/Src/Dependencies/Boost/boost/variant/variant_fwd.hpp

  1//-----------------------------------------------------------------------------
  2// boost variant/variant_fwd.hpp header file
  3// See http://www.boost.org for updates, documentation, and revision history.
  4//-----------------------------------------------------------------------------
  5//
  6// Copyright (c) 2003
  7// Eric Friedman, Itay Maman
  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_VARIANT_FWD_HPP
 14#define BOOST_VARIANT_VARIANT_FWD_HPP
 15
 16#include "boost/variant/detail/config.hpp"
 17
 18#include "boost/blank_fwd.hpp"
 19#include "boost/mpl/arg.hpp"
 20#include "boost/mpl/limits/arity.hpp"
 21#include "boost/mpl/aux_/na.hpp"
 22#include "boost/preprocessor/cat.hpp"
 23#include "boost/preprocessor/enum.hpp"
 24#include "boost/preprocessor/enum_params.hpp"
 25#include "boost/preprocessor/enum_shifted_params.hpp"
 26#include "boost/preprocessor/repeat.hpp"
 27
 28///////////////////////////////////////////////////////////////////////////////
 29// macro BOOST_VARIANT_LIMIT_TYPES
 30//
 31// Implementation-defined preprocessor symbol describing the actual
 32// length of variant's pseudo-variadic template parameter list.
 33//
 34#include "boost/mpl/limits/list.hpp"
 35#define BOOST_VARIANT_LIMIT_TYPES \
 36    BOOST_MPL_LIMIT_LIST_SIZE
 37
 38///////////////////////////////////////////////////////////////////////////////
 39// macro BOOST_VARIANT_NO_REFERENCE_SUPPORT
 40//
 41// Defined if variant does not support references as bounded types. 
 42//
 43#if defined(BOOST_VARIANT_AUX_BROKEN_CONSTRUCTOR_TEMPLATE_ORDERING) \
 44 && !defined(BOOST_VARIANT_AUX_HAS_CONSTRUCTOR_TEMPLATE_ORDERING_SFINAE_WKND) \
 45 && !defined(BOOST_VARIANT_NO_REFERENCE_SUPPORT)
 46#   define BOOST_VARIANT_NO_REFERENCE_SUPPORT
 47#endif
 48
 49///////////////////////////////////////////////////////////////////////////////
 50// macro BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT
 51//
 52// Defined if variant does not support make_variant_over (see below). 
 53//
 54#if defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE)
 55#   define BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT
 56#endif
 57
 58///////////////////////////////////////////////////////////////////////////////
 59// macro BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT
 60//
 61// Defined if make_recursive_variant cannot be supported as documented.
 62//
 63// Note: Currently, MPL lambda facility is used as workaround if defined, and
 64// so only types declared w/ MPL lambda workarounds will work.
 65//
 66
 67#include "boost/variant/detail/substitute_fwd.hpp"
 68
 69#if defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE) \
 70 && !defined(BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT)
 71#   define BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT
 72#endif
 73
 74///////////////////////////////////////////////////////////////////////////////
 75// macro BOOST_VARIANT_RECURSIVE_VARIANT_MAX_ARITY
 76//
 77// Exposes maximum allowed arity of class templates with recursive_variant
 78// arguments. That is,
 79//   make_recursive_variant< ..., T<[1], recursive_variant_, ... [N]> >.
 80//
 81#include "boost/mpl/limits/arity.hpp"
 82#define BOOST_VARIANT_RECURSIVE_VARIANT_MAX_ARITY \
 83    BOOST_MPL_LIMIT_METAFUNCTION_ARITY
 84
 85///////////////////////////////////////////////////////////////////////////////
 86// macro BOOST_VARIANT_ENUM_PARAMS
 87//
 88// Convenience macro for enumeration of BOOST_VARIANT_LIMIT_TYPES params.
 89//
 90// Rationale: Cleaner, simpler code for clients of variant library.
 91//
 92#define BOOST_VARIANT_ENUM_PARAMS( param )  \
 93    BOOST_PP_ENUM_PARAMS(BOOST_VARIANT_LIMIT_TYPES, param)
 94
 95///////////////////////////////////////////////////////////////////////////////
 96// macro BOOST_VARIANT_ENUM_SHIFTED_PARAMS
 97//
 98// Convenience macro for enumeration of BOOST_VARIANT_LIMIT_TYPES-1 params.
 99//
100#define BOOST_VARIANT_ENUM_SHIFTED_PARAMS( param )  \
101    BOOST_PP_ENUM_SHIFTED_PARAMS(BOOST_VARIANT_LIMIT_TYPES, param)
102
103
104namespace boost {
105
106namespace detail { namespace variant {
107
108///////////////////////////////////////////////////////////////////////////////
109// (detail) class void_ and class template convert_void
110// 
111// Provides the mechanism by which void(NN) types are converted to
112// mpl::void_ (and thus can be passed to mpl::list).
113//
114// Rationale: This is particularly needed for the using-declarations
115// workaround (below), but also to avoid associating mpl namespace with
116// variant in argument dependent lookups (which used to happen because of
117// defaulting of template parameters to mpl::void_).
118//
119
120struct void_;
121
122template <typename T>
123struct convert_void
124{
125    typedef T type;
126};
127
128template <>
129struct convert_void< void_ >
130{
131    typedef mpl::na type;
132};
133
134///////////////////////////////////////////////////////////////////////////////
135// (workaround) BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE
136//
137// Needed to work around compilers that don't support using-declaration
138// overloads. (See the variant::initializer workarounds below.)
139//
140
141#if defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE)
142
143// (detail) tags voidNN -- NN defined on [0, BOOST_VARIANT_LIMIT_TYPES)
144//
145// Defines void types that are each unique and specializations of
146// convert_void that yields mpl::na for each voidNN type.
147//
148
149#define BOOST_VARIANT_DETAIL_DEFINE_VOID_N(z,N,_)          \
150    struct BOOST_PP_CAT(void,N);                           \
151                                                           \
152    template <>                                            \
153    struct convert_void< BOOST_PP_CAT(void,N) >            \
154    {                                                      \
155        typedef mpl::na type;                              \
156    };                                                     \
157    /**/
158
159BOOST_PP_REPEAT(
160      BOOST_VARIANT_LIMIT_TYPES
161    , BOOST_VARIANT_DETAIL_DEFINE_VOID_N
162    , _
163    )
164
165#undef BOOST_VARIANT_DETAIL_DEFINE_VOID_N
166
167#endif // BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE workaround
168
169}} // namespace detail::variant
170
171///////////////////////////////////////////////////////////////////////////////
172// (detail) macro BOOST_VARIANT_AUX_DECLARE_PARAM
173//
174// Template parameter list for variant and recursive_variant declarations.
175//
176
177#if !defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE)
178
179#   define BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL(z, N, T) \
180    typename BOOST_PP_CAT(T,N) = detail::variant::void_ \
181    /**/
182
183#else // defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE)
184
185#   define BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL(z, N, T) \
186    typename BOOST_PP_CAT(T,N) = BOOST_PP_CAT(detail::variant::void,N) \
187    /**/
188
189#endif // BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE workaround
190
191#define BOOST_VARIANT_AUX_DECLARE_PARAMS \
192    BOOST_PP_ENUM( \
193          BOOST_VARIANT_LIMIT_TYPES \
194        , BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL \
195        , T \
196        ) \
197    /**/
198
199///////////////////////////////////////////////////////////////////////////////
200// class template variant (concept inspired by Andrei Alexandrescu)
201//
202// Efficient, type-safe bounded discriminated union.
203//
204// Preconditions:
205//  - Each type must be unique.
206//  - No type may be const-qualified.
207//
208// Proper declaration form:
209//   variant<types>    (where types is a type-sequence)
210// or
211//   variant<T0,T1,...,Tn>  (where T0 is NOT a type-sequence)
212//
213template < BOOST_VARIANT_AUX_DECLARE_PARAMS > class variant;
214
215///////////////////////////////////////////////////////////////////////////////
216// metafunction make_recursive_variant
217//
218// Exposes a boost::variant with recursive_variant_ tags (below) substituted
219// with the variant itself (wrapped as needed with boost::recursive_wrapper).
220//
221template < BOOST_VARIANT_AUX_DECLARE_PARAMS > struct make_recursive_variant;
222
223#undef BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL
224#undef BOOST_VARIANT_AUX_DECLARE_PARAMS
225
226///////////////////////////////////////////////////////////////////////////////
227// type recursive_variant_
228//
229// Tag type indicates where recursive variant substitution should occur.
230//
231#if !defined(BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT)
232    struct recursive_variant_ {};
233#else
234    typedef mpl::arg<1> recursive_variant_;
235#endif
236
237///////////////////////////////////////////////////////////////////////////////
238// metafunction make_variant_over
239//
240// Result is a variant w/ types of the specified type sequence.
241//
242template <typename Types> struct make_variant_over;
243
244///////////////////////////////////////////////////////////////////////////////
245// metafunction make_recursive_variant_over
246//
247// Result is a recursive variant w/ types of the specified type sequence.
248//
249template <typename Types> struct make_recursive_variant_over;
250
251} // namespace boost
252
253#endif // BOOST_VARIANT_VARIANT_FWD_HPP