Override base function, function from parent class, to have polymorphism - C++ Class

C++ examples for Class:Polymorphism

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Introduction

In polymorphism, one function might have multiple forms.

Demo Code

                                                                                                             
#include <iostream>
#include <cmath>
using namespace std;
const double PI = 2.0 * asin(1.0);
// declaration section
class Circle//  ww w. jav  a 2s.c o m
{
   protected:
   double radius;
   public:
   Circle(double = 1.0);  // constructor
   double calcval();
};
// implementation section for Circle
Circle::Circle(double r)   // constructor
{
   radius = r;
}
// calculate the area of a Circle
double Circle::calcval()
{
   return(PI * radius * radius);
}
// declaration section where Cylinder is derived from Circle
class Cylinder : public Circle
{
   protected:
   double length;  // add one data member and
   public:           // two member functions
   Cylinder(double r = 1.0, double l = 1.0) : Circle(r), length(l) {}
   double calcval();
};
// implementation section for Cylinder
double Cylinder::calcval()   // calculates a volume
{
   return (length * Circle::calcval());  // note the base function call
}
int main()
{
   Circle circle_1, circle_2(2);  // create two Circle objects
   Cylinder cylinder_1(3,4);      // create one Cylinder object
   cout << "The area of circle_1 is " << circle_1.calcval() << endl;
   cout << "The area of circle_2 is " << circle_2.calcval() << endl;
   cout << "The volume of cylinder_1 is " << cylinder_1.calcval() << endl;
   circle_1 = cylinder_1;  // assign a Cylinder to a Circle
   cout << "\nThe area of circle_1 is now " << circle_1.calcval() << endl;
   return 0;
}

Result


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