Hello everybody, 1) I tried to use a simple boost::counting_iterator<size_t> but ran into the following compiler error: error C4244: '+=' : conversion from '__int64' to 'size_t', possible loss of data void advance(typename super_t::difference_type n) { BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(random_access_traversal_tag) m_iterator += n; } Obviously, the default difference_type for size_t (and for int by the way) is __int64 as defined by template <class T> struct numeric_difference { typedef typename boost::detail::numeric_traits<T>::difference_type type; }; (counting_iterator.hpp:73 called from counting_iterator_base::ctor) I think I understand why __int64 may be a sensible choice for calculations with size_t (or int) values. You prevent some overflows this way. - Why does the counting_iterator insist on the numeric_traits difference type? Why allowing an advance operation with an argument possibly larger than m_iterator itself? 2) If I manually instantiate the counting_iterator with difference_type size_t (or int) as boost::counting_iterator<size_t, boost::use_default, size_t> it will still fail at location // A policy for wrapped numbers template <class Difference, class Incrementable1, class Incrementable2> struct number_distance { static Difference distance(Incrementable1 x, Incrementable2 y) { return numeric_distance(x, y); } }; Instantiated from template <class OtherIncrementable> difference_type distance_to(counting_iterator<OtherIncrementable, CategoryOrTraversal, Difference> const& y) const { typedef typename mpl::if_< detail::is_numeric<Incrementable> , detail::number_distance<difference_type, Incrementable, OtherIncrementable> , detail::iterator_distance<difference_type, Incrementable, OtherIncrementable> >::type d; return d::distance(this->base(), y.base()); } With error message error C4244: 'return' : conversion from '__int64' to '__w64 unsigned int', possible loss of data. Again, numeric_distance insists on using __int64 as a difference type and fails to convert the value properly. I would greatly appreciate any advice on this because using counting_iterator would save me a lot of code. Thanks for everybody's great work, Sebastian -- Sebastian Theophil . stheophil@think-cell.com Software Engineer think-cell Software GmbH . Invalidenstr. 34 . 10115 Berlin, Germany http://www.think-cell.com . phone +49-30-666473-10 . fax +49-30-666473-19 Geschaftsfuhrer: Dr. Markus Hannebauer, Arno Schoedl . Amtsgericht Charlottenburg, HRB 85229