Imported Upstream version 1.61.0

Change-Id: I96a1f878d1e6164f01e9aadd5147f38fca448d90
Signed-off-by: DongHun Kwak <dh0128.kwak@samsung.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/boost/hana/extract.hpp b/boost/hana/extract.hpp
new file mode 100644
index 0000000000..f72ddfce13
--- /dev/null
+++ b/boost/hana/extract.hpp
@@ -0,0 +1,45 @@
+/*!
+@file
+Defines `boost::hana::extract`.
+
+@copyright Louis Dionne 2013-2016
+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_EXTRACT_HPP
+#define BOOST_HANA_EXTRACT_HPP
+
+#include <boost/hana/fwd/extract.hpp>
+
+#include <boost/hana/concept/comonad.hpp>
+#include <boost/hana/config.hpp>
+#include <boost/hana/core/dispatch.hpp>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+    //! @cond
+    template <typename W_>
+    constexpr decltype(auto) extract_t::operator()(W_&& w) const {
+        using W = typename hana::tag_of<W_>::type;
+        using Extract = BOOST_HANA_DISPATCH_IF(extract_impl<W>,
+            hana::Comonad<W>::value
+        );
+
+    #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
+        static_assert(hana::Comonad<W>::value,
+        "hana::extract(w) requires 'w' to be a Comonad");
+    #endif
+
+        return Extract::apply(static_cast<W_&&>(w));
+    }
+    //! @endcond
+
+    template <typename W, bool condition>
+    struct extract_impl<W, when<condition>> : default_ {
+        template <typename ...Args>
+        static constexpr auto apply(Args&& ...args) = delete;
+    };
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_EXTRACT_HPP