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1 | /*! |
2 | @file | |
3 | Defines `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_ZIP_WITH_HPP | |
11 | #define BOOST_HANA_ZIP_WITH_HPP | |
12 | ||
13 | #include <boost/hana/fwd/zip_with.hpp> | |
14 | ||
15 | #include <boost/hana/at.hpp> | |
16 | #include <boost/hana/concept/sequence.hpp> | |
17 | #include <boost/hana/config.hpp> | |
18 | #include <boost/hana/core/dispatch.hpp> | |
19 | #include <boost/hana/core/make.hpp> | |
20 | #include <boost/hana/detail/fast_and.hpp> | |
21 | #include <boost/hana/length.hpp> | |
22 | ||
23 | #include <cstddef> | |
24 | #include <utility> | |
25 | ||
26 | ||
27 | BOOST_HANA_NAMESPACE_BEGIN | |
28 | //! @cond | |
29 | template <typename F, typename Xs, typename ...Ys> | |
30 | constexpr auto zip_with_t::operator()(F&& f, Xs&& xs, Ys&& ...ys) const { | |
31 | #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS | |
32 | static_assert(detail::fast_and< | |
33 | hana::Sequence<Xs>::value, hana::Sequence<Ys>::value... | |
34 | >::value, | |
35 | "hana::zip_with(f, xs, ys...) requires 'xs' and 'ys...' to be Sequences"); | |
36 | #endif | |
37 | ||
38 | return zip_with_impl<typename hana::tag_of<Xs>::type>::apply( | |
39 | static_cast<F&&>(f), | |
40 | static_cast<Xs&&>(xs), | |
41 | static_cast<Ys&&>(ys)... | |
42 | ); | |
43 | } | |
44 | //! @endcond | |
45 | ||
46 | template <typename S> | |
47 | struct zip_with_impl<S, when<Sequence<S>::value>> { | |
48 | template <std::size_t N, typename F, typename ...Xs> | |
49 | static constexpr decltype(auto) transverse(F&& f, Xs&& ...xs) { | |
50 | return static_cast<F&&>(f)(hana::at_c<N>(static_cast<Xs&&>(xs))...); | |
51 | } | |
52 | ||
53 | template <std::size_t ...N, typename F, typename ...Xs> | |
54 | static constexpr auto | |
55 | zip_helper(std::index_sequence<N...>, F&& f, Xs&& ...xs) { | |
56 | return hana::make<S>(transverse<N>(f, xs...)...); | |
57 | } | |
58 | ||
59 | template <typename F, typename X, typename ...Xs> | |
60 | static constexpr auto | |
61 | apply(F&& f, X&& x, Xs&& ...xs) { | |
62 | constexpr std::size_t N = decltype(hana::length(x))::value; | |
63 | return zip_helper(std::make_index_sequence<N>{}, | |
64 | static_cast<F&&>(f), | |
65 | static_cast<X&&>(x), static_cast<Xs&&>(xs)...); | |
66 | } | |
67 | }; | |
68 | BOOST_HANA_NAMESPACE_END | |
69 | ||
70 | #endif // !BOOST_HANA_ZIP_WITH_HPP |