Page473_weak_ptr.cpp

#include <memory>
using std::make_shared;
using std::shared_ptr;
using std::weak_ptr;
int main()
{
    shared_ptr<int> sp = make_shared<int>(42);
    weak_ptr<int> wp(sp);
    if(shared_ptr<int> np = wp.lock()) //true if np is not null, an artful way to use condition
    {// inside if, np shares its object with sp
        // do something
    }
    return 0;
}