[Boost-users] Container using an item's ordinal position in a sorted list

Hi, First, could you confirm my belief that there is no STL or Boost container that can sort a list of values such that one can insert arbitrary values in O(log n) and also find the nth highest value in O(log n) time (see http://stackoverflow.com/questions/1746402/whats-a-qt-or-open-source-c-templ... for some discussion)? Second, I'm implementing such a container on top of a simple b-tree template. Would there be any interest in my cleaning it up and contributing it to boost? (I'd mostly have to add smart pointers for copy-on-write compatibility).