#include <memory>
#include <iostream>

int main()
{
  auto p = std::make_shared<double>(3.1415);
  std::weak_ptr<double> w(p);
	
  std::cout << "Objekt noch vorhanden: " 
            << std::boolalpha << !w.expired() << '\n';
	
  if (auto q = w.lock()) *q = 2.718;
  else std::cout << "Objekt verloren\n";
	
  std::cout << *p << '\n';	
}