Function Call Operator Overloading in C++

February 14, 2023

How to overload function call operator in C++?

The operator “()” is known as function call operator. When a function call operator is overloaded it does not modify how functions are called but, it modifies how the operator is to be explained when passed through objects of a given type.

Function call operator overloading is a sub part of operator overloading in C++. On this page, we will learn more about function call operator overloading in C++. But if you want to know more about operator overloading click the button below.

Function call operator overloading in C++

Function call operator is overloaded by instance of the class and it is also known as function object.
When we overload function call operator, we are not creating a new way to call a function. But, we are creating an operator function that can be passed a number of parameters.
It only modifies how the operator is to be fetched by the object.

Syntax for function call operator overloading in C++

class class_name
{ 
    public: 
        void operator ()(); 
};

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Program to overload function call operator in C++

Run

#include <iostream>
using namespace std;
 
class Length
{
   private:
      int kmeter;                   
      int meter;           
      
      
   public:
      Length()//Constructor. 
      {
         kmeter = 0;
         meter = 0;
      }
      Length(int km, int m) 
      {
         kmeter = km;
         meter = m;
      }
      
      
      Length operator()(int x, int y, int z)//Overload function call operator.
      {
         Length l;
         
         l.kmeter = x + z + 10;
         l.meter = y + z + 100 ;
         return l;
      }
      
      //Method to display length.
      void disLength() {
         cout << kmeter <<"Km " << meter << "M" << endl;
      }   
};

int main() 
{   
   Length l1(1, 112), l2;

   cout << "First length: "; 
   l1.disLength();

   l2 = l1(6, 7, 8); //Invoking function call operator.
   cout << "Second length:"; 
   l2.disLength();

   return 0;
}

Output:

First length: 1Km 112M
Second length:24Km 115M

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