| 1 | /*! |
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| 2 | @file |
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| 3 | Forward declares `boost::hana::zip`. |
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| 4 | |
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| 5 | Copyright Louis Dionne 2013-2022 |
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| 6 | Distributed under the Boost Software License, Version 1.0. |
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| 7 | (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) |
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| 8 | */ |
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| 9 | |
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| 10 | #ifndef BOOST_HANA_FWD_ZIP_HPP |
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| 11 | #define BOOST_HANA_FWD_ZIP_HPP |
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| 12 | |
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| 13 | #include <boost/hana/config.hpp> |
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| 14 | #include <boost/hana/core/when.hpp> |
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| 15 | |
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| 16 | |
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| 17 | namespace boost { namespace hana { |
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| 18 | //! Zip one sequence or more. |
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| 19 | //! @ingroup group-Sequence |
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| 20 | //! |
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| 21 | //! Given `n` sequences `s1, ..., sn`, `zip` produces a sequence whose |
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| 22 | //! `i`-th element is a tuple of `(s1[i], ..., sn[i])`, where `sk[i]` |
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| 23 | //! denotes the `i`-th element of the `k`-th sequence. In other words, |
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| 24 | //! `zip` produces a sequence of the form |
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| 25 | //! @code |
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| 26 | //! [ |
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| 27 | //! make_tuple(s1[0], ..., sn[0]), |
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| 28 | //! make_tuple(s1[1], ..., sn[1]), |
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| 29 | //! ... |
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| 30 | //! make_tuple(s1[M], ..., sn[M]) |
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| 31 | //! ] |
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| 32 | //! @endcode |
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| 33 | //! where `M` is the length of the sequences, which are all assumed to |
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| 34 | //! have the same length. Assuming the sequences to all have the same size |
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| 35 | //! allows the library to perform some optimizations. To zip sequences |
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| 36 | //! that may have different lengths, `zip_shortest` should be used |
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| 37 | //! instead. Also note that it is an error to provide no sequence at all, |
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| 38 | //! i.e. `zip` expects at least one sequence. |
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| 39 | //! |
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| 40 | //! |
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| 41 | //! Example |
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| 42 | //! ------- |
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| 43 | //! @include example/zip.cpp |
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| 44 | #ifdef BOOST_HANA_DOXYGEN_INVOKED |
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| 45 | constexpr auto zip = [](auto&& x1, ..., auto&& xn) { |
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| 46 | return tag-dispatched; |
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| 47 | }; |
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| 48 | #else |
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| 49 | template <typename S, typename = void> |
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| 50 | struct zip_impl : zip_impl<S, when<true>> { }; |
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| 51 | |
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| 52 | struct zip_t { |
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| 53 | template <typename Xs, typename ...Ys> |
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| 54 | constexpr auto operator()(Xs&& xs, Ys&& ...ys) const; |
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| 55 | }; |
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| 56 | |
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| 57 | BOOST_HANA_INLINE_VARIABLE constexpr zip_t zip{}; |
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| 58 | #endif |
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| 59 | }} // end namespace boost::hana |
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| 60 | |
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| 61 | #endif // !BOOST_HANA_FWD_ZIP_HPP |
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| 62 | |
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