C++ program for friend function and friend class.

 Objective: Write a C++ program to show the use of friend function and friend class.

Code:

#include <iostream>  

using namespace std;  

class B;  // forward declaration

class A  

{  

    int x;  

public:  

    void setdata(int i)  

    {  

        x = i;  

    }  

    // Declare class B as a friend class

    friend class B;  

    // Declare the min function as a friend function

    friend void min(A, B);  

};  

class B  

{  

    int y;  

public:  

    void setdata(int i)  

    {  

        y = i;  

    }  

    // Member function of B accessing private member x of A

    void showAdata(A& a)  

    {  

        cout << "Value of x from class A: " << a.x << endl;  

    }  

    // Declare the min function as a friend function

    friend void min(A, B);  

};  

void min(A a, B b)  

{  

    if (a.x <= b.y)  

        cout << a.x << std::endl;  

    else  

        cout << b.y << std::endl;  

}  

int main()  

{  

    A a;  

    B b;  

    a.setdata(10);  

    b.setdata(20);  

    // Calling friend function

    min(a, b);  

    // Using friend class functionality

    b.showAdata(a);  

    return 0;  

}  

Output: