1/*!
2@file
3Defines common methods for all Boost.Fusion sequences.
4
5Copyright Louis Dionne 2013-2022
6Distributed under the Boost Software License, Version 1.0.
7(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
8 */
9
10#ifndef BOOST_HANA_EXT_BOOST_FUSION_DETAIL_COMMON_HPP
11#define BOOST_HANA_EXT_BOOST_FUSION_DETAIL_COMMON_HPP
12
13#include <boost/hana/bool.hpp>
14#include <boost/hana/config.hpp>
15#include <boost/hana/core/when.hpp>
16#include <boost/hana/fwd/at.hpp>
17#include <boost/hana/fwd/concept/sequence.hpp>
18#include <boost/hana/fwd/is_empty.hpp>
19#include <boost/hana/fwd/length.hpp>
20#include <boost/hana/integral_constant.hpp>
21
22#include <boost/fusion/sequence/intrinsic/at.hpp>
23#include <boost/fusion/sequence/intrinsic/empty.hpp>
24#include <boost/fusion/sequence/intrinsic/size.hpp>
25
26#include <cstddef>
27
28
29namespace boost { namespace hana {
30 namespace detail {
31 template <typename T>
32 struct is_fusion_sequence {
33 static constexpr bool value = false;
34 };
35 }
36
37 //////////////////////////////////////////////////////////////////////////
38 // Iterable
39 //////////////////////////////////////////////////////////////////////////
40 template <typename S>
41 struct at_impl<S, when<detail::is_fusion_sequence<S>::value>> {
42 template <typename Xs, typename N>
43 static constexpr decltype(auto) apply(Xs&& xs, N const&) {
44 constexpr std::size_t n = N::value;
45 return boost::fusion::at_c<n>(static_cast<Xs&&>(xs));
46 }
47 };
48
49 template <typename S>
50 struct is_empty_impl<S, when<detail::is_fusion_sequence<S>::value>> {
51 template <typename Xs>
52 static constexpr auto apply(Xs&& xs) {
53 using Empty = decltype(boost::fusion::empty(xs));
54 return hana::bool_c<Empty::value>;
55 }
56 };
57
58 //////////////////////////////////////////////////////////////////////////
59 // Foldable
60 //////////////////////////////////////////////////////////////////////////
61 template <typename S>
62 struct length_impl<S, when<detail::is_fusion_sequence<S>::value>> {
63 template <typename Xs>
64 static constexpr auto apply(Xs const&) {
65 using Size = typename boost::fusion::result_of::size<Xs>::type;
66 return hana::size_c<Size::value>;
67 }
68 };
69
70 //////////////////////////////////////////////////////////////////////////
71 // Sequence
72 //////////////////////////////////////////////////////////////////////////
73 template <typename S>
74 struct Sequence<S, when<detail::is_fusion_sequence<S>::value>> {
75 static constexpr bool value = true;
76 };
77}} // end namespace boost::hana
78
79#endif // !BOOST_HANA_EXT_BOOST_FUSION_DETAIL_COMMON_HPP
80

source code of boost/libs/hana/include/boost/hana/ext/boost/fusion/detail/common.hpp