[boost] [Filesystem] has_root_path()

Boost 1.33.1 used to support has_root_path() on directory_iterators. 1.36 seems to use a slightly different mechanism for directory_iterators, based on instantiating basic_directory_iterator, and I'm struggling to see what has happened to has_root_path(). It's there somewhere, but not accessible in quite the same way as it was. How do I express directory_iterator -> has_root_path() in 1.36.0 ? Thanks - Rob.