inline bool operator!=(const_iterator const &i) const { return _iter != i._iter; };
inline bool operator==(const_iterator const &i) const { return _iter == i._iter; };
friend std::ostream& operator<<(std::ostream& out, const_iterator i) { return operator<<(out, *i); }
inline bool operator!=(const_iterator const &i) const { return _iter != i._iter; };
inline bool operator==(const_iterator const &i) const { return _iter == i._iter; };
friend std::ostream& operator<<(std::ostream& out, const_iterator i) { return operator<<(out, *i); }