update boost

linx64/include/boost/math/tools/is_detected.hpp

@@ -0,0 +1,56 @@
+//  Copyright Matt Borland 2021.
+//  Use, modification and distribution are subject to the
+//  Boost Software License, Version 1.0. (See accompanying file
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+//  https://en.cppreference.com/w/cpp/experimental/is_detected
+
+#ifndef BOOST_MATH_TOOLS_IS_DETECTED_HPP
+#define BOOST_MATH_TOOLS_IS_DETECTED_HPP
+
+#include <type_traits>
+
+namespace boost { namespace math { namespace tools {
+
+template <typename...>
+using void_t = void;
+
+namespace detail {
+
+template <typename Default, typename AlwaysVoid, template<typename...> class Op, typename... Args>
+struct detector
+{
+    using value_t = std::false_type;
+    using type = Default;
+};
+
+template <typename Default, template<typename...> class Op, typename... Args>
+struct detector<Default, void_t<Op<Args...>>, Op, Args...>
+{
+    using value_t = std::true_type;
+    using type = Op<Args...>;
+};
+
+} // Namespace detail
+
+// Special type to indicate detection failure
+struct nonesuch
+{
+    nonesuch() = delete;
+    ~nonesuch() = delete;
+    nonesuch(const nonesuch&) = delete;
+    void operator=(const nonesuch&) = delete;
+};
+
+template <template<typename...> class Op, typename... Args>
+using is_detected = typename detail::detector<nonesuch, void, Op, Args...>::value_t;
+
+template <template<typename...> class Op, typename... Args>
+using detected_t = typename detail::detector<nonesuch, void, Op, Args...>::type;
+
+template <typename Default, template<typename...> class Op, typename... Args>
+using detected_or = detail::detector<Default, void, Op, Args...>;
+
+}}} // Namespaces boost math tools
+
+#endif // BOOST_MATH_TOOLS_IS_DETECTED_HPP