source: NonGTP/Boost/boost/variant/visitor_ptr.hpp @ 857

Revision 857, 3.0 KB checked in by igarcia, 19 years ago (diff)
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[857]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/type_traits/add_reference.hpp"
22#include "boost/type_traits/is_reference.hpp"
23#include "boost/type_traits/is_void.hpp"
24
25namespace boost {
26
27//////////////////////////////////////////////////////////////////////////
28// function template visitor_ptr
29//
30// Adapts a function pointer for use as visitor capable of handling
31// values of a single type. Throws bad_visit if inappropriately applied.
32//
33template <typename T, typename R>
34class visitor_ptr_t
35    : public static_visitor<R>
36{
37private: // representation
38
39    typedef R (*visitor_t)(T);
40
41    visitor_t visitor_;
42
43public: // typedefs
44
45    typedef R result_type;
46
47private: // private typedefs
48
49    typedef typename mpl::eval_if<
50          is_reference<T>
51        , mpl::identity<T>
52        , add_reference<const T>
53        >::type argument_fwd_type;
54
55public: // structors
56
57    explicit visitor_ptr_t(visitor_t visitor)
58      : visitor_(visitor)
59    {
60    }
61
62public: // static visitor interfaces
63
64    template <typename U>
65    result_type operator()(const U&) const
66    {
67        throw bad_visit();
68    }
69
70#if !defined(BOOST_NO_VOID_RETURNS)
71
72public: // static visitor interfaces, cont.
73
74    result_type operator()(argument_fwd_type operand) const
75    {
76        return visitor_(operand);
77    }
78
79#else // defined(BOOST_NO_VOID_RETURNS)
80
81private: // helpers, for static visitor interfaces (below)
82
83    result_type execute_impl(argument_fwd_type operand, mpl::false_) const
84    {
85        return visitor_(operand);
86    }
87
88        BOOST_VARIANT_AUX_RETURN_VOID_TYPE
89    execute_impl(argument_fwd_type operand, mpl::true_) const
90    {
91        visitor_(operand);
92        BOOST_VARIANT_AUX_RETURN_VOID;
93    }
94
95public: // static visitor interfaces, cont.
96
97        BOOST_VARIANT_AUX_GENERIC_RESULT_TYPE(result_type)
98    operator()(argument_fwd_type operand) const
99    {
100        typedef typename is_void<result_type>::type has_void_result;
101        return execute_impl(operand, has_void_result());
102    }
103
104#endif // BOOST_NO_VOID_RETURNS workaround
105
106};
107
108template <typename R, typename T>
109inline visitor_ptr_t<T,R> visitor_ptr(R (*visitor)(T))
110{
111    return visitor_ptr_t<T,R>(visitor);
112}
113
114} // namespace boost
115
116#endif// BOOST_VISITOR_VISITOR_PTR_HPP
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