66 lines
2.0 KiB
C++
66 lines
2.0 KiB
C++
/*!
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@file
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Defines `boost::hana::members`.
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@copyright Louis Dionne 2013-2016
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_MEMBERS_HPP
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#define BOOST_HANA_MEMBERS_HPP
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#include <boost/hana/fwd/members.hpp>
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#include <boost/hana/accessors.hpp>
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#include <boost/hana/concept/struct.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/dispatch.hpp>
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#include <boost/hana/second.hpp>
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#include <boost/hana/transform.hpp>
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BOOST_HANA_NAMESPACE_BEGIN
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//! @cond
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template <typename Object>
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constexpr auto members_t::operator()(Object&& object) const {
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using S = typename hana::tag_of<Object>::type;
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using Members = BOOST_HANA_DISPATCH_IF(members_impl<S>,
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hana::Struct<S>::value
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);
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#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
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static_assert(hana::Struct<S>::value,
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"hana::members(object) requires 'object' to be a Struct");
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#endif
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return Members::apply(static_cast<Object&&>(object));
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}
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//! @endcond
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namespace struct_detail {
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template <typename Holder, typename Forward>
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struct members_helper {
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Holder object;
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template <typename Accessor>
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constexpr decltype(auto) operator()(Accessor&& accessor) const {
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return hana::second(static_cast<Accessor&&>(accessor))(
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static_cast<Forward>(object)
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);
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}
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};
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}
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template <typename S, bool condition>
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struct members_impl<S, when<condition>> : default_ {
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template <typename Object>
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static constexpr auto apply(Object&& object) {
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return hana::transform(hana::accessors<S>(),
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struct_detail::members_helper<Object&, Object&&>{object}
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);
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}
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_MEMBERS_HPP
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