boost/hana/zip_shortest_with.hpp

0001 /*!
0002 @file
0003 Defines `boost::hana::zip_shortest_with`.
0004
0005 Copyright Louis Dionne 2013-2022
0006 Distributed under the Boost Software License, Version 1.0.
0007 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0008  */
0009
0010 #ifndef BOOST_HANA_ZIP_SHORTEST_WITH_HPP
0011 #define BOOST_HANA_ZIP_SHORTEST_WITH_HPP
0012
0013 #include <boost/hana/fwd/zip_shortest_with.hpp>
0014
0015 #include <boost/hana/concept/sequence.hpp>
0016 #include <boost/hana/core/dispatch.hpp>
0017 #include <boost/hana/config.hpp>
0018 #include <boost/hana/detail/algorithm.hpp>
0019 #include <boost/hana/detail/fast_and.hpp>
0020 #include <boost/hana/integral_constant.hpp>
0021 #include <boost/hana/length.hpp>
0022 #include <boost/hana/take_front.hpp>
0023 #include <boost/hana/zip_with.hpp>
0024
0025 #include <cstddef>
0026
0027
0028 namespace boost { namespace hana {
0029     //! @cond
0030     template <typename F, typename Xs, typename ...Ys>
0031     constexpr auto
0032     zip_shortest_with_t::operator()(F&& f, Xs&& xs, Ys&& ...ys) const {
0033     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
0034         static_assert(detail::fast_and<
0035             hana::Sequence<Xs>::value, hana::Sequence<Ys>::value...
0036         >::value,
0037         "hana::zip_shortest_with(f, xs, ys...) requires 'xs' and 'ys...' to be Sequences");
0038     #endif
0039
0040         return zip_shortest_with_impl<typename hana::tag_of<Xs>::type>::apply(
0041             static_cast<F&&>(f),
0042             static_cast<Xs&&>(xs),
0043             static_cast<Ys&&>(ys)...
0044         );
0045     }
0046     //! @endcond
0047
0048     template <typename S, bool condition>
0049     struct zip_shortest_with_impl<S, when<condition>> : default_ {
0050         template <typename F, typename ...Xs>
0051         static constexpr decltype(auto) apply(F&& f, Xs&& ...xs) {
0052             constexpr std::size_t lengths[] = {
0053                 decltype(hana::length(xs))::value...
0054             };
0055             constexpr std::size_t min_len =
0056                 *detail::min_element(lengths, lengths + sizeof...(xs));
0057             return hana::zip_with(static_cast<F&&>(f),
0058                 hana::take_front(static_cast<Xs&&>(xs), hana::size_c<min_len>)...
0059             );
0060         }
0061     };
0062 }} // end namespace boost::hana
0063
0064 #endif // !BOOST_HANA_ZIP_SHORTEST_WITH_HPP