1 /*!
2 @file
3 Defines `boost::hana::Constant`.
4 
5 @copyright Louis Dionne 2013-2017
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/detail/integral_constant.hpp>
19 #include <boost/hana/value.hpp>
20 
21 
22 BOOST_HANA_NAMESPACE_BEGIN
23     template <typename C>
24     struct Constant
25         : hana::integral_constant<bool,
26             !is_default<value_impl<typename tag_of<C>::type>>::value
27         >
28     { };
29 BOOST_HANA_NAMESPACE_END
30 
31 #endif // !BOOST_HANA_CONCEPT_CONSTANT_HPP
32