calendar Namespace Reference

Namespaces
namespace	detail
namespace	jieqi
namespace	lunar

Classes
struct	Datetime
	Represents a date and a time in the form of year_month_day and hh_mm_ss. More...

Concepts
concept	IsDuration
	Checks if a type is of std::chrono::duration.
concept	Fractionable
	Checks if a type can cast to std::chrono::nanoseconds, which is the assumption of function fraction.

Typedefs
using	days
using	seconds
using	nanoseconds
using	microseconds
using	system_clock
using	year_month_day
using	sys_days

Functions
template<IsDuration Duration>
consteval auto	in_a_day () -> uint64_t
	Returns the number of the given duration in a day.
template<Fractionable Duration>
constexpr auto	to_fraction (const Duration &elapsed) -> double
	Returns the fraction of a day.
constexpr auto	from_fraction (const double fraction) -> hh_mm_ss< nanoseconds >
	Returns the nanoseconds of fraction days.
constexpr auto	validate_fraction (const double fraction) -> double
	Validate the fraction of a day, before any narrowing conversion happens.
constexpr auto	add_seconds (const Datetime &dt, const double offset_sec) -> Datetime
	Returns dt shifted by offset_sec seconds, carrying whole days into the date part.

Typedef Documentation

days

using calendar::days

microseconds

using calendar::microseconds

nanoseconds

using calendar::nanoseconds

seconds

using calendar::seconds

sys_days

using calendar::sys_days

system_clock

using calendar::system_clock

year_month_day

using calendar::year_month_day

Function Documentation

add_seconds()

auto calendar::add_seconds ( const Datetime & dt, const double offset_sec )->Datetime

nodiscardconstexpr

Returns dt shifted by offset_sec seconds, carrying whole days into the date part.

Parameters

dt	The datetime to shift.
offset_sec	The offset in seconds. Can be negative, and is not limited to one day.

Returns

The shifted datetime.

Exceptions

std::invalid_argument

if offset_sec is not finite, or if the shifted date leaves std::chrono::year_month_day's representable years.

from_fraction()

auto calendar::from_fraction ( const double fraction ) ->hh_mm_ss< nanoseconds >

nodiscardconstexpr

Returns the nanoseconds of fraction days.

Parameters

fraction

The fraction.

Returns

The nanoseconds of fraction days.

Example

from_fraction(0.0) == 00:00:00.000000000

Example

from_fraction(0.5) == 12:00:00.000000000

Example

from_fraction(1.0) == 24:00:00.000000000

Example

from_fraction(2.0) == 48:00:00.000000000

Note

The precision of the returned value is std::chrono::nanoseconds.

Exceptions

std::invalid_argument

if fraction days do not fit an int64_t count of nanoseconds (which includes NaN and either infinity).

Note

Unlike validate_fraction this does not require [0.0, 1.0) — whole days are the documented contract. What it requires is that the product survives the cast, which is undefined outside int64's range; the guard's negated form is validate_fraction's NaN-safe shape (#67, #86).

in_a_day()

template<IsDuration Duration>

auto calendar::in_a_day ( ) ->uint64_t

nodiscardconsteval

Returns the number of the given duration in a day.

Template Parameters

Duration

The duration type.

Returns

The number of the given duration in a day.

Example

in_a_day<days>() == 1

Example

in_a_day<seconds>() == 86400 (There are 86400 seconds in a day.)

to_fraction()

template<Fractionable Duration>

auto calendar::to_fraction ( const Duration & elapsed ) ->double

nodiscardconstexpr

Returns the fraction of a day.

Parameters

elapsed

The elapsed time.

Template Parameters

Duration

The type of input elapsed.

Returns

The fraction of a day, of type double.

Note

The type of input elapsed should be convertible to std::chrono::nanoseconds.

Negative and multi-day durations are allowed; the result may be < 0.0 or >= 1.0.

Exceptions

std::invalid_argument

if the nanosecond count is not representable or the input is not finite.

validate_fraction()

auto calendar::validate_fraction ( const double fraction ) ->double

nodiscardconstexpr

Validate the fraction of a day, before any narrowing conversion happens.

Parameters

fraction

The fraction of a day, expected in [0.0, 1.0).

Returns

fraction, unchanged.

Exceptions

std::invalid_argument

if fraction is outside [0.0, 1.0).

Note

#67: written as not (x >= lo and x < hi) so NaN fails the check too — a plain fraction < 0.0 or fraction >= 1.0 test is always false for NaN and lets it through to the undefined double→int64 cast in from_fraction.