How to Overload the Addition Operator in C++

Operator overloading is a technique in which a programmer can redefine the meaning of an operator. It is a mechanism that allows programmers to extend the syntax of their programming language by adding new meanings to symbols and keywords.

Operators can be classified as unary, binary, or ternary. Unary operators take one operand, binary operators take two operands, and ternary operators take three operands.

You can overload operators using a friend function, a member function, or a normal function. This article will only focus on overloading the addition operator using the friend function in C++.

The friend keyword is used in the C++ language to specify which classes can access private data members of a class. It is important to note that a friend function is not a class member but is given permission to access some or all of that class’s private data and functions.

Friend classes are often used to provide helper functions for other classes. The friend functions are sometimes called non-member functions since they are not members of the class.

In C++, if you want to overload an operator using the friend function, you need to declare it as a friend. The friend declaration tells the compiler that this function will be used with other functions and objects of the same class.

Overload the Addition Operator Using the friend Function in C++

In C++, the overloaded addition operator is a binary operator that takes two operands of the same type and performs addition on them.

The following steps are used to overload the addition operator in C++ using the friend function:

Example code:

#include <iostream>
class Demo {
 private:
  int e_demo{};

 public:
  Demo(int demo) : e_demo{demo} {}
  friend Demo operator+(const Demo& x1, const Demo& x2);
  int getDemo() const { return e_demo; }
};
Demo operator+(const Demo& x1, const Demo& x2) {
  return Demo{x1.e_demo + x2.e_demo};
}
int main() {
  Demo demo1{5};
  Demo demo2{5};
  Demo demoSum{demo1 + demo2};
  std::cout << "Total Count is " << demoSum.getDemo();
  return 0;
}

Output:

Total Count is 10

Click here to check the live demonstration of the code mentioned above.