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1 | //----------------------------------------------------------------------------- |
2 | // boost variant/recursive_variant.hpp header file | |
3 | // See http://www.boost.org for updates, documentation, and revision history. | |
4 | //----------------------------------------------------------------------------- | |
5 | // | |
6 | // Copyright (c) 2003 Eric Friedman | |
1e59de90 | 7 | // Copyright (c) 2013-2022 Antony Polukhin |
7c673cae FG |
8 | // |
9 | // Distributed under the Boost Software License, Version 1.0. (See | |
10 | // accompanying file LICENSE_1_0.txt or copy at | |
11 | // http://www.boost.org/LICENSE_1_0.txt) | |
12 | ||
13 | #ifndef BOOST_VARIANT_RECURSIVE_VARIANT_HPP | |
14 | #define BOOST_VARIANT_RECURSIVE_VARIANT_HPP | |
15 | ||
16 | #include <boost/variant/variant_fwd.hpp> | |
17 | #include <boost/variant/detail/enable_recursive.hpp> | |
18 | #include <boost/variant/detail/substitute_fwd.hpp> | |
19 | #include <boost/variant/detail/make_variant_list.hpp> | |
20 | #include <boost/variant/detail/over_sequence.hpp> | |
21 | ||
22 | #include <boost/mpl/aux_/lambda_arity_param.hpp> | |
23 | ||
24 | #include <boost/mpl/equal.hpp> | |
25 | #include <boost/mpl/eval_if.hpp> | |
26 | #include <boost/mpl/identity.hpp> | |
27 | #include <boost/mpl/if.hpp> | |
28 | #include <boost/mpl/protect.hpp> | |
29 | #include <boost/mpl/transform.hpp> | |
30 | #include <boost/type_traits/is_same.hpp> | |
31 | #include <boost/preprocessor/cat.hpp> | |
32 | #include <boost/preprocessor/repeat.hpp> | |
33 | ||
34 | #include <boost/mpl/bool.hpp> | |
35 | #include <boost/mpl/is_sequence.hpp> | |
36 | #include <boost/variant/variant.hpp> | |
37 | ||
38 | namespace boost { | |
39 | ||
40 | namespace detail { namespace variant { | |
41 | ||
42 | /////////////////////////////////////////////////////////////////////////////// | |
43 | // (detail) metafunction specialization substitute | |
44 | // | |
45 | // Handles embedded variant types when substituting for recursive_variant_. | |
46 | // | |
47 | ||
48 | #if !defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE) | |
49 | ||
50 | template < | |
51 | BOOST_VARIANT_ENUM_PARAMS(typename T) | |
52 | , typename RecursiveVariant | |
53 | BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(typename Arity) | |
54 | > | |
55 | struct substitute< | |
56 | ::boost::variant< | |
57 | recursive_flag< T0 > | |
58 | , BOOST_VARIANT_ENUM_SHIFTED_PARAMS(T) | |
59 | > | |
60 | , RecursiveVariant | |
61 | , ::boost::recursive_variant_ | |
62 | BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(Arity) | |
63 | > | |
64 | { | |
65 | typedef ::boost::variant< | |
66 | recursive_flag< T0 > | |
67 | , BOOST_VARIANT_ENUM_SHIFTED_PARAMS(T) | |
68 | > type; | |
69 | }; | |
70 | ||
71 | template < | |
72 | BOOST_VARIANT_ENUM_PARAMS(typename T) | |
73 | , typename RecursiveVariant | |
74 | BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(typename Arity) | |
75 | > | |
76 | struct substitute< | |
77 | ::boost::variant< | |
78 | ::boost::detail::variant::over_sequence< T0 > | |
79 | , BOOST_VARIANT_ENUM_SHIFTED_PARAMS(T) | |
80 | > | |
81 | , RecursiveVariant | |
82 | , ::boost::recursive_variant_ | |
83 | BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(Arity) | |
84 | > | |
85 | { | |
86 | private: | |
87 | ||
88 | typedef T0 initial_types; | |
89 | ||
90 | typedef typename mpl::transform< | |
91 | initial_types | |
92 | , mpl::protect< quoted_enable_recursive<RecursiveVariant,mpl::true_> > | |
93 | >::type types; | |
94 | ||
95 | public: | |
96 | ||
97 | typedef typename mpl::if_< | |
98 | mpl::equal<initial_types, types, ::boost::is_same<mpl::_1, mpl::_2> > | |
99 | , ::boost::variant< | |
100 | ::boost::detail::variant::over_sequence< T0 > | |
101 | , BOOST_VARIANT_ENUM_SHIFTED_PARAMS(T) | |
102 | > | |
103 | , ::boost::variant< over_sequence<types> > | |
104 | >::type type; | |
105 | }; | |
106 | ||
107 | template < | |
108 | BOOST_VARIANT_ENUM_PARAMS(typename T) | |
109 | , typename RecursiveVariant | |
110 | BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(typename Arity) | |
111 | > | |
112 | struct substitute< | |
113 | ::boost::variant< BOOST_VARIANT_ENUM_PARAMS(T) > | |
114 | , RecursiveVariant | |
115 | , ::boost::recursive_variant_ | |
116 | BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(Arity) | |
117 | > | |
118 | { | |
119 | #if !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES) | |
120 | ||
121 | typedef ::boost::variant< | |
122 | typename enable_recursive< | |
123 | T0 | |
124 | , RecursiveVariant | |
125 | , mpl::true_ | |
126 | >::type, | |
127 | typename enable_recursive< | |
128 | TN | |
129 | , RecursiveVariant | |
130 | , mpl::true_ | |
131 | >::type... | |
132 | > type; | |
133 | ||
134 | #else // defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES) | |
135 | ||
136 | private: // helpers, for metafunction result (below) | |
137 | ||
138 | #define BOOST_VARIANT_AUX_ENABLE_RECURSIVE_TYPEDEFS(z,N,_) \ | |
139 | typedef typename enable_recursive< \ | |
140 | BOOST_PP_CAT(T,N) \ | |
141 | , RecursiveVariant \ | |
142 | , mpl::true_ \ | |
143 | >::type BOOST_PP_CAT(wknd_T,N); \ | |
144 | /**/ | |
145 | ||
146 | BOOST_PP_REPEAT( | |
147 | BOOST_VARIANT_LIMIT_TYPES | |
148 | , BOOST_VARIANT_AUX_ENABLE_RECURSIVE_TYPEDEFS | |
149 | , _ | |
150 | ) | |
151 | ||
152 | #undef BOOST_VARIANT_AUX_ENABLE_RECURSIVE_TYPEDEFS | |
153 | ||
154 | public: // metafunction result | |
155 | ||
156 | typedef ::boost::variant< BOOST_VARIANT_ENUM_PARAMS(wknd_T) > type; | |
157 | #endif // BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES workaround | |
158 | }; | |
159 | ||
160 | #else // defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE) | |
161 | ||
162 | // | |
163 | // no specializations: embedded variants unsupported on these compilers! | |
164 | // | |
165 | ||
166 | #endif // !defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE) | |
167 | ||
168 | }} // namespace detail::variant | |
169 | ||
170 | /////////////////////////////////////////////////////////////////////////////// | |
171 | // metafunction make_recursive_variant | |
172 | // | |
173 | // See docs and boost/variant/variant_fwd.hpp for more information. | |
174 | // | |
175 | template < BOOST_VARIANT_ENUM_PARAMS(typename T) > | |
176 | struct make_recursive_variant | |
177 | { | |
178 | public: // metafunction result | |
179 | ||
180 | typedef boost::variant< | |
181 | detail::variant::recursive_flag< T0 > | |
182 | , BOOST_VARIANT_ENUM_SHIFTED_PARAMS(T) | |
183 | > type; | |
184 | ||
185 | }; | |
186 | ||
187 | /////////////////////////////////////////////////////////////////////////////// | |
188 | // metafunction make_recursive_variant_over | |
189 | // | |
190 | // See docs and boost/variant/variant_fwd.hpp for more information. | |
191 | // | |
192 | template <typename Types> | |
193 | struct make_recursive_variant_over | |
194 | { | |
195 | private: // precondition assertions | |
196 | ||
197 | BOOST_STATIC_ASSERT(( ::boost::mpl::is_sequence<Types>::value )); | |
198 | ||
199 | public: // metafunction result | |
200 | ||
201 | typedef typename make_recursive_variant< | |
202 | detail::variant::over_sequence< Types > | |
203 | >::type type; | |
204 | ||
205 | }; | |
206 | ||
207 | } // namespace boost | |
208 | ||
209 | #endif // BOOST_VARIANT_RECURSIVE_VARIANT_HPP |