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diff --git a/boost/hana/fwd/drop_back.hpp b/boost/hana/fwd/drop_back.hpp
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+/*!
+@file
+Forward declares `boost::hana::drop_back`.
+
+@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_FWD_DROP_BACK_HPP
+#define BOOST_HANA_FWD_DROP_BACK_HPP
+
+#include <boost/hana/config.hpp>
+#include <boost/hana/core/when.hpp>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+    //! Drop the last `n` elements of a finite sequence, and return the rest.
+    //! @ingroup group-Sequence
+    //!
+    //! Given a finite `Sequence` `xs` with a linearization of `[x1, ..., xm]`
+    //! and a non-negative `IntegralConstant` `n`, `drop_back(xs, n)` is a
+    //! sequence with the same tag as `xs` whose linearization is
+    //! `[x1, ..., xm-n]`. If `n` is not given, it defaults to an
+    //! `IntegralConstant` with a value equal to `1`.
+    //!
+    //! In case `length(xs) <= n`, `drop_back` will simply drop the whole
+    //! sequence without failing, thus returning an empty sequence.
+    //!
+    //!
+    //! @param xs
+    //! The sequence from which elements are dropped.
+    //!
+    //! @param n
+    //! A non-negative `IntegralConstant` representing the number of elements
+    //! to be dropped from the end of the sequence. If `n` is not given, it
+    //! defaults to an `IntegralConstant` with a value equal to `1`.
+    //!
+    //!
+    //! Example
+    //! -------
+    //! @include example/drop_back.cpp
+#ifdef BOOST_HANA_DOXYGEN_INVOKED
+    constexpr auto drop_back = [](auto&& xs[, auto const& n]) {
+        return tag-dispatched;
+    };
+#else
+    template <typename S, typename = void>
+    struct drop_back_impl : drop_back_impl<S, when<true>> { };
+
+    struct drop_back_t {
+        template <typename Xs, typename N>
+        constexpr auto operator()(Xs&& xs, N const& n) const;
+
+        template <typename Xs>
+        constexpr auto operator()(Xs&& xs) const;
+    };
+
+    constexpr drop_back_t drop_back{};
+#endif
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_FWD_DROP_BACK_HPP