Hi Ion, This library looks great. A quick comment about range-insertion in the flat containers, e.g.: template<typename InputIterator> void insert(InputIterator first, InputIterator last); Requires: i, j are not iterators into *this. Effects: inserts each element from the range [i,j) . Complexity: N log(size()+N) (N is the distance from i to j) search time plus N*size() insertion time. (Note typo: i,j vs, first,last) What implementation are you assuming to get that complexity? It seems to me that it is worse than it could be if you implement it something like this (PSEUDO-CODE): template<typename InputIterator> void insert(InputIterator first, InputIterator last) { iterator m = end(); insert(end(), first, last); sort(m,end()); inplace_merge(begin(),m,end()); } (I've only ever done this with multi* containers. For set and map you'll need something to avoid duplicates.) Regards, Phil. p.s. Having typed that I have developed a feeling of deja vu. Have I asked you this before?