Operator Overloading (Binary & Unary) in C++

Definition
Operator overloading allows you to redefine or “overload” the behavior of C++ operators (+, -, , ++, etc.) for **user-defined data types (classes/objects).*

Syntax:

return_type operator operator_symbol (parameters) {
    // operation definition
}

For example:

Complex operator + (Complex obj);

Why Use Operator Overloading?

• Improves code readability – You can write expressions like obj1 + obj2 instead of calling a function.
• Extends usability of operators to user-defined types (like classes).
• Makes code intuitive – Works naturally with custom data types such as Complex, Matrix, Vector, etc.
• Encapsulation – Keeps the logic of object operations within the class.

Unary Operator Overloading (Example: ++ operator)

#include <iostream>
using namespace std;

class Number {
    int x;
public:
    Number(int a = 0) {
        x = a;
    }

    // Unary operator overloading for ++
    void operator ++() {
        x = x + 1;   // x ko increase kar diya
    }

    void display() {
        cout << "Value of x: " << x << endl;
    }
};

int main() {
    Number n1(5);

    cout << "Before increment: ";
    n1.display();

    ++n1;   // yahan operator overloading call hui

    cout << "After increment: ";
    n1.display();

    return 0;
}

Output

Before increment: Value of x: 5
After increment: Value of x: 6

Example Without Constructor (Unary Operator Overloading)

#include <iostream>
using namespace std;

class Number {
public:
    int x;  // public rakha taki direct assign kar sake

    // Unary operator overloading
    void operator ++() {
        x = x + 1;
    }

    void show() {
        cout << "Value of x: " << x << endl;
    }
};

int main() {
    Number n1;
    n1.x = 10;   // value manually set ki, constructor nahi use hua

    ++n1;        // operator overloading call hua
    n1.show();

    return 0;
}

Binary Operator Overloading (Example: + operator)

#include <iostream>
using namespace std;

class Add {
    int a;
public:
    Add(int x = 0) {
        a = x;
    }

    // Binary operator overloading for +
    Add operator + (Add obj) {
        Add temp;
        temp.a = a + obj.a;  // dono object ki value add
        return temp;
    }

    void display() {
        cout << "Sum: " << a << endl;
    }
};

int main() {
    Add obj1(5), obj2(10), obj3;

    obj3 = obj1 + obj2;   // operator overloading call hui

    obj3.display();

    return 0;
}

Output

Sum: 15

Example Without Constructor (Binary Operator Overloading)

#include <iostream>
using namespace std;

class Add {
public:
    int a;

    Add operator + (Add obj) {
        Add temp;
        temp.a = a + obj.a;
        return temp;
    }

    void show() {
        cout << "Sum: " << a << endl;
    }
};

int main() {
    Add obj1, obj2, obj3;

    obj1.a = 5;
    obj2.a = 15;

    obj3 = obj1 + obj2;   // operator overloading call hua
    obj3.show();

    return 0;
}