std::chrono::weekday::operator+=, std::chrono::weekday::operator-=

 

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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>

 

constexpr std::chrono::weekday& operator+=( const std::chrono::days& d ) noexcept;	(1)	(since C++20)
constexpr std::chrono::weekday& operator-=( const std::chrono::days& d ) noexcept;	(2)	(since C++20)

Adds or subtracts d.count() from the weekday value, reducing the result modulo 7 to an integer in the range [0, 6].

1) Performs *this = *this + d;

2) Performs *this = *this - d;

Return value

A reference to this weekday after modification.

Notes

After a call to one of these functions, ok() is always true if no overflow occurred during the operation.

Example

Run this code

#include <iostream>
#include <chrono>
 
int main()
{
    std::cout << std::boolalpha;
 
    std::chrono::weekday wd {5}; // Friday is 5
    wd += std::chrono::days(2);
    std::cout << (wd == std::chrono::weekday(0)) << ' '
              << (wd == std::chrono::Sunday) << ' ';
 
    wd -= std::chrono::days(3);
    std::cout << (wd == std::chrono::weekday(4)) << ' '
              << (wd == std::chrono::Thursday) << ' ';
 
    wd = std::chrono::Wednesday;
    wd += std::chrono::days{8}; // ((3 += 8 == 11) % 7) == 4;
    std::cout << (wd == std::chrono::Thursday) << ' ';
 
    wd -= (std::chrono::Sunday - std::chrono::Tuesday); // -= -2
    // (4 -= -2) == 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- (C++20)	performs arithmetic on weekdays (function)