std::chrono::operator+, std::chrono::operator- (std::chrono::weekday)

 

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C-style date and time

 

std::chrono::weekday

Member functions

weekday::weekday

weekday::operator++weekday::operator--

weekday::operator+=weekday::operator-=

weekday::c_encodingweekday::iso_encoding

weekday::ok

weekday::operator[]

Nonmember functions

operator==

operator+operator-

operator<<

from_stream

Helper classes

formatter<std::chrono::weekday>

formatter<std::chrono::hash> (C++26)

 

Defined in header <chrono>
constexpr std::chrono::weekday operator+( const std::chrono::weekday& wd,                                           const std::chrono::days& d ) noexcept;	(1)	(since C++20)
constexpr std::chrono::weekday operator+( const std::chrono::days& d,                                           const std::chrono::weekday& wd ) noexcept;	(2)	(since C++20)
constexpr std::chrono::weekday operator-( const std::chrono::weekday& wd,                                           const std::chrono::days& d ) noexcept;	(3)	(since C++20)
constexpr std::chrono::days operator-( const std::chrono::weekday& wd1,                                        const std::chrono::weekday& wd2 ) noexcept;	(4)	(since C++20)

1,2) Adds d.count() days to wd. The weekday value held in the result is computed by first evaluating static_cast<long long>(wd.c_encoding()) + d.count() and reducing it modulo 7 to an integer in the range [​0​, 6].

3) Subtracts d.count() days from wd. Equivalent to return wd + -d;.

4) If wd1.ok() and wd2.ok() are both true, returns a std::chrono::days value d such that d.count() is in the range [​0​, 6] and wd2 + d == wd1. Otherwise the returned value is unspecified.

Return value

1-3) A std::chrono::weekday holding a weekday value calculated as described above.

4) A std::chrono::days representing the distance between wd1 and wd2.

Notes

As long as the computation doesn't overflow, (1-3) always return a valid weekday even if wd.ok() is false.

Example

Run this code

#include <chrono>
#include <iostream>
 
int main()
{
    std::cout << std::boolalpha;
 
    std::chrono::weekday wd{4};
    wd = wd + std::chrono::days(2);
    std::cout << (wd == std::chrono::weekday(6)) << ' '
              << (wd == std::chrono::Saturday) << ' ';
 
    wd = wd - std::chrono::days(3);
    std::cout << (wd == std::chrono::weekday(3)) << ' '
              << (wd == std::chrono::Wednesday) << ' ';
 
    wd = std::chrono::Tuesday;
    wd = wd + std::chrono::days{8}; // (((2 + 8) == 10) % 7) == 3;
    std::cout << (wd == std::chrono::Wednesday) << ' ';
 
    wd = wd + (std::chrono::Sunday - std::chrono::Thursday); // (3 + 3) == 6
    std::cout << (wd == std::chrono::Saturday) << '\n';
}

Output:

true true true true true true

See also

operator++operator++(int)operator--operator--(int)	increments or decrements the weekday (public member function)
operator+=operator-=	adds or subtracts a number of days (public member function)