1//-----------------------------------------------------------------------------
2// boost variant/detail/apply_visitor_delayed.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_DETAIL_APPLY_VISITOR_DELAYED_HPP
14#define BOOST_VARIANT_DETAIL_APPLY_VISITOR_DELAYED_HPP
15
16#include <boost/variant/detail/apply_visitor_unary.hpp>
17#include <boost/variant/detail/apply_visitor_binary.hpp>
18#include <boost/variant/variant_fwd.hpp> // for BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES
19
20
21#include <boost/variant/detail/has_result_type.hpp>
22#include <boost/core/enable_if.hpp>
23
24namespace boost {
25
26//////////////////////////////////////////////////////////////////////////
27// function template apply_visitor(visitor)
28//
29// Returns a function object, overloaded for unary and binary usage, that
30// visits its arguments using visitor (or a copy of visitor) via
31// * apply_visitor( visitor, [argument] )
32// under unary invocation, or
33// * apply_visitor( visitor, [argument1], [argument2] )
34// under binary invocation.
35//
36// NOTE: Unlike other apply_visitor forms, the visitor object must be
37// non-const; this prevents user from giving temporary, to disastrous
38// effect (i.e., returned function object would have dead reference).
39//
40
41template <typename Visitor>
42class apply_visitor_delayed_t
43{
44public: // visitor typedefs
45
46 typedef typename Visitor::result_type
47 result_type;
48
49private: // representation
50
51 Visitor& visitor_;
52
53public: // structors
54
55 explicit apply_visitor_delayed_t(Visitor& visitor) BOOST_NOEXCEPT
56 : visitor_(visitor)
57 {
58 }
59
60#if !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
61
62public: // N-ary visitor interface
63 template <typename... Visitables>
64 result_type operator()(Visitables&... visitables) const
65 {
66 return apply_visitor(visitor_, visitables...);
67 }
68
69#else // !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
70
71public: // unary visitor interface
72
73 template <typename Visitable>
74 result_type operator()(Visitable& visitable) const
75 {
76 return apply_visitor(visitor_, visitable);
77 }
78
79public: // binary visitor interface
80
81 template <typename Visitable1, typename Visitable2>
82 result_type operator()(Visitable1& visitable1, Visitable2& visitable2) const
83 {
84 return apply_visitor(visitor_, visitable1, visitable2);
85 }
86
87#endif // !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
88
89private:
90 apply_visitor_delayed_t& operator=(const apply_visitor_delayed_t&);
91
92};
93
94template <typename Visitor>
95inline typename boost::enable_if<
96 boost::detail::variant::has_result_type<Visitor>,
97 apply_visitor_delayed_t<Visitor>
98 >::type apply_visitor(Visitor& visitor)
99{
100 return apply_visitor_delayed_t<Visitor>(visitor);
101}
102
103#if !defined(BOOST_NO_CXX14_DECLTYPE_AUTO) && !defined(BOOST_NO_CXX11_DECLTYPE_N3276) \
104 && !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
105
106template <typename Visitor>
107class apply_visitor_delayed_cpp14_t
108{
109private: // representation
110 Visitor& visitor_;
111
112public: // structors
113
114 explicit apply_visitor_delayed_cpp14_t(Visitor& visitor) BOOST_NOEXCEPT
115 : visitor_(visitor)
116 {
117 }
118
119public: // N-ary visitor interface
120 template <typename... Visitables>
121 decltype(auto) operator()(Visitables&... visitables) const
122 {
123 return apply_visitor(visitor_, visitables...);
124 }
125
126private:
127 apply_visitor_delayed_cpp14_t& operator=(const apply_visitor_delayed_cpp14_t&);
128
129};
130
131template <typename Visitor>
132inline typename boost::disable_if<
133 boost::detail::variant::has_result_type<Visitor>,
134 apply_visitor_delayed_cpp14_t<Visitor>
135 >::type apply_visitor(Visitor& visitor)
136{
137 return apply_visitor_delayed_cpp14_t<Visitor>(visitor);
138}
139
140#endif // !defined(BOOST_NO_CXX14_DECLTYPE_AUTO) && !defined(BOOST_NO_CXX11_DECLTYPE_N3276)
141 // && !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)
142
143
144} // namespace boost
145
146#endif // BOOST_VARIANT_DETAIL_APPLY_VISITOR_DELAYED_HPP
147