template<class T> void destroy_at(T* location);
location->~T();
template<class ForwardIterator> void destroy(ForwardIterator first, ForwardIterator last);
for (; first!=last; ++first) destroy_at(addressof(*first));
template<class ForwardIterator, class Size> ForwardIterator destroy_n(ForwardIterator first, Size n);
for (; n > 0; (void)++first, --n) destroy_at(addressof(*first)); return first;