C++ Polymorphism

Polymorphism is a core concept of object-oriented programming in C++ that allows objects of different classes to be treated as objects of a common base class. It means “many forms” and enables the same function or operator to behave differently based on the context.

Types of Polymorphism

Function overloading and operator overloading implement compile-time polymorphism.
Virtual functions implement run-time polymorphism, enabling dynamic behavior based on object type.
Polymorphism improves code flexibility and reusability in object-oriented programming.

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Compile-time (or Static) Polymorphism: Achieved using function overloading and operator overloading.
Run-time (or Dynamic) Polymorphism: Achieved using virtual functions and inheritance.

Example: Compile-time Polymorphism (Function Overloading)

#include <iostream>
using namespace std;

class Math {
public:
    // Function to add two integers
    int add(int a, int b) {
        return a + b;
    }

    // Function to add three integers
    int add(int a, int b, int c) {
        return a + b + c;
    }
};

int main() {
    Math m;

    cout << "Sum of 2 and 3: " << m.add(2, 3) << endl;
    cout << "Sum of 2, 3, 4: " << m.add(2, 3, 4) << endl;

    return 0;
}

Output

Sum of 2 and 3: 5
Sum of 2, 3, 4: 9

Example: Run-time Polymorphism (Virtual Function)

#include <iostream>
using namespace std;

class Animal {
public:
    virtual void sound() {  // Virtual function
        cout << "Some generic sound" << endl;
    }
};

class Dog : public Animal {
public:
    void sound() override {
        cout << "Woof Woof" << endl;
    }
};

class Cat : public Animal {
public:
    void sound() override {
        cout << "Meow" << endl;
    }
};

int main() {
    Animal *a1;
    Dog d;
    Cat c;

    a1 = &d;
    a1->sound();  // Calls Dog's sound()

    a1 = &c;
    a1->sound();  // Calls Cat's sound()

    return 0;
}

Output

Woof Woof
Meow

Important Notes

Function overloading and operator overloading implement compile-time polymorphism.
Virtual functions implement run-time polymorphism, enabling dynamic behavior based on object type.
Polymorphism improves code flexibility and reusability in object-oriented programming.

Next Topic

Next, learn about Function Overriding in C++.