// -*- C++ -*- operator<=> three-way comparison support. // Copyright (C) 2019-2020 Free Software Foundation, Inc. // // This file is part of GCC. // // GCC is free software; you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by // the Free Software Foundation; either version 3, or (at your option) // any later version. // // GCC is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see // <http://www.gnu.org/licenses/>. /** @file compare * This is a Standard C++ Library header. */ #ifndef _COMPARE #define _COMPARE #pragma GCC system_header #if __cplusplus > 201703L && __cpp_impl_three_way_comparison >= 201907L #pragma GCC visibility push(default) #include <concepts> #if __cpp_lib_concepts # define __cpp_lib_three_way_comparison 201907L #endif namespace std { // [cmp.categories], comparison category types namespace __cmp_cat { using type = signed char; enum class _Ord : type { equivalent = 0, less = -1, greater = 1 }; enum class _Ncmp : type { _Unordered = 2 }; struct __unspec { constexpr __unspec(__unspec*) noexcept { } }; } class partial_ordering { // less=0xff, equiv=0x00, greater=0x01, unordered=0x02 __cmp_cat::type _M_value; constexpr explicit partial_ordering(__cmp_cat::_Ord __v) noexcept : _M_value(__cmp_cat::type(__v)) { } constexpr explicit partial_ordering(__cmp_cat::_Ncmp __v) noexcept : _M_value(__cmp_cat::type(__v)) { } friend class weak_ordering; friend class strong_ordering; public: // valid values static const partial_ordering less; static const partial_ordering equivalent; static const partial_ordering greater; static const partial_ordering unordered; // comparisons friend constexpr bool operator==(partial_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value == 0; } friend constexpr bool operator==(partial_ordering, partial_ordering) noexcept = default; friend constexpr bool operator< (partial_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value == -1; } friend constexpr bool operator> (partial_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value == 1; } friend constexpr bool operator<=(partial_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value <= 0; } friend constexpr bool operator>=(partial_ordering __v, __cmp_cat::__unspec) noexcept { return __cmp_cat::type(__v._M_value & 1) == __v._M_value; } friend constexpr bool operator< (__cmp_cat::__unspec, partial_ordering __v) noexcept { return __v._M_value == 1; } friend constexpr bool operator> (__cmp_cat::__unspec, partial_ordering __v) noexcept { return __v._M_value == -1; } friend constexpr bool operator<=(__cmp_cat::__unspec, partial_ordering __v) noexcept { return __cmp_cat::type(__v._M_value & 1) == __v._M_value; } friend constexpr bool operator>=(__cmp_cat::__unspec, partial_ordering __v) noexcept { return 0 >= __v._M_value; } friend constexpr partial_ordering operator<=>(partial_ordering __v, __cmp_cat::__unspec) noexcept { return __v; } friend constexpr partial_ordering operator<=>(__cmp_cat::__unspec, partial_ordering __v) noexcept { if (__v._M_value & 1) return partial_ordering(__cmp_cat::_Ord(-__v._M_value)); else return __v; } }; // valid values' definitions inline constexpr partial_ordering partial_ordering::less(__cmp_cat::_Ord::less); inline constexpr partial_ordering partial_ordering::equivalent(__cmp_cat::_Ord::equivalent); inline constexpr partial_ordering partial_ordering::greater(__cmp_cat::_Ord::greater); inline constexpr partial_ordering partial_ordering::unordered(__cmp_cat::_Ncmp::_Unordered); class weak_ordering { __cmp_cat::type _M_value; constexpr explicit weak_ordering(__cmp_cat::_Ord __v) noexcept : _M_value(__cmp_cat::type(__v)) { } friend class strong_ordering; public: // valid values static const weak_ordering less; static const weak_ordering equivalent; static const weak_ordering greater; constexpr operator partial_ordering() const noexcept { return partial_ordering(__cmp_cat::_Ord(_M_value)); } // comparisons friend constexpr bool operator==(weak_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value == 0; } friend constexpr bool operator==(weak_ordering, weak_ordering) noexcept = default; friend constexpr bool operator< (weak_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value < 0; } friend constexpr bool operator> (weak_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value > 0; } friend constexpr bool operator<=(weak_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value <= 0; } friend constexpr bool operator>=(weak_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value >= 0; } friend constexpr bool operator< (__cmp_cat::__unspec, weak_ordering __v) noexcept { return 0 < __v._M_value; } friend constexpr bool operator> (__cmp_cat::__unspec, weak_ordering __v) noexcept { return 0 > __v._M_value; } friend constexpr bool operator<=(__cmp_cat::__unspec, weak_ordering __v) noexcept { return 0 <= __v._M_value; } friend constexpr bool operator>=(__cmp_cat::__unspec, weak_ordering __v) noexcept { return 0 >= __v._M_value; } friend constexpr weak_ordering operator<=>(weak_ordering __v, __cmp_cat::__unspec) noexcept { return __v; } friend constexpr weak_ordering operator<=>(__cmp_cat::__unspec, weak_ordering __v) noexcept { return weak_ordering(__cmp_cat::_Ord(-__v._M_value)); } }; // valid values' definitions inline constexpr weak_ordering weak_ordering::less(__cmp_cat::_Ord::less); inline constexpr weak_ordering weak_ordering::equivalent(__cmp_cat::_Ord::equivalent); inline constexpr weak_ordering weak_ordering::greater(__cmp_cat::_Ord::greater); class strong_ordering { __cmp_cat::type _M_value; constexpr explicit strong_ordering(__cmp_cat::_Ord __v) noexcept : _M_value(__cmp_cat::type(__v)) { } public: // valid values static const strong_ordering less; static const strong_ordering equal; static const strong_ordering equivalent; static const strong_ordering greater; constexpr operator partial_ordering() const noexcept { return partial_ordering(__cmp_cat::_Ord(_M_value)); } constexpr operator weak_ordering() const noexcept { return weak_ordering(__cmp_cat::_Ord(_M_value)); } // comparisons friend constexpr bool operator==(strong_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value == 0; } friend constexpr bool operator==(strong_ordering, strong_ordering) noexcept = default; friend constexpr bool operator< (strong_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value < 0; } friend constexpr bool operator> (strong_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value > 0; } friend constexpr bool operator<=(strong_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value <= 0; } friend constexpr bool operator>=(strong_ordering __v, __cmp_cat::__unspec) noexcept { return __v._M_value >= 0; } friend constexpr bool operator< (__cmp_cat::__unspec, strong_ordering __v) noexcept { return 0 < __v._M_value; } friend constexpr bool operator> (__cmp_cat::__unspec, strong_ordering __v) noexcept { return 0 > __v._M_value; } friend constexpr bool operator<=(__cmp_cat::__unspec, strong_ordering __v) noexcept { return 0 <= __v._M_value; } friend constexpr bool operator>=(__cmp_cat::__unspec, strong_ordering __v) noexcept { return 0 >= __v._M_value; } friend constexpr strong_ordering operator<=>(strong_ordering __v, __cmp_cat::__unspec) noexcept { return __v; } friend constexpr strong_ordering operator<=>(__cmp_cat::__unspec, strong_ordering __v) noexcept { return strong_ordering(__cmp_cat::_Ord(-__v._M_value)); } }; // valid values' definitions inline constexpr strong_ordering strong_ordering::less(__cmp_cat::_Ord::less); inline constexpr strong_ordering strong_ordering::equal(__cmp_cat::_Ord::equivalent); inline constexpr strong_ordering strong_ordering::equivalent(__cmp_cat::_Ord::equivalent); inline constexpr strong_ordering strong_ordering::greater(__cmp_cat::_Ord::greater); // named comparison functions constexpr bool is_eq(partial_ordering __cmp) noexcept { return __cmp == 0; } constexpr bool is_neq(partial_ordering __cmp) noexcept { return __cmp != 0; } constexpr bool is_lt (partial_ordering __cmp) noexcept { return __cmp < 0; } constexpr bool is_lteq(partial_ordering __cmp) noexcept { return __cmp <= 0; } constexpr bool is_gt (partial_ordering __cmp) noexcept { return __cmp > 0; } constexpr bool is_gteq(partial_ordering __cmp) noexcept { return __cmp >= 0; } namespace __detail { template<typename _Tp> inline constexpr unsigned __cmp_cat_id = 1; template<> inline constexpr unsigned __cmp_cat_id<partial_ordering> = 2; template<> inline constexpr unsigned __cmp_cat_id<weak_ordering> = 4; template<> inline constexpr unsigned __cmp_cat_id<strong_ordering> = 8; template<typename... _Ts> constexpr auto __common_cmp_cat() { constexpr unsigned __cats = (__cmp_cat_id<_Ts> | ...); // If any Ti is not a comparison category type, U is void. if constexpr (__cats & 1) return; // Otherwise, if at least one Ti is std::partial_ordering, // U is std::partial_ordering. else if constexpr (bool(__cats & __cmp_cat_id<partial_ordering>)) return partial_ordering::equivalent; // Otherwise, if at least one Ti is std::weak_ordering, // U is std::weak_ordering. else if constexpr (bool(__cats & __cmp_cat_id<weak_ordering>)) return weak_ordering::equivalent; // Otherwise, U is std::strong_ordering. else return strong_ordering::equivalent; } } // namespace __detail // [cmp.common], common comparison category type template<typename... _Ts> struct common_comparison_category { using type = decltype(__detail::__common_cmp_cat<_Ts...>()); }; // Partial specializations for one and zero argument cases. template<typename _Tp> struct common_comparison_category<_Tp> { using type = void; }; template<> struct common_comparison_category<partial_ordering> { using type = partial_ordering; }; template<> struct common_comparison_category<weak_ordering> { using type = weak_ordering; }; template<> struct common_comparison_category<strong_ordering> { using type = strong_ordering; }; template<> struct common_comparison_category<> { using type = strong_ordering; }; template<typename... _Ts> using common_comparison_category_t = typename common_comparison_category<_Ts...>::type; #if __cpp_lib_concepts namespace __detail { template<typename _Tp, typename _Cat> concept __compares_as = same_as<common_comparison_category_t<_Tp, _Cat>, _Cat>; } // namespace __detail // [cmp.concept], concept three_way_comparable template<typename _Tp, typename _Cat = partial_ordering> concept three_way_comparable = __detail::__weakly_eq_cmp_with<_Tp, _Tp> && __detail::__partially_ordered_with<_Tp, _Tp> && requires(const remove_reference_t<_Tp>& __a, const remove_reference_t<_Tp>& __b) { { __a <=> __b } -> __detail::__compares_as<_Cat>; }; template<typename _Tp, typename _Up, typename _Cat = partial_ordering> concept three_way_comparable_with = three_way_comparable<_Tp, _Cat> && three_way_comparable<_Up, _Cat> && common_reference_with<const remove_reference_t<_Tp>&, const remove_reference_t<_Up>&> && three_way_comparable< common_reference_t<const remove_reference_t<_Tp>&, const remove_reference_t<_Up>&>, _Cat> && __detail::__weakly_eq_cmp_with<_Tp, _Up> && __detail::__partially_ordered_with<_Tp, _Up> && requires(const remove_reference_t<_Tp>& __t, const remove_reference_t<_Up>& __u) { { __t <=> __u } -> __detail::__compares_as<_Cat>; { __u <=> __t } -> __detail::__compares_as<_Cat>; }; namespace __detail { template<typename _Tp, typename _Up> using __cmp3way_res_t = decltype(std::declval<_Tp>() <=> std::declval<_Up>()); // Implementation of std::compare_three_way_result. // It is undefined for a program to add specializations of // std::compare_three_way_result, so the std::compare_three_way_result_t // alias ignores std::compare_three_way_result and uses // __detail::__cmp3way_res_impl directly instead. template<typename _Tp, typename _Up> struct __cmp3way_res_impl { }; template<typename _Tp, typename _Up> requires requires { typename __cmp3way_res_t<__cref<_Tp>, __cref<_Up>>; } struct __cmp3way_res_impl<_Tp, _Up> { using type = __cmp3way_res_t<__cref<_Tp>, __cref<_Up>>; }; } // namespace __detail /// [cmp.result], result of three-way comparison template<typename _Tp, typename _Up = _Tp> struct compare_three_way_result : __detail::__cmp3way_res_impl<_Tp, _Up> { }; /// [cmp.result], result of three-way comparison template<typename _Tp, typename _Up = _Tp> using compare_three_way_result_t = typename __detail::__cmp3way_res_impl<_Tp, _Up>::type; namespace __detail { // BUILTIN-PTR-THREE-WAY(T, U) template<typename _Tp, typename _Up> concept __3way_builtin_ptr_cmp = requires(_Tp&& __t, _Up&& __u) { static_cast<_Tp&&>(__t) <=> static_cast<_Up&&>(__u); } && convertible_to<_Tp, const volatile void*> && convertible_to<_Up, const volatile void*> && ! requires(_Tp&& __t, _Up&& __u) { operator<=>(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u)); } && ! requires(_Tp&& __t, _Up&& __u) { static_cast<_Tp&&>(__t).operator<=>(static_cast<_Up&&>(__u)); }; } // namespace __detail // [cmp.object], typename compare_three_way struct compare_three_way { template<typename _Tp, typename _Up> requires three_way_comparable_with<_Tp, _Up> || __detail::__3way_builtin_ptr_cmp<_Tp, _Up> constexpr auto operator()(_Tp&& __t, _Up&& __u) const noexcept(noexcept(std::declval<_Tp>() <=> std::declval<_Up>())) { if constexpr (__detail::__3way_builtin_ptr_cmp<_Tp, _Up>) { auto __pt = static_cast<const volatile void*>(__t); auto __pu = static_cast<const volatile void*>(__u); if (__builtin_is_constant_evaluated()) return __pt <=> __pu; auto __it = reinterpret_cast<__UINTPTR_TYPE__>(__pt); auto __iu = reinterpret_cast<__UINTPTR_TYPE__>(__pu); return __it <=> __iu; } else return static_cast<_Tp&&>(__t) <=> static_cast<_Up&&>(__u); } using is_transparent = void; }; namespace __cmp_cust { template<floating_point _Tp> constexpr weak_ordering __fp_weak_ordering(_Tp __e, _Tp __f) { // Returns an integer with the same sign as the argument, and magnitude // indicating the classification: zero=1 subnorm=2 norm=3 inf=4 nan=5 auto __cat = [](_Tp __fp) -> int { const int __sign = __builtin_signbit(__fp) ? -1 : 1; if (__builtin_isnormal(__fp)) return (__fp == 0 ? 1 : 3) * __sign; if (__builtin_isnan(__fp)) return 5 * __sign; if (int __inf = __builtin_isinf_sign(__fp)) return 4 * __inf; return 2 * __sign; }; auto __po = __e <=> __f; if (is_lt(__po)) return weak_ordering::less; else if (is_gt(__po)) return weak_ordering::greater; else if (__po == partial_ordering::equivalent) return weak_ordering::equivalent; else // unordered, at least one argument is NaN { // return -1 for negative nan, +1 for positive nan, 0 otherwise. auto __isnan_sign = [](_Tp __fp) -> int { return __builtin_isnan(__fp) ? __builtin_signbit(__fp) ? -1 : 1 : 0; }; auto __ord = __isnan_sign(__e) <=> __isnan_sign(__f); if (is_eq(__ord)) return weak_ordering::equivalent; else if (is_lt(__ord)) return weak_ordering::less; else return weak_ordering::greater; } } template<typename _Tp, typename _Up> concept __adl_strong = requires(_Tp&& __t, _Up&& __u) { strong_ordering(strong_order(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u))); }; template<typename _Tp, typename _Up> concept __adl_weak = requires(_Tp&& __t, _Up&& __u) { weak_ordering(weak_order(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u))); }; template<typename _Tp, typename _Up> concept __adl_partial = requires(_Tp&& __t, _Up&& __u) { partial_ordering(partial_order(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u))); }; template<typename _Ord, typename _Tp, typename _Up> concept __cmp3way = requires(_Tp&& __t, _Up&& __u, compare_three_way __c) { _Ord(__c(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u))); }; template<typename _Tp, typename _Up> concept __strongly_ordered = __adl_strong<_Tp, _Up> // FIXME: || floating_point<remove_reference_t<_Tp>> || __cmp3way<strong_ordering, _Tp, _Up>; class _Strong_order { template<typename _Tp, typename _Up> static constexpr bool _S_noexcept() { if constexpr (floating_point<decay_t<_Tp>>) return true; else if constexpr (__adl_strong<_Tp, _Up>) return noexcept(strong_ordering(strong_order(std::declval<_Tp>(), std::declval<_Up>()))); else if constexpr (__cmp3way<strong_ordering, _Tp, _Up>) return noexcept(compare_three_way()(std::declval<_Tp>(), std::declval<_Up>())); } friend class _Weak_order; friend class _Strong_fallback; public: template<typename _Tp, typename _Up> requires __strongly_ordered<_Tp, _Up> constexpr strong_ordering operator()(_Tp&& __e, _Up&& __f) const noexcept(_S_noexcept<_Tp, _Up>()) { static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>); /* FIXME: if constexpr (floating_point<decay_t<_Tp>>) return __cmp_cust::__fp_strong_order(__e, __f); else */ if constexpr (__adl_strong<_Tp, _Up>) return strong_ordering(strong_order(static_cast<_Tp&&>(__e), static_cast<_Up&&>(__f))); else if constexpr (__cmp3way<strong_ordering, _Tp, _Up>) return compare_three_way()(static_cast<_Tp&&>(__e), static_cast<_Up&&>(__f)); } }; template<typename _Tp, typename _Up> concept __weakly_ordered = floating_point<remove_reference_t<_Tp>> || __adl_weak<_Tp, _Up> || __cmp3way<weak_ordering, _Tp, _Up> || __strongly_ordered<_Tp, _Up>; class _Weak_order { template<typename _Tp, typename _Up> static constexpr bool _S_noexcept() { if constexpr (floating_point<decay_t<_Tp>>) return true; else if constexpr (__adl_weak<_Tp, _Up>) return noexcept(weak_ordering(weak_order(std::declval<_Tp>(), std::declval<_Up>()))); else if constexpr (__cmp3way<weak_ordering, _Tp, _Up>) return noexcept(compare_three_way()(std::declval<_Tp>(), std::declval<_Up>())); else if constexpr (__strongly_ordered<_Tp, _Up>) return _Strong_order::_S_noexcept<_Tp, _Up>(); } friend class _Partial_order; friend class _Weak_fallback; public: template<typename _Tp, typename _Up> requires __weakly_ordered<_Tp, _Up> constexpr weak_ordering operator()(_Tp&& __e, _Up&& __f) const noexcept(_S_noexcept<_Tp, _Up>()) { static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>); if constexpr (floating_point<decay_t<_Tp>>) return __cmp_cust::__fp_weak_ordering(__e, __f); else if constexpr (__adl_weak<_Tp, _Up>) return weak_ordering(weak_order(static_cast<_Tp&&>(__e), static_cast<_Up&&>(__f))); else if constexpr (__cmp3way<weak_ordering, _Tp, _Up>) return compare_three_way()(static_cast<_Tp&&>(__e), static_cast<_Up&&>(__f)); else if constexpr (__strongly_ordered<_Tp, _Up>) return _Strong_order{}(static_cast<_Tp&&>(__e), static_cast<_Up&&>(__f)); } }; template<typename _Tp, typename _Up> concept __partially_ordered = __adl_partial<_Tp, _Up> || __cmp3way<partial_ordering, _Tp, _Up> || __weakly_ordered<_Tp, _Up>; class _Partial_order { template<typename _Tp, typename _Up> static constexpr bool _S_noexcept() { if constexpr (__adl_partial<_Tp, _Up>) return noexcept(partial_ordering(partial_order(std::declval<_Tp>(), std::declval<_Up>()))); else if constexpr (__cmp3way<partial_ordering, _Tp, _Up>) return noexcept(compare_three_way()(std::declval<_Tp>(), std::declval<_Up>())); else if constexpr (__weakly_ordered<_Tp, _Up>) return _Weak_order::_S_noexcept<_Tp, _Up>(); } friend class _Partial_fallback; public: template<typename _Tp, typename _Up> requires __partially_ordered<_Tp, _Up> constexpr partial_ordering operator()(_Tp&& __e, _Up&& __f) const noexcept(_S_noexcept<_Tp, _Up>()) { static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>); if constexpr (__adl_partial<_Tp, _Up>) return partial_ordering(partial_order(static_cast<_Tp&&>(__e), static_cast<_Up&&>(__f))); else if constexpr (__cmp3way<partial_ordering, _Tp, _Up>) return compare_three_way()(static_cast<_Tp&&>(__e), static_cast<_Up&&>(__f)); else if constexpr (__weakly_ordered<_Tp, _Up>) return _Weak_order{}(static_cast<_Tp&&>(__e), static_cast<_Up&&>(__f)); } }; template<typename _Tp, typename _Up> concept __op_eq_lt = requires(_Tp&& __t, _Up&& __u) { { static_cast<_Tp&&>(__t) == static_cast<_Up&&>(__u) } -> convertible_to<bool>; { static_cast<_Tp&&>(__t) < static_cast<_Up&&>(__u) } -> convertible_to<bool>; }; class _Strong_fallback { template<typename _Tp, typename _Up> static constexpr bool _S_noexcept() { if constexpr (__strongly_ordered<_Tp, _Up>) return _Strong_order::_S_noexcept<_Tp, _Up>(); else return noexcept(bool(std::declval<_Tp>() == std::declval<_Up>())) && noexcept(bool(std::declval<_Tp>() < std::declval<_Up>())); } public: template<typename _Tp, typename _Up> requires __strongly_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up> constexpr decltype(auto) operator()(_Tp&& __e, _Up&& __f) const noexcept(_S_noexcept<_Tp, _Up>()) { static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>); if constexpr (__strongly_ordered<_Tp, _Up>) return _Strong_order{}(static_cast<_Tp&&>(__e), static_cast<_Up&&>(__f)); else if constexpr (__op_eq_lt<_Tp, _Up>) return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f) ? strong_ordering::equal : static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f) ? strong_ordering::less : strong_ordering::greater; } }; class _Weak_fallback { template<typename _Tp, typename _Up> static constexpr bool _S_noexcept() { if constexpr (__weakly_ordered<_Tp, _Up>) return _Weak_order::_S_noexcept<_Tp, _Up>(); else return noexcept(bool(std::declval<_Tp>() == std::declval<_Up>())) && noexcept(bool(std::declval<_Tp>() < std::declval<_Up>())); } public: template<typename _Tp, typename _Up> requires __weakly_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up> constexpr decltype(auto) operator()(_Tp&& __e, _Up&& __f) const noexcept(_S_noexcept<_Tp, _Up>()) { static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>); if constexpr (__weakly_ordered<_Tp, _Up>) return _Weak_order{}(static_cast<_Tp&&>(__e), static_cast<_Up&&>(__f)); else if constexpr (__op_eq_lt<_Tp, _Up>) return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f) ? weak_ordering::equivalent : static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f) ? weak_ordering::less : weak_ordering::greater; } }; class _Partial_fallback { template<typename _Tp, typename _Up> static constexpr bool _S_noexcept() { if constexpr (__partially_ordered<_Tp, _Up>) return _Partial_order::_S_noexcept<_Tp, _Up>(); else return noexcept(bool(std::declval<_Tp>() == std::declval<_Up>())) && noexcept(bool(std::declval<_Tp>() < std::declval<_Up>())); } public: template<typename _Tp, typename _Up> requires __partially_ordered<_Tp, _Up> || __op_eq_lt<_Tp, _Up> constexpr decltype(auto) operator()(_Tp&& __e, _Up&& __f) const noexcept(_S_noexcept<_Tp, _Up>()) { static_assert(same_as<decay_t<_Tp>, decay_t<_Up>>); if constexpr (__partially_ordered<_Tp, _Up>) return _Partial_order{}(static_cast<_Tp&&>(__e), static_cast<_Up&&>(__f)); else if constexpr (__op_eq_lt<_Tp, _Up>) return static_cast<_Tp&&>(__e) == static_cast<_Up&&>(__f) ? partial_ordering::equivalent : static_cast<_Tp&&>(__e) < static_cast<_Up&&>(__f) ? partial_ordering::less : static_cast<_Up&&>(__f) < static_cast<_Tp&&>(__e) ? partial_ordering::greater : partial_ordering::unordered; } }; } // namespace __cmp_cust // [cmp.alg], comparison algorithms inline namespace __cmp_alg { inline constexpr __cmp_cust::_Strong_order strong_order{}; inline constexpr __cmp_cust::_Weak_order weak_order{}; inline constexpr __cmp_cust::_Partial_order partial_order{}; inline constexpr __cmp_cust::_Strong_fallback compare_strong_order_fallback{}; inline constexpr __cmp_cust::_Weak_fallback compare_weak_order_fallback{}; inline constexpr __cmp_cust::_Partial_fallback compare_partial_order_fallback{}; } namespace __detail { // [expos.only.func] synth-three-way inline constexpr struct _Synth3way { template<typename _Tp, typename _Up> static constexpr bool _S_noexcept(const _Tp* __t = nullptr, const _Up* __u = nullptr) { if constexpr (three_way_comparable_with<_Tp, _Up>) return noexcept(*__t <=> *__u); else return noexcept(*__t < *__u) && noexcept(*__u < *__t); } template<typename _Tp, typename _Up> constexpr auto operator()(const _Tp& __t, const _Up& __u) const noexcept(_S_noexcept<_Tp, _Up>()) requires requires { { __t < __u } -> __boolean_testable; { __u < __t } -> __boolean_testable; } { if constexpr (three_way_comparable_with<_Tp, _Up>) return __t <=> __u; else { if (__t < __u) return weak_ordering::less; else if (__u < __t) return weak_ordering::greater; else return weak_ordering::equivalent; } } } __synth3way = {}; // [expos.only.func] synth-three-way-result template<typename _Tp, typename _Up = _Tp> using __synth3way_t = decltype(__detail::__synth3way(std::declval<_Tp&>(), std::declval<_Up&>())); } // namespace __detail #endif // concepts } // namespace std #pragma GCC visibility pop #endif // C++20 #endif // _COMPARE