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1 | /*! |
2 | @file | |
3 | Defines `boost::hana::Constant`. | |
4 | ||
5 | @copyright Louis Dionne 2013-2016 | |
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_CONCEPT_CONSTANT_HPP | |
11 | #define BOOST_HANA_CONCEPT_CONSTANT_HPP | |
12 | ||
13 | #include <boost/hana/fwd/concept/constant.hpp> | |
14 | ||
15 | #include <boost/hana/config.hpp> | |
16 | #include <boost/hana/core/default.hpp> | |
17 | #include <boost/hana/core/tag_of.hpp> | |
18 | #include <boost/hana/value.hpp> | |
19 | ||
20 | ||
21 | BOOST_HANA_NAMESPACE_BEGIN | |
22 | template <typename C> | |
23 | struct Constant { | |
24 | using Tag = typename tag_of<C>::type; | |
25 | static constexpr bool value = !is_default<value_impl<Tag>>::value; | |
26 | }; | |
27 | BOOST_HANA_NAMESPACE_END | |
28 | ||
29 | #endif // !BOOST_HANA_CONCEPT_CONSTANT_HPP |