detail/polyfills/disjunction.hpp

0001 /*
0002 Copyright Barrett Adair 2015-2017
0003
0004 Distributed under the Boost Software License, Version 1.0.
0005 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0006
0007 */
0008
0009 #ifndef BOOST_CLBL_TRTS_DETAIL_POLYFILLS_DISJUNCTION_HPP
0010 #define BOOST_CLBL_TRTS_DETAIL_POLYFILLS_DISJUNCTION_HPP
0011
0012 #undef BOOST_CLBL_TRTS_DISJUNCTION
0013 #define BOOST_CLBL_TRTS_DISJUNCTION(...) \
0014     ::boost::callable_traits::detail::disjunction<__VA_ARGS__>
0015
0016 namespace boost { namespace callable_traits { namespace detail {
0017
0018 //polyfill for C++17 std::disjunction
0019 template<typename...>
0020 struct disjunction : std::false_type {};
0021
0022 template<typename T>
0023 struct disjunction<T> : T {};
0024
0025 template<typename T, typename... Ts>
0026 struct disjunction<T, Ts...>
0027     : std::conditional<T::value != false, T, disjunction<Ts...>>::type {};
0028
0029 }}} // namespace boost::callable_traits::detail
0030
0031 #endif // #ifndef BOOST_CLBL_TRTS_DETAIL_POLYFILLS_DISJUNCTION_HPP