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

 

C++

Compiler support

Freestanding and hosted

Language

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Utilities library

Language support Type support (basic types, RTTI) Library feature-test macros (C++20) Dynamic memory management Program utilities Coroutine support (C++20) Variadic functions is_constant_evaluated (C++20) launder (C++17) initializer_list (C++11) source_location (C++20) Three-way comparison (C++20) three_way_comparablethree_way_comparable_with (C++20)(C++20) strong_ordering (C++20) weak_ordering (C++20) partial_ordering (C++20) common_comparison_category (C++20) compare_three_way_result (C++20) compare_three_way (C++20) strong_order (C++20) weak_order (C++20) partial_order (C++20) compare_strong_order_fallback (C++20) compare_weak_order_fallback (C++20) compare_partial_order_fallback (C++20)    is_eqis_neqis_ltis_lteqis_gtis_gteq (C++20)(C++20)(C++20)(C++20)(C++20)(C++20)

General utilities Date and time Function objects Formatting library (C++20) bitset hash (C++11) Relational operators (deprecated in C++20) rel_ops::operator!=rel_ops::operator> rel_ops::operator<=rel_ops::operator>= Integer comparison functions cmp_equalcmp_lesscmp_less_than (C++20)(C++20)(C++20)    cmp_not_equalcmp_greatercmp_greater_than (C++20)(C++20)(C++20) in_range (C++20) Swap and type operations swap ranges::swap (C++20) exchange (C++14) declval (C++11) to_underlying (C++23) forward (C++11) forward_like (C++23) move (C++11) move_if_noexcept (C++11) as_const (C++17) Common vocabulary types pair tuple (C++11) optional (C++17) any (C++17) variant (C++17) tuple_size (C++11) tuple_element (C++11) apply (C++17) make_from_tuple (C++17) expected (C++23) Elementary string conversions to_chars (C++17) from_chars (C++17) chars_format (C++17)

 

Date and time utilities

Time point
time_point (C++11)	clock_time_conversion (C++20)	clock_cast (C++20)
Duration
duration (C++11)
Clocks
system_clock (C++11) steady_clock (C++11) high_resolution_clock (C++11)	is_clock (C++20) utc_clock (C++20) tai_clock (C++20)	gps_clock (C++20) file_clock (C++20) local_t (C++20)
Time of day
is_amis_pm (C++20)(C++20)	make12make24 (C++20)(C++20)	hh_mm_ss (C++20)
Calendars
day (C++20) month (C++20) year (C++20) weekday (C++20) operator/ (C++20) year_month_day (C++20)	year_month_day_last (C++20) year_month_weekday (C++20) year_month_weekday_last (C++20)       weekday_indexed (C++20) weekday_last (C++20) month_day (C++20)	month_day_last (C++20) month_weekday (C++20) month_weekday_last (C++20) year_month (C++20) last_speclast (C++20)(C++20)
Time zones
tzdb (C++20) tzdb_list (C++20) get_tzdbget_tzdb_listreload_tzdbremote_version (C++20)(C++20)(C++20)(C++20) sys_info (C++20)	local_info (C++20) nonexistent_local_time (C++20) ambiguous_local_time (C++20) locate_zone (C++20) current_zone (C++20) time_zone (C++20) choose (C++20)	zoned_traits (C++20) zoned_time (C++20) time_zone_link (C++20) leap_second (C++20) leap_second_info (C++20) get_leap_second_info (C++20)
chrono I/O
parse (C++20)
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>

 

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 <iostream>
#include <chrono>
 
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)