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 |
7 | // Copyright (c) 2013 Antony Polukhin |
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 |
210 | |