using namespace std;
int main() {
// creates smart pointers to double variables,
// each holds a value of 4.2
shared_ptr<double> pd1 = make_shared<double>(4.2);
shared_ptr<double> pd2(new double(4.2)); // alternatively
// pd2 is reassigned to a new memory location,
// older memory content is no longer pointed to
// and is therefore freed up automatically
pd2 = make_shared<double>(8.4);
// several shared_ptr objects may point to the same memory
shared_ptr<double> pd3 = pd2;
return 0;