BOOST_INTRUSIVE_FORCEINLINE friend typename Iterator::difference_type operator- (const transform_iterator& i, const transform_iterator& i2) { return i2.distance_to(i); }
friend typename Iterator::difference_type operator- (const transform_iterator& i, const transform_iterator& i2) { return i2.distance_to(i); }
friend typename std::iterator_traits<Iterator>::difference_type operator- (const transform_iterator& i, const transform_iterator& i2) { return i2.distance_to(i); }