How to use operator overloading in C++

In C++, an “operator” is a special function that is used to perform operations on objects.

Operators can be overloaded, which means you can set or redefine the way operators work for user-defined data types.

Let’s see some common examples of operators and how they can be overloaded in C++!

Arithmetic Operators

Arithmetic operators perform basic mathematical operations.

Example of Addition Operator Overloading (+)

#include <iostream>

class Complex {
 public:
 real float, image;

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

 // Operator overloading +
 Complex operator + (const Complex& obj) {
 return Complex(real + obj.real, imag + obj.imag);
 }
};

int main() {
 Complex c1(3.0, 4.0), c2(1.0, 2.0);
 Complex c3 = c1 + c2;
 std::cout << "Result: " << c3.real << " + " << c3.imag << "i" << std::endl;
 return 0;
}

Relational Operators

Relational operators compare two values.

Equality Operator Overloading Example (==)

#include <iostream>

class Complex {
 public:
 real float, image;

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

 // Operator overloading ==
 bool operator == (const Complex& obj) {
 return (real == obj.real && imag == obj.imag);
 }
};

int main() {
 Complex c1(3.0, 4.0), c2(3.0, 4.0);
 if (c1 == c2) {
 std::cout << "Complex numbers are equal." << std::endl;
 } else {
 std::cout << "Complex numbers are different." << std::endl;
 }
 return 0;
}

Assignment Operators

Assignment operators assign a value to a variable.

Assignment Operator Overloading Example (=)

#include <iostream>

class Complex {
 public:
 real float, image;

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

 // Operator overloading =
 Complex& operator = (const Complex& obj) {
 if (this != &obj) {
 real = obj.real;
 imag = obj.imag;
 }
 return *this;
 }
};

int main() {
 Complex c1(3.0, 4.0), c2;
 c2 = c1;
 std::cout << "c2: " << c2.real << " + " << c2.imag << "i" << std::endl;
 return 0;
}

Insertion and Extraction Operators

The insertion (<<) and extraction (>>) operators are used for data input and output.

Example of Insertion Operator Overloading (<<)

#include <iostream>

class Complex {
 public:
 real float, image;

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

 // Operator overloading <<
 friend std::ostream& operator << (std::ostream& out, const Complex& obj) {
 out << obj.real << " + " << obj.imag << "i";
 return out;
 }
};

int main() {
 Complex c1(3.0, 4.0);
 std::cout << "Complex number: " << c1 << std::endl;
 return 0;
}

Unary Operators

Unary operators operate on a single operand.

Example of Negation Operator Overloading (-)

#include <iostream>

class Complex {
 public:
 real float, image;

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

 // Unary operator overloading -
 Complex operator - () const {
 return Complex(-real, -imag);
 }
};

int main() {
 Complex c1(3.0, 4.0);
 Complex c2 = -c1;
 std::cout << "c2: " << c2.real << " + " << c2.imag << "i" << std::endl;
 return 0;
}

These are just some examples of operators in C++ and how they can be overloaded. Operator overloading allows you to define the behavior of operators for custom data types, making your code more intuitive and readable.