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Friend function in c++

Hello friends, in this post today, we learn about Friend function in c++ and how to use Friend function in c++. so lets start...

Friend function in c++, Friend function
Friend function in c++





Friend function:-

Friend  function as a friend of a class and can allow that friend function to access private and protected data members of that class.


Friend functions are mostly used where two or more classes want to share a common function.


Important points about Friend Function. 


friend is a keyword. A friend function is created by placing the keyword friend in the function declaration but not in function definition. And function definition must be defined outside the class to which it is friend.


It is not a member function of the class but it have full access to the public, private and protected data member of the class.


A friend function is not a member function of the class and cannot be called from any object of the class using dot operator.


The arguments of friend functions are usually objects of the class to which it is a friend.


It should not be defined with membership label.


It cannot access the member names directly.


A friend function can be friend of more than one class.


A function of one class can be a friend of another class.


We can have whole class as a friend of another class.


We use friend function usually with multiple classes but can used with single class also.


A friend function can be declared in the public or private visibility mode without affecting its meaning.


There can be any number of friend functions of a class.


It is not in the scope of the class to which it has been declared as friend.



Syntax of friend function:-

class class_demo
{
   Access modifiers:
   data members;
   members functions;

  friend data_type function_name (parameters);  // friend function declaration
};

data_type function_name (parameters)  //definition
{
   function definition;
}

.

Example:

#include <iostream>
using namespace std;
class friend_fn
{
   public:
   int n;

   public:
   void input(int x)
    {
      n=x;
    }

    friend int square(friend_fn);
    friend int cube(friend_fn);
};


   int square(friend_fn f)
   {
     return f.n * f.n;
   }


int cube(friend_fn f)
   {
     return f.n*f.n*f.n;
   }


int main( )
{

  friend_fn F;
  F.input(6);
  cout<<"Square is="<<square(F)<<endl;;
  cout<<"cube is="<<cube(F)<<endl;
  return 0;
}

Output:-

Square is=36
cube is=216




I hope that whatever information I have given in this post today, you have liked it and you have understood it.so keep learning and wait for the next post that will help you to increase your knowledge with the something new information.

Thank you so much for reading. And take care about yourself and your family.



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