class Shape {
public:
  virtual void draw() =  0 ;
  virtual void erase() =  0 ;
  virtual ~Shape() {}
  class BadShapeCreation : public logic_error {
  public:
    BadShapeCreation(string type)
    : logic_error("Cannot create type " + type) {}
  };
  static Shape* factory(const string& type)
    throw(BadShapeCreation);
};
 
class Circle : public Shape {
  Circle() {} // Private constructor
  friend class Shape;
public:
  void draw() { cout << "Circle::draw” << endl; }
  void erase() { cout << "Circle::erase” << endl; }
  ~Circle() { cout << "Circle::~Circle” << endl; }
};
 
class Square : public Shape {
  Square() {}
  friend class Shape;
public:
  void draw() { cout << "Square::draw” << endl; }
  void erase() { cout << "Square::erase” << endl; }
  ~Square() { cout << "Square::~Square” << endl; }
};
 
Shape* Shape::factory(const string& type)
  throw(Shape::BadShapeCreation) {
  if(type == "Circle") return new Circle;
  if(type == "Square") return new Square;
  throw BadShapeCreation(type);
}
 
char* sl[] = { "Circle", "Square", "Square",
  "Circle", "Circle", "Circle", "Square" };
 
int main() {
  vector<Shape*> shapes;
  try {
    for(size_t i =  0 ; i < sizeof sl / sizeof sl[ 0 ]; i++)
      shapes.push_back(Shape::factory(sl[i]));
  } catch(Shape::BadShapeCreation e) {
    cout << e.what() << endl;
    purge(shapes);
    return EXIT_FAILURE;
  }
  for(size_t i =  0 ; i < shapes.size(); i++) {
    shapes[i]->draw();
    shapes[i]->erase();
  }
  purge(shapes);
} ///:~