stabilize build system: depends, installer, boost/bdb fixes, cross targets groundwork

depends/x86_64-pc-linux-gnu/include/boost/hana/detail/variadic/take.hpp

@@ -0,0 +1,51 @@
+/*!
+@file
+Defines `boost::hana::detail::variadic::take`.
+
+@copyright Louis Dionne 2013-2017
+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_DETAIL_VARIADIC_TAKE_HPP
+#define BOOST_HANA_DETAIL_VARIADIC_TAKE_HPP
+
+#include <boost/hana/config.hpp>
+#include <boost/hana/detail/variadic/split_at.hpp>
+#include <boost/hana/functional/always.hpp>
+#include <boost/hana/functional/reverse_partial.hpp>
+
+#include <cstddef>
+
+
+BOOST_HANA_NAMESPACE_BEGIN namespace detail { namespace variadic {
+    struct take_impl2 {
+        template <typename F, typename ...Xs>
+        constexpr decltype(auto) operator()(F&& f, Xs&& ...xs) const {
+            return static_cast<F&&>(f)(static_cast<Xs&&>(xs)...);
+        }
+    };
+
+    struct take_impl1 {
+        template <typename ...Xs>
+        constexpr auto operator()(Xs&& ...xs) const {
+            return hana::always(
+                reverse_partial(take_impl2{},
+                    static_cast<Xs&&>(xs)...)
+            );
+        }
+    };
+
+    template <std::size_t n>
+    struct take_t {
+        template <typename ...Xs>
+        constexpr decltype(auto) operator()(Xs&& ...xs) const {
+            return variadic::split_at<n>(static_cast<Xs&&>(xs)...)(take_impl1{});
+        }
+    };
+
+    template <std::size_t n>
+    constexpr take_t<n> take{};
+}} BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_DETAIL_VARIADIC_TAKE_HPP