62 lines
2.0 KiB
C++
62 lines
2.0 KiB
C++
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/*!
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@file
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Forward declares `boost::hana::zip_shortest`.
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@copyright Louis Dionne 2013-2017
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_FWD_ZIP_SHORTEST_HPP
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#define BOOST_HANA_FWD_ZIP_SHORTEST_HPP
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/when.hpp>
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namespace boost { namespace hana {
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//! Zip one sequence or more.
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//! @ingroup group-Sequence
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//!
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//! Given `n` sequences `s1, ..., sn`, `zip_shortest` produces a sequence
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//! whose `i`-th element is a tuple of `(s1[i], ..., sn[i])`, where `sk[i]`
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//! denotes the `i`-th element of the `k`-th sequence. In other words,
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//! `zip_shortest` produces a sequence of the form
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//! @code
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//! [
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//! make_tuple(s1[0], ..., sn[0]),
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//! make_tuple(s1[1], ..., sn[1]),
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//! ...
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//! make_tuple(s1[M], ..., sn[M])
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//! ]
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//! @endcode
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//! where `M` is the length of the shortest sequence. Hence, the returned
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//! sequence stops when the shortest input sequence is exhausted. If you
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//! know that all the sequences you are about to zip have the same length,
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//! you should use `zip` instead, since it can be more optimized. Also
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//! note that it is an error to provide no sequence at all, i.e.
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//! `zip_shortest` expects at least one sequence.
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//!
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//!
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//! Example
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//! -------
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//! @include example/zip_shortest.cpp
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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constexpr auto zip_shortest = [](auto&& x1, ..., auto&& xn) {
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return tag-dispatched;
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};
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#else
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template <typename S, typename = void>
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struct zip_shortest_impl : zip_shortest_impl<S, when<true>> { };
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struct zip_shortest_t {
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template <typename Xs, typename ...Ys>
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constexpr auto operator()(Xs&& xs, Ys&& ...ys) const;
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};
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BOOST_HANA_INLINE_VARIABLE constexpr zip_shortest_t zip_shortest{};
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#endif
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}} // end namespace boost::hana
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#endif // !BOOST_HANA_FWD_ZIP_SHORTEST_HPP
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