utilmm: utilmm: utils.hh Source File

00001 /* -*- C++ -*-
00002  * $Id: utils.hh 957 2005-03-07 16:01:20Z sjoyeux $
00003  */
00004 #ifndef UTILMM_FUNCTIONAL_UTILS_HEADER
00005 # define UTILMM_FUNCTIONAL_UTILS_HEADER
00006 
00007 #include "utilmm/functional/arg_traits.hh"
00008 # include <functional>
00009 
00010 namespace utilmm {
00011 
00023   template<typename Ty>
00024   struct identity :public std::unary_function<Ty, Ty> {
00025   private:
00026     typedef typename arg_traits<Ty>::type arg_type;
00027     
00028   public:
00033     arg_type operator()(arg_type x) const {
00034       return x;
00035     }
00036   }; // struct utilmm::identity<>
00037 
00049   template<class Pair>
00050   struct select_1st
00051     :public std::unary_function<Pair, typename Pair::first_type> {
00057     typename Pair::first_type const &operator()(Pair const &p) const {
00058       return p.first;
00059     }
00060   }; // struct utilmm::select_1st<>
00061 
00073   template<class Pair>
00074   struct select_2nd
00075     :public std::unary_function<Pair, typename Pair::second_type> {
00081     typename Pair::second_type const &operator()(Pair const &p) const {
00082       return p.second;
00083     }
00084   }; // struct utilmm::select_2nd<>
00085 
00086 } // namespace utilmm
00087 
00088 #endif // UTILMM_FUNCTIONAL_UTILS_HEADER 
00089