233 lines
6.6 KiB
C++
233 lines
6.6 KiB
C++
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//
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// execution/context_as.hpp
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// ~~~~~~~~~~~~~~~~~~~~~~~~
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//
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// Copyright (c) 2003-2023 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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#ifndef ASIO_EXECUTION_CONTEXT_AS_HPP
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#define ASIO_EXECUTION_CONTEXT_AS_HPP
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#if defined(_MSC_VER) && (_MSC_VER >= 1200)
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# pragma once
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#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
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#include "asio/detail/config.hpp"
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#include "asio/detail/type_traits.hpp"
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#include "asio/execution/context.hpp"
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#include "asio/execution/executor.hpp"
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#include "asio/execution/scheduler.hpp"
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#include "asio/execution/sender.hpp"
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#include "asio/is_applicable_property.hpp"
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#include "asio/query.hpp"
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#include "asio/traits/query_static_constexpr_member.hpp"
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#include "asio/traits/static_query.hpp"
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#include "asio/detail/push_options.hpp"
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namespace asio {
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#if defined(GENERATING_DOCUMENTATION)
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namespace execution {
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/// A property that is used to obtain the execution context that is associated
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/// with an executor.
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template <typename U>
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struct context_as_t
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{
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/// The context_as_t property applies to executors, senders, and schedulers.
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template <typename T>
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static constexpr bool is_applicable_property_v =
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is_executor_v<T> || is_sender_v<T> || is_scheduler_v<T>;
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/// The context_t property cannot be required.
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static constexpr bool is_requirable = false;
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/// The context_t property cannot be preferred.
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static constexpr bool is_preferable = false;
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/// The type returned by queries against an @c any_executor.
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typedef T polymorphic_query_result_type;
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};
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/// A special value used for accessing the context_as_t property.
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template <typename U>
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constexpr context_as_t context_as;
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} // namespace execution
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#else // defined(GENERATING_DOCUMENTATION)
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namespace execution {
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template <typename T>
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struct context_as_t
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{
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#if defined(ASIO_HAS_VARIABLE_TEMPLATES)
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# if defined(ASIO_NO_DEPRECATED)
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template <typename U>
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ASIO_STATIC_CONSTEXPR(bool,
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is_applicable_property_v = (
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is_executor<U>::value));
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# else // defined(ASIO_NO_DEPRECATED)
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template <typename U>
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ASIO_STATIC_CONSTEXPR(bool,
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is_applicable_property_v = (
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is_executor<U>::value
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|| conditional<
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is_executor<U>::value,
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false_type,
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is_sender<U>
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>::type::value
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|| conditional<
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is_executor<U>::value,
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false_type,
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is_scheduler<U>
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>::type::value
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));
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# endif // defined(ASIO_NO_DEPRECATED)
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#endif // defined(ASIO_HAS_VARIABLE_TEMPLATES)
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ASIO_STATIC_CONSTEXPR(bool, is_requirable = false);
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ASIO_STATIC_CONSTEXPR(bool, is_preferable = false);
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typedef T polymorphic_query_result_type;
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ASIO_CONSTEXPR context_as_t()
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{
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}
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ASIO_CONSTEXPR context_as_t(context_t)
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{
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}
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#if defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \
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&& defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
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template <typename E>
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static ASIO_CONSTEXPR
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typename context_t::query_static_constexpr_member<E>::result_type
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static_query()
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ASIO_NOEXCEPT_IF((
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context_t::query_static_constexpr_member<E>::is_noexcept))
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{
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return context_t::query_static_constexpr_member<E>::value();
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}
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template <typename E, typename U = decltype(context_as_t::static_query<E>())>
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static ASIO_CONSTEXPR const U static_query_v
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= context_as_t::static_query<E>();
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#endif // defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT)
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// && defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
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template <typename Executor, typename U>
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friend ASIO_CONSTEXPR U query(
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const Executor& ex, const context_as_t<U>&,
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typename enable_if<
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is_same<T, U>::value
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>::type* = 0,
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typename enable_if<
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can_query<const Executor&, const context_t&>::value
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>::type* = 0)
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#if !defined(__clang__) // Clang crashes if noexcept is used here.
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#if defined(ASIO_MSVC) // Visual C++ wants the type to be qualified.
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ASIO_NOEXCEPT_IF((
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is_nothrow_query<const Executor&, const context_t&>::value))
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#else // defined(ASIO_MSVC)
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ASIO_NOEXCEPT_IF((
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is_nothrow_query<const Executor&, const context_t&>::value))
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#endif // defined(ASIO_MSVC)
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#endif // !defined(__clang__)
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{
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return asio::query(ex, context);
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}
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};
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#if defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \
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&& defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
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template <typename T> template <typename E, typename U>
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const U context_as_t<T>::static_query_v;
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#endif // defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT)
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// && defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
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#if (defined(ASIO_HAS_VARIABLE_TEMPLATES) \
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&& defined(ASIO_HAS_CONSTEXPR)) \
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|| defined(GENERATING_DOCUMENTATION)
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template <typename T>
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constexpr context_as_t<T> context_as{};
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#endif // (defined(ASIO_HAS_VARIABLE_TEMPLATES)
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// && defined(ASIO_HAS_CONSTEXPR))
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// || defined(GENERATING_DOCUMENTATION)
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} // namespace execution
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#if !defined(ASIO_HAS_VARIABLE_TEMPLATES)
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template <typename T, typename U>
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struct is_applicable_property<T, execution::context_as_t<U> >
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: integral_constant<bool,
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execution::is_executor<T>::value
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#if !defined(ASIO_NO_DEPRECATED)
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|| conditional<
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execution::is_executor<T>::value,
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false_type,
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execution::is_sender<T>
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>::type::value
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|| conditional<
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execution::is_executor<T>::value,
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false_type,
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execution::is_scheduler<T>
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>::type::value
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#endif // !defined(ASIO_NO_DEPRECATED)
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>
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{
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};
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#endif // !defined(ASIO_HAS_VARIABLE_TEMPLATES)
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namespace traits {
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#if !defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \
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|| !defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
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template <typename T, typename U>
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struct static_query<T, execution::context_as_t<U>,
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typename enable_if<
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static_query<T, execution::context_t>::is_valid
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>::type> : static_query<T, execution::context_t>
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{
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};
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#endif // !defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT)
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// || !defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
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#if !defined(ASIO_HAS_DEDUCED_QUERY_FREE_TRAIT)
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template <typename T, typename U>
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struct query_free<T, execution::context_as_t<U>,
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typename enable_if<
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can_query<const T&, const execution::context_t&>::value
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>::type>
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{
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ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept =
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(is_nothrow_query<const T&, const execution::context_t&>::value));
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typedef U result_type;
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};
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#endif // !defined(ASIO_HAS_DEDUCED_QUERY_FREE_TRAIT)
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} // namespace traits
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#endif // defined(GENERATING_DOCUMENTATION)
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} // namespace asio
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#include "asio/detail/pop_options.hpp"
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#endif // ASIO_EXECUTION_CONTEXT_AS_HPP
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