim derived-class pointer at derived-class 
   // object and print
   circlePtr = &circle;
   cout << "\n\nCalling virtual function print with "
        << "\nderived-class pointer to derived-class object "
        << "\ninvokes derived-class print function:\n";
   circlePtr->print();

   // aim base-class pointer at derived-class object and print
   pointPtr = &circle;
   cout << "\n\nCalling virtual function print with base-class"
        << "\npointer to derived-class object "
        << "\ninvokes derived-class print function:\n";
   pointPtr->print();  // polymorphism: invokes circle's print
   cout << endl;

   return 0;

} // end main

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