bug#11272: 24.1.50; `holiday-sexp' not always sufficient

[Michael Heerdegen <michael_heerdegen@web.de>]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> > I wonder if we could provide a function `holiday-list', so that it
> > would be possible to do this:
> >
> > (add-to-list 'calendar-holidays
> >  '(holidays-list '(holiday-sundays-after-trinitatis)))

> I don't use the calendar much myself, but if I understand the report
> correctly, what you're suggesting makes sense to me.  This was ten years
> ago, though, so perhaps you've chosen to do something else?

Now I'm using my own extension library for diary sexps, it also handles
holidays.

AFAIR, one problem (with holidays) I later faced had been that it was
not possible at all to use the calendar holiday definitions in diary
sexps.  You can mark and list holidays in the calendar, but it is
not possible to use a diary sexp for date definitions like "Every Monday
meet Peter unless it's a holiday".

So I wrote some glue code to make things like that possible, but it's
all a bit hackish because Calendar and Diary are written in a way that I
don't like, like Ediff, with lots of special variables and weird
references to global state.

So now I'm using only the basic mechanisms from Calendar and Diary, and
the stuff I need to hack is only my own code.  Not sure yet what I will
do with that code.  Touching the calendar and diary libs is nothing I
look forward to, to be honest.

Michael.