#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
enum e_type {
	ENTITY,
	GEOMETRY,
	MODEL
};

struct visitor_base;
struct visitable 
{
    virtual void accept(visitor_base & obj) = 0;
};

struct visitor_base
{
    virtual void visit(visitable &, enum e_type type) = 0;
};

struct entity : visitable
{
    void accept(visitor_base & obj)
    {
        obj.visit(*this, ENTITY);
    }
};

struct geometry : entity
{
	void accept(visitor_base & obj)
    {
        obj.visit(*this, GEOMETRY);
    }
};

struct model : geometry
{
    void accept(visitor_base & obj)
    {
        obj.visit(*this, MODEL);
    }
};

struct test_visitor : visitor_base
{
    void visit(visitable & obj, enum e_type type)
    {
		switch(type)
		{
			case	ENTITY:
				{
					entity	&ent = (entity&)obj;  // its enough safe
					cout << "Visited ENTITY" << endl;
					break;
				}
			case	GEOMETRY:
				{
					geometry	&geo = (geometry&)obj;
					cout << "Visited GEOMETRY" << endl;
					break;
				}
			case	MODEL:
				{
					model	&mod = (model&)obj;
					cout << "Visited MODEL" << endl;
					break;
				}
			default:
				// TRAP
				;
		}
	}
};

struct modern_visitor : test_visitor // extension for new objects
{
	// add new methods for new visitables, call parent otherwise
};


int main() {
	entity E;
	geometry G;
	model M;
	vector<entity*> vec = {&E, &G, &M};
	test_visitor visi;
	for_each(vec.begin(), vec.end(), [&](entity *i){ i->accept(visi); });

	// your code goes here
	return 0;
}