Re: Inspiration for a better calendar package?

[Wilhelm Spickermann <jwos.20.unbenutzbar@spamgourmet.com>]

Dmitry A. Kazakov wrote:

> On Tue, 16 Dec 2008 06:50:40 +0100, Wilhelm Spickermann wrote:
> 
>> Dmitry A. Kazakov wrote:
>> 
>>> This specification does not specify time. It is a text
>>> pattern which may match or not some time point(s) in the
>>> future. It exactly same as "when leaves will turn red."
>> 
>> Yes, it does not specify a point in time -- but it will do.
> 
> Where you know that from?

I do not know it, but the program will know that too and give an
appropriate error message. (see below)

> 
>> We need it, because someone in some plant has to specify a
>> report to be printed on the 1-jul-2009 00:00 UTC. You cannot
>> tell him, that he should wait a month from now until the IERS
>> has published it's decision about leap second insertion at the
>> end of next June.
> 
> No we don't. You cannot show a code that neither:
> 
> 1. Waits a fixed amount of time (delay until)
> 
> 2. Periodically polls actual time (delay delta, look at the
> time).
> 
> There is simply no other way to determine if the report has to
> be printed. In either case you don't need another "time."
> 
> It can be shown even simpler, printing is an action in real
> time. You cannot present any physical action that happens in
> political time.
> 
> Political fictions are incomputable. (:-))
> 

Hmmm, now some secretary is trying to type in the dates of her
next summer holiday and the computer tells her "Cannot do it,
it's just a political fiction"? :-)

The program would first wait for about 3 months and then try to
convert the "wall time" into a "time". If it is still impossible
then, because the leap second second tables weren't updated, the
program should give a warning and perhaps rescedule the check. 

Stricly spoken, we depend on some things, which may change. But
if the earth starts rotating in a way that we need leap seconds
every few minutes, then the program will still give appropriate
warnings or errors (and probably no one will read them, because
we have bigger problems to solve).

I think, there are many computable things within "wall time",
like easter dates or the number of days between the third
Thusdays in January and February in 2010 or the existence of
29-feb-2014. It is however typical for it, that some
computations need additional information, which is not available
now. It's the main purpose of this type, to check everything
checkable and to refuse an answer, if there is none at the time
of the call.

Wilhelm

PS: Sorry for answering late. I'm in the process of moving to
another town and already swapping...