[boost] [iterators] Iterator Operations

Hi, A few days ago, I made a comment about std::distance() and std::advance() being reimplemented for the new style iterator concepts. Dave said that patches are welcome. So I sat down and wrote some preliminary versions of the two functions. They are in the attached file. The file parses cleanly, but I have not tried instantiating any of the templates yet. I have a question, though. Does it make sense to implement boost::distance for single pass iterators? Is there anything useful that could be done with the resulting information? Aside from that, I'd be happy to receive any suggestions for code improvement, adherence to Boost standards, and so on. Sebastian Redl