011AFunctionFriendlyToTwoClasses5_9.cpp

#include<iostream>
using namespace std;

class ABC;	//Known as Forward declaration
//---------------------------------//
class XYZ
{
	int x;
	public:
		void setvalue(int i){x = i;}
		friend void max(XYZ, ABC);
};
//---------------------------------//

class ABC
{
	int a;
	public:
		void setvalue(int i){a = i;}
		friend void max(XYZ, ABC);
};

//---------------------------------//
void max(XYZ m, ABC n)	//Definition of Friend
{
	if(m.x >= n.a)
		cout<< m.x<<endl;
	else
		cout<< n.a<<endl;
}
//--------------------------------//
int main()
{
	ABC abc;
	abc.setvalue(10);
	
	XYZ xyz;
	xyz.setvalue(20);
	
	max(xyz, abc);	
	return 0;
}