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

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Diagnostics library

Memory management library

Metaprogramming library (C++11)

General utilities library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Strings library

Text processing library

Numerics library

Date and time library

Input/output library

Filesystem library (C++17)

Concurrency support library (C++11)

Execution control library (C++26)

Technical specifications

Symbols index

External libraries

 

Date and time library

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) is_clock (C++20) utc_clock (C++20) tai_clock (C++20) high_resolution_clock (C++11) 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)

Calendar 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) chrono I/O parse (C++20)

Time zone 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) C-style date and time

 

std::chrono::month

Member functions

month::month

month::operator++month::operator--

month::operator+=month::operator-=

month::operator unsigned

month::ok

Nonmember functions

operator==operator<=>

operator+operator-

operator<<

from_stream

Helper classes

formatter<std::chrono::month>

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

 

constexpr std::chrono::month& operator+=( const std::chrono::months& m ) noexcept;	(1)	(since C++20)
constexpr std::chrono::month& operator-=( const std::chrono::months& m ) noexcept;	(2)	(since C++20)

Adds or subtracts m.count() from the month value, reducing the result modulo 12 to an integer in the range [1, 12].

1) Performs *this = *this + m;.

2) Performs *this = *this - m;.

Return value

A reference to this month 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 <chrono>
#include <iostream>
 
int main()
{
    std::cout << std::boolalpha;
 
    std::chrono::month m{6};
    m += std::chrono::months(2);
    std::cout << (m == std::chrono::month(8) << ' '
              << (m == std::chrono::August) << ' ';
 
    m -= std::chrono::months(3);
    std::cout << (m == std::chrono::month(5) << ' '
              << (m == std::chrono::May) << ' ';
 
    m = std::chrono::October;
    m += std::chrono::months{8}; / ((10 += 8 == 18) % 12) == 6;
    std::cout << (m == std::chrono::June) << ' ';
 
    m -= std::chrono::months{std::chrono::December - std::chrono::February}; / -= 10
    / (6 -= 10) == -4; -4 % 12 == (12 - 4) == 8
    std::cout << (m == std::chrono::August) << '\n';
}

Output:

true true true true true true

See also

operator++operator++(int)operator--operator--(int)	increments or decrements the month (public member function)
operator+operator- (C++20)	performs arithmetic on months (function)

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