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97 lines
2.5 KiB
97 lines
2.5 KiB
//----------------------------------------------------------------------------- |
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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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#if BOOST_WORKAROUND(BOOST_MSVC, < 1300) |
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# include "boost/type_traits/is_same.hpp" |
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#endif |
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// should be the last #include |
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#include "boost/type_traits/detail/bool_trait_def.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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static_visitor() { } |
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~static_visitor() { } |
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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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BOOST_TT_AUX_BOOL_TRAIT_DEF1( |
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is_static_visitor |
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, T |
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, (::boost::detail::is_static_visitor_impl<T>::value) |
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) |
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} // namespace boost |
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#include "boost/type_traits/detail/bool_trait_undef.hpp" |
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#endif // BOOST_VARIANT_STATIC_VISITOR_HPP
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