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295 lines
8.6 KiB
295 lines
8.6 KiB
//----------------------------------------------------------------------------- |
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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/assert.hpp" |
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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/variant/detail/has_nothrow_move.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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# define BOOST_VARIANT_VISITATION_UNROLLING_LIMIT \ |
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BOOST_VARIANT_LIMIT_TYPES |
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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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#if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |
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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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#else // defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION) |
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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::eval_if< |
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is_same<Iter, LastIter> |
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, mpl::identity<apply_visitor_unrolled> |
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, Iter |
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>::type type; |
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typedef typename mpl::eval_if< |
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is_same<type, apply_visitor_unrolled> //is_same<Iter, LastIter> |
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, mpl::identity<LastIter> |
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, mpl::next<Iter> |
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>::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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#endif // BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION workaround |
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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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, has_nothrow_move_constructor<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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BOOST_ASSERT(false); |
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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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BOOST_ASSERT(false); |
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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: BOOST_ASSERT(!"Boost.Variant internal error: 'which' out of range."); |
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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 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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