278 lines
8.4 KiB
C++
278 lines
8.4 KiB
C++
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//-----------------------------------------------------------------------------
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// boost variant/detail/visitation_impl.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
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// Eric Friedman
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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_DETAIL_VISITATION_IMPL_HPP
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#define BOOST_VARIANT_DETAIL_VISITATION_IMPL_HPP
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#include <boost/config.hpp>
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#include <boost/variant/detail/backup_holder.hpp>
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#include <boost/variant/detail/cast_storage.hpp>
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#include <boost/variant/detail/forced_return.hpp>
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#include <boost/variant/detail/generic_result_type.hpp>
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#include <boost/variant/variant_fwd.hpp> // for BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES
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#include <boost/mpl/eval_if.hpp>
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#include <boost/mpl/bool.hpp>
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#include <boost/mpl/identity.hpp>
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#include <boost/mpl/int.hpp>
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#include <boost/mpl/next.hpp>
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#include <boost/mpl/deref.hpp>
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#include <boost/mpl/or.hpp>
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#include <boost/preprocessor/cat.hpp>
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#include <boost/preprocessor/inc.hpp>
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#include <boost/preprocessor/repeat.hpp>
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#include <boost/type_traits/is_same.hpp>
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#include <boost/type_traits/has_nothrow_copy.hpp>
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#include <boost/type_traits/is_nothrow_move_constructible.hpp>
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#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
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# pragma warning (push)
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# pragma warning (disable : 4702) //unreachable code
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#endif
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///////////////////////////////////////////////////////////////////////////////
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// BOOST_VARIANT_VISITATION_UNROLLING_LIMIT
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//
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// Unrolls variant's visitation mechanism to reduce template instantiation
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// and potentially increase runtime performance. (TODO: Investigate further.)
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//
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#if !defined(BOOST_VARIANT_VISITATION_UNROLLING_LIMIT)
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#ifndef BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES
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# include <boost/mpl/limits/list.hpp>
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# define BOOST_VARIANT_VISITATION_UNROLLING_LIMIT \
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BOOST_MPL_LIMIT_LIST_SIZE
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#else
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# define BOOST_VARIANT_VISITATION_UNROLLING_LIMIT \
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BOOST_VARIANT_LIMIT_TYPES
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#endif
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#endif
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namespace boost {
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namespace detail { namespace variant {
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///////////////////////////////////////////////////////////////////////////////
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// (detail) class apply_visitor_unrolled
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//
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// Tag type indicates when visitation_impl is unrolled.
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//
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struct apply_visitor_unrolled {};
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///////////////////////////////////////////////////////////////////////////////
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// (detail) class template visitation_impl_step
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//
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// "Never ending" iterator range facilitates visitation_impl unrolling.
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//
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template <typename Iter, typename LastIter>
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struct visitation_impl_step
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{
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typedef typename mpl::deref<Iter>::type type;
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typedef typename mpl::next<Iter>::type next_iter;
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typedef visitation_impl_step<
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next_iter, LastIter
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> next;
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};
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template <typename LastIter>
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struct visitation_impl_step< LastIter,LastIter >
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{
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typedef apply_visitor_unrolled type;
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typedef visitation_impl_step next;
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};
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///////////////////////////////////////////////////////////////////////////////
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// (detail) function template visitation_impl_invoke
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//
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// Invokes the given visitor on the specified type in the given storage.
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//
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template <typename Visitor, typename VoidPtrCV, typename T>
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inline
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BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
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visitation_impl_invoke_impl(
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int, Visitor& visitor, VoidPtrCV storage, T*
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, mpl::true_// never_uses_backup
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)
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{
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return visitor.internal_visit(
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cast_storage<T>(storage), 1L
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);
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}
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template <typename Visitor, typename VoidPtrCV, typename T>
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inline
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BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
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visitation_impl_invoke_impl(
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int internal_which, Visitor& visitor, VoidPtrCV storage, T*
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, mpl::false_// never_uses_backup
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)
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{
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if (internal_which >= 0)
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{
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return visitor.internal_visit(
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cast_storage<T>(storage), 1L
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);
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}
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else
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{
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return visitor.internal_visit(
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cast_storage< backup_holder<T> >(storage), 1L
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);
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}
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}
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template <typename Visitor, typename VoidPtrCV, typename T, typename NoBackupFlag>
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inline
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BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
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visitation_impl_invoke(
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int internal_which, Visitor& visitor, VoidPtrCV storage, T* t
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, NoBackupFlag
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, int
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)
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{
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typedef typename mpl::or_<
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NoBackupFlag
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, is_nothrow_move_constructible<T>
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, has_nothrow_copy<T>
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>::type never_uses_backup;
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return (visitation_impl_invoke_impl)(
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internal_which, visitor, storage, t
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, never_uses_backup()
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);
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}
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template <typename Visitor, typename VoidPtrCV, typename NBF>
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inline
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BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
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visitation_impl_invoke(int, Visitor&, VoidPtrCV, apply_visitor_unrolled*, NBF, long)
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{
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// should never be here at runtime!
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typedef typename Visitor::result_type result_type;
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return ::boost::detail::variant::forced_return< result_type >();
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}
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///////////////////////////////////////////////////////////////////////////////
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// (detail) function template visitation_impl
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//
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// Invokes the given visitor on the type in the given variant storage.
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//
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template <
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typename W, typename S
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, typename Visitor, typename VPCV
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, typename NBF
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>
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inline
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BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
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visitation_impl(
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int, int, Visitor&, VPCV
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, mpl::true_ // is_apply_visitor_unrolled
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, NBF, W* = 0, S* = 0
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)
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{
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// should never be here at runtime!
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typedef typename Visitor::result_type result_type;
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return ::boost::detail::variant::forced_return< result_type >();
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}
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template <
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typename Which, typename step0
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, typename Visitor, typename VoidPtrCV
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, typename NoBackupFlag
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>
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inline
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BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(typename Visitor::result_type)
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visitation_impl(
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const int internal_which, const int logical_which
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, Visitor& visitor, VoidPtrCV storage
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, mpl::false_ // is_apply_visitor_unrolled
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, NoBackupFlag no_backup_flag
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, Which* = 0, step0* = 0
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)
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{
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// Typedef apply_visitor_unrolled steps and associated types...
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# define BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_TYPEDEF(z, N, _) \
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typedef typename BOOST_PP_CAT(step,N)::type BOOST_PP_CAT(T,N); \
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typedef typename BOOST_PP_CAT(step,N)::next \
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BOOST_PP_CAT(step, BOOST_PP_INC(N)); \
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/**/
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BOOST_PP_REPEAT(
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BOOST_VARIANT_VISITATION_UNROLLING_LIMIT
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, BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_TYPEDEF
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, _
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)
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# undef BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_TYPEDEF
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// ...switch on the target which-index value...
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switch (logical_which)
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{
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// ...applying the appropriate case:
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# define BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_CASE(z, N, _) \
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case (Which::value + (N)): \
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return (visitation_impl_invoke)( \
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internal_which, visitor, storage \
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, static_cast<BOOST_PP_CAT(T,N)*>(0) \
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, no_backup_flag, 1L \
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); \
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/**/
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BOOST_PP_REPEAT(
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BOOST_VARIANT_VISITATION_UNROLLING_LIMIT
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, BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_CASE
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, _
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)
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# undef BOOST_VARIANT_AUX_APPLY_VISITOR_STEP_CASE
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default: break;
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}
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// If not handled in this iteration, continue unrolling:
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typedef mpl::int_<
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Which::value + (BOOST_VARIANT_VISITATION_UNROLLING_LIMIT)
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> next_which;
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typedef BOOST_PP_CAT(step, BOOST_VARIANT_VISITATION_UNROLLING_LIMIT)
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next_step;
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typedef typename next_step::type next_type;
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typedef typename is_same< next_type,apply_visitor_unrolled >::type
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is_apply_visitor_unrolled;
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return detail::variant::visitation_impl(
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internal_which, logical_which
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, visitor, storage
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, is_apply_visitor_unrolled()
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, no_backup_flag
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, static_cast<next_which*>(0), static_cast<next_step*>(0)
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);
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}
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}} // namespace detail::variant
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} // namespace boost
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#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
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# pragma warning(pop)
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#endif
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#endif // BOOST_VARIANT_DETAIL_VISITATION_IMPL_HPP
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