#include <iostream>
#include <memory>
 
class parent {
	public:
		virtual std::string who() { return "parent"; }
		virtual ~parent(){}
};
 
class child1 : public parent {
	public:
		std::string who() override { return "child1"; }
};
 
class child2 : public parent {
	public:
		std::string who() override { return "child2"; }
};
 
using fn_ptr = std::string (parent::*)();
using parent_ptr = std::shared_ptr<parent>;
 
std::string run(parent_ptr x, fn_ptr fnc)
{
	return (x.get()->*fnc)();
}
 
int main()
{
	parent_ptr c1 = std::make_shared<child1>();
	parent_ptr c2 = std::make_shared<child2>();
	fn_ptr who = &parent::who;
 
	std::cout << run(c1, who) << '\n';
	std::cout << run(c2, who) << '\n';
}
 

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