1#ifndef BOOST_MP11_INTEGER_SEQUENCE_HPP_INCLUDED
2#define BOOST_MP11_INTEGER_SEQUENCE_HPP_INCLUDED
3
4// Copyright 2015, 2017, 2019 Peter Dimov.
5//
6// Distributed under the Boost Software License, Version 1.0.
7//
8// See accompanying file LICENSE_1_0.txt or copy at
9// http://www.boost.org/LICENSE_1_0.txt
10
11#include <boost/mp11/version.hpp>
12#include <cstddef>
13
14#if defined(__has_builtin)
15# if __has_builtin(__make_integer_seq)
16# define BOOST_MP11_HAS_MAKE_INTEGER_SEQ
17# endif
18#endif
19
20namespace boost
21{
22namespace mp11
23{
24
25// integer_sequence
26template<class T, T... I> struct integer_sequence
27{
28};
29
30#if defined(BOOST_MP11_HAS_MAKE_INTEGER_SEQ)
31
32template<class T, T N> using make_integer_sequence = __make_integer_seq<integer_sequence, T, N>;
33
34#else
35
36// detail::make_integer_sequence_impl
37namespace detail
38{
39
40// iseq_if_c
41template<bool C, class T, class E> struct iseq_if_c_impl;
42
43template<class T, class E> struct iseq_if_c_impl<true, T, E>
44{
45 using type = T;
46};
47
48template<class T, class E> struct iseq_if_c_impl<false, T, E>
49{
50 using type = E;
51};
52
53template<bool C, class T, class E> using iseq_if_c = typename iseq_if_c_impl<C, T, E>::type;
54
55// iseq_identity
56template<class T> struct iseq_identity
57{
58 using type = T;
59};
60
61template<class S1, class S2> struct append_integer_sequence;
62
63template<class T, T... I, T... J> struct append_integer_sequence<integer_sequence<T, I...>, integer_sequence<T, J...>>
64{
65 using type = integer_sequence< T, I..., ( J + sizeof...(I) )... >;
66};
67
68template<class T, T N> struct make_integer_sequence_impl;
69
70template<class T, T N> struct make_integer_sequence_impl_
71{
72private:
73
74 static_assert( N >= 0, "make_integer_sequence<T, N>: N must not be negative" );
75
76 static T const M = N / 2;
77 static T const R = N % 2;
78
79 using S1 = typename make_integer_sequence_impl<T, M>::type;
80 using S2 = typename append_integer_sequence<S1, S1>::type;
81 using S3 = typename make_integer_sequence_impl<T, R>::type;
82 using S4 = typename append_integer_sequence<S2, S3>::type;
83
84public:
85
86 using type = S4;
87};
88
89template<class T, T N> struct make_integer_sequence_impl: iseq_if_c<N == 0, iseq_identity<integer_sequence<T>>, iseq_if_c<N == 1, iseq_identity<integer_sequence<T, 0>>, make_integer_sequence_impl_<T, N> > >
90{
91};
92
93} // namespace detail
94
95// make_integer_sequence
96template<class T, T N> using make_integer_sequence = typename detail::make_integer_sequence_impl<T, N>::type;
97
98#endif // defined(BOOST_MP11_HAS_MAKE_INTEGER_SEQ)
99
100// index_sequence
101template<std::size_t... I> using index_sequence = integer_sequence<std::size_t, I...>;
102
103// make_index_sequence
104template<std::size_t N> using make_index_sequence = make_integer_sequence<std::size_t, N>;
105
106// index_sequence_for
107template<class... T> using index_sequence_for = make_integer_sequence<std::size_t, sizeof...(T)>;
108
109} // namespace mp11
110} // namespace boost
111
112#endif // #ifndef BOOST_MP11_INTEGER_SEQUENCE_HPP_INCLUDED
113

source code of include/boost/mp11/integer_sequence.hpp