ding iterators based on these extended concepts and includes
      several useful iterator adaptors. The extended iterator concepts have been
      carefully designed so that old-style iterators can fit in the new concepts
      and so that new-style iterators will be compatible with old-style algorithms,
      though algorithms may need to be updated if they want to take full advantage
      of the new-style iterator capabilities. Several components of this library
      have been accepted into the C++ sta