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1 | /*! | |
2 | @file | |
3 | Defines `boost::hana::scan_right`. | |
4 | ||
5 | @copyright Louis Dionne 2013-2016 | |
6 | Distributed 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_SCAN_RIGHT_HPP | |
11 | #define BOOST_HANA_SCAN_RIGHT_HPP | |
12 | ||
13 | #include <boost/hana/fwd/scan_right.hpp> | |
14 | ||
15 | #include <boost/hana/at.hpp> | |
16 | #include <boost/hana/concept/sequence.hpp> | |
17 | #include <boost/hana/config.hpp> | |
18 | #include <boost/hana/core/dispatch.hpp> | |
19 | #include <boost/hana/core/make.hpp> | |
20 | #include <boost/hana/empty.hpp> | |
21 | #include <boost/hana/front.hpp> | |
22 | #include <boost/hana/length.hpp> | |
23 | #include <boost/hana/prepend.hpp> | |
24 | ||
25 | #include <cstddef> | |
26 | #include <utility> | |
27 | ||
28 | ||
29 | BOOST_HANA_NAMESPACE_BEGIN | |
30 | //! @cond | |
31 | template <typename Xs, typename F> | |
32 | constexpr auto scan_right_t::operator()(Xs&& xs, F const& f) const { | |
33 | using S = typename hana::tag_of<Xs>::type; | |
34 | using ScanRight = BOOST_HANA_DISPATCH_IF(scan_right_impl<S>, | |
35 | hana::Sequence<S>::value | |
36 | ); | |
37 | ||
38 | #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS | |
39 | static_assert(hana::Sequence<S>::value, | |
40 | "hana::scan_right(xs, f) requires 'xs' to be a Sequence"); | |
41 | #endif | |
42 | ||
43 | return ScanRight::apply(static_cast<Xs&&>(xs), f); | |
44 | } | |
45 | ||
46 | template <typename Xs, typename State, typename F> | |
47 | constexpr auto scan_right_t::operator()(Xs&& xs, State&& state, F const& f) const { | |
48 | using S = typename hana::tag_of<Xs>::type; | |
49 | using ScanRight = BOOST_HANA_DISPATCH_IF(scan_right_impl<S>, | |
50 | hana::Sequence<S>::value | |
51 | ); | |
52 | ||
53 | #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS | |
54 | static_assert(hana::Sequence<S>::value, | |
55 | "hana::scan_right(xs, state, f) requires 'xs' to be a Sequence"); | |
56 | #endif | |
57 | ||
58 | return ScanRight::apply(static_cast<Xs&&>(xs), | |
59 | static_cast<State&&>(state), f); | |
60 | } | |
61 | //! @endcond | |
62 | ||
63 | template <typename S, bool condition> | |
64 | struct scan_right_impl<S, when<condition>> : default_ { | |
65 | // Without initial state | |
66 | template <typename Xs, typename F, std::size_t n1, std::size_t n2, std::size_t ...ns> | |
67 | static constexpr auto | |
68 | apply1_impl(Xs&& xs, F const& f, std::index_sequence<n1, n2, ns...>) { | |
69 | auto rest = scan_right_impl::apply1_impl(static_cast<Xs&&>(xs), | |
70 | f, std::index_sequence<n2, ns...>{}); | |
71 | auto element = f(hana::at_c<n1>(static_cast<Xs&&>(xs)), hana::front(rest)); | |
72 | return hana::prepend(std::move(rest), std::move(element)); | |
73 | } | |
74 | ||
75 | template <typename Xs, typename F, std::size_t n> | |
76 | static constexpr auto apply1_impl(Xs&& xs, F const&, std::index_sequence<n>) { | |
77 | return hana::make<S>(hana::at_c<n>(static_cast<Xs&&>(xs))); | |
78 | } | |
79 | ||
80 | template <typename Xs, typename F> | |
81 | static constexpr auto apply1_impl(Xs&&, F const&, std::index_sequence<>) { | |
82 | return hana::empty<S>(); | |
83 | } | |
84 | ||
85 | template <typename Xs, typename F> | |
86 | static constexpr auto apply(Xs&& xs, F const& f) { | |
87 | constexpr std::size_t Len = decltype(hana::length(xs))::value; | |
88 | return scan_right_impl::apply1_impl(static_cast<Xs&&>(xs), | |
89 | f, std::make_index_sequence<Len>{}); | |
90 | } | |
91 | ||
92 | ||
93 | // With initial state | |
94 | template <typename Xs, typename State, typename F, | |
95 | std::size_t n1, std::size_t n2, std::size_t ...ns> | |
96 | static constexpr auto | |
97 | apply_impl(Xs&& xs, State&& state, F const& f, | |
98 | std::index_sequence<n1, n2, ns...>) | |
99 | { | |
100 | auto rest = scan_right_impl::apply_impl(static_cast<Xs&&>(xs), | |
101 | static_cast<State&&>(state), | |
102 | f, std::index_sequence<n2, ns...>{}); | |
103 | auto element = f(hana::at_c<n1>(static_cast<Xs&&>(xs)), hana::front(rest)); | |
104 | return hana::prepend(std::move(rest), std::move(element)); | |
105 | } | |
106 | ||
107 | template <typename Xs, typename State, typename F, std::size_t n> | |
108 | static constexpr auto | |
109 | apply_impl(Xs&& xs, State&& state, F const& f, std::index_sequence<n>) { | |
110 | auto element = f(hana::at_c<n>(static_cast<Xs&&>(xs)), state); | |
111 | return hana::make<S>(std::move(element), static_cast<State&&>(state)); | |
112 | } | |
113 | ||
114 | template <typename Xs, typename State, typename F> | |
115 | static constexpr auto | |
116 | apply_impl(Xs&&, State&& state, F const&, std::index_sequence<>) { | |
117 | return hana::make<S>(static_cast<State&&>(state)); | |
118 | } | |
119 | ||
120 | template <typename Xs, typename State, typename F> | |
121 | static constexpr auto apply(Xs&& xs, State&& state, F const& f) { | |
122 | constexpr std::size_t Len = decltype(hana::length(xs))::value; | |
123 | return scan_right_impl::apply_impl(static_cast<Xs&&>(xs), | |
124 | static_cast<State&&>(state), | |
125 | f, std::make_index_sequence<Len>{}); | |
126 | } | |
127 | }; | |
128 | BOOST_HANA_NAMESPACE_END | |
129 | ||
130 | #endif // !BOOST_HANA_SCAN_RIGHT_HPP |