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1 | /*! |
2 | @file | |
3 | Forward declares `boost::hana::zip_with`. | |
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_WITH_HPP | |
11 | #define BOOST_HANA_FWD_ZIP_WITH_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 with a given function. | |
19 | //! @ingroup group-Sequence | |
20 | //! | |
21 | //! Given a `n`-ary function `f` and `n` sequences `s1, ..., sn`, | |
22 | //! `zip_with` produces a sequence whose `i`-th element is | |
23 | //! `f(s1[i], ..., sn[i])`, where `sk[i]` denotes the `i`-th element of | |
24 | //! the `k`-th sequence. In other words, `zip_with` produces a sequence | |
25 | //! of the form | |
26 | //! @code | |
27 | //! [ | |
28 | //! f(s1[0], ..., sn[0]), | |
29 | //! f(s1[1], ..., sn[1]), | |
30 | //! ... | |
31 | //! f(s1[M], ..., sn[M]) | |
32 | //! ] | |
33 | //! @endcode | |
34 | //! where `M` is the length of the sequences, which are all assumed to | |
35 | //! have the same length. Assuming the sequences to all have the same size | |
36 | //! allows the library to perform some optimizations. To zip sequences | |
37 | //! that may have different lengths, `zip_shortest_with` should be used | |
38 | //! instead. Also note that it is an error to provide no sequence at all, | |
39 | //! i.e. `zip_with` expects at least one sequence. | |
40 | //! | |
41 | //! | |
42 | //! Example | |
43 | //! ------- | |
44 | //! @include example/zip_with.cpp | |
45 | #ifdef BOOST_HANA_DOXYGEN_INVOKED | |
46 | constexpr auto zip_with = [](auto&& f, auto&& x1, ..., auto&& xn) { | |
47 | return tag-dispatched; | |
48 | }; | |
49 | #else | |
50 | template <typename S, typename = void> | |
51 | struct zip_with_impl : zip_with_impl<S, when<true>> { }; | |
52 | ||
53 | struct zip_with_t { | |
54 | template <typename F, typename Xs, typename ...Ys> | |
55 | constexpr auto operator()(F&& f, Xs&& xs, Ys&& ...ys) const; | |
56 | }; | |
57 | ||
58 | constexpr zip_with_t zip_with{}; | |
59 | #endif | |
60 | BOOST_HANA_NAMESPACE_END | |
61 | ||
62 | #endif // !BOOST_HANA_FWD_ZIP_WITH_HPP |