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

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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) (since C++11)
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) (since C++11)
(until C++20)
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) (since C++11)
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) (since C++11)
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) (since C++11)
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) (since C++11)
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) (since C++20)

Compares two durations. Let CT be std:: common_type < std:: chrono :: duration < Rep1, Period1 > , std:: chrono :: duration < Rep2, Period2 >> :: type :

1,2) Checks if lhs and rhs are equal, i.e. the number of ticks for the type common to both durations are equal.
3-6) Compares lhs to rhs , i.e. compares the number of ticks for the type common to both durations.
7) Compares lhs to rhs , i.e. compares the number of ticks for the type common to both durations. The return type is deduced from CT ( lhs ) . count ( ) <=> CT ( rhs ) . count ( ) .

The != operator is synthesized from operator== .

(since C++20)

Parameters

lhs - duration on the left-hand side of the operator
rhs - duration on the right-hand side of the operator

Return value

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 ( )

Example

Run this code 
#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);
}

Output: 

2s == 2000ms
61s > 1min
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