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

   1 /*!
   2 @file
   3 Defines `boost::hana::for_each`.
   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_FOR_EACH_HPP
  11 #define BOOST_HANA_FOR_EACH_HPP
  12
  13 #include <boost/hana/fwd/for_each.hpp>
  14
  15 #include <boost/hana/concept/foldable.hpp>
  16 #include <boost/hana/config.hpp>
  17 #include <boost/hana/core/dispatch.hpp>
  18 #include <boost/hana/unpack.hpp>
  19
  20
  21 BOOST_HANA_NAMESPACE_BEGIN
  22     //! @cond
  23     template <typename Xs, typename F>
  24     constexpr void for_each_t::operator()(Xs&& xs, F&& f) const {
  25         using S = typename hana::tag_of<Xs>::type;
  26         using ForEach = BOOST_HANA_DISPATCH_IF(for_each_impl<S>,
  27             hana::Foldable<S>::value
  28         );
  29
  30     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
  31         static_assert(hana::Foldable<S>::value,
  32         "hana::for_each(xs, f) requires 'xs' to be Foldable");
  33     #endif
  34
  35         return ForEach::apply(static_cast<Xs&&>(xs), static_cast<F&&>(f));
  36     }
  37     //! @endcond
  38
  39     namespace detail {
  40         template <typename F>
  41         struct on_each {
  42             F f;
  43             template <typename ...Xs>
  44             constexpr void operator()(Xs&& ...xs) const {
  45                 using Swallow = int[];
  46                 (void)Swallow{0, ((void)(*f)(static_cast<Xs&&>(xs)), 0)...};
  47             }
  48         };
  49     }
  50
  51     template <typename T, bool condition>
  52     struct for_each_impl<T, when<condition>> : default_ {
  53         template <typename Xs, typename F>
  54         static constexpr void apply(Xs&& xs, F&& f) {
  55             // We use a pointer instead of a reference to avoid a Clang ICE.
  56             hana::unpack(static_cast<Xs&&>(xs),
  57                          detail::on_each<decltype(&f)>{&f});
  58         }
  59     };
  60 BOOST_HANA_NAMESPACE_END
  61
  62 #endif // !BOOST_HANA_FOR_EACH_HPP