// In header: <boost/proto/functional/std/utility.hpp>

struct second :  proto::callable {
  // member classes/structs/unions
  template<typename This, typename Pair> 
  struct result<This(Pair)> {
    // types
    typedef typename Pair::second_type type;
  };
  template<typename This, typename Pair> 
  struct result<This(Pair &)> {
    // types
    typedef typename Pair::second_type & type;
  };
  template<typename This, typename Pair> 
  struct result<This(Pair const &)> {
    // types
    typedef typename Pair::second_type const & type;
  };
  // public member functions
  template<typename Pair> 
    typename Pair::second_type & operator()(Pair &) const;
  template<typename Pair> 
    typename Pair::second_type const & operator()(Pair const &) const;
};