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323 lines
12 KiB
C++
323 lines
12 KiB
C++
//-----------------------------------------------------------------------------
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// boost variant/variant_fwd.hpp header file
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// See http://www.boost.org for updates, documentation, and revision history.
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//-----------------------------------------------------------------------------
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//
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// Copyright (c) 2003 Eric Friedman, Itay Maman
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// Copyright (c) 2013-2019 Antony Polukhin
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_VARIANT_VARIANT_FWD_HPP
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#define BOOST_VARIANT_VARIANT_FWD_HPP
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#include <boost/variant/detail/config.hpp>
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#include <boost/blank_fwd.hpp>
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#include <boost/mpl/arg.hpp>
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#include <boost/mpl/limits/arity.hpp>
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#include <boost/mpl/aux_/na.hpp>
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#include <boost/preprocessor/cat.hpp>
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#include <boost/preprocessor/enum.hpp>
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#include <boost/preprocessor/enum_params.hpp>
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#include <boost/preprocessor/enum_shifted_params.hpp>
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#include <boost/preprocessor/repeat.hpp>
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///////////////////////////////////////////////////////////////////////////////
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// macro BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT
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//
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// Defined if variant does not support make_variant_over (see below).
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//
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#if defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE)
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# define BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT
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#endif
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///////////////////////////////////////////////////////////////////////////////
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// macro BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT
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//
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// Defined if make_recursive_variant cannot be supported as documented.
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//
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// Note: Currently, MPL lambda facility is used as workaround if defined, and
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// so only types declared w/ MPL lambda workarounds will work.
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//
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#include <boost/variant/detail/substitute_fwd.hpp>
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#if defined(BOOST_VARIANT_DETAIL_NO_SUBSTITUTE) \
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&& !defined(BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT)
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# define BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT
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#endif
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///////////////////////////////////////////////////////////////////////////////
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// macro BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES
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//
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/*
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GCC before 4.0 had no variadic tempaltes;
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GCC 4.6 has incomplete implementation of variadic templates.
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MSVC2015 Update 1 has variadic templates, but they have issues.
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NOTE: Clang compiler defines __GNUC__
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*/
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#if defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES) \
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|| (!defined(__clang__) && defined(__GNUC__) && (__GNUC__ == 4) && (__GNUC_MINOR__ < 7)) \
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|| (defined(_MSC_VER) && (_MSC_VER <= 1900)) \
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|| defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE) \
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|| defined (BOOST_VARIANT_NO_TYPE_SEQUENCE_SUPPORT)
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#ifndef BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES
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# define BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES
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#endif
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#endif
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#if !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
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#include <boost/preprocessor/seq/size.hpp>
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#define BOOST_VARIANT_CLASS_OR_TYPENAME_TO_SEQ_class class)(
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#define BOOST_VARIANT_CLASS_OR_TYPENAME_TO_SEQ_typename typename)(
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#define BOOST_VARIANT_CLASS_OR_TYPENAME_TO_VARIADIC_class class...
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#define BOOST_VARIANT_CLASS_OR_TYPENAME_TO_VARIADIC_typename typename...
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#define ARGS_VARIADER_1(x) x ## N...
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#define ARGS_VARIADER_2(x) BOOST_VARIANT_CLASS_OR_TYPENAME_TO_VARIADIC_ ## x ## N
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#define BOOST_VARIANT_MAKE_VARIADIC(sequence, x) BOOST_VARIANT_MAKE_VARIADIC_I(BOOST_PP_SEQ_SIZE(sequence), x)
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#define BOOST_VARIANT_MAKE_VARIADIC_I(argscount, x) BOOST_VARIANT_MAKE_VARIADIC_II(argscount, x)
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#define BOOST_VARIANT_MAKE_VARIADIC_II(argscount, orig) ARGS_VARIADER_ ## argscount(orig)
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///////////////////////////////////////////////////////////////////////////////
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// BOOST_VARIANT_ENUM_PARAMS and BOOST_VARIANT_ENUM_SHIFTED_PARAMS
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//
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// Convenience macro for enumeration of variant params.
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// When variadic templates are available expands:
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// BOOST_VARIANT_ENUM_PARAMS(class Something) => class Something0, class... SomethingN
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// BOOST_VARIANT_ENUM_PARAMS(typename Something) => typename Something0, typename... SomethingN
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// BOOST_VARIANT_ENUM_PARAMS(Something) => Something0, SomethingN...
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// BOOST_VARIANT_ENUM_PARAMS(Something) => Something0, SomethingN...
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// BOOST_VARIANT_ENUM_SHIFTED_PARAMS(class Something) => class... SomethingN
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// BOOST_VARIANT_ENUM_SHIFTED_PARAMS(typename Something) => typename... SomethingN
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// BOOST_VARIANT_ENUM_SHIFTED_PARAMS(Something) => SomethingN...
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// BOOST_VARIANT_ENUM_SHIFTED_PARAMS(Something) => SomethingN...
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//
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// Rationale: Cleaner, simpler code for clients of variant library. Minimal
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// code modifications to move from C++03 to C++11.
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//
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// With BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES defined
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// will be used BOOST_VARIANT_ENUM_PARAMS and BOOST_VARIANT_ENUM_SHIFTED_PARAMS from below `#else`
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//
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#define BOOST_VARIANT_ENUM_PARAMS(x) \
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x ## 0, \
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BOOST_VARIANT_MAKE_VARIADIC( (BOOST_VARIANT_CLASS_OR_TYPENAME_TO_SEQ_ ## x), x) \
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/**/
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#define BOOST_VARIANT_ENUM_SHIFTED_PARAMS(x) \
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BOOST_VARIANT_MAKE_VARIADIC( (BOOST_VARIANT_CLASS_OR_TYPENAME_TO_SEQ_ ## x), x) \
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/**/
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#else // defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
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///////////////////////////////////////////////////////////////////////////////
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// macro BOOST_VARIANT_LIMIT_TYPES
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//
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// Implementation-defined preprocessor symbol describing the actual
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// length of variant's pseudo-variadic template parameter list.
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//
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#include <boost/mpl/limits/list.hpp>
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#define BOOST_VARIANT_LIMIT_TYPES \
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BOOST_MPL_LIMIT_LIST_SIZE
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///////////////////////////////////////////////////////////////////////////////
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// macro BOOST_VARIANT_RECURSIVE_VARIANT_MAX_ARITY
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//
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// Exposes maximum allowed arity of class templates with recursive_variant
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// arguments. That is,
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// make_recursive_variant< ..., T<[1], recursive_variant_, ... [N]> >.
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//
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#include <boost/mpl/limits/arity.hpp>
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#define BOOST_VARIANT_RECURSIVE_VARIANT_MAX_ARITY \
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BOOST_MPL_LIMIT_METAFUNCTION_ARITY
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///////////////////////////////////////////////////////////////////////////////
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// macro BOOST_VARIANT_ENUM_PARAMS
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//
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// Convenience macro for enumeration of BOOST_VARIANT_LIMIT_TYPES params.
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//
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// Rationale: Cleaner, simpler code for clients of variant library.
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//
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#define BOOST_VARIANT_ENUM_PARAMS( param ) \
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BOOST_PP_ENUM_PARAMS(BOOST_VARIANT_LIMIT_TYPES, param)
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///////////////////////////////////////////////////////////////////////////////
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// macro BOOST_VARIANT_ENUM_SHIFTED_PARAMS
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//
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// Convenience macro for enumeration of BOOST_VARIANT_LIMIT_TYPES-1 params.
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//
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#define BOOST_VARIANT_ENUM_SHIFTED_PARAMS( param ) \
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BOOST_PP_ENUM_SHIFTED_PARAMS(BOOST_VARIANT_LIMIT_TYPES, param)
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#endif // BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES workaround
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namespace boost {
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namespace detail { namespace variant {
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///////////////////////////////////////////////////////////////////////////////
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// (detail) class void_ and class template convert_void
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//
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// Provides the mechanism by which void(NN) types are converted to
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// mpl::void_ (and thus can be passed to mpl::list).
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//
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// Rationale: This is particularly needed for the using-declarations
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// workaround (below), but also to avoid associating mpl namespace with
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// variant in argument dependent lookups (which used to happen because of
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// defaulting of template parameters to mpl::void_).
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//
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struct void_;
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template <typename T>
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struct convert_void
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{
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typedef T type;
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};
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template <>
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struct convert_void< void_ >
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{
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typedef mpl::na type;
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};
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///////////////////////////////////////////////////////////////////////////////
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// (workaround) BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE
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//
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// Needed to work around compilers that don't support using-declaration
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// overloads. (See the variant::initializer workarounds below.)
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//
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#if defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE)
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// (detail) tags voidNN -- NN defined on [0, BOOST_VARIANT_LIMIT_TYPES)
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//
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// Defines void types that are each unique and specializations of
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// convert_void that yields mpl::na for each voidNN type.
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//
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#define BOOST_VARIANT_DETAIL_DEFINE_VOID_N(z,N,_) \
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struct BOOST_PP_CAT(void,N); \
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\
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template <> \
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struct convert_void< BOOST_PP_CAT(void,N) > \
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{ \
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typedef mpl::na type; \
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}; \
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/**/
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BOOST_PP_REPEAT(
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BOOST_VARIANT_LIMIT_TYPES
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, BOOST_VARIANT_DETAIL_DEFINE_VOID_N
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, _
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)
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#undef BOOST_VARIANT_DETAIL_DEFINE_VOID_N
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#endif // BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE workaround
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}} // namespace detail::variant
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#if !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
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# define BOOST_VARIANT_AUX_DECLARE_PARAMS BOOST_VARIANT_ENUM_PARAMS(typename T)
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#else // defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
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///////////////////////////////////////////////////////////////////////////////
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// (detail) macro BOOST_VARIANT_AUX_DECLARE_PARAM
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//
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// Template parameter list for variant and recursive_variant declarations.
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//
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#if !defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE)
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# define BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL(z, N, T) \
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typename BOOST_PP_CAT(T,N) = detail::variant::void_ \
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/**/
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#else // defined(BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE)
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# define BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL(z, N, T) \
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typename BOOST_PP_CAT(T,N) = BOOST_PP_CAT(detail::variant::void,N) \
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/**/
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#endif // BOOST_NO_USING_DECLARATION_OVERLOADS_FROM_TYPENAME_BASE workaround
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#define BOOST_VARIANT_AUX_DECLARE_PARAMS \
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BOOST_PP_ENUM( \
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BOOST_VARIANT_LIMIT_TYPES \
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, BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL \
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, T \
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) \
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/**/
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#endif // BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES workaround
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///////////////////////////////////////////////////////////////////////////////
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// class template variant (concept inspired by Andrei Alexandrescu)
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//
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// Efficient, type-safe bounded discriminated union.
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//
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// Preconditions:
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// - Each type must be unique.
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// - No type may be const-qualified.
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//
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// Proper declaration form:
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// variant<types> (where types is a type-sequence)
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// or
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// variant<T0,T1,...,Tn> (where T0 is NOT a type-sequence)
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//
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template < BOOST_VARIANT_AUX_DECLARE_PARAMS > class variant;
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///////////////////////////////////////////////////////////////////////////////
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// metafunction make_recursive_variant
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//
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// Exposes a boost::variant with recursive_variant_ tags (below) substituted
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// with the variant itself (wrapped as needed with boost::recursive_wrapper).
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//
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template < BOOST_VARIANT_AUX_DECLARE_PARAMS > struct make_recursive_variant;
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#undef BOOST_VARIANT_AUX_DECLARE_PARAMS_IMPL
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#undef BOOST_VARIANT_AUX_DECLARE_PARAMS
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///////////////////////////////////////////////////////////////////////////////
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// type recursive_variant_
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//
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// Tag type indicates where recursive variant substitution should occur.
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//
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#if !defined(BOOST_VARIANT_NO_FULL_RECURSIVE_VARIANT_SUPPORT)
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struct recursive_variant_ {};
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#else
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typedef mpl::arg<1> recursive_variant_;
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#endif
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///////////////////////////////////////////////////////////////////////////////
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// metafunction make_variant_over
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//
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// Result is a variant w/ types of the specified type sequence.
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//
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template <typename Types> struct make_variant_over;
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///////////////////////////////////////////////////////////////////////////////
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// metafunction make_recursive_variant_over
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//
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// Result is a recursive variant w/ types of the specified type sequence.
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//
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template <typename Types> struct make_recursive_variant_over;
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} // namespace boost
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#endif // BOOST_VARIANT_VARIANT_FWD_HPP
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