标准库标头 <compare> (C++20)

 

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语言支持 <cfloat> <climits> <compare>(C++20) <contracts>(C++26) <coroutine>(C++20) <csetjmp> <csignal> <cstdarg> <cstddef> <cstdint>(C++11) <cstdlib> <exception> <initializer_list>(C++11)    <limits> <new> <source_location>(C++20) <stdfloat>(C++23) <typeinfo> <version>(C++20) 概念 <concepts>(C++20) 诊断 <cassert> <cerrno> <debugging>(C++26) <stacktrace>(C++23) <stdexcept> <system_error>(C++11) 内存管理 <memory> <memory_resource>(C++17) <scoped_allocator>(C++11) 元编程 <type_traits>(C++11) <ratio>(C++11)

通用工具 <any>(C++17) <bitset> <bit>(C++20) <charconv>(C++17) <expected>(C++23) <format>(C++20) <functional> <optional>(C++17) <stdbit.h>(C++26) <tuple>(C++11) <typeindex>(C++11) <utility> <variant>(C++17) 容器 <array>(C++11) <deque> <flat_map>(C++23) <flat_set>(C++23) <forward_list>(C++11) <hive>(C++26) <inplace_vector>(C++26)    <list> <map> <mdspan>(C++23) <queue> <set> <span>(C++20) <stack> <unordered_map>(C++11) <unordered_set>(C++11) <vector> 迭代器 <iterator> 范围 <generator>(C++23) <ranges>(C++20)

算法 <algorithm> <numeric> 字符串 <cctype> <cstring> <cuchar>(C++11) <cwchar> <cwctype> <string_view>(C++17) <string> 文本处理 <clocale> <codecvt>(C++11/17/26*) <locale> <regex>(C++11) <text_encoding>(C++26)    cpp/header#数值库数值 <cfenv>(C++11) <cmath> <complex> <linalg>(C++26) <numbers>(C++20) <random>(C++11) <simd>(C++26) <stdckdint.h>(C++26) <valarray> 时间 <chrono>(C++11) <ctime> C 兼容性 <ccomplex>(C++11/17/20*) <ciso646>(C++20 前) <cstdalign>(C++11/17/20*) <cstdbool>(C++11/17/20*) <ctgmath>(C++11/17/20*)

输入/输出 <cinttypes>(C++11) <cstdio> <filesystem>(C++17) <fstream> <iomanip> <iosfwd> <iostream> <ios> <istream> <ostream> <print>(C++23) <spanstream>(C++23) <sstream> <streambuf> <strstream>(C++98/26*) <syncstream>(C++20) 并发支持 <atomic>(C++11) <barrier>(C++20) <condition_variable>(C++11) <future>(C++11) <hazard_pointer>(C++26) <latch>(C++20) <mutex>(C++11) <rcu>(C++26) <semaphore>(C++20) <shared_mutex>(C++14) <stdatomic.h>(C++23) <stop_token>(C++20) <thread>(C++11) 执行支持 <execution>(C++17)

 

此头文件是语言支持库的一部分。

概念
three_way_comparablethree_way_comparable_with (C++20)	指定运算符 <=> 在给定类型上产生一致的结果 (概念)
类
partial_ordering (C++20)	三路比较的结果类型，支持所有 6 种运算符且不可替换，并允许不可比较的值 (类)
weak_ordering (C++20)	三路比较的结果类型，支持所有 6 种运算符且不可替换 (类)
strong_ordering (C++20)	三路比较的结果类型，支持所有 6 种运算符且可替换 (类)
common_comparison_category (C++20)	给定的全部类型都能转换到的最强比较类别 (类模板)
compare_three_way_result (C++20)	获得三路比较运算符 <=> 在给定类型上的结果 (类模板)
compare_three_way (C++20)	实现 x <=> y 的受约束函数对象 (类)
定制点对象
strong_order (C++20)	进行三路比较并产生 std::strong_ordering 类型的结果 (定制点对象)
weak_order (C++20)	进行三路比较并产生 std::weak_ordering 类型的结果 (定制点对象)
partial_order (C++20)	进行三路比较并产生 std::partial_ordering 类型的结果 (定制点对象)
compare_strong_order_fallback (C++20)	进行三路比较并产生 std::strong_ordering 类型的结果，即使 operator<=> 不可用 (定制点对象)
compare_weak_order_fallback (C++20)	进行三路比较并产生 std::weak_ordering 类型的结果，即使 operator<=> 不可用 (定制点对象)
compare_partial_order_fallback (C++20)	进行三路比较并产生 std::partial_ordering 类型的结果，即使 operator<=> 不可用 (定制点对象)
函数
is_eqis_neqis_ltis_lteqis_gtis_gteq (C++20)	具名比较函数 (函数)

概要

namespace std {// 比较类别类型class partial_ordering;class weak_ordering;class strong_ordering;   // 具名比较函数constexprbool is_eq (partial_ordering cmp)noexcept{return cmp ==0;}constexprbool is_neq (partial_ordering cmp)noexcept{return cmp !=0;}constexprbool is_lt (partial_ordering cmp)noexcept{return cmp <0;}constexprbool is_lteq(partial_ordering cmp)noexcept{return cmp <=0;}constexprbool is_gt (partial_ordering cmp)noexcept{return cmp >0;}constexprbool is_gteq(partial_ordering cmp)noexcept{return cmp >=0;}   // 公共比较类别类型template<class... Ts>struct common_comparison_category {using type =/* 见描述 */;};template<class... Ts>using common_comparison_category_t =typename common_comparison_category<Ts...>::type;   // 概念 three_way_comparabletemplate<class T, class Cat = partial_ordering> concept three_way_comparable =/* 见描述 */;template<class T, class U, class Cat = partial_ordering> concept three_way_comparable_with =/* 见描述 */;   // 三路比较的结果template<class T, class U = T>struct compare_three_way_result;   template<class T, class U = T>using compare_three_way_result_t =typename compare_three_way_result<T, U>::type;   // 类 compare_three_waystruct compare_three_way;   // 比较算法inlinenamespace/* 未指明 */{inlineconstexpr/* 未指明 */ strong_order =/* 未指明 */;inlineconstexpr/* 未指明 */ weak_order =/* 未指明 */;inlineconstexpr/* 未指明 */ partial_order =/* 未指明 */;inlineconstexpr/* 未指明 */ compare_strong_order_fallback =/* 未指明 */;inlineconstexpr/* 未指明 */ compare_weak_order_fallback =/* 未指明 */;inlineconstexpr/* 未指明 */ compare_partial_order_fallback =/* 未指明 */;}}

概念 three_way_comparable

namespace std {template<class T, class Cat> concept __ComparesAs =// 仅用于阐释 same_as<common_comparison_category_t<T, Cat>, Cat>;   template<class T, class U> concept __PartiallyOrderedWith =// 仅用于阐释 requires(const remove_reference_t<T>& t, const remove_reference_t<U>& u){{ t < u }->boolean-testable;{ t > u }->boolean-testable;{ t <= u }->boolean-testable;{ t >= u }->boolean-testable;{ u < t }->boolean-testable;{ u > t }->boolean-testable;{ u <= t }->boolean-testable;{ u >= t }->boolean-testable;};   template<class T, class Cat = partial_ordering> concept three_way_comparable = __WeaklyEqualityComparableWith<T, T>&& __PartiallyOrderedWith<T, T>&& requires(const remove_reference_t<T>& a, const remove_reference_t<T>& b){{ a <=> b }-> __ComparesAs<Cat>;};}

概念 three_way_comparable_with

namespace std {template<class T, class U, class Cat = partial_ordering> concept three_way_comparable_with = __WeaklyEqualityComparableWith<T, U>&& __PartiallyOrderedWith<T, U>&& three_way_comparable<T, Cat>&& three_way_comparable<U, Cat>&& common_reference_with<const remove_reference_t<T>&, const remove_reference_t<U>&>&& three_way_comparable< common_reference_t<const remove_reference_t<T>&, const remove_reference_t<U>&>, Cat>&& requires(const remove_reference_t<T>& t, const remove_reference_t<U>& u){{ t <=> u }-> __ComparesAs<Cat>;{ u <=> t }-> __ComparesAs<Cat>;};}

类 std::partial_ordering

namespace std {class partial_ordering {int value;// 仅用于阐释bool is_ordered;// 仅用于阐释   // 仅用于阐释的构造函数constexprexplicit partial_ordering(eq v)noexcept: value(int(v)), is_ordered(true){}// 仅用于阐释constexprexplicit partial_ordering(ord v)noexcept: value(int(v)), is_ordered(true){}// 仅用于阐释constexprexplicit partial_ordering(ncmp v)noexcept: value(int(v)), is_ordered(false){}// 仅用于阐释   public:// 合法值staticconst partial_ordering less;staticconst partial_ordering equivalent;staticconst partial_ordering greater;staticconst partial_ordering unordered;   // 比较friendconstexprbool operator==(partial_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator==(partial_ordering v, partial_ordering w)noexcept=default;friendconstexprbool operator<(partial_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator>(partial_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator<=(partial_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator>=(partial_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator<(/* 未指明 */, partial_ordering v)noexcept;friendconstexprbool operator>(/* 未指明 */, partial_ordering v)noexcept;friendconstexprbool operator<=(/* 未指明 */, partial_ordering v)noexcept;friendconstexprbool operator>=(/* 未指明 */, partial_ordering v)noexcept;friendconstexpr partial_ordering operator<=>(partial_ordering v, /* 未指明 */)noexcept;friendconstexpr partial_ordering operator<=>(/* 未指明 */, partial_ordering v)noexcept;};   // 合法值的定义inlineconstexpr partial_ordering partial_ordering::less(ord::less);inlineconstexpr partial_ordering partial_ordering::equivalent(eq::equivalent);inlineconstexpr partial_ordering partial_ordering::greater(ord::greater);inlineconstexpr partial_ordering partial_ordering::unordered(ncmp::unordered);}

类 std::weak_ordering

namespace std {class weak_ordering {int value;// 仅用于阐释   // 仅用于阐释的构造函数constexprexplicit weak_ordering(eq v)noexcept: value(int(v)){}// 仅用于阐释constexprexplicit weak_ordering(ord v)noexcept: value(int(v)){}// 仅用于阐释   public:// 合法值staticconst weak_ordering less;staticconst weak_ordering equivalent;staticconst weak_ordering greater;   // 转换constexpr operator partial_ordering()constnoexcept;   // 比较friendconstexprbool operator==(weak_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator==(weak_ordering v, weak_ordering w)noexcept=default;friendconstexprbool operator<(weak_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator>(weak_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator<=(weak_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator>=(weak_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator<(/* 未指明 */, weak_ordering v)noexcept;friendconstexprbool operator>(/* 未指明 */, weak_ordering v)noexcept;friendconstexprbool operator<=(/* 未指明 */, weak_ordering v)noexcept;friendconstexprbool operator>=(/* 未指明 */, weak_ordering v)noexcept;friendconstexpr weak_ordering operator<=>(weak_ordering v, /* 未指明 */)noexcept;friendconstexpr weak_ordering operator<=>(/* 未指明 */, weak_ordering v)noexcept;};   // 合法值的定义inlineconstexpr weak_ordering weak_ordering::less(ord::less);inlineconstexpr weak_ordering weak_ordering::equivalent(eq::equivalent);inlineconstexpr weak_ordering weak_ordering::greater(ord::greater);}

类 std::strong_ordering

namespace std {class strong_ordering {int value;// 仅用于阐释   // 仅用于阐释的构造函数constexprexplicit strong_ordering(eq v)noexcept: value(int(v)){}// 仅用于阐释constexprexplicit strong_ordering(ord v)noexcept: value(int(v)){}// 仅用于阐释   public:// 合法值staticconst strong_ordering less;staticconst strong_ordering equal;staticconst strong_ordering equivalent;staticconst strong_ordering greater;   // 转换constexpr operator partial_ordering()constnoexcept;constexpr operator weak_ordering()constnoexcept;   // 比较friendconstexprbool operator==(strong_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator==(strong_ordering v, strong_ordering w)noexcept=default;friendconstexprbool operator<(strong_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator>(strong_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator<=(strong_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator>=(strong_ordering v, /* 未指明 */)noexcept;friendconstexprbool operator<(/* 未指明 */, strong_ordering v)noexcept;friendconstexprbool operator>(/* 未指明 */, strong_ordering v)noexcept;friendconstexprbool operator<=(/* 未指明 */, strong_ordering v)noexcept;friendconstexprbool operator>=(/* 未指明 */, strong_ordering v)noexcept;friendconstexpr strong_ordering operator<=>(strong_ordering v, /* 未指明 */)noexcept;friendconstexpr strong_ordering operator<=>(/* 未指明 */, strong_ordering v)noexcept;};   // 合法值的定义inlineconstexpr strong_ordering strong_ordering::less(ord::less);inlineconstexpr strong_ordering strong_ordering::equal(eq::equal);inlineconstexpr strong_ordering strong_ordering::equivalent(eq::equivalent);inlineconstexpr strong_ordering strong_ordering::greater(ord::greater);}

类 std::compare_three_way

namespace std {struct compare_three_way {template<class T, class U>constexprauto operator()(T&& t, U&& u)const;   using is_transparent =/* 未指明 */;};}

参阅

三路比较运算符 表达式 lhs<=>rhs(C++20)