105 lines
2.6 KiB
C++
105 lines
2.6 KiB
C++
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//
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// traits/equality_comparable.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_TRAITS_EQUALITY_COMPARABLE_HPP
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#define ASIO_TRAITS_EQUALITY_COMPARABLE_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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#if defined(ASIO_HAS_DECLTYPE) \
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&& defined(ASIO_HAS_NOEXCEPT) \
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&& defined(ASIO_HAS_WORKING_EXPRESSION_SFINAE)
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# define ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT 1
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#endif // defined(ASIO_HAS_DECLTYPE)
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// && defined(ASIO_HAS_NOEXCEPT)
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// && defined(ASIO_HAS_WORKING_EXPRESSION_SFINAE)
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namespace asio {
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namespace traits {
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template <typename T, typename = void>
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struct equality_comparable_default;
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template <typename T, typename = void>
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struct equality_comparable;
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} // namespace traits
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namespace detail {
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struct no_equality_comparable
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{
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ASIO_STATIC_CONSTEXPR(bool, is_valid = false);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept = false);
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};
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#if defined(ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT)
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template <typename T, typename = void>
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struct equality_comparable_trait : no_equality_comparable
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{
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};
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template <typename T>
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struct equality_comparable_trait<T,
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typename void_type<
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decltype(
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static_cast<void>(
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static_cast<bool>(declval<const T>() == declval<const T>())
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),
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static_cast<void>(
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static_cast<bool>(declval<const T>() != declval<const T>())
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)
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)
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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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noexcept(declval<const T>() == declval<const T>())
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&& noexcept(declval<const T>() != declval<const T>()));
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};
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#else // defined(ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT)
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template <typename T, typename = void>
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struct equality_comparable_trait :
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conditional<
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is_same<T, typename decay<T>::type>::value,
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no_equality_comparable,
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traits::equality_comparable<typename decay<T>::type>
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>::type
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{
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};
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#endif // defined(ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT)
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} // namespace detail
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namespace traits {
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template <typename T, typename>
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struct equality_comparable_default : detail::equality_comparable_trait<T>
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{
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};
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template <typename T, typename>
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struct equality_comparable : equality_comparable_default<T>
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{
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};
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} // namespace traits
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} // namespace asio
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#endif // ASIO_TRAITS_EQUALITY_COMPARABLE_HPP
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