C++ operator Keyword

The operator keyword in C++ is used to define or overload operators for user-defined data types. Operator overloading allows you to redefine the behavior of operators (such as +, -, *, etc.) when they are applied to objects of a class or structure.

By overloading operators, you can make user-defined types behave like built-in types, improving code readability and usability.

Syntax

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return_type operator symbol(parameters) {
    // Operator functionality
}

return_type: The type of value returned by the overloaded operator.
operator: The keyword used to define or overload an operator.
symbol: The operator to be overloaded (e.g., +, -, *, etc.).
parameters: The operands for the operator. The number of parameters depends on the operator being overloaded.

Examples

Example 1: Overloading the `+` Operator

In this example, you will learn how to overload the + operator for a class.

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#include <iostream>
using namespace std;

class Complex {
private:
    double real, imag;

public:
    Complex(double r = 0, double i = 0) : real(r), imag(i) {}

    // Overload the + operator
    Complex operator+(const Complex& other) const {
        return Complex(real + other.real, imag + other.imag);
    }

    void display() const {
        cout << real << " + " << imag << "i" << endl;
    }
};

int main() {
    Complex c1(2.5, 3.5), c2(1.5, 2.5);
    Complex c3 = c1 + c2;

    cout << "Result: ";
    c3.display();

    return 0;
}

Output:

Result: 4 + 6i

Explanation:

The Complex class has two private members: real and imag, representing the real and imaginary parts of a complex number.
The operator+ function is overloaded to add two complex numbers by summing their real and imaginary parts separately.
In the main function, two complex numbers c1 and c2 are added using the overloaded + operator, and the result is displayed.

Example 2: Overloading the `==` Operator

In this example, you will learn how to overload the == operator to compare two objects.

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#include <iostream>
using namespace std;

class Point {
private:
    int x, y;

public:
    Point(int x = 0, int y = 0) : x(x), y(y) {}

    // Overload the == operator
    bool operator==(const Point& other) const {
        return (x == other.x && y == other.y);
    }

    void display() const {
        cout << "(" << x << ", " << y << ")" << endl;
    }
};

int main() {
    Point p1(3, 4), p2(3, 4), p3(5, 6);

    if (p1 == p2) {
        cout << "p1 and p2 are equal." << endl;
    } else {
        cout << "p1 and p2 are not equal." << endl;
    }

    if (p1 == p3) {
        cout << "p1 and p3 are equal." << endl;
    } else {
        cout << "p1 and p3 are not equal." << endl;
    }

    return 0;
}

Output:

p1 and p2 are equal.
p1 and p3 are not equal.

Explanation:

The Point class represents a point in 2D space with coordinates x and y.
The operator== function is overloaded to compare two points by checking if their x and y coordinates are equal.
The if conditions in main test the equality of points and print appropriate messages.

Key Points about `operator` Keyword

The operator keyword is used to overload operators for user-defined data types.
Not all operators can be overloaded (e.g., ::, sizeof, and ?: cannot be overloaded).
Overloading allows custom behavior for operators when applied to objects of a class or structure.
When overloading an operator, at least one operand must be a user-defined type.

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C++ operator Keyword