hana/fwd/members.hpp

0001 /*!
0002 @file
0003 Forward declares `boost::hana::members`.
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_FWD_MEMBERS_HPP
0011 #define BOOST_HANA_FWD_MEMBERS_HPP
0012
0013 #include <boost/hana/config.hpp>
0014 #include <boost/hana/core/when.hpp>
0015
0016
0017 namespace boost { namespace hana {
0018     //! Returns a `Sequence` containing the members of a `Struct`.
0019     //! @ingroup group-Struct
0020     //!
0021     //! Given a `Struct` object, `members` returns a `Sequence` containing
0022     //! all the members of the `Struct`, in the same order as their respective
0023     //! accessor appears in the `accessors` sequence.
0024     //!
0025     //!
0026     //! Example
0027     //! -------
0028     //! @include example/members.cpp
0029 #ifdef BOOST_HANA_DOXYGEN_INVOKED
0030     constexpr auto members = [](auto&& object) {
0031         return tag-dispatched;
0032     };
0033 #else
0034     template <typename S, typename = void>
0035     struct members_impl : members_impl<S, when<true>> { };
0036
0037     struct members_t {
0038         template <typename Object>
0039         constexpr auto operator()(Object&& object) const;
0040     };
0041
0042     BOOST_HANA_INLINE_VARIABLE constexpr members_t members{};
0043 #endif
0044 }} // end namespace boost::hana
0045
0046 #endif // !BOOST_HANA_FWD_MEMBERS_HPP