#include <iostream> using namespace std; class B; class A{ private: int a; public: void setData(int x){ a=x; } friend void fun(A,B); }; class B{ private: int b; public: void setData(int y){ b=y; } friend void fun(A,B); }; void fun(A o1, B o2){ cout<< "Sum is "<<o1.a + o2.b; } int main(){ A obj1; B obj2; obj1.setData(5); obj2.setData(6); fun(obj1, obj2); }