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Filename : disjunction.hpp

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/*
Copyright Barrett Adair 2015-2017

Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)

*/

#ifndef BOOST_CLBL_TRTS_DETAIL_POLYFILLS_DISJUNCTION_HPP
#define BOOST_CLBL_TRTS_DETAIL_POLYFILLS_DISJUNCTION_HPP

#undef BOOST_CLBL_TRTS_DISJUNCTION
#define BOOST_CLBL_TRTS_DISJUNCTION(...) \
    ::boost::callable_traits::detail::disjunction<__VA_ARGS__>

namespace boost { namespace callable_traits { namespace detail {

//polyfill for C++17 std::disjunction
template<typename...>
struct disjunction : std::false_type {};

template<typename T>
struct disjunction<T> : T {};

template<typename T, typename... Ts>
struct disjunction<T, Ts...>
    : std::conditional<T::value != false, T, disjunction<Ts...>>::type {};

}}} // namespace boost::callable_traits::detail

#endif // #ifndef BOOST_CLBL_TRTS_DETAIL_POLYFILLS_DISJUNCTION_HPP