C++: 8. Polymorphism

Polymorphism is an important concept of object-oriented programming. It simply means more than one form. That is, the same entity (function or operator) behaves differently in different scenarios.

Function Overloading in C++

In C++, two or more functions can have the same name if the number and/or type of parameters are different, this is called function overloading.

Example:- 

#include <iostream>

using namespace std;

int add(int a, int b) {

    return a+b;

}

int add(int a, int b, int c) {

    return a+b+c;

}

double add(double a, double b) {

    return a+b;

}

int main() {

  int x = 3, y = 7, z = 12;

  double n1 = 4.56, n2 = 13.479;

  cout<<"x+y = "<<add(x,y)<<endl;

  cout<<"x+y+z = "<<add(x,y,z)<<endl;

  cout<<"n1+n2 = "<<add(n1,n2);

  return 0;

}

Output:- 

x+y = 10

x+y+z = 22

n1+n2 = 18.039

Function Overriding in C++

When a member function of a base class is redefined in its derived class with the same parameters and return type, it is called function overriding in C++. The base class function is said to be overridden.

Example:- 

#include <iostream>

using namespace std;

class base {

    public:

    virtual void display() {

        cout<<"Function of base class"<<endl;

    }

};

class derived : public base {

    public:

    void display() {

        cout<<"Function of derived class"<<endl;

    }

};

int main() {

  derived d1;

  d1.display();

  return 0;

}

Output:- 

Function of derived class

Virtual Function in C++

A virtual function is a function defined in the base class with virtual keyword. The purpose of virtual function is to ensure that the function is overridden.

Example:- 

#include <iostream>

using namespace std;

class base {

    public:

    void display() {

        cout<<"Function of base class"<<endl;

    }

};

class derived : public base {

    public:

    void display() {

        cout<<"Function of derived class"<<endl;

    }

};

int main() {

  derived d;

  base *b = &d;   //base class pointer

  b->display();   //base class function executes

  return 0;

}

Output:- 

Function of base class