1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
|
// Copyright (C) 2019 Andrzej Krzemienski.
//
// Use, modification, and distribution is subject to the Boost Software
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/lib/optional for documentation.
//
// You are welcome to contact the author at:
// akrzemi1@gmail.com
#include "boost/optional/optional.hpp"
#ifdef BOOST_BORLANDC
#pragma hdrstop
#endif
#ifndef BOOST_OPTIONAL_DETAIL_NO_IS_CONSTRUCTIBLE_TRAIT
#ifndef BOOST_OPTIONAL_DETAIL_NO_SFINAE_FRIENDLY_CONSTRUCTORS
template <typename, typename>
struct void_t
{
typedef void type;
};
template <typename T, typename = void>
struct trait
{
};
// the following trait emulates properties std::iterator_traits
template <typename T>
struct trait<T, BOOST_DEDUCED_TYPENAME void_t<BOOST_DEDUCED_TYPENAME T::value_type,
BOOST_DEDUCED_TYPENAME boost::enable_if<boost::is_constructible<T, T&> >::type
>::type>
{
typedef BOOST_DEDUCED_TYPENAME T::value_type value_type;
};
// This class emulates the properties of std::filesystem::path
struct Path
{
#if __cplusplus >= 201103
template <typename T, typename = BOOST_DEDUCED_TYPENAME trait<T>::value_type>
Path(T const&);
#else
template <typename T>
Path(T const&, BOOST_DEDUCED_TYPENAME trait<T>::value_type* = 0);
#endif
};
#endif
#endif
int main()
{
#ifndef BOOST_OPTIONAL_DETAIL_NO_IS_CONSTRUCTIBLE_TRAIT
#ifndef BOOST_OPTIONAL_DETAIL_NO_SFINAE_FRIENDLY_CONSTRUCTORS
boost::optional<Path> optFs1;
boost::optional<Path> optFs2;
optFs1 = optFs2;
// the following still fails although it shouldn't
//BOOST_STATIC_ASSERT((std::is_copy_constructible<boost::optional<Path>>::value));
#endif
#endif
}
|
