#include <iostream>
#include <cstdlib>
#include <string>
#include <map>
using namespace std;

//A pointer_t is a pointer to a function that dynamically allocates a new object
//of a class derived from class base, and returns the address of the new object.
class base;
typedef base *(*pointer_t)();

class base {
	static map<string, pointer_t> m;
public:
	struct namer {namer(const string& s, pointer_t p) {base::m[s] = p;}};
	friend namer::namer(const string& s, pointer_t p);
	static base *f(const string& s) {return m[s]();}
	virtual void print() const = 0;
};
map<string, pointer_t> base::m;

class child1: public base {
	static base *alloc() {return new child1;}
	static namer n;
public:
	void print() const {cout << "child1\n";}
};
base::namer child1::n("child1", alloc);

class child2: public base {
	static base *alloc() {return new child2;}
	static namer n;
public:
	void print() const {cout << "child2\n";}
};
base::namer child2::n("child2", alloc);

class grandchild: public child2 {
	static base *alloc() {return new grandchild;}
	static namer n;
public:
	void print() const {cout << "grandchild\n";}
};
base::namer grandchild::n("grandchild", alloc);

int main()
{
	base *p = base::f("child1");
	p->print();
	delete p;

	p = base::f("child2");
	p->print();
	delete p;

	p = base::f("grandchild");
	p->print();
	delete p;

	return EXIT_SUCCESS;
}