Added thirdparty: boost library

thirdparty/include/boost/hana/at_key.hpp

@@ -0,0 +1,97 @@
+/*!
+@file
+Defines `boost::hana::at_key`.
+
+Copyright Louis Dionne 2013-2022
+Copyright Jason Rice 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_HANA_AT_KEY_HPP
+#define BOOST_HANA_AT_KEY_HPP
+
+#include <boost/hana/fwd/at_key.hpp>
+
+#include <boost/hana/accessors.hpp>
+#include <boost/hana/at.hpp>
+#include <boost/hana/concept/searchable.hpp>
+#include <boost/hana/concept/struct.hpp>
+#include <boost/hana/config.hpp>
+#include <boost/hana/core/dispatch.hpp>
+#include <boost/hana/detail/decay.hpp>
+#include <boost/hana/equal.hpp>
+#include <boost/hana/find.hpp>
+#include <boost/hana/find_if.hpp>
+#include <boost/hana/first.hpp>
+#include <boost/hana/functional/on.hpp>
+#include <boost/hana/index_if.hpp>
+#include <boost/hana/length.hpp>
+#include <boost/hana/optional.hpp>
+#include <boost/hana/second.hpp>
+
+#include <cstddef>
+#include <utility>
+
+
+namespace boost { namespace hana {
+    //! @cond
+    template <typename Xs, typename Key>
+    constexpr decltype(auto) at_key_t::operator()(Xs&& xs, Key const& key) const {
+        using S = typename hana::tag_of<Xs>::type;
+        using AtKey = BOOST_HANA_DISPATCH_IF(at_key_impl<S>,
+            hana::Searchable<S>::value
+        );
+
+    #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
+        static_assert(hana::Searchable<S>::value,
+        "hana::at_key(xs, key) requires 'xs' to be Searchable");
+    #endif
+
+        return AtKey::apply(static_cast<Xs&&>(xs), key);
+    }
+    //! @endcond
+
+    template <typename S, bool condition>
+    struct at_key_impl<S, when<condition>> : default_ {
+        template <typename Xs, typename Key>
+        static constexpr auto apply(Xs&& xs, Key const& key) {
+            return hana::find(static_cast<Xs&&>(xs), key).value();
+        }
+    };
+
+    namespace at_key_detail {
+        template <typename T>
+        struct equal_to {
+            T const& t;
+            template <typename U>
+            constexpr auto operator()(U const& u) const {
+                return hana::equal(t, u);
+            }
+        };
+    }
+
+    template <typename S>
+    struct at_key_impl<S, when<hana::Sequence<S>::value>> {
+        template <typename Xs, typename Key>
+        static constexpr decltype(auto) apply(Xs&& xs, Key const& key) {
+            using Result = decltype(hana::index_if(
+                static_cast<Xs&&>(xs), at_key_detail::equal_to<Key>{key}));
+
+            return hana::at(static_cast<Xs&&>(xs), Result{}.value());
+        }
+    };
+
+    template <typename S>
+    struct at_key_impl<S, when<hana::Struct<S>::value>> {
+        template <typename X, typename Key>
+        static constexpr decltype(auto) apply(X&& x, Key const& key) {
+            auto accessor = hana::second(*hana::find_if(hana::accessors<S>(),
+                hana::equal.to(key) ^hana::on^ hana::first
+            ));
+            return accessor(static_cast<X&&>(x));
+        }
+    };
+}} // end namespace boost::hana
+
+#endif // !BOOST_HANA_AT_KEY_HPP