1//
2// Boost.Pointer Container
3//
4// Copyright Thorsten Ottosen 2003-2005. Use, modification and
5// distribution is subject to the Boost Software License, Version
6// 1.0. (See accompanying file LICENSE_1_0.txt or copy at
7// http://www.boost.org/LICENSE_1_0.txt)
8//
9// For more information, see http://www.boost.org/libs/ptr_container/
10//
11
12
13#ifndef BOOST_INDIRECT_CONTAINER_NULLABLE_HPP
14#define BOOST_INDIRECT_CONTAINER_NULLABLE_HPP
15
16#if defined(_MSC_VER) && (_MSC_VER >= 1200)
17# pragma once
18#endif
19
20#include <boost/type_traits/detail/yes_no_type.hpp>
21#include <boost/type_traits/is_const.hpp>
22#include <boost/mpl/eval_if.hpp>
23#include <boost/mpl/identity.hpp>
24#include <boost/config.hpp>
25
26namespace boost
27{
28
29 template< class T >
30 struct nullable
31 {
32 typedef T type;
33 };
34
35 namespace ptr_container_detail
36 {
37 template< class T >
38 type_traits::yes_type is_nullable( const nullable<T>* );
39
40 type_traits::no_type is_nullable( ... );
41 }
42
43 template< class T >
44 struct is_nullable
45 {
46 private:
47 BOOST_STATIC_CONSTANT( T*, var );
48 public:
49
50#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
51#pragma warning(push)
52#pragma warning(disable:6334)
53#endif
54
55 BOOST_STATIC_CONSTANT(bool, value = sizeof( ptr_container_detail::is_nullable( var ) )
56 == sizeof( type_traits::yes_type ) );
57#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
58#pragma warning(pop)
59#endif
60
61 };
62
63 template< class T >
64 struct remove_nullable
65 {
66 typedef BOOST_DEDUCED_TYPENAME mpl::eval_if< is_nullable<T>,
67 T,
68 mpl::identity<T> >::type
69 type;
70 };
71
72 namespace ptr_container_detail
73 {
74 template< class T >
75 struct void_ptr
76 {
77 typedef BOOST_DEDUCED_TYPENAME
78 mpl::if_c< boost::is_const<
79 BOOST_DEDUCED_TYPENAME boost::remove_nullable<T>::type >::value,
80 const void*, void* >::type type;
81 };
82 }
83}
84
85#endif
86

source code of boost/libs/ptr_container/include/boost/ptr_container/nullable.hpp