make_index_sequence.hpp

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/*
Copyright Barrett Adair 2016-2017
 
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
*/
 
#ifndef BOOST_CLBL_TRTS_DETAIL_POLYFILLS_MAKE_INDEX_SEQUENCE_HPP
#define BOOST_CLBL_TRTS_DETAIL_POLYFILLS_MAKE_INDEX_SEQUENCE_HPP
 
#undef BOOST_CLBL_TRTS_IX_SEQ
#define BOOST_CLBL_TRTS_IX_SEQ(...) \
    ::boost::callable_traits::detail::index_sequence<__VA_ARGS__>
 
#undef BOOST_CLBL_TRTS_MAKE_IX_SEQ
#define BOOST_CLBL_TRTS_MAKE_IX_SEQ(...) \
    ::boost::callable_traits::detail::make_index_sequence<__VA_ARGS__>
 
namespace boost { namespace callable_traits { namespace detail { 
 
template<std::size_t...>
struct index_sequence { using type = index_sequence; };
 
template<typename, typename>
struct concat;
 
template<std::size_t... I1, std::size_t... I2>
struct concat<index_sequence<I1...>, index_sequence<I2...>>
    : index_sequence<I1..., (sizeof...(I1)+I2)...> {};
 
template<std::size_t N>
    struct make_index_sequence_t;
 
template<std::size_t N>
struct make_index_sequence_t : concat< 
    typename make_index_sequence_t<N/2>::type,
    typename make_index_sequence_t<N - N/2>::type >::type {};
 
template<>
struct make_index_sequence_t<0> : index_sequence<> {};
 
template<>
struct make_index_sequence_t<1> : index_sequence<0> {};
 
template<std::size_t... I>
using make_index_sequence = typename make_index_sequence_t<I...>::type;
 
}}} // namespace boost::callable_traits::detail
 
#endif // #ifndef BOOST_CLBL_TRTS_DETAIL_POLYFILLS_MAKE_INDEX_SEQUENCE_HPP