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

   1 /*!
   2 @file
   3 Defines `boost::hana::accessors`.
   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_ACCESSORS_HPP
  11 #define BOOST_HANA_ACCESSORS_HPP
  12
  13 #include <boost/hana/fwd/accessors.hpp>
  14
  15 #include <boost/hana/concept/struct.hpp>
  16 #include <boost/hana/config.hpp>
  17 #include <boost/hana/core/dispatch.hpp>
  18
  19
  20 BOOST_HANA_NAMESPACE_BEGIN
  21     template <typename S>
  22     struct accessors_t {
  23     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
  24         static_assert(hana::Struct<S>::value,
  25         "hana::accessors<S> requires 'S' to be a Struct");
  26     #endif
  27
  28         constexpr decltype(auto) operator()() const {
  29             using Accessors = BOOST_HANA_DISPATCH_IF(accessors_impl<S>,
  30                 hana::Struct<S>::value
  31             );
  32
  33             return Accessors::apply();
  34         }
  35     };
  36
  37     template <typename S, bool condition>
  38     struct accessors_impl<S, when<condition>> : default_ {
  39         template <typename ...Args>
  40         static constexpr auto apply(Args&& ...) = delete;
  41     };
  42
  43     namespace struct_detail {
  44         template <typename ...>
  45         struct is_valid { static constexpr bool value = true; };
  46     }
  47
  48     template <typename S>
  49     struct accessors_impl<S, when<
  50         struct_detail::is_valid<typename S::hana_accessors_impl>::value
  51     >>
  52         : S::hana_accessors_impl
  53     { };
  54 BOOST_HANA_NAMESPACE_END
  55
  56 #endif // !BOOST_HANA_ACCESSORS_HPP