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145 lines
4.8 KiB
C++
145 lines
4.8 KiB
C++
//-----------------------------------------------------------------------------
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// boost variant/detail/apply_visitor_unary.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) 2002-2003 Eric Friedman
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// Copyright (c) 2014-2019 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_DETAIL_APPLY_VISITOR_UNARY_HPP
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#define BOOST_VARIANT_DETAIL_APPLY_VISITOR_UNARY_HPP
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#include <boost/config.hpp>
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#include <boost/move/utility.hpp>
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#if !defined(BOOST_NO_CXX14_DECLTYPE_AUTO) && !defined(BOOST_NO_CXX11_DECLTYPE_N3276)
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# include <boost/mpl/distance.hpp>
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# include <boost/mpl/advance.hpp>
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# include <boost/mpl/deref.hpp>
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# include <boost/mpl/size.hpp>
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# include <boost/utility/declval.hpp>
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# include <boost/core/enable_if.hpp>
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# include <boost/type_traits/copy_cv_ref.hpp>
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# include <boost/type_traits/remove_reference.hpp>
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# include <boost/variant/detail/has_result_type.hpp>
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#endif
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namespace boost {
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//////////////////////////////////////////////////////////////////////////
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// function template apply_visitor(visitor, visitable)
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//
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// Visits visitable with visitor.
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//
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//
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// nonconst-visitor version:
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//
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#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
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template <typename Visitor, typename Visitable>
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inline typename Visitor::result_type
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apply_visitor(Visitor& visitor, Visitable&& visitable)
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{
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return ::boost::forward<Visitable>(visitable).apply_visitor(visitor);
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}
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#else
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template <typename Visitor, typename Visitable>
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inline typename Visitor::result_type
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apply_visitor(Visitor& visitor, Visitable& visitable)
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{
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return visitable.apply_visitor(visitor);
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}
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#endif
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//
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// const-visitor version:
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//
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#ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
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template <typename Visitor, typename Visitable>
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inline typename Visitor::result_type
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apply_visitor(const Visitor& visitor, Visitable&& visitable)
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{
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return ::boost::forward<Visitable>(visitable).apply_visitor(visitor);
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}
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#else
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template <typename Visitor, typename Visitable>
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inline typename Visitor::result_type
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apply_visitor(const Visitor& visitor, Visitable& visitable)
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{
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return visitable.apply_visitor(visitor);
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}
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#endif
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#if !defined(BOOST_NO_CXX14_DECLTYPE_AUTO) && !defined(BOOST_NO_CXX11_DECLTYPE_N3276)
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#define BOOST_VARIANT_HAS_DECLTYPE_APPLY_VISITOR_RETURN_TYPE
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// C++14
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namespace detail { namespace variant {
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// This class serves only metaprogramming purposes. none of its methods must be called at runtime!
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template <class Visitor, class Variant>
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struct result_multideduce1 {
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typedef typename remove_reference<Variant>::type::types types;
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typedef typename boost::mpl::begin<types>::type begin_it;
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typedef typename boost::mpl::advance<
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begin_it, boost::mpl::int_<boost::mpl::size<types>::type::value - 1>
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>::type last_it;
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template <class It, class Dummy = void> // avoid explicit specialization in class scope
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struct deduce_impl {
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typedef typename boost::mpl::next<It>::type next_t;
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typedef typename boost::mpl::deref<It>::type value_t;
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typedef decltype(true ? boost::declval< Visitor& >()( boost::declval< copy_cv_ref_t< value_t, Variant > >() )
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: boost::declval< typename deduce_impl<next_t>::type >()) type;
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};
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template <class Dummy>
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struct deduce_impl<last_it, Dummy> {
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typedef typename boost::mpl::deref<last_it>::type value_t;
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typedef decltype(boost::declval< Visitor& >()( boost::declval< copy_cv_ref_t< value_t, Variant > >() )) type;
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};
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typedef typename deduce_impl<begin_it>::type type;
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};
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template <class Visitor, class Variant>
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struct result_wrapper1
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{
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typedef typename result_multideduce1<Visitor, Variant>::type result_type;
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Visitor&& visitor_;
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explicit result_wrapper1(Visitor&& visitor) BOOST_NOEXCEPT
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: visitor_(::boost::forward<Visitor>(visitor))
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{}
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template <class T>
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result_type operator()(T&& val) const {
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return visitor_(::boost::forward<T>(val));
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}
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};
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}} // namespace detail::variant
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template <typename Visitor, typename Visitable>
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inline decltype(auto) apply_visitor(Visitor&& visitor, Visitable&& visitable,
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typename boost::disable_if<
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boost::detail::variant::has_result_type<Visitor>
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>::type* = 0)
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{
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boost::detail::variant::result_wrapper1<Visitor, Visitable> cpp14_vis(::boost::forward<Visitor>(visitor));
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return ::boost::forward<Visitable>(visitable).apply_visitor(cpp14_vis);
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}
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#endif // !defined(BOOST_NO_CXX14_DECLTYPE_AUTO) && !defined(BOOST_NO_CXX11_DECLTYPE_N3276)
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} // namespace boost
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#endif // BOOST_VARIANT_DETAIL_APPLY_VISITOR_UNARY_HPP
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