equality_comparable.hpp
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//
// traits/equality_comparable.hpp
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2020 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#ifndef ASIO_TRAITS_EQUALITY_COMPARABLE_HPP
#define ASIO_TRAITS_EQUALITY_COMPARABLE_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include "asio/detail/config.hpp"
#include "asio/detail/type_traits.hpp"
#if defined(ASIO_HAS_DECLTYPE) \
&& defined(ASIO_HAS_NOEXCEPT) \
&& defined(ASIO_HAS_WORKING_EXPRESSION_SFINAE)
# define ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT 1
#endif // defined(ASIO_HAS_DECLTYPE)
// && defined(ASIO_HAS_NOEXCEPT)
// && defined(ASIO_HAS_WORKING_EXPRESSION_SFINAE)
namespace asio {
namespace traits {
template <typename T, typename = void>
struct equality_comparable_default;
template <typename T, typename = void>
struct equality_comparable;
} // namespace traits
namespace detail {
struct no_equality_comparable
{
ASIO_STATIC_CONSTEXPR(bool, is_valid = false);
ASIO_STATIC_CONSTEXPR(bool, is_noexcept = false);
};
#if defined(ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT)
template <typename T, typename = void>
struct equality_comparable_trait : no_equality_comparable
{
};
template <typename T>
struct equality_comparable_trait<T,
typename void_type<
decltype(
static_cast<void>(
static_cast<bool>(declval<const T>() == declval<const T>())
),
static_cast<void>(
static_cast<bool>(declval<const T>() != declval<const T>())
)
)
>::type>
{
ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
ASIO_STATIC_CONSTEXPR(bool, is_noexcept =
noexcept(declval<const T>() == declval<const T>())
&& noexcept(declval<const T>() != declval<const T>()));
};
#else // defined(ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT)
template <typename T, typename = void>
struct equality_comparable_trait :
conditional<
is_same<T, typename decay<T>::type>::value,
no_equality_comparable,
traits::equality_comparable<typename decay<T>::type>
>::type
{
};
#endif // defined(ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT)
} // namespace detail
namespace traits {
template <typename T, typename>
struct equality_comparable_default : detail::equality_comparable_trait<T>
{
};
template <typename T, typename>
struct equality_comparable : equality_comparable_default<T>
{
};
} // namespace traits
} // namespace asio
#endif // ASIO_TRAITS_EQUALITY_COMPARABLE_HPP