#ifndef constant_iterator_H #define constant_iterator_H #include <boost/iterator/iterator_facade.hpp> #include <iterator> namespace boost { template<typename scalar_t> class constant_iterator : public boost::iterator_facade< constant_iterator<scalar_t>, scalar_t, boost::random_access_traversal_tag, scalar_t > { public: typedef typename boost::iterator_facade< constant_iterator<scalar_t>, scalar_t, boost::random_access_traversal_tag, scalar_t> super_t; typedef typename super_t::difference_type difference_type; typedef typename super_t::reference reference; typedef typename super_t::value_type value_type; explicit constant_iterator (scalar_t const& _k, int _cnt=0) : k (_k), cnt (_cnt) {} private: friend class boost::iterator_core_access; void increment () { --cnt; } difference_type distance_to (constant_iterator<scalar_t> const& y) const { return -(cnt - y.cnt); } bool equal (constant_iterator<scalar_t> const& y) const { return distance_to (y) == 0; } reference dereference() const { return k; } void advance (difference_type d) { cnt -= d; } private: scalar_t k; int cnt; }; template<typename scalar_t> constant_iterator<scalar_t> make_constant_iterator(scalar_t k, int cnt=0) { return constant_iterator<scalar_t> (k, cnt); } } //namespace boost #endif