1// Copyright David Abrahams 2004. Use, modification and distribution is
2// subject to the Boost Software License, Version 1.0. (See accompanying
3// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
4#ifndef IS_INCREMENTABLE_DWA200415_HPP
5# define IS_INCREMENTABLE_DWA200415_HPP
6
7# include <boost/type_traits/integral_constant.hpp>
8# include <boost/type_traits/remove_cv.hpp>
9# include <boost/detail/workaround.hpp>
10
11namespace boost { namespace detail {
12
13// is_incrementable<T> metafunction
14//
15// Requires: Given x of type T&, if the expression ++x is well-formed
16// it must have complete type; otherwise, it must neither be ambiguous
17// nor violate access.
18
19// This namespace ensures that ADL doesn't mess things up.
20namespace is_incrementable_
21{
22 // a type returned from operator++ when no increment is found in the
23 // type's own namespace
24 struct tag {};
25
26 // any soaks up implicit conversions and makes the following
27 // operator++ less-preferred than any other such operator that
28 // might be found via ADL.
29 struct any { template <class T> any(T const&); };
30
31 // This is a last-resort operator++ for when none other is found
32# if BOOST_WORKAROUND(__GNUC__, == 4) && __GNUC_MINOR__ == 0 && __GNUC_PATCHLEVEL__ == 2
33
34}
35
36namespace is_incrementable_2
37{
38 is_incrementable_::tag operator++(is_incrementable_::any const&);
39 is_incrementable_::tag operator++(is_incrementable_::any const&,int);
40}
41using namespace is_incrementable_2;
42
43namespace is_incrementable_
44{
45
46# else
47
48 tag operator++(any const&);
49 tag operator++(any const&,int);
50
51# endif
52
53# if BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3202))
54# define BOOST_comma(a,b) (a)
55# else
56 // In case an operator++ is found that returns void, we'll use ++x,0
57 tag operator,(tag,int);
58# define BOOST_comma(a,b) (a,b)
59# endif
60
61# if defined(BOOST_MSVC)
62# pragma warning(push)
63# pragma warning(disable:4913) // Warning about operator,
64# endif
65
66 // two check overloads help us identify which operator++ was picked
67 char (& check_(tag) )[2];
68
69 template <class T>
70 char check_(T const&);
71
72
73 template <class T>
74 struct impl
75 {
76 static typename boost::remove_cv<T>::type& x;
77
78 BOOST_STATIC_CONSTANT(
79 bool
80 , value = sizeof(is_incrementable_::check_(BOOST_comma(++x,0))) == 1
81 );
82 };
83
84 template <class T>
85 struct postfix_impl
86 {
87 static typename boost::remove_cv<T>::type& x;
88
89 BOOST_STATIC_CONSTANT(
90 bool
91 , value = sizeof(is_incrementable_::check_(BOOST_comma(x++,0))) == 1
92 );
93 };
94
95# if defined(BOOST_MSVC)
96# pragma warning(pop)
97# endif
98
99}
100
101# undef BOOST_comma
102
103template<typename T>
104struct is_incrementable :
105 public boost::integral_constant<bool, boost::detail::is_incrementable_::impl<T>::value>
106{
107};
108
109template<typename T>
110struct is_postfix_incrementable :
111 public boost::integral_constant<bool, boost::detail::is_incrementable_::postfix_impl<T>::value>
112{
113};
114
115} // namespace detail
116
117} // namespace boost
118
119# include <boost/type_traits/detail/bool_trait_undef.hpp>
120
121#endif // IS_INCREMENTABLE_DWA200415_HPP
122