Example to operate on Objects of two Different class using friend Function

Example to operate on Objects of two Different class using friend Function

#include <iostream>
using namespace std;
class B;     // forward declaration
class A {
    private:
      int data;
    public:
      A(): data(12){ }
      friend int func(A , B);   //friend function Declaration
};
class B {
    private:
       int data;
    public:
       B(): data(1){ }
       friend int func(A , B);  //friend function Declaration
};
int func(A d1,B d2)
/*Function func() is the friend function of both classes A and B. So, the private data of both class can be accessed from this function.*/
{
   return (d1.data+d2.data);
}
int main()
    {
        A a;
        B b;
        cout<<"Data: "<<func(a,b);
        return 0;
    }