ceph/src/boost/boost/hana/keys.hpp

   1 /*!
   2 @file
   3 Defines `boost::hana::keys`.
   4
   5 @copyright Louis Dionne 2013-2017
   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_KEYS_HPP
  11 #define BOOST_HANA_KEYS_HPP
  12
  13 #include <boost/hana/fwd/keys.hpp>
  14
  15 #include <boost/hana/accessors.hpp>
  16 #include <boost/hana/concept/struct.hpp>
  17 #include <boost/hana/config.hpp>
  18 #include <boost/hana/core/dispatch.hpp>
  19 #include <boost/hana/first.hpp>
  20 #include <boost/hana/transform.hpp>
  21
  22
  23 namespace boost { namespace hana {
  24     //! @cond
  25     template <typename Map>
  26     constexpr auto keys_t::operator()(Map&& map) const {
  27         return keys_impl<typename hana::tag_of<Map>::type>::apply(
  28             static_cast<Map&&>(map)
  29         );
  30     }
  31     //! @endcond
  32
  33     template <typename T, bool condition>
  34     struct keys_impl<T, when<condition>> : default_ {
  35         template <typename ...Args>
  36         static constexpr auto apply(Args&& ...) = delete;
  37     };
  38
  39     template <typename S>
  40     struct keys_impl<S, when<hana::Struct<S>::value>> {
  41         template <typename Object>
  42         static constexpr auto apply(Object const&) {
  43             return hana::transform(hana::accessors<S>(), hana::first);
  44         }
  45     };
  46 }} // end namespace boost::hana
  47
  48 #endif // !BOOST_HANA_KEYS_HPP