1 //-----------------------------------------------------------------------------
2 // boost variant/detail/enable_recursive.hpp header file
3 // See http://www.boost.org for updates, documentation, and revision history.
4 //-----------------------------------------------------------------------------
5 //
6 // Copyright (c) 2003
7 // Eric Friedman
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_DETAIL_ENABLE_RECURSIVE_HPP
14 #define BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_HPP
15 
16 #include <boost/variant/detail/enable_recursive_fwd.hpp>
17 #include <boost/variant/variant_fwd.hpp>
18 
19 #if !defined(BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT)
20 #   include <boost/mpl/apply.hpp>
21 #   include <boost/mpl/eval_if.hpp>
22 #   include <boost/mpl/lambda.hpp>
23 #endif
24 
25 #include <boost/variant/detail/substitute.hpp>
26 #include <boost/mpl/aux_/config/ctps.hpp>
27 #include <boost/mpl/bool_fwd.hpp>
28 #include <boost/mpl/if.hpp>
29 #include <boost/mpl/or.hpp>
30 #include <boost/type_traits/is_pointer.hpp>
31 #include <boost/type_traits/is_reference.hpp>
32 #include <boost/type_traits/is_same.hpp>
33 
34 #include <boost/variant/recursive_wrapper.hpp>
35 
36 namespace boost {
37 namespace detail { namespace variant {
38 
39 #if !defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE)
40 
41 #   define BOOST_VARIANT_AUX_ENABLE_RECURSIVE_IMPL(T,Dest,Source) \
42     substitute< T , Dest , Source > \
43     /**/
44 
45 #else // defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE)
46 
47 ///////////////////////////////////////////////////////////////////////////////
48 // (detail) class template rebind1
49 //
50 // Limited workaround in case 'substitute' metafunction unavailable.
51 //
52 
53 template <typename T, typename U1>
54 struct rebind1
55 {
56 private:
57     typedef typename mpl::lambda<
58           mpl::identity<T>
59         >::type le_;
60 
61 public:
62     typedef typename mpl::eval_if<
63           is_same< le_, mpl::identity<T> >
64         , le_ // identity<T>
65         , mpl::apply1<le_, U1>
66         >::type type;
67 };
68 
69 #   define BOOST_VARIANT_AUX_ENABLE_RECURSIVE_IMPL(T,Dest,Source) \
70     rebind1< T , Dest > \
71     /**/
72 
73 #endif // !defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE)
74 
75 ///////////////////////////////////////////////////////////////////////////////
76 // (detail) metafunction enable_recursive
77 //
78 // See boost/variant/detail/enable_recursive_fwd.hpp for more information.
79 //
80 
81 
82 template <typename T, typename RecursiveVariant, typename NoWrapper>
83 struct enable_recursive
84     : BOOST_VARIANT_AUX_ENABLE_RECURSIVE_IMPL(
85           T, RecursiveVariant, ::boost::recursive_variant_
86         )
87 {
88 };
89 
90 template <typename T, typename RecursiveVariant>
91 struct enable_recursive< T,RecursiveVariant,mpl::false_ >
92 {
93 private: // helpers, for metafunction result (below)
94 
95     typedef typename BOOST_VARIANT_AUX_ENABLE_RECURSIVE_IMPL(
96           T, RecursiveVariant, ::boost::recursive_variant_
97         )::type t_;
98 
99 public: // metafunction result
100 
101     // [Wrap with recursive_wrapper only if rebind really changed something:]
102     typedef typename mpl::if_<
103           mpl::or_<
104               is_same< t_,T >
105             , is_reference<t_>
106             , is_pointer<t_>
107             >
108         , t_
109         , boost::recursive_wrapper<t_>
110         >::type type;
111 
112 };
113 
114 
115 ///////////////////////////////////////////////////////////////////////////////
116 // (detail) metafunction class quoted_enable_recursive
117 //
118 // Same behavior as enable_recursive metafunction (see above).
119 //
120 template <typename RecursiveVariant, typename NoWrapper>
121 struct quoted_enable_recursive
122 {
123     template <typename T>
124     struct apply
125         : enable_recursive<T, RecursiveVariant, NoWrapper>
126     {
127     };
128 };
129 
130 }} // namespace detail::variant
131 } // namespace boost
132 
133 #endif // BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_HPP
134