ceph/src/boost/boost/fusion/sequence/intrinsic/empty.hpp

   1 /*=============================================================================
   2     Copyright (c) 2001-2011 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(FUSION_EMPTY_09162005_0335)
   8 #define FUSION_EMPTY_09162005_0335
   9
  10 #include <boost/fusion/support/config.hpp>
  11 #include <boost/fusion/sequence/intrinsic_fwd.hpp>
  12 #include <boost/fusion/sequence/intrinsic/size.hpp>
  13 #include <boost/mpl/bool.hpp>
  14 #include <boost/fusion/support/tag_of.hpp>
  15
  16 namespace boost { namespace fusion
  17 {
  18     // Special tags:
  19     struct sequence_facade_tag;
  20     struct mpl_sequence_tag; // mpl sequence tag
  21
  22     namespace extension
  23     {
  24         template <typename Tag>
  25         struct empty_impl
  26         {
  27             template <typename Sequence>
  28             struct apply
  29                 : mpl::bool_<(result_of::size<Sequence>::value == 0)>
  30             {};
  31         };
  32
  33         template <>
  34         struct empty_impl<sequence_facade_tag>
  35         {
  36             template <typename Sequence>
  37             struct apply : Sequence::template empty<Sequence> {};
  38         };
  39
  40         template <>
  41         struct empty_impl<mpl_sequence_tag>;
  42     }
  43
  44     namespace result_of
  45     {
  46         template <typename Sequence>
  47         struct empty
  48             : extension::empty_impl<typename detail::tag_of<Sequence>::type>::
  49                 template apply<Sequence>
  50         {};
  51     }
  52
  53     template <typename Sequence>
  54     BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  55     inline typename result_of::empty<Sequence>::type
  56     empty(Sequence const&)
  57     {
  58         typedef typename result_of::empty<Sequence>::type result;
  59         return result();
  60     }
  61 }}
  62
  63 #endif