llvm-project/libcxx/include/__concepts/equality_comparable.h

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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___CONCEPTS_EQUALITY_COMPARABLE_H
#define _LIBCPP___CONCEPTS_EQUALITY_COMPARABLE_H
#include <__concepts/boolean_testable.h>
#include <__concepts/common_reference_with.h>
#include <__config>
#include <type_traits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
// [concept.equalitycomparable]
template<class _Tp, class _Up>
concept __weakly_equality_comparable_with =
requires(__make_const_lvalue_ref<_Tp> __t, __make_const_lvalue_ref<_Up> __u) {
{ __t == __u } -> __boolean_testable;
{ __t != __u } -> __boolean_testable;
{ __u == __t } -> __boolean_testable;
{ __u != __t } -> __boolean_testable;
};
template<class _Tp>
concept equality_comparable = __weakly_equality_comparable_with<_Tp, _Tp>;
template<class _Tp, class _Up>
concept equality_comparable_with =
equality_comparable<_Tp> && equality_comparable<_Up> &&
common_reference_with<__make_const_lvalue_ref<_Tp>, __make_const_lvalue_ref<_Up>> &&
equality_comparable<
common_reference_t<
__make_const_lvalue_ref<_Tp>,
__make_const_lvalue_ref<_Up>>> &&
__weakly_equality_comparable_with<_Tp, _Up>;
#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_CONCEPTS)
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___CONCEPTS_EQUALITY_COMPARABLE_H