- 
            iterator_rangeis now implemented
            by implementing the member functionssize(),operator[]via inheritance of base-classes specialized
            by the traversal type of the underlying iterator. This is normally requires
            no alteration of code. It does mean that types that derive from iterator_range
            may need to prefixthis->to the various member functions.
            Additionally it has been noted that some calling code was relying on
            member functions such assize()being present despite the underlying
            iterators not being random-access due toiterator_reference<Iter>::typenot being a reference. The suggested refactoring is to useboost::size(rng).
- 
            The undocumented iterator_rangepop_front()has been deprecated and is replaced bydrop_front(). Similarly
            pop_back() has been replaced
            by drop_back()`.