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+/*!
+@file
+Forward declares `boost::hana::zip_with`.
+
+@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_ZIP_WITH_HPP
+#define BOOST_HANA_FWD_ZIP_WITH_HPP
+
+#include <boost/hana/config.hpp>
+#include <boost/hana/core/when.hpp>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+    //! Zip one sequence or more with a given function.
+    //! @ingroup group-Sequence
+    //!
+    //! Given a `n`-ary function `f` and `n` sequences `s1, ..., sn`,
+    //! `zip_with` produces a sequence whose `i`-th element is
+    //! `f(s1[i], ..., sn[i])`, where `sk[i]` denotes the `i`-th element of
+    //! the `k`-th sequence. In other words, `zip_with` produces a sequence
+    //! of the form
+    //! @code
+    //!     [
+    //!         f(s1[0], ..., sn[0]),
+    //!         f(s1[1], ..., sn[1]),
+    //!         ...
+    //!         f(s1[M], ..., sn[M])
+    //!     ]
+    //! @endcode
+    //! where `M` is the length of the sequences, which are all assumed to
+    //! have the same length. Assuming the sequences to all have the same size
+    //! allows the library to perform some optimizations. To zip sequences
+    //! that may have different lengths, `zip_shortest_with` should be used
+    //! instead. Also note that it is an error to provide no sequence at all,
+    //! i.e. `zip_with` expects at least one sequence.
+    //!
+    //!
+    //! Example
+    //! -------
+    //! @include example/zip_with.cpp
+#ifdef BOOST_HANA_DOXYGEN_INVOKED
+    constexpr auto zip_with = [](auto&& f, auto&& x1, ..., auto&& xn) {
+        return tag-dispatched;
+    };
+#else
+    template <typename S, typename = void>
+    struct zip_with_impl : zip_with_impl<S, when<true>> { };
+
+    struct zip_with_t {
+        template <typename F, typename Xs, typename ...Ys>
+        constexpr auto operator()(F&& f, Xs&& xs, Ys&& ...ys) const;
+    };
+
+    constexpr zip_with_t zip_with{};
+#endif
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_FWD_ZIP_WITH_HPP