1 /*!
2 @file
3 Defines `boost::hana::zip_with`.
4 
5 @copyright Louis Dionne 2013-2017
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>
operator ()(F && f,Xs && xs,Ys &&...ys) const30     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>
transversezip_with_impl49         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
zip_helperzip_with_impl55         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
applyzip_with_impl61         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
71