557f7e1398
Only the [cmp.alg] part (for `comparison_meow_fallback` CPOs) in the paper required changes. Other parts merely fixed preconditions of some standard library functions. I strongly feel that P2167R3 should be a DR despite that it is not a DR officially: CPOs -> C++20; remain parts -> C++98/11 (except that _`boolean-testable`_ should be transformed into the original _BooleanTestable_ requirements in the old resolution of LWG2114). Note that P2167R3 damaged the resolution of LWG3465: the type of `F < E` was left underconstrained. I've tried to submit an LWG issue for this, which is now LWG4157. Drive-by change: - enable some test coverages in `compare_strong_order_fallback.pass.cpp` when `TEST_LONG_DOUBLE_IS_DOUBLE`, following up #106742 Closes #105241.
73 lines
2.9 KiB
C++
73 lines
2.9 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___COMPARE_COMPARE_STRONG_ORDER_FALLBACK
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#define _LIBCPP___COMPARE_COMPARE_STRONG_ORDER_FALLBACK
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#include <__compare/ordering.h>
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#include <__compare/strong_order.h>
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#include <__concepts/boolean_testable.h>
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#include <__config>
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#include <__type_traits/decay.h>
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#include <__type_traits/is_same.h>
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#include <__utility/forward.h>
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#include <__utility/priority_tag.h>
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#ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
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# pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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#if _LIBCPP_STD_VER >= 20
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// [cmp.alg]
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namespace __compare_strong_order_fallback {
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struct __fn {
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template <class _Tp, class _Up>
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requires is_same_v<decay_t<_Tp>, decay_t<_Up>>
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_LIBCPP_HIDE_FROM_ABI static constexpr auto __go(_Tp&& __t, _Up&& __u, __priority_tag<1>) noexcept(
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noexcept(std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))))
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-> decltype(std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u))) {
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return std::strong_order(std::forward<_Tp>(__t), std::forward<_Up>(__u));
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}
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template <class _Tp, class _Up>
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requires is_same_v<decay_t<_Tp>, decay_t<_Up>> && requires(_Tp&& __t, _Up&& __u) {
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{ std::forward<_Tp>(__t) == std::forward<_Up>(__u) } -> __boolean_testable;
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{ std::forward<_Tp>(__t) < std::forward<_Up>(__u) } -> __boolean_testable;
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}
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_LIBCPP_HIDE_FROM_ABI static constexpr strong_ordering __go(_Tp&& __t, _Up&& __u, __priority_tag<0>) noexcept(
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noexcept(std::forward<_Tp>(__t) == std::forward<_Up>(__u) ? strong_ordering::equal
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: std::forward<_Tp>(__t) < std::forward<_Up>(__u) ? strong_ordering::less
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: strong_ordering::greater)) {
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return std::forward<_Tp>(__t) == std::forward<_Up>(__u) ? strong_ordering::equal
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: std::forward<_Tp>(__t) < std::forward<_Up>(__u)
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? strong_ordering::less
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: strong_ordering::greater;
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}
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template <class _Tp, class _Up>
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_LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Tp&& __t, _Up&& __u) const
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noexcept(noexcept(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>())))
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-> decltype(__go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>())) {
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return __go(std::forward<_Tp>(__t), std::forward<_Up>(__u), __priority_tag<1>());
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}
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};
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} // namespace __compare_strong_order_fallback
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inline namespace __cpo {
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inline constexpr auto compare_strong_order_fallback = __compare_strong_order_fallback::__fn{};
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} // namespace __cpo
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#endif // _LIBCPP_STD_VER >= 20
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP___COMPARE_COMPARE_STRONG_ORDER_FALLBACK
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