Hello, I try to write a cyclic Iterator using boost::iterator_adaptors. Unfortunally, the advance function doesn't work for negative distances correct: template<class Iterator> class cycle_iterator_policies { public: cycle_iterator_policies(const Iterator& begin, const Iterator& end) : m_begin( begin ), m_end( end ) { assert( m_begin != m_end ); } .... template void advance( IteratorAdaptor& x, DifferenceType n ) { n %= std::distance( m_begin, m_end ); DifferenceType rest = std::distance( x.base(), m_end ); if( n < rest ) std::advance( x.base(), n ); else std::advance( x.base() = m_begin, n - rest ); } .... private: Iterator m_begin; Iterator m_end; }; It seems to be an algorithmic problem for me. How can I corrected it? Thanks Olaf