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