55 lines
1.6 KiB
C++
55 lines
1.6 KiB
C++
// Copyright Louis Dionne 2013-2017
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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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#ifndef BOOST_HANA_TEST_STRUCT_MINIMAL_STRUCT_HPP
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#define BOOST_HANA_TEST_STRUCT_MINIMAL_STRUCT_HPP
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#include <boost/hana/at.hpp>
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#include <boost/hana/fwd/accessors.hpp>
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#include <boost/hana/pair.hpp>
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#include <boost/hana/range.hpp>
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#include <boost/hana/tuple.hpp>
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#include <boost/hana/unpack.hpp>
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template <int N>
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struct minimal_struct_tag;
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template <typename ...Members>
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struct minimal_struct_t {
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boost::hana::tuple<Members...> members;
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using hana_tag = minimal_struct_tag<sizeof...(Members)>;
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};
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struct obj_t {
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template <typename ...Members>
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constexpr minimal_struct_t<Members...> operator()(Members ...members) const {
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return {{static_cast<Members&&>(members)...}};
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}
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};
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constexpr obj_t obj{};
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namespace boost { namespace hana {
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template <int N>
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struct accessors_impl<minimal_struct_tag<N>> {
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template <typename K>
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struct get_member {
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template <typename Struct>
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constexpr decltype(auto) operator()(Struct&& s) const {
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return hana::at_c<K::value>(static_cast<Struct&&>(s).members);
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}
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};
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static auto apply() {
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return hana::unpack(hana::range_c<int, 0, N>, [](auto ...k) {
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return hana::make_tuple(
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hana::make_pair(k, get_member<decltype(k)>{})...
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);
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});
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}
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};
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}}
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#endif // !BOOST_HANA_TEST_STRUCT_MINIMAL_STRUCT_HPP
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