source: NonGTP/Boost/boost/variant/detail/enable_recursive.hpp @ 857

Revision 857, 4.7 KB checked in by igarcia, 19 years ago (diff)
Line 
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
36namespace boost {
37namespace 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
53template <typename T, typename U1>
54struct rebind1
55{
56private:
57    typedef typename mpl::lambda<
58          mpl::identity<T>
59        >::type le_;
60
61public:
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#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
82
83template <typename T, typename RecursiveVariant, typename NoWrapper>
84struct enable_recursive
85    : BOOST_VARIANT_AUX_ENABLE_RECURSIVE_IMPL(
86          T, RecursiveVariant, ::boost::recursive_variant_
87        )
88{
89};
90
91template <typename T, typename RecursiveVariant>
92struct enable_recursive< T,RecursiveVariant,mpl::false_ >
93{
94private: // helpers, for metafunction result (below)
95
96    typedef typename BOOST_VARIANT_AUX_ENABLE_RECURSIVE_IMPL(
97          T, RecursiveVariant, ::boost::recursive_variant_
98        )::type t_;
99
100public: // metafunction result
101
102    // [Wrap with recursive_wrapper only if rebind really changed something:]
103    typedef typename mpl::if_<
104          mpl::or_<
105              is_same< t_,T >
106            , is_reference<t_>
107            , is_pointer<t_>
108            >
109        , t_
110        , boost::recursive_wrapper<t_>
111        >::type type;
112
113};
114
115#else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
116
117template <typename T, typename RecursiveVariant, typename NoWrapper>
118struct enable_recursive
119{
120private: // helpers, for metafunction result (below)
121
122    typedef typename BOOST_VARIANT_AUX_ENABLE_RECURSIVE_IMPL(
123          T, RecursiveVariant, ::boost::recursive_variant_
124        )::type t_;
125
126public: // metafunction result
127
128    // [Wrap with recursive_wrapper only if rebind really changed something:]
129    typedef typename mpl::if_<
130          mpl::or_<
131              NoWrapper
132            , is_same< t_,T >
133            , is_reference<t_>
134            , is_pointer<t_>
135            >
136        , t_
137        , boost::recursive_wrapper<t_>
138        >::type type;
139
140};
141
142#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround
143
144///////////////////////////////////////////////////////////////////////////////
145// (detail) metafunction class quoted_enable_recursive
146//
147// Same behavior as enable_recursive metafunction (see above).
148//
149template <typename RecursiveVariant, typename NoWrapper>
150struct quoted_enable_recursive
151{
152    template <typename T>
153    struct apply
154        : enable_recursive<T, RecursiveVariant, NoWrapper>
155    {
156    };
157};
158
159}} // namespace detail::variant
160} // namespace boost
161
162#endif // BOOST_VARIANT_DETAIL_ENABLE_RECURSIVE_HPP
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