| 1 | //----------------------------------------------------------------------------- |
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| 2 | // boost variant/static_visitor.hpp header file |
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| 3 | // See http://www.boost.org for updates, documentation, and revision history. |
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| 4 | //----------------------------------------------------------------------------- |
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| 5 | // |
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| 6 | // Copyright (c) 2002-2003 |
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| 7 | // Eric Friedman |
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| 8 | // |
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| 9 | // Distributed under the Boost Software License, Version 1.0. (See |
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| 10 | // accompanying file LICENSE_1_0.txt or copy at |
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| 11 | // http://www.boost.org/LICENSE_1_0.txt) |
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| 12 | |
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| 13 | #ifndef BOOST_VARIANT_STATIC_VISITOR_HPP |
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| 14 | #define BOOST_VARIANT_STATIC_VISITOR_HPP |
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| 15 | |
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| 16 | #include <boost/config.hpp> |
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| 17 | #include <boost/detail/workaround.hpp> |
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| 18 | |
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| 19 | #include <boost/mpl/if.hpp> |
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| 20 | #include <boost/type_traits/is_base_and_derived.hpp> |
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| 21 | |
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| 22 | #include <boost/type_traits/integral_constant.hpp> |
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| 23 | #include <boost/mpl/aux_/lambda_support.hpp> |
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| 24 | |
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| 25 | namespace boost { |
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| 26 | |
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| 27 | ////////////////////////////////////////////////////////////////////////// |
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| 28 | // class template static_visitor |
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| 29 | // |
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| 30 | // An empty base class that typedefs the return type of a deriving static |
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| 31 | // visitor. The class is analogous to std::unary_function in this role. |
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| 32 | // |
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| 33 | |
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| 34 | namespace detail { |
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| 35 | |
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| 36 | struct is_static_visitor_tag { }; |
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| 37 | |
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| 38 | typedef void static_visitor_default_return; |
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| 39 | |
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| 40 | } // namespace detail |
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| 41 | |
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| 42 | template <typename R = ::boost::detail::static_visitor_default_return> |
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| 43 | class static_visitor |
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| 44 | : public detail::is_static_visitor_tag |
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| 45 | { |
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| 46 | public: // typedefs |
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| 47 | |
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| 48 | typedef R result_type; |
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| 49 | |
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| 50 | protected: // for use as base class only |
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| 51 | #if !defined(BOOST_NO_CXX11_DEFAULTED_FUNCTIONS) && !defined(BOOST_NO_CXX11_NON_PUBLIC_DEFAULTED_FUNCTIONS) |
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| 52 | static_visitor() = default; |
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| 53 | #else |
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| 54 | static_visitor() BOOST_NOEXCEPT { } |
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| 55 | #endif |
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| 56 | }; |
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| 57 | |
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| 58 | ////////////////////////////////////////////////////////////////////////// |
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| 59 | // metafunction is_static_visitor |
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| 60 | // |
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| 61 | // Value metafunction indicates whether the specified type derives from |
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| 62 | // static_visitor<...>. |
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| 63 | // |
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| 64 | // NOTE #1: This metafunction does NOT check whether the specified type |
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| 65 | // fulfills the requirements of the StaticVisitor concept. |
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| 66 | // |
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| 67 | // NOTE #2: This template never needs to be specialized! |
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| 68 | // |
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| 69 | |
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| 70 | namespace detail { |
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| 71 | |
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| 72 | template <typename T> |
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| 73 | struct is_static_visitor_impl |
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| 74 | { |
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| 75 | BOOST_STATIC_CONSTANT(bool, value = |
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| 76 | (::boost::is_base_and_derived< |
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| 77 | detail::is_static_visitor_tag, |
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| 78 | T |
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| 79 | >::value)); |
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| 80 | }; |
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| 81 | |
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| 82 | } // namespace detail |
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| 83 | |
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| 84 | template< typename T > struct is_static_visitor |
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| 85 | : public ::boost::integral_constant<bool,(::boost::detail::is_static_visitor_impl<T>::value)> |
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| 86 | { |
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| 87 | public: |
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| 88 | BOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_static_visitor,(T)) |
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| 89 | }; |
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| 90 | |
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| 91 | } // namespace boost |
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| 92 | |
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| 93 | #endif // BOOST_VARIANT_STATIC_VISITOR_HPP |
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| 94 | |
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