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 20 namespace boost 21 { 22 namespace mp11 23 { 24 25 // integer_sequence 26 template<class T, T... I> struct integer_sequence 27 { 28 }; 29 30 #if defined(BOOST_MP11_HAS_MAKE_INTEGER_SEQ) 31 32 template<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 37 namespace detail 38 { 39 40 // iseq_if_c 41 template<bool C, class T, class E> struct iseq_if_c_impl; 42 43 template<class T, class E> struct iseq_if_c_impl<true, T, E> 44 { 45 using type = T; 46 }; 47 48 template<class T, class E> struct iseq_if_c_impl<false, T, E> 49 { 50 using type = E; 51 }; 52 53 template<bool C, class T, class E> using iseq_if_c = typename iseq_if_c_impl<C, T, E>::type; 54 55 // iseq_identity 56 template<class T> struct iseq_identity 57 { 58 using type = T; 59 }; 60 61 template<class S1, class S2> struct append_integer_sequence; 62 63 template<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 68 template<class T, T N> struct make_integer_sequence_impl; 69 70 template<class T, T N> struct make_integer_sequence_impl_ 71 { 72 private: 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 84 public: 85 86 using type = S4; 87 }; 88 89 template<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 96 template<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 101 template<std::size_t... I> using index_sequence = integer_sequence<std::size_t, I...>; 102 103 // make_index_sequence 104 template<std::size_t N> using make_index_sequence = make_integer_sequence<std::size_t, N>; 105 106 // index_sequence_for 107 template<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