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done_as_optional.hpp
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done_as_optional.hpp
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/*
* Copyright (c) Facebook, Inc. and its affiliates.
*
* Licensed under the Apache License Version 2.0 with LLVM Exceptions
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* https://llvm.org/LICENSE.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include <optional>
#include <unifex/config.hpp>
#include <unifex/bind_back.hpp>
#include <unifex/just.hpp>
#include <unifex/let_done.hpp>
#include <unifex/sender_concepts.hpp>
#include <unifex/then.hpp>
#include <unifex/type_traits.hpp>
#include <unifex/detail/prologue.hpp>
namespace unifex {
namespace _done_as_opt {
namespace _cpo {
inline const struct _fn {
template(typename Sender) //
(requires _single_sender<Sender>) //
auto
operator()(Sender&& predecessor) const {
using optional_t = std::optional<
non_void_t<std::decay_t<sender_single_value_return_type_t<Sender>>>>;
return let_done(
then(
(Sender &&) predecessor,
[](auto&&... ts) noexcept(
noexcept(optional_t{std::in_place, (decltype(ts))ts...})) {
return optional_t{std::in_place, (decltype(ts))ts...};
}),
[]() noexcept { return just(optional_t{}); });
}
constexpr auto operator()() const noexcept -> bind_back_result_t<_fn> {
return bind_back(*this);
}
} done_as_optional{};
} // namespace _cpo
} // namespace _done_as_opt
using _done_as_opt::_cpo::done_as_optional;
} // namespace unifex
#include <unifex/detail/epilogue.hpp>