How to Overload the Less-Than (<) Operator in C++?

Last Updated : 12 Feb, 2024

In C++ we have an operator called less than operator (<) which checks if the left side operand is smaller than the right side operand or not. In this article, we will learn how to overload the less-than operator in C++.

Overloading Less-Than Operator in C++

In C++, we can overload the less-than operator using the operator function declared as shown:

Syntax to Overload Less-Than Operator

bool operator<(const className& right) const;

Here, className is the name of the class and right is the name of the right-hand side operand.

C++ Program to Overload Less-Than Operator

The below program demonstrates how we can overload less-than operators using operator overloading in C++.

C++

// C++ program to overload the less than < operator #include <iostream> using namespace std;  // creating class Coordinates class Coordinates { public:     // constructor     Coordinates(int x, int y)         : x(x)         , y(y)     {     }      // Overloading the less-than operator for the Point     // objects     bool operator<(const Coordinates& other) const     {         return (x < other.x)                || ((x == other.x) && (y < other.y));     }  private:     int x, y; };  int main() {      // initializing two coordinates p1 and p2     Coordinates p1(1, 2);     Coordinates p2(3, 4);      // checking if p1 is less than p2     if (p1 < p2) {         cout << "p1 is less than p2." << endl;     }     else {         cout << "p1 is not less than p2." << endl;     }     return 0; }

Output

p1 is less than p2.

Explanation: In the above example, we are overloading the less than (<) operator to compare between the given points for that we first compare the x coordinates of two Points p1 and p2 and if they are equal then we compare the y coordinates, and return the smaller one.