ceph/src/boost/libs/fusion/include/boost/fusion/support/detail/index_sequence.hpp

   1 /*=============================================================================
   2     Copyright (c) 2015 Agustin K-ballo Berge
   3     Copyright (c) 2015 Kohei Takahashi
   4
   5     Distributed under the Boost Software License, Version 1.0. (See accompanying
   6     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   7 ==============================================================================*/
   8
   9 #ifndef BOOST_FUSION_SUPPORT_DETAIL_INDEX_SEQUENCE_06232015_1038
  10 #define BOOST_FUSION_SUPPORT_DETAIL_INDEX_SEQUENCE_06232015_1038
  11
  12 #include <boost/fusion/support/config.hpp>
  13 #include <cstddef>
  14
  15 // GCC5 has O(logN) implementation, see https://gcc.gnu.org/PR66059 .
  16 #if (defined(__cpp_lib_integer_sequence) && __cpp_lib_integer_sequence >= 201304) \
  17  || (defined(BOOST_LIBSTDCXX_VERSION) \
  18      && BOOST_LIBSTDCXX_VERSION >= 500000 && __cplusplus >= 201402)
  19 #include <utility>
  20 #define BOOST_FUSION_STDLIB_HAS_INTEGER_SEQUENCE
  21 #endif
  22
  23 namespace boost { namespace fusion { namespace detail
  24 {
  25 #ifdef BOOST_FUSION_STDLIB_HAS_INTEGER_SEQUENCE
  26     // Use aliasing templates without checking availability, the compiler should work.
  27     template <std::size_t ...Ints>
  28     using index_sequence = std::index_sequence<Ints...>;
  29
  30     template <std::size_t N>
  31     struct make_index_sequence
  32     {
  33         using type = std::make_index_sequence<N>;
  34     };
  35 #else
  36     template <std::size_t ...Ints>
  37     struct index_sequence
  38     {
  39         typedef std::size_t value_type;
  40
  41         BOOST_CONSTEXPR BOOST_FUSION_GPU_ENABLED
  42         static std::size_t size() BOOST_NOEXCEPT
  43         { return sizeof...(Ints); }
  44
  45         // non standard extension
  46         typedef index_sequence type;
  47     };
  48
  49     template <typename Left, typename Right>
  50     struct _make_index_sequence_join;
  51
  52     template <std::size_t... Left, std::size_t... Right>
  53     struct _make_index_sequence_join<
  54         index_sequence<Left...>, index_sequence<Right...>
  55     > : index_sequence<Left..., (sizeof...(Left) + Right)...>
  56     {};
  57
  58     template <std::size_t N>
  59     struct make_index_sequence
  60       : _make_index_sequence_join<
  61             typename make_index_sequence<N / 2>::type
  62           , typename make_index_sequence<N - N / 2>::type
  63         >
  64     {};
  65
  66     template <>
  67     struct make_index_sequence<1>
  68       : index_sequence<0>
  69     {};
  70
  71     template <>
  72     struct make_index_sequence<0>
  73       : index_sequence<>
  74     {};
  75 #endif
  76 }}}
  77
  78 #endif
  79