ceph/src/boost/libs/hana/test/concept/struct/minimal_struct.hpp

   1 // Copyright Louis Dionne 2013-2017
   2 // Distributed under the Boost Software License, Version 1.0.
   3 // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   4
   5 #ifndef BOOST_HANA_TEST_STRUCT_MINIMAL_STRUCT_HPP
   6 #define BOOST_HANA_TEST_STRUCT_MINIMAL_STRUCT_HPP
   7
   8 #include <boost/hana/at.hpp>
   9 #include <boost/hana/fwd/accessors.hpp>
  10 #include <boost/hana/pair.hpp>
  11 #include <boost/hana/range.hpp>
  12 #include <boost/hana/tuple.hpp>
  13 #include <boost/hana/unpack.hpp>
  14
  15
  16 template <int N>
  17 struct minimal_struct_tag;
  18
  19 template <typename ...Members>
  20 struct minimal_struct_t {
  21     boost::hana::tuple<Members...> members;
  22     using hana_tag = minimal_struct_tag<sizeof...(Members)>;
  23 };
  24
  25 struct obj_t {
  26     template <typename ...Members>
  27     constexpr minimal_struct_t<Members...> operator()(Members ...members) const {
  28         return {{static_cast<Members&&>(members)...}};
  29     }
  30 };
  31 constexpr obj_t obj{};
  32
  33 namespace boost { namespace hana {
  34     template <int N>
  35     struct accessors_impl<minimal_struct_tag<N>> {
  36         template <typename K>
  37         struct get_member {
  38             template <typename Struct>
  39             constexpr decltype(auto) operator()(Struct&& s) const {
  40                 return hana::at_c<K::value>(static_cast<Struct&&>(s).members);
  41             }
  42         };
  43
  44         static auto apply() {
  45             return hana::unpack(hana::range_c<int, 0, N>, [](auto ...k) {
  46                 return hana::make_tuple(
  47                     hana::make_pair(k, get_member<decltype(k)>{})...
  48                 );
  49             });
  50         }
  51     };
  52 }}
  53
  54 #endif // !BOOST_HANA_TEST_STRUCT_MINIMAL_STRUCT_HPP