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operator==,!=,<,<=,>,>=,<=> (std::chrono::duration)

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C++
Date and time library
std::chrono::duration
Member functions
Non-member functions
operator== operator!= operator< operator<= operator> operator>= operator<=>
(until C++20) (C++20)
(C++20)
Helper classes
template < class Rep1, class Period1, class Rep2, class Period2 >

constexpr bool operator == ( const std:: chrono :: duration < Rep1, Period1 > & lhs,

const std:: chrono :: duration < Rep2, Period2 > & rhs ) ;
(1) (自 C++11 起)
template < class Rep1, class Period1, class Rep2, class Period2 >

constexpr bool operator ! = ( const std:: chrono :: duration < Rep1, Period1 > & lhs,

const std:: chrono :: duration < Rep2, Period2 > & rhs ) ;
(2) (自 C++11 起)
(至 C++20 止)
template < class Rep1, class Period1, class Rep2, class Period2 >

constexpr bool operator < ( const std:: chrono :: duration < Rep1, Period1 > & lhs,

const std:: chrono :: duration < Rep2, Period2 > & rhs ) ;
(3) (自 C++11 起)
template < class Rep1, class Period1, class Rep2, class Period2 >

constexpr bool operator <= ( const std:: chrono :: duration < Rep1, Period1 > & lhs,

const std:: chrono :: duration < Rep2, Period2 > & rhs ) ;
(4) (自 C++11 起)
template < class Rep1, class Period1, class Rep2, class Period2 >

constexpr bool operator > ( const std:: chrono :: duration < Rep1, Period1 > & lhs,

const std:: chrono :: duration < Rep2, Period2 > & rhs ) ;
(5) (自 C++11 起)
template < class Rep1, class Period1, class Rep2, class Period2 >

constexpr bool operator >= ( const std:: chrono :: duration < Rep1, Period1 > & lhs,

const std:: chrono :: duration < Rep2, Period2 > & rhs ) ;
(6) (自 C++11 起)
template < class Rep1, class Period1, class Rep2, class Period2 >

requires std:: three_way_comparable < std:: common_type_t < Rep1, Rep2 >>
constexpr auto operator <=> ( const std:: chrono :: duration < Rep1, Period1 > & lhs,

const std:: chrono :: duration < Rep2, Period2 > & rhs ) ;
(7) (自 C++20 起)

比较两个时长。令 CT 为 std:: common_type < std:: chrono :: duration < Rep1, Period1 > , std:: chrono :: duration < Rep2, Period2 >> :: type ：

1,2) 检查 lhs 与 rhs 是否相等，即两种时长在共同类型下的 tick 计数是否相等。
3-6) 将 lhs 与 rhs 进行比较，即比较两种时长在共同类型下的时钟周期数。
7) 比较 lhs 与 rhs ，即比较两种时长公共类型的滴答计数。返回类型由 CT ( lhs ) . count ( ) <=> CT ( rhs ) . count ( ) 推导得出。

!= 运算符由 operator== 合成生成 。

(C++20 起)

参数

lhs - 运算符左侧的时间长度
rhs - 运算符右侧的时间长度

返回值

1) CT ( lhs ) . count ( ) == CT ( rhs ) . count ( )
2) ! ( lhs == rhs )
3) CT ( lhs ) . count ( ) < CT ( rhs ) . count ( )
4) ! ( rhs < lhs )
5) rhs < lhs
6) ! ( lhs < rhs )
7) CT ( lhs ) . count ( ) <=> CT ( rhs ) . count ( )

示例

运行此代码 
#include <chrono>
#include <iostream>
int main()
{
    constexpr auto t1 = std::chrono::seconds(2);
    constexpr auto t2 = std::chrono::milliseconds(2000);
    if constexpr (t1 == t2)
        std::cout << t1 << " == " << t2 << '\n';
    else
        std::cout << t1 << " != " << t2 << '\n';
    constexpr auto t3 = std::chrono::seconds(61);
    constexpr auto t4 = std::chrono::minutes(1);
    if constexpr (t3 > t4)
        std::cout << t3 << " > " << t4 << '\n';
    else
        std::cout << t3 << " <= " << t4 << '\n';
    using namespace std::chrono_literals;
    static_assert(1h == 60min);
    static_assert(1min == 60s);
    static_assert(1s == 1'000ms);
    static_assert(1ms == 1'000us);
    static_assert(1us == 1'000ns);
}

输出： 

2s == 2000ms
61s > 1min