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2 | // (C) Copyright John Maddock 2015. | |
3 | // Use, modification and distribution are subject to the Boost Software License, | |
4 | // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at | |
5 | // http://www.boost.org/LICENSE_1_0.txt). | |
6 | // | |
7 | // See http://www.boost.org/libs/type_traits for most recent version including documentation. | |
8 | ||
9 | #ifndef BOOST_TT_IS_ASSIGNABLE_HPP_INCLUDED | |
10 | #define BOOST_TT_IS_ASSIGNABLE_HPP_INCLUDED | |
11 | ||
12 | #include <cstddef> // size_t | |
13 | #include <boost/type_traits/integral_constant.hpp> | |
14 | #include <boost/detail/workaround.hpp> | |
15 | ||
16 | namespace boost{ | |
17 | ||
18 | template <class T, class U = T> struct is_assignable; | |
19 | ||
20 | } | |
21 | ||
22 | #if !defined(BOOST_NO_CXX11_DECLTYPE) && !BOOST_WORKAROUND(BOOST_MSVC, < 1800) | |
23 | ||
24 | #include <boost/type_traits/detail/yes_no_type.hpp> | |
25 | #include <boost/type_traits/declval.hpp> | |
26 | ||
27 | namespace boost{ | |
28 | ||
29 | namespace detail{ | |
30 | ||
31 | struct is_assignable_imp | |
32 | { | |
33 | template<typename T, typename U, typename = decltype(boost::declval<T>() = boost::declval<U>())> | |
34 | static boost::type_traits::yes_type test(int); | |
35 | ||
36 | template<typename, typename> | |
37 | static boost::type_traits::no_type test(...); | |
38 | }; | |
39 | ||
40 | } | |
41 | ||
42 | template <class T, class U> struct is_assignable : public integral_constant<bool, sizeof(detail::is_assignable_imp::test<T, U>(0)) == sizeof(boost::type_traits::yes_type)>{}; | |
43 | template <class T, std::size_t N, class U> struct is_assignable<T[N], U> : public is_assignable<T, U>{}; | |
44 | template <class T, std::size_t N, class U> struct is_assignable<T(&)[N], U> : public is_assignable<T&, U>{}; | |
45 | template <class T, class U> struct is_assignable<T[], U> : public is_assignable<T, U>{}; | |
46 | template <class T, class U> struct is_assignable<T(&)[], U> : public is_assignable<T&, U>{}; | |
47 | template <class U> struct is_assignable<void, U> : public integral_constant<bool, false>{}; | |
48 | template <class U> struct is_assignable<void const, U> : public integral_constant<bool, false>{}; | |
49 | template <class U> struct is_assignable<void volatile, U> : public integral_constant<bool, false>{}; | |
50 | template <class U> struct is_assignable<void const volatile, U> : public integral_constant<bool, false>{}; | |
51 | ||
52 | #else | |
53 | ||
54 | #include <boost/type_traits/has_trivial_assign.hpp> | |
55 | #include <boost/type_traits/remove_reference.hpp> | |
56 | ||
57 | namespace boost{ | |
58 | ||
59 | // We don't know how to implement this: | |
60 | template <class T, class U> struct is_assignable : public integral_constant<bool, false>{}; | |
61 | template <class T, class U> struct is_assignable<T&, U> : public integral_constant<bool, is_pod<T>::value && is_pod<typename remove_reference<U>::type>::value>{}; | |
62 | template <class T, class U> struct is_assignable<const T&, U> : public integral_constant<bool, false>{}; | |
63 | template <class U> struct is_assignable<void, U> : public integral_constant<bool, false>{}; | |
64 | template <class U> struct is_assignable<void const, U> : public integral_constant<bool, false>{}; | |
65 | template <class U> struct is_assignable<void volatile, U> : public integral_constant<bool, false>{}; | |
66 | template <class U> struct is_assignable<void const volatile, U> : public integral_constant<bool, false>{}; | |
67 | /* | |
68 | template <> struct is_assignable<void, void> : public integral_constant<bool, false>{}; | |
69 | template <> struct is_assignable<void const, void const> : public integral_constant<bool, false>{}; | |
70 | template <> struct is_assignable<void volatile, void volatile> : public integral_constant<bool, false>{}; | |
71 | template <> struct is_assignable<void const volatile, void const volatile> : public integral_constant<bool, false>{}; | |
72 | */ | |
73 | #endif | |
74 | ||
75 | } // namespace boost | |
76 | ||
77 | #endif // BOOST_TT_IS_ASSIGNABLE_HPP_INCLUDED |