std::chrono::year_month_day::operatorsys_days,std::chrono::year_month_day::operator (3) - Linux Man Pages

std::chrono::year_month_day::operatorsys_days,std::chrono::year_month_day::operator: std::chrono::year_month_day::operatorsys_days,std::chrono::year_month_day::operator

NAME

std::chrono::year_month_day::operatorsys_days,std::chrono::year_month_day::operator - std::chrono::year_month_day::operatorsys_days,std::chrono::year_month_day::operator

Synopsis


constexpr operator std::chrono::sys_days() const noexcept;         (1) (since C++20)
explicit constexpr operator std::chrono::local_days() const        (2) (since C++20)
noexcept;


Converts *this to a std::chrono::time_point representing the same date as this
year_month_day.


1) If ok() is true, the return value holds a count of days from the
std::chrono::system_clock epoch (1970-01-01) to *this. The result is negative if
*this represent a date prior to it.
Otherwise, if the stored year and month are valid (year().ok() && month().ok() is
true), then the returned value is sys_days(year()/month()/1d) (day() - 1d).
Otherwise (if year().ok() && month().ok() is false), the return value is
unspecified.
A sys_days in the range [std::chrono::days{-12687428}, std::chrono::days{11248737}],
when converted to year_month_day and back, yields the same value.
2) Same as (1) but returns local_days instead. Equivalent to return
local_days(sys_days(*this).time_since_epoch());.

Notes


Converting to sys_days and back can be used to normalize a year_month_day that
contains an invalid day but a valid year and month:


 using namespace std::chrono;
 auto ymd 2017y/January/0;
 ymd sys_days{ymd};
 // ymd is now 2016y/December/31


Normalizing the year and month can be done by adding (or subtracting) zero
std::chrono::months:


 using namespace std::chrono;
 constexpr year_month_day normalize(year_month_day ymd){
  ymd += months{0}; // normalizes year and month
  return sys_days{ymd}; // normalizes day
 }
 static_assert(normalize(2017y/33/59) == 2019y/10/29);

Example


 This section is incomplete
 Reason: no example