ceph/src/boost/libs/hana/include/boost/hana/zip_with.hpp

   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