Added thirdparty: boost library

2026-08-23 23:58:08 +00:00 · 2024-01-06 19:55:56 +02:00
parent bf49f439e1
commit bccd1e7051
15683 changed files with 3239840 additions and 0 deletions
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+/*!
+@file
+Defines `boost::hana::detail::CanonicalConstant`.
+
+Copyright Louis Dionne 2013-2022
+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_HANA_DETAIL_CANONICAL_CONSTANT_HPP
+#define BOOST_HANA_DETAIL_CANONICAL_CONSTANT_HPP
+
+#include <boost/hana/config.hpp>
+
+
+namespace boost { namespace hana { namespace detail {
+    //! @ingroup group-details
+    //! Tag representing a canonical `Constant`.
+    //!
+    //! This is an implementation detail used to provide many models for
+    //! stuff like `Monoid`, `Group`, etc. To create a `CanonicalConstant`,
+    //! simply create an object with a nested `hana_tag` equal to the proper
+    //! specialization of `CanonicalConstant<T>`, and then also provide a
+    //! `constexpr` static member `::%value` holding the value of the constant.
+    template <typename T>
+    struct CanonicalConstant {
+        using value_type = T;
+    };
+} }} // end namespace boost::hana
+
+
+#include <boost/hana/concept/constant.hpp>
+#include <boost/hana/concept/integral_constant.hpp>
+#include <boost/hana/core/to.hpp>
+#include <boost/hana/core/when.hpp>
+
+#include <type_traits>
+
+
+namespace boost { namespace hana {
+    //////////////////////////////////////////////////////////////////////////
+    // Constant
+    //////////////////////////////////////////////////////////////////////////
+    template <typename T>
+    struct value_impl<detail::CanonicalConstant<T>> {
+        template <typename X>
+        static constexpr decltype(auto) apply()
+        { return X::value; }
+    };
+
+    namespace detail {
+        template <typename T, typename X>
+        struct canonical_constant {
+            static constexpr auto value = hana::to<T>(hana::value<X>());
+            using hana_tag = detail::CanonicalConstant<T>;
+        };
+    }
+
+    template <typename T, typename C>
+    struct to_impl<detail::CanonicalConstant<T>, C, when<
+        hana::Constant<C>::value &&
+        is_convertible<typename C::value_type, T>::value
+    >>
+        : embedding<is_embedded<typename C::value_type, T>::value>
+    {
+        template <typename X>
+        static constexpr detail::canonical_constant<T, X> apply(X const&)
+        { return {}; }
+    };
+
+    //////////////////////////////////////////////////////////////////////////
+    // IntegralConstant (when value_type is integral)
+    //////////////////////////////////////////////////////////////////////////
+    template <typename T>
+    struct IntegralConstant<detail::CanonicalConstant<T>> {
+        static constexpr bool value = std::is_integral<T>::value;
+    };
+}} // end namespace boost::hana
+
+#endif // !BOOST_HANA_DETAIL_CANONICAL_CONSTANT_HPP