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 Hu Chunming
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/*!
@file
Defines `boost::hana::zip_with`.
Copyright Louis Dionne 2013-2022
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
*/
#ifndef BOOST_HANA_ZIP_WITH_HPP
#define BOOST_HANA_ZIP_WITH_HPP
#include <boost/hana/fwd/zip_with.hpp>
#include <boost/hana/at.hpp>
#include <boost/hana/concept/sequence.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/core/dispatch.hpp>
#include <boost/hana/core/make.hpp>
#include <boost/hana/detail/fast_and.hpp>
#include <boost/hana/length.hpp>
#include <cstddef>
#include <utility>
namespace boost { namespace hana {
//! @cond
template <typename F, typename Xs, typename ...Ys>
constexpr auto zip_with_t::operator()(F&& f, Xs&& xs, Ys&& ...ys) const {
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(detail::fast_and<
hana::Sequence<Xs>::value, hana::Sequence<Ys>::value...
>::value,
"hana::zip_with(f, xs, ys...) requires 'xs' and 'ys...' to be Sequences");
#endif
return zip_with_impl<typename hana::tag_of<Xs>::type>::apply(
static_cast<F&&>(f),
static_cast<Xs&&>(xs),
static_cast<Ys&&>(ys)...
);
}
//! @endcond
template <typename S>
struct zip_with_impl<S, when<Sequence<S>::value>> {
template <std::size_t N, typename F, typename ...Xs>
static constexpr decltype(auto) transverse(F&& f, Xs&& ...xs) {
return static_cast<F&&>(f)(hana::at_c<N>(static_cast<Xs&&>(xs))...);
}
template <std::size_t ...N, typename F, typename ...Xs>
static constexpr auto
zip_helper(std::index_sequence<N...>, F&& f, Xs&& ...xs) {
return hana::make<S>(transverse<N>(f, xs...)...);
}
template <typename F, typename X, typename ...Xs>
static constexpr auto
apply(F&& f, X&& x, Xs&& ...xs) {
constexpr std::size_t N = decltype(hana::length(x))::value;
return zip_helper(std::make_index_sequence<N>{},
static_cast<F&&>(f),
static_cast<X&&>(x), static_cast<Xs&&>(xs)...);
}
};
}} // end namespace boost::hana
#endif // !BOOST_HANA_ZIP_WITH_HPP
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