text: //
  // 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
  