17. post-review question: should Range mean lowest common denominator? or
    perhaps Forward Range? problem with not being explicit.
    
18. maybe iterator_range operator==() should be defined when rhs or lhs
    take a forward  range argument; this comparison function should
    then call std::lexigraphical_compare(....). Example:
    
    sub_range<string> sub = ...;
    if( sub == "foo" )
    
        /*     
        namespace range_detail
        {
             template< class Range >
             inline iterator_range< BOOST_DEDUCED_TYPENAME range_result_iterator<Range>::type >
             make_sub_range_impl( Range& r, 
                                  BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_begin,
                                  BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_end )
             {
                 BOOST_ASSERT( advance_begin >= 0 );
                 BOOST_ASSERT( advance_end >= 0 );
                 
                 BOOST_DEDUCED_TYPENAME range_result_iterator<Range>::type 
                     new_begin = begin( r ),
                     new_end   = end( r );
                 std::advance( new_begin, advance_begin );
                 std::advance( new_end, -advance_end );
                 return make_iterator_range( new_begin, new_end );
             }
             
             
             
            template< class Range >
            inline iterator_range< BOOST_DEDUCED_TYPENAME range_result_iterator<Range>::type >
            make_super_range_impl( Range& r, 
                                   BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_begin,
                                   BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_end )
            {
                BOOST_ASSERT( advance_begin >= 0 );
                BOOST_ASSERT( advance_end >= 0 );
            
                BOOST_DEDUCED_TYPENAME range_result_iterator<Range>::type 
                    new_begin = begin( r ),
                    new_end   = end( r );
                std::advance( new_begin, -advance_begin );
                std::advance( new_end, advance_end );
                return make_iterator_range( new_begin, new_end );
            }

        }*/

        /*
        template< class Range >
        inline iterator_range< BOOST_DEDUCED_TYPENAME range_result_iterator<Range>::type >
        make_sub_range( Range& r, 
                        BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_begin,
                        BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_end = 0 )
        {
            return range_detail::make_sub_range_impl( r, advance_begin, advance_end );
        }
        
        
        
        template< class Range >
        inline iterator_range< BOOST_DEDUCED_TYPENAME range_result_iterator<Range>::type >
        make_super_range( Range& r, 
                          BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_begin,
                          BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_end = 0 )
        {
            return range_detail::make_super_range_impl( r, advance_begin, advance_end );
        }*/
        /*
        template< class Range >
        inline iterator_range< BOOST_DEDUCED_TYPENAME range_iterator<Range>::type >
        make_sub_range( Range& r, 
                        BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_begin,
                        BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_end = 0 )
        {
            return range_detail::make_sub_range_impl( r, advance_begin, advance_end );
        }
        
        template< class Range >
        inline iterator_range< BOOST_DEDUCED_TYPENAME range_const_iterator<Range>::type >
        make_sub_range( const Range& r, 
                        BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_begin,
                        BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_end = 0 )
        {
            return range_detail::make_sub_range_impl( r, advance_begin, advance_end );
        }

        
        
        template< class Range >
        inline iterator_range< BOOST_DEDUCED_TYPENAME range_iterator<Range>::type >
        make_super_range( Range& r, 
                          BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_begin,
                          BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_end = 0 )
        {
            return range_detail::make_super_range_impl( r, advance_begin, advance_end );
        }
        
        
        template< class Range >
        inline iterator_range< BOOST_DEDUCED_TYPENAME range_const_iterator<Range>::type >
        make_super_range( const Range& r, 
                          BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_begin,
                          BOOST_DEDUCED_TYPENAME range_difference<Range>::type advance_end = 0 )
        {
            return range_detail::make_super_range_impl( r, advance_begin, advance_end );
        }*/