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
26namespace 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//
34template <typename T, typename R>
35class visitor_ptr_t
36 : public static_visitor<R>
37{
38private: // representation
39
40 typedef R (*visitor_t)(T);
41
42 visitor_t visitor_;
43
44public: // typedefs
45
46 typedef R result_type;
47
48private: // 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
56public: // structors
57
58 explicit visitor_ptr_t(visitor_t visitor) BOOST_NOEXCEPT
59 : visitor_(visitor)
60 {
61 }
62
63public: // static visitor interfaces
64
65 template <typename U>
66 result_type operator()(const U&) const
67 {
68 boost::throw_exception(e: bad_visit());
69 }
70
71public: // static visitor interfaces, cont.
72
73 result_type operator()(argument_fwd_type operand) const
74 {
75 return visitor_(operand);
76 }
77
78};
79
80template <typename R, typename T>
81inline visitor_ptr_t<T,R> visitor_ptr(R (*visitor)(T))
82{
83 return visitor_ptr_t<T,R>(visitor);
84}
85
86} // namespace boost
87
88#endif// BOOST_VISITOR_VISITOR_PTR_HPP
89