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1 | /*! |
2 | @file | |
3 | Forward declares `boost::hana::zip_shortest`. | |
4 | ||
5 | @copyright Louis Dionne 2013-2016 | |
6 | Distributed under the Boost Software License, Version 1.0. | |
7 | (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) | |
8 | */ | |
9 | ||
10 | #ifndef BOOST_HANA_FWD_ZIP_SHORTEST_HPP | |
11 | #define BOOST_HANA_FWD_ZIP_SHORTEST_HPP | |
12 | ||
13 | #include <boost/hana/config.hpp> | |
14 | #include <boost/hana/core/when.hpp> | |
15 | ||
16 | ||
17 | BOOST_HANA_NAMESPACE_BEGIN | |
18 | //! Zip one sequence or more. | |
19 | //! @ingroup group-Sequence | |
20 | //! | |
21 | //! Given `n` sequences `s1, ..., sn`, `zip_shortest` produces a sequence | |
22 | //! whose `i`-th element is a tuple of `(s1[i], ..., sn[i])`, where `sk[i]` | |
23 | //! denotes the `i`-th element of the `k`-th sequence. In other words, | |
24 | //! `zip_shortest` produces a sequence of the form | |
25 | //! @code | |
26 | //! [ | |
27 | //! make_tuple(s1[0], ..., sn[0]), | |
28 | //! make_tuple(s1[1], ..., sn[1]), | |
29 | //! ... | |
30 | //! make_tuple(s1[M], ..., sn[M]) | |
31 | //! ] | |
32 | //! @endcode | |
33 | //! where `M` is the length of the shortest sequence. Hence, the returned | |
34 | //! sequence stops when the shortest input sequence is exhausted. If you | |
35 | //! know that all the sequences you are about to zip have the same length, | |
36 | //! you should use `zip` instead, since it can be more optimized. Also | |
37 | //! note that it is an error to provide no sequence at all, i.e. | |
38 | //! `zip_shortest` expects at least one sequence. | |
39 | //! | |
40 | //! | |
41 | //! Example | |
42 | //! ------- | |
43 | //! @include example/zip_shortest.cpp | |
44 | #ifdef BOOST_HANA_DOXYGEN_INVOKED | |
45 | constexpr auto zip_shortest = [](auto&& x1, ..., auto&& xn) { | |
46 | return tag-dispatched; | |
47 | }; | |
48 | #else | |
49 | template <typename S, typename = void> | |
50 | struct zip_shortest_impl : zip_shortest_impl<S, when<true>> { }; | |
51 | ||
52 | struct zip_shortest_t { | |
53 | template <typename Xs, typename ...Ys> | |
54 | constexpr auto operator()(Xs&& xs, Ys&& ...ys) const; | |
55 | }; | |
56 | ||
57 | constexpr zip_shortest_t zip_shortest{}; | |
58 | #endif | |
59 | BOOST_HANA_NAMESPACE_END | |
60 | ||
61 | #endif // !BOOST_HANA_FWD_ZIP_SHORTEST_HPP |