1/*!
2@file
3Adapts `boost::tuple` for use with Hana.
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_TUPLE_HPP
11#define BOOST_HANA_EXT_BOOST_TUPLE_HPP
12
13#include <boost/hana/bool.hpp>
14#include <boost/hana/config.hpp>
15#include <boost/hana/detail/decay.hpp>
16#include <boost/hana/fwd/at.hpp>
17#include <boost/hana/fwd/core/make.hpp>
18#include <boost/hana/fwd/core/tag_of.hpp>
19#include <boost/hana/fwd/drop_front.hpp>
20#include <boost/hana/fwd/is_empty.hpp>
21#include <boost/hana/fwd/length.hpp>
22#include <boost/hana/integral_constant.hpp>
23
24#include <boost/tuple/tuple.hpp>
25
26#include <cstddef>
27#include <utility>
28
29
30#ifdef BOOST_HANA_DOXYGEN_INVOKED
31namespace boost {
32 //! @ingroup group-ext-boost
33 //! Adapter for `boost::tuple`s.
34 //!
35 //!
36 //! Modeled concepts
37 //! ----------------
38 //! A `boost::tuple` is a model of the `Sequence` concept, and all the
39 //! concepts it refines. That makes it essentially the same as a Hana
40 //! tuple, although the complexity of some operations might differ from
41 //! that of Hana's tuple.
42 //!
43 //! @include example/ext/boost/tuple.cpp
44 template <typename ...T>
45 struct tuple { };
46}
47#endif
48
49
50namespace boost { namespace hana {
51 namespace ext { namespace boost { struct tuple_tag; }}
52
53 template <typename ...Xs>
54 struct tag_of<boost::tuple<Xs...>> {
55 using type = ext::boost::tuple_tag;
56 };
57
58 template <typename H, typename T>
59 struct tag_of<boost::tuples::cons<H, T>> {
60 using type = ext::boost::tuple_tag;
61 };
62
63 template <>
64 struct tag_of<boost::tuples::null_type> {
65 using type = ext::boost::tuple_tag;
66 };
67
68 //////////////////////////////////////////////////////////////////////////
69 // Iterable
70 //////////////////////////////////////////////////////////////////////////
71 template <>
72 struct at_impl<ext::boost::tuple_tag> {
73 template <typename Xs, typename N>
74 static constexpr decltype(auto) apply(Xs&& xs, N const&) {
75 constexpr std::size_t n = N::value;
76 return static_cast<Xs&&>(xs).template get<n>();
77 }
78 };
79
80 template <>
81 struct drop_front_impl<ext::boost::tuple_tag> {
82 template <std::size_t n, typename Xs, std::size_t ...i>
83 static constexpr auto drop_front_helper(Xs&& xs, std::index_sequence<i...>) {
84 return hana::make<ext::boost::tuple_tag>(
85 hana::at_c<n + i>(static_cast<Xs&&>(xs))...
86 );
87 }
88
89 template <typename Xs, typename N>
90 static constexpr auto apply(Xs&& xs, N const&) {
91 constexpr std::size_t n = N::value;
92 constexpr std::size_t len = decltype(hana::length(xs))::value;
93 return drop_front_helper<n>(static_cast<Xs&&>(xs),
94 std::make_index_sequence<(n < len ? len - n : 0)>{});
95 }
96 };
97
98 template <>
99 struct is_empty_impl<ext::boost::tuple_tag> {
100 static constexpr auto apply(boost::tuples::null_type const&)
101 { return hana::true_c; }
102
103 template <typename H, typename T>
104 static constexpr auto apply(boost::tuples::cons<H, T> const&)
105 { return hana::false_c; }
106 };
107
108 //////////////////////////////////////////////////////////////////////////
109 // Foldable
110 //////////////////////////////////////////////////////////////////////////
111 template <>
112 struct length_impl<ext::boost::tuple_tag> {
113 template <typename Xs>
114 static constexpr auto apply(Xs const&) {
115 return hana::size_c<boost::tuples::length<Xs>::value>;
116 }
117 };
118
119 //////////////////////////////////////////////////////////////////////////
120 // Sequence
121 //////////////////////////////////////////////////////////////////////////
122 template <>
123 struct Sequence<ext::boost::tuple_tag> {
124 static constexpr bool value = true;
125 };
126
127 template <>
128 struct make_impl<ext::boost::tuple_tag> {
129 template <typename ...Xs>
130 static constexpr auto apply(Xs&& ...xs) {
131 return boost::tuples::tuple<
132 typename detail::decay<Xs>::type...
133 >{static_cast<Xs&&>(xs)...};
134 }
135 };
136}} // end namespace boost::hana
137
138#endif // !BOOST_HANA_EXT_BOOST_TUPLE_HPP
139

source code of boost/libs/hana/include/boost/hana/ext/boost/tuple.hpp