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bug#11272: 24.1.50; `holiday-sexp' not always sufficient
From: |
Michael Heerdegen |
Subject: |
bug#11272: 24.1.50; `holiday-sexp' not always sufficient |
Date: |
Wed, 18 Apr 2012 19:28:52 +0200 |
Hello,
I wonder why it is currently not possible to have `holiday-sexp' or a
similar function return a _list_ of entries for a given year, instead of
only one (or nil). Could we provide such a feature?
Some background (just an example): I have a function like this:
(defun sundays-after-trinitatis (year)
"List of sundays after Trinitatis in year YEAR."
(let ((i 1)
(results ())
(easterday (tagnummer-ostertag year))
(3lSoKj (3lSoKj year)))
(while (<= i 24)
(let* ((day (+ easterday 56 (* 7 i))))
(when (< day 3lSoKj)
(push (list (calendar-gregorian-from-absolute
(+ (calendar-absolute-from-gregorian (list 1 1 year))
-1 day))
(format "%s. sunday after Trinitatis" i))
results)))
(setq i (+ i 1)))
results))
For any year, according to certain rules, certain sundays are named "nth
sunday after Trinitatis", depending on `year'. The above function
returns the list of them for any given year. But I can't use it
directly with `holiday-sexp' - I have to write my own interface function
for the calendar:
(defun holiday-sundays-after-trinitatis ()
"List of visible sundays after Trinitatis in `calendar'."
(let ((year displayed-year))
(holiday-filter-visible-calendar
(append (sonntage-nach-trinitatis year)
(sonntage-nach-trinitatis (+ 1 year))))))
(eval-after-load "holidays"
'(add-to-list 'calendar-holidays '(holiday-sundays-after-trinitatis)))
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)))
It would no doubt be useful for other cases as well. It could look
similar to this:
(defun holiday-list (sexp)
(let ((y displayed-year)
year dates)
(holiday-filter-visible-calendar
(append
(progn
(setq year y)
(eval sexp))
(progn
(setq year (1+ y))
(eval sexp))))))
Please tell me what you think.
If you don't want to add something like that, maybe we could at least
improve the manual a bit. Under "Holiday Customization", there is this
paragraph:
| Some holidays just don't fit into any of these forms because special
| calculations are involved in their determination. In such cases you
| must write a Lisp function to do the calculation. To include eclipses,
| for example, add `(eclipses)' to `holiday-other-holidays' and write an
| Emacs Lisp function `eclipses' that returns a (possibly empty) list of
| the relevant Gregorian dates among the range visible in the calendar
| window, with descriptive strings, like this:
|
| (((6 4 2012) "Lunar Eclipse") ((11 13 2012) "Solar Eclipse") ... )
I think it would be good to add a simple example for how such a
function could look like. No user not browsing the sources will know
about `holiday-filter-visible-calendar'. At least that function
should be mentioned somewhere.
Thanks,
Michael.
In GNU Emacs 24.1.50.1 (i486-pc-linux-gnu, GTK+ Version 3.2.3)
of 2012-04-10 on zelenka, modified by Debian
(emacs-snapshot package, version 2:20120410-1)
Windowing system distributor `The X.Org Foundation', version 11.0.11104000
Configured using:
`configure '--build' 'i486-linux-gnu' '--host' 'i486-linux-gnu'
'--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib'
'--localstatedir=/var' '--infodir=/usr/share/info'
'--mandir=/usr/share/man' '--with-pop=yes'
'--enable-locallisppath=/etc/emacs-snapshot:/etc/emacs:/usr/local/share/emacs/24.1.50/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.1.50/site-lisp:/usr/share/emacs/site-lisp'
'--without-compress-info' '--with-crt-dir=/usr/lib/i386-linux-gnu/'
'--with-x=yes' '--with-x-toolkit=gtk3' '--with-imagemagick=yes'
'build_alias=i486-linux-gnu' 'host_alias=i486-linux-gnu'
'CFLAGS=-DDEBIAN -DSITELOAD_PURESIZE_EXTRA=5000 -g -O2''
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