96 lines
2.7 KiB
C++
96 lines
2.7 KiB
C++
//-----------------------------------------------------------------------------
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// boost variant/static_visitor.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
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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_STATIC_VISITOR_HPP
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#define BOOST_VARIANT_STATIC_VISITOR_HPP
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#include <boost/config.hpp>
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#include <boost/detail/workaround.hpp>
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#include <boost/mpl/if.hpp>
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#include <boost/type_traits/is_base_and_derived.hpp>
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#include <boost/type_traits/integral_constant.hpp>
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#include <boost/mpl/aux_/lambda_support.hpp>
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namespace boost {
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//////////////////////////////////////////////////////////////////////////
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// class template static_visitor
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//
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// An empty base class that typedefs the return type of a deriving static
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// visitor. The class is analogous to std::unary_function in this role.
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//
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namespace detail {
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struct is_static_visitor_tag { };
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typedef void static_visitor_default_return;
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} // namespace detail
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template <typename R = ::boost::detail::static_visitor_default_return>
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class static_visitor
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: public detail::is_static_visitor_tag
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{
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public: // typedefs
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typedef R result_type;
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protected: // for use as base class only
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#if !defined(BOOST_NO_CXX11_DEFAULTED_FUNCTIONS) && !defined(BOOST_NO_CXX11_NON_PUBLIC_DEFAULTED_FUNCTIONS)
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static_visitor() = default;
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~static_visitor() = default;
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#else
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static_visitor() BOOST_NOEXCEPT { }
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~static_visitor() BOOST_NOEXCEPT { }
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#endif
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};
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//////////////////////////////////////////////////////////////////////////
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// metafunction is_static_visitor
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//
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// Value metafunction indicates whether the specified type derives from
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// static_visitor<...>.
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//
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// NOTE #1: This metafunction does NOT check whether the specified type
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// fulfills the requirements of the StaticVisitor concept.
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//
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// NOTE #2: This template never needs to be specialized!
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//
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namespace detail {
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template <typename T>
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struct is_static_visitor_impl
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{
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BOOST_STATIC_CONSTANT(bool, value =
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(::boost::is_base_and_derived<
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detail::is_static_visitor_tag,
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T
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>::value));
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};
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} // namespace detail
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template< typename T > struct is_static_visitor
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: public ::boost::integral_constant<bool,(::boost::detail::is_static_visitor_impl<T>::value)>
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{
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public:
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BOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_static_visitor,(T))
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};
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} // namespace boost
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#endif // BOOST_VARIANT_STATIC_VISITOR_HPP
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