#include <iostream>
#include <memory>

class DoSomething
{
public:
	virtual ~DoSomething() { }
	virtual std::auto_ptr<DoSomething> clone() const=0;
	virtual void do_it()=0;
};

class HelloWorld : public DoSomething
{
public:
	std::auto_ptr<DoSomething> clone() const
	{
		return std::auto_ptr<DoSomething>(new HelloWorld);
	}
	void do_it()
	{
		std::cout << "Hello world!" << std::endl;
	}
};

void hello_world(const DoSomething & something)
{
	std::auto_ptr<DoSomething> clone = something.clone();
	clone->do_it();
}

int main()
{
	hello_world(HelloWorld());
	return 0;
}