Hi, I think it would speed up inserting range of elements into set and map, when in tree.hpp we replace: template <class InputIterator> void insert_equal(InputIterator first, InputIterator last) { //Insert with end hint, to achieve linear //complexity if [first, last) is ordered const_iterator end(this->cend()); for( ; first != last; ++first) this->insert_equal(end, *first); } with: template <class InputIterator> void insert_equal(InputIterator first, InputIterator last) { //Insert with hint, to achieve linear //complexity if data is even partially ordered const_iterator it(this->cend()); for( ; first != last; ++first) it = this->insert_equal(it, *first); } I will make almost linear complexity when data is ordered ascending, descending, and even partially ordered. Because when inserting with end hint (btw. wasn't here a bug? because "end" wasn't updated) it's only linear if we insert elements in ascending order.