#include <iostream>

// uncomment the next line to make mutual friend classes.
#define DOUBLE_FRIENDS 1
//  or just delete all the pre-processor directives below.

using namespace std;

class OpenT {
    public:
       friend ostream & operator << (ostream & s ,const  OpenT & data);
       friend class FillerT;
#ifdef DOUBLE_FRIENDS
       void MakeBuddy(class FillerT & pal);
#endif

    private:
       short intData;
       float floatData;
};

class FillerT {
     public:

#ifdef DOUBLE_FRIENDS
         friend class OpenT;
#endif

         ~FillerT() {
             cout << "I depart with " << friendCount << " friends." << endl;
         }

         void FillFriend(OpenT & buddy) {
              buddy.intData = myInt;
              buddy.floatData = myFloat;

              myFloat += 2.1;
              ++ myInt;
         }

     private:
         int myInt{0};
         float myFloat{1.0};
         int friendCount{0};
};

#ifdef DOUBLE_FRIENDS
void OpenT::MakeBuddy(class FillerT & pal) {
           ++pal.friendCount;
}
#endif


ostream & operator << (ostream & s ,const  OpenT & data) {
    s << data.intData << " " << data.floatData;
    return s;
}

int main() {
     OpenT someVars[10];
     FillerT filler;
     size_t i;

     for(i = 0; i < 10; ++i) {
        filler.FillFriend(someVars[i]);
#ifdef DOUBLE_FRIENDS
        someVars[i].MakeBuddy(filler);
#endif
     }

     for(i = 0; i < 10; ++i) {
         cout << "someVars[" << i << "] = " << someVars[i] << endl;
     }
  
     return 0;
}