boost/hana/accessors.hpp

0001 /*!
0002 @file
0003 Defines `boost::hana::accessors`.
0004
0005 Copyright Louis Dionne 2013-2022
0006 Distributed under the Boost Software License, Version 1.0.
0007 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0008  */
0009
0010 #ifndef BOOST_HANA_ACCESSORS_HPP
0011 #define BOOST_HANA_ACCESSORS_HPP
0012
0013 #include <boost/hana/fwd/accessors.hpp>
0014
0015 #include <boost/hana/concept/struct.hpp>
0016 #include <boost/hana/config.hpp>
0017 #include <boost/hana/core/dispatch.hpp>
0018
0019
0020 namespace boost { namespace hana {
0021     template <typename S>
0022     struct accessors_t {
0023     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
0024         static_assert(hana::Struct<S>::value,
0025         "hana::accessors<S> requires 'S' to be a Struct");
0026     #endif
0027
0028         constexpr decltype(auto) operator()() const {
0029             using Accessors = BOOST_HANA_DISPATCH_IF(accessors_impl<S>,
0030                 hana::Struct<S>::value
0031             );
0032
0033             return Accessors::apply();
0034         }
0035     };
0036
0037     template <typename S, bool condition>
0038     struct accessors_impl<S, when<condition>> : default_ {
0039         template <typename ...Args>
0040         static constexpr auto apply(Args&& ...) = delete;
0041     };
0042
0043     namespace struct_detail {
0044         template <typename ...>
0045         struct is_valid { static constexpr bool value = true; };
0046     }
0047
0048     template <typename S>
0049     struct accessors_impl<S, when<
0050         struct_detail::is_valid<typename S::hana_accessors_impl>::value
0051     >>
0052         : S::hana_accessors_impl
0053     { };
0054 }} // end namespace boost::hana
0055
0056 #endif // !BOOST_HANA_ACCESSORS_HPP