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1 | /*! |
2 | @file | |
3 | Defines `boost::hana::tag_of` and `boost::hana::tag_of_t`. | |
4 | ||
b32b8144 | 5 | @copyright Louis Dionne 2013-2017 |
7c673cae FG |
6 | Distributed under the Boost Software License, Version 1.0. |
7 | (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) | |
8 | */ | |
9 | ||
10 | #ifndef BOOST_HANA_CORE_TAG_OF_HPP | |
11 | #define BOOST_HANA_CORE_TAG_OF_HPP | |
12 | ||
13 | #include <boost/hana/fwd/core/tag_of.hpp> | |
14 | ||
15 | #include <boost/hana/config.hpp> | |
16 | #include <boost/hana/core/when.hpp> | |
17 | ||
20effc67 TL |
18 | #include <type_traits> |
19 | ||
7c673cae | 20 | |
1e59de90 | 21 | namespace boost { namespace hana { |
7c673cae FG |
22 | //! @cond |
23 | template <typename T, typename> | |
24 | struct tag_of : tag_of<T, when<true>> { }; | |
25 | //! @endcond | |
26 | ||
27 | namespace core_detail { | |
28 | template <typename ...> | |
29 | struct is_valid { static constexpr bool value = true; }; | |
30 | } | |
31 | ||
32 | template <typename T, bool condition> | |
33 | struct tag_of<T, when<condition>> { | |
34 | using type = T; | |
35 | }; | |
36 | ||
37 | template <typename T> | |
38 | struct tag_of<T, when< | |
39 | core_detail::is_valid<typename T::hana_tag>::value | |
40 | >> { | |
41 | using type = typename T::hana_tag; | |
42 | }; | |
43 | ||
44 | template <typename T> struct tag_of<T const> : tag_of<T> { }; | |
45 | template <typename T> struct tag_of<T volatile> : tag_of<T> { }; | |
46 | template <typename T> struct tag_of<T const volatile> : tag_of<T> { }; | |
47 | template <typename T> struct tag_of<T&> : tag_of<T> { }; | |
48 | template <typename T> struct tag_of<T&&> : tag_of<T> { }; | |
20effc67 TL |
49 | |
50 | namespace detail { | |
51 | template <typename T> | |
52 | struct has_idempotent_tag | |
53 | : std::is_same<hana::tag_of_t<T>, | |
54 | std::remove_const_t<std::remove_reference_t<T>>> | |
55 | { }; | |
56 | } | |
1e59de90 | 57 | }} // end namespace boost::hana |
7c673cae FG |
58 | |
59 | #endif // !BOOST_HANA_CORE_TAG_OF_HPP |