1.37.1 Send methods

date ->advance: with=int, unit=[{second,minute,hour,day,week}]

Advance date object with the given amount of the specified unit. The default unit is second. Please note that larger units are omitted due to their unclear semantics. Units are converted to seconds. Given that the fields are in local time, creating a time from fields, date->advance and get the fields may yield strange results. For example:

?-	new(D, date(0, 0, 0, 30, 10, 2005)),
        send(D, advance, 1, day),
        get(D, string, string(Date))

Date = 'Sun Oct 30 23:00:00 2005'

See also date->month, etc.

date ->after: date

Test if date is after argument. See also date->before and date->equal.

date ->before: date

Test if date is before argument. See also date->equal and date->after.

date ->convert: description=char_array

Conversion of a textual representation of a date into a date object. These methods exploit the GNU-project get_date() library and convert various commonly used representations of a date. Unfortunately this library is undocumented ...

date ->current:

Make the date object reflect the current time.

date ->equal: date

Succeeds if both date objects represent the same point in time. See also date->before, date->after and date<-difference.

date ->initialise: seconds=[0..59], minutes=[0..59], hours=[0..23], day=[1..31], month=[1..12], year=[1970..2050]

Create a date object from its components. Any defaulted value defaults to the current value. Thus

?- new(D, date(0, 35, 14)).

Represents 14.35h today.

See date->set for details and limitations.

date ->posix_value: real

Communicate the represented time-stamp as a POSIX time stamp, i.e. the number of seconds elapsed since the epoch, Jan 1, 1970.

This value is passed as a float to avoid the limited range supported by the XPCE int type.

Inherits description from: date<-posix_value

date ->set: seconds=[0..59], minutes=[0..59], hours=[0..23], day=[1..31], month=[1..12], year=[1970..2050]

Set all non-default components. This method is also used by date->initialise if arguments are provided.

It uses the mktime() function which appears to have different behaviour on different systems on timestamps before the epoch at Jan. 1, 1970 UTC. On some systems it returns negative values, while on others it returns the error code -1. Note that even on systems with negative values the last second before the epoch cannot be represented. An error is returned if mktime() returns -1.