#include <iostream>
#include <vector>
using namespace std;

class Gates {
public:
   void closeGates() { cout << "gates close\n"; }
};

class Lighting {
public:
   void turnOnLights() { cout << "lights up\n"; }
};

class Surveillance {
public:
   void trainCameras() { cout << "cameras train\n"; }
};

class SensorSystem {
   Gates        gates;
   Lighting     lights;
   Surveillance cameras;
public:
   void soundTheAlarm() {
      gates.closeGates();
      lights.turnOnLights();
      cameras.trainCameras();
}  };

void main( void ) {
   SensorSystem ss;
   ss.soundTheAlarm();
}


#if 0

class AlarmListener { public:
   virtual void alarm() = 0;
};

class SensorSystem {
   vector<AlarmListener*> listeners;
public:
   void registerListener( AlarmListener* al ) {
      listeners.push_back( al );
   }
   void soundTheAlarm() {
      for (int i=0; i < listeners.size(); i++)
         listeners[i]->alarm();
}  };

class Gates : public AlarmListener {
public:
   void alarm() { cout << "gates close\n"; }
};

class Lighting : public AlarmListener {
public:
   void alarm() { cout << "lights up\n"; }
};

class Surveillance : public AlarmListener {
public:
   void alarm() { cout << "cameras train\n"; }
};

void main( void ) {
   SensorSystem ss;
   ss.registerListener( new Gates() );
   ss.registerListener( new Lighting() );
   ss.registerListener( new Surveillance() );
   ss.registerListener( new Gates() );
   ss.soundTheAlarm();
}

#endif