63 lines
1.2 KiB
C++
63 lines
1.2 KiB
C++
//
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// cpp03/require_concept_free.cpp
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// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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//
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// Copyright (c) 2003-2021 Christopher M. Kohlhoff (chris at kohlhoff dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#include <boost/asio/require_concept.hpp>
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#include <cassert>
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template <int>
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struct prop
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{
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static const bool is_requirable_concept = true;
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};
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template <int>
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struct object
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{
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template <int N>
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friend object<N> require_concept(const object&, prop<N>)
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{
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return object<N>();
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}
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};
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namespace boost {
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namespace asio {
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template<int N, int M>
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struct is_applicable_property<object<N>, prop<M> >
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{
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static const bool value = true;
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};
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namespace traits {
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template<int N, int M>
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struct require_concept_free<object<N>, prop<M> >
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{
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static const bool is_valid = true;
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static const bool is_noexcept = true;
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typedef object<M> result_type;
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};
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} // namespace traits
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} // namespace asio
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} // namespace boost
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int main()
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{
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object<1> o1 = {};
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object<2> o2 = boost::asio::require_concept(o1, prop<2>());
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(void)o2;
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const object<1> o3 = {};
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object<2> o4 = boost::asio::require_concept(o3, prop<2>());
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(void)o4;
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}
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