I have an std::list<std::pair<double, float> > internal to a class. I'd like to expose begin() and end() functions from this class, that iterate over the second element of the list. So basically I want the user of the class to only see a sequence of floats. transform_iterator seems to fit the bill, but I think I'm seriously overcomplicating this. I've tried the following and it's not working. I feel like this pair_second / pair_first, and iterator should either already all be defined somewhere that I'm just not aware of, or be much shorter to write than this. template<class First, class Second> struct pair_second : public std::unary_function<std::pair<First, Second>, const Second&> { const Second& operator()(std::pair<First,Second>& pair) const { return pair.second; } }; template<class First, class Second> struct pair_first : public std::unary_function<std::pair<First, Second>, const First&> { const First& operator()(std::pair<First,Second>& pair) const { return pair.first; } }; template<class pair_type> struct first_iterator { typedef boost::transform_iterator< pair_first<typename pair_type::first_type, typename pair_type::second_type>, typename pair_type > type; }; template<class pair_type> struct second_iterator { typedef boost::transform_iterator< pair_second<typename pair_type::first_type, typename pair_type::second_type>, typename pair_type > type; }; typedef typename first_iterator<double_float_pair>::type float_iterator; float_iterator begin() { return float_iterator(items_.begin(), second_iterator<double_float_pair>()); } float_iterator end() { return float_iterator(items_.end(), second_iterator<double_float_pair>()); } Any advice would be appreciated. Thanks Zach