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1 | //----------------------------------------------------------------------------- |
2 | // boost variant/visitor_ptr.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_VISITOR_PTR_HPP | |
14 | #define BOOST_VARIANT_VISITOR_PTR_HPP | |
15 | ||
16 | #include <boost/variant/bad_visit.hpp> | |
17 | #include <boost/variant/static_visitor.hpp> | |
18 | ||
19 | #include <boost/mpl/eval_if.hpp> | |
20 | #include <boost/mpl/identity.hpp> | |
21 | #include <boost/throw_exception.hpp> | |
22 | #include <boost/type_traits/add_reference.hpp> | |
23 | #include <boost/type_traits/is_reference.hpp> | |
24 | #include <boost/type_traits/is_void.hpp> | |
25 | ||
26 | namespace boost { | |
27 | ||
28 | ////////////////////////////////////////////////////////////////////////// | |
29 | // function template visitor_ptr | |
30 | // | |
31 | // Adapts a function pointer for use as visitor capable of handling | |
32 | // values of a single type. Throws bad_visit if inappropriately applied. | |
33 | // | |
34 | template <typename T, typename R> | |
35 | class visitor_ptr_t | |
36 | : public static_visitor<R> | |
37 | { | |
38 | private: // representation | |
39 | ||
40 | typedef R (*visitor_t)(T); | |
41 | ||
42 | visitor_t visitor_; | |
43 | ||
44 | public: // typedefs | |
45 | ||
46 | typedef R result_type; | |
47 | ||
48 | private: // private typedefs | |
49 | ||
50 | typedef typename mpl::eval_if< | |
51 | is_reference<T> | |
52 | , mpl::identity<T> | |
53 | , add_reference<const T> | |
54 | >::type argument_fwd_type; | |
55 | ||
56 | public: // structors | |
57 | ||
58 | explicit visitor_ptr_t(visitor_t visitor) BOOST_NOEXCEPT | |
59 | : visitor_(visitor) | |
60 | { | |
61 | } | |
62 | ||
63 | public: // static visitor interfaces | |
64 | ||
65 | template <typename U> | |
66 | result_type operator()(const U&) const | |
67 | { | |
68 | boost::throw_exception(bad_visit()); | |
69 | } | |
70 | ||
71 | #if !defined(BOOST_NO_VOID_RETURNS) | |
72 | ||
73 | public: // static visitor interfaces, cont. | |
74 | ||
75 | result_type operator()(argument_fwd_type operand) const | |
76 | { | |
77 | return visitor_(operand); | |
78 | } | |
79 | ||
80 | #else // defined(BOOST_NO_VOID_RETURNS) | |
81 | ||
82 | private: // helpers, for static visitor interfaces (below) | |
83 | ||
84 | result_type execute_impl(argument_fwd_type operand, mpl::false_) const | |
85 | { | |
86 | return visitor_(operand); | |
87 | } | |
88 | ||
89 | BOOST_VARIANT_AUX_RETURN_VOID_TYPE | |
90 | execute_impl(argument_fwd_type operand, mpl::true_) const | |
91 | { | |
92 | visitor_(operand); | |
93 | BOOST_VARIANT_AUX_RETURN_VOID; | |
94 | } | |
95 | ||
96 | public: // static visitor interfaces, cont. | |
97 | ||
98 | BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type) | |
99 | operator()(argument_fwd_type operand) const | |
100 | { | |
101 | typedef typename is_void<result_type>::type has_void_result; | |
102 | return execute_impl(operand, has_void_result()); | |
103 | } | |
104 | ||
105 | #endif // BOOST_NO_VOID_RETURNS workaround | |
106 | ||
107 | }; | |
108 | ||
109 | template <typename R, typename T> | |
110 | inline visitor_ptr_t<T,R> visitor_ptr(R (*visitor)(T)) | |
111 | { | |
112 | return visitor_ptr_t<T,R>(visitor); | |
113 | } | |
114 | ||
115 | } // namespace boost | |
116 | ||
117 | #endif// BOOST_VISITOR_VISITOR_PTR_HPP |