ceph/src/boost/boost/fusion/container/map/detail/value_at_key_impl.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2013 Joel de Guzman
   3
   4     Distributed under the Boost Software License, Version 1.0. (See accompanying
   5     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 ==============================================================================*/
   7 #if !defined(BOOST_FUSION_MAP_DETAIL_VALUE_AT_KEY_IMPL_02042013_0821)
   8 #define BOOST_FUSION_MAP_DETAIL_VALUE_AT_KEY_IMPL_02042013_0821
   9
  10 #include <boost/fusion/support/config.hpp>
  11 #include <boost/fusion/support/detail/access.hpp>
  12 #include <boost/type_traits/is_const.hpp>
  13 #include <boost/mpl/at.hpp>
  14 #include <boost/mpl/identity.hpp>
  15 #include <boost/utility/declval.hpp>
  16
  17 namespace boost { namespace fusion
  18 {
  19     struct map_tag;
  20
  21     namespace extension
  22     {
  23         template <typename Tag>
  24         struct value_at_key_impl;
  25
  26         template <>
  27         struct value_at_key_impl<map_tag>
  28         {
  29             template <typename Sequence, typename Key>
  30             struct apply
  31             {
  32                 typedef
  33                     decltype(boost::declval<Sequence>().get_val(mpl::identity<Key>()))
  34                 type;
  35             };
  36         };
  37     }
  38 }}
  39
  40 #endif