C++ da Friend Sınıflar Örneği

//www.ethemsulan.com
#include <cstdlib>
#include <iostream>
using namespace std;
class truck;
class car{
      int passengers;
      int speed;
      public:
car(int p,int s){passengers=p;speed=s;}
             int sinif(truck t);
      };
class truck{
      int weight;
      int speed;
      public:
truck(int w,int s){weight=w;speed=s;}
   friend int car::sinif(truck t);
      };
int car::sinif(truck t){
    return speed-t.speed;
    }
int main(int argc, char *argv[])
{
    int t;
    car c1(6,55),c2(2,120);
    truck t1(10000,55),t2(2000,72);
    cout<<"c1 ve t1 karsilastiriliyor\n";
    t=c1.sinif(t1);
    if(t<0)cout<<"truck daha hizli\n";
    else if(t==0) cout<<"car ve truck hizlari ayni\n";
    else cout<<"car daha hizli\n";
    cout<<"c2 ve t2 karsilastiriliyor\n";
    t=c2.sinif(t2);
    if(t<0)cout<<"truck daha hizli\n";
    else if(t==0) cout<<"car ve truck hizlari ayni\n";
    else cout<<"car daha hizli\n";
    system("PAUSE");
    return EXIT_SUCCESS;
}