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diff --git a/boost/hana/fill.hpp b/boost/hana/fill.hpp
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+/*!
+@file
+Defines `boost::hana::fill`.
+
+@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_FILL_HPP
+#define BOOST_HANA_FILL_HPP
+
+#include <boost/hana/fwd/fill.hpp>
+
+#include <boost/hana/concept/functor.hpp>
+#include <boost/hana/concept/sequence.hpp>
+#include <boost/hana/config.hpp>
+#include <boost/hana/core/dispatch.hpp>
+#include <boost/hana/core/make.hpp>
+#include <boost/hana/functional/always.hpp>
+#include <boost/hana/transform.hpp>
+#include <boost/hana/unpack.hpp>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+    //! @cond
+    template <typename Xs, typename Value>
+    constexpr auto fill_t::operator()(Xs&& xs, Value&& value) const {
+        using S = typename hana::tag_of<Xs>::type;
+        using Fill = BOOST_HANA_DISPATCH_IF(fill_impl<S>,
+            hana::Functor<S>::value
+        );
+
+    #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
+        static_assert(hana::Functor<S>::value,
+        "hana::fill(xs, value) requires 'xs' to be a Functor");
+    #endif
+
+        return Fill::apply(static_cast<Xs&&>(xs),
+                           static_cast<Value&&>(value));
+    }
+    //! @endcond
+
+    template <typename Fun, bool condition>
+    struct fill_impl<Fun, when<condition>> : default_ {
+        template <typename Xs, typename Value>
+        static constexpr auto apply(Xs&& xs, Value&& v) {
+            return hana::transform(static_cast<Xs&&>(xs),
+                                   hana::always(static_cast<Value&&>(v))
+            );
+        }
+    };
+
+    template <typename S>
+    struct fill_impl<S, when<Sequence<S>::value>> {
+        //! @cond
+        template <typename V>
+        struct filler {
+            V const& v;
+            template <typename ...Xs>
+            constexpr auto operator()(Xs const& ...xs) const {
+                return hana::make<S>(((void)xs, v)...);
+            }
+        };
+        //! @endcond
+
+        template <typename Xs, typename V>
+        static constexpr auto apply(Xs const& xs, V const& v) {
+            return hana::unpack(xs, filler<V>{v});
+        }
+    };
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_FILL_HPP