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
23namespace 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
80