71 lines
2.3 KiB
C++
71 lines
2.3 KiB
C++
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/*!
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@file
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Defines `boost::hana::zip_with`.
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@copyright Louis Dionne 2013-2016
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_ZIP_WITH_HPP
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#define BOOST_HANA_ZIP_WITH_HPP
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#include <boost/hana/fwd/zip_with.hpp>
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#include <boost/hana/at.hpp>
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#include <boost/hana/concept/sequence.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/dispatch.hpp>
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#include <boost/hana/core/make.hpp>
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#include <boost/hana/detail/fast_and.hpp>
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#include <boost/hana/length.hpp>
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#include <cstddef>
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#include <utility>
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BOOST_HANA_NAMESPACE_BEGIN
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//! @cond
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template <typename F, typename Xs, typename ...Ys>
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constexpr auto zip_with_t::operator()(F&& f, Xs&& xs, Ys&& ...ys) const {
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(detail::fast_and<
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hana::Sequence<Xs>::value, hana::Sequence<Ys>::value...
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>::value,
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"hana::zip_with(f, xs, ys...) requires 'xs' and 'ys...' to be Sequences");
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#endif
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return zip_with_impl<typename hana::tag_of<Xs>::type>::apply(
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static_cast<F&&>(f),
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static_cast<Xs&&>(xs),
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static_cast<Ys&&>(ys)...
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);
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}
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//! @endcond
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template <typename S>
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struct zip_with_impl<S, when<Sequence<S>::value>> {
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template <std::size_t N, typename F, typename ...Xs>
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static constexpr decltype(auto) transverse(F&& f, Xs&& ...xs) {
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return static_cast<F&&>(f)(hana::at_c<N>(static_cast<Xs&&>(xs))...);
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}
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template <std::size_t ...N, typename F, typename ...Xs>
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static constexpr auto
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zip_helper(std::index_sequence<N...>, F&& f, Xs&& ...xs) {
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return hana::make<S>(transverse<N>(f, xs...)...);
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}
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template <typename F, typename X, typename ...Xs>
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static constexpr auto
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apply(F&& f, X&& x, Xs&& ...xs) {
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constexpr std::size_t N = decltype(hana::length(x))::value;
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return zip_helper(std::make_index_sequence<N>{},
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static_cast<F&&>(f),
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static_cast<X&&>(x), static_cast<Xs&&>(xs)...);
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}
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_ZIP_WITH_HPP
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