hana/core/default.hpp

0001 /*!
0002 @file
0003 Defines `boost::hana::default_` and `boost::hana::is_default`.
0004
0005 Copyright Louis Dionne 2013-2022
0006 Distributed under the Boost Software License, Version 1.0.
0007 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0008  */
0009
0010 #ifndef BOOST_HANA_CORE_DEFAULT_HPP
0011 #define BOOST_HANA_CORE_DEFAULT_HPP
0012
0013 #include <boost/hana/fwd/core/default.hpp>
0014
0015 #include <boost/hana/config.hpp>
0016
0017 #include <type_traits>
0018
0019
0020 namespace boost { namespace hana {
0021     template <typename Method, typename>
0022     struct is_default : std::false_type { };
0023
0024     template <typename Method>
0025     struct is_default<Method, decltype((void)
0026         static_cast<default_>(*(Method*)0)
0027     )>
0028         : std::true_type
0029     { };
0030 }} // end namespace boost::hana
0031
0032 #endif // !BOOST_HANA_CORE_DEFAULT_HPP