57 lines
1.6 KiB
C++
57 lines
1.6 KiB
C++
// Copyright Matt Borland 2021.
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// Use, modification and distribution are subject to the
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// Boost Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// https://en.cppreference.com/w/cpp/experimental/is_detected
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#ifndef BOOST_MATH_TOOLS_IS_DETECTED_HPP
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#define BOOST_MATH_TOOLS_IS_DETECTED_HPP
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#include <type_traits>
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namespace boost { namespace math { namespace tools {
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template <typename...>
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using void_t = void;
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namespace detail {
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template <typename Default, typename AlwaysVoid, template<typename...> class Op, typename... Args>
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struct detector
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{
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using value_t = std::false_type;
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using type = Default;
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};
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template <typename Default, template<typename...> class Op, typename... Args>
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struct detector<Default, void_t<Op<Args...>>, Op, Args...>
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{
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using value_t = std::true_type;
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using type = Op<Args...>;
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};
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} // Namespace detail
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// Special type to indicate detection failure
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struct nonesuch
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{
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nonesuch() = delete;
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~nonesuch() = delete;
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nonesuch(const nonesuch&) = delete;
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void operator=(const nonesuch&) = delete;
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};
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template <template<typename...> class Op, typename... Args>
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using is_detected = typename detail::detector<nonesuch, void, Op, Args...>::value_t;
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template <template<typename...> class Op, typename... Args>
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using detected_t = typename detail::detector<nonesuch, void, Op, Args...>::type;
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template <typename Default, template<typename...> class Op, typename... Args>
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using detected_or = detail::detector<Default, void, Op, Args...>;
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}}} // Namespaces boost math tools
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#endif // BOOST_MATH_TOOLS_IS_DETECTED_HPP
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