OPERATOR OVERLOADING IN C++

In this post we are going to understand one of the most important and often considered complex topic, Operator Overloading. We will get into the depth of Operator Overloading, we will be learning some handy rules, examples and important questions about Operator Overloading.

Concept :

• If we create two or more members having the same name but having different number of type and different parameter, is known as C++ overloading.
• In C++, we can make operators to work for user defined classes. This is called Operator Overloading.
• For example, we can overload the operator ‘+’ in a class like ‘String’ so that we can concatenate two strings by just using ‘+’ (str1 + str2).

Syntax :

return_type class_name :: operator operator_symbol(args)
{
    /* functionalities here */
}

SOME HANDY RULES :

EXAMPLE :

#include<iostream> 
using namespace std; 

class Complex 
{ 
    private: 
        int real, imag; 
    public: 
        Complex(int r = 0, int i =0)  
        {real = r ;   imag = i;} 

        // This is automatically called when '+' is used with between two Complex objects 
        Complex operator + (Complex const &obj) 
        { 
             Complex res; 
             res.real = real + obj.real; 
             res.imag = imag + obj.imag; 
             return res; 
        } 
        void print() 
        { cout << real << " + i" << imag << endl; } 
}; 

int main() 
{ 
    Complex c1(10, 5), c2(2, 4); 
    Complex c3 = c1 + c2;
        /* Call as : c3 = c1.operator+(c2) */
    c3.print(); 
}

// OUTPUT : 12 + i9

NOTE :

Operator overloading makes a program more readable. Suppose a program is to add two matrices ‘a’ and ‘b’;
instead of using function call of the form —
c = mat_add(a, b);
a more intuitive form will be —
c = a + b;

SOME QUESTIONS :

(1) Which operator can not be overloaded ?
Operators that can’t be overloaded are ‘.’, ‘::’, ‘?’, ‘:’

(2) What is the precendence of overloaded operators ?
The operators will have the same precedence as the intrinsic operations that use the same operators.
There is no way to change operator precedence.