1 ;;; cal-islam.el --- calendar functions for the Islamic calendar
3 ;; Copyright (C) 1995, 1997, 2001, 2002, 2003, 2004, 2005, 2006
4 ;; Free Software Foundation, Inc.
6 ;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
7 ;; Maintainer: Glenn Morris <rgm@gnu.org>
9 ;; Human-Keywords: Islamic calendar, calendar, diary
11 ;; This file is part of GNU Emacs.
13 ;; GNU Emacs is free software; you can redistribute it and/or modify
14 ;; it under the terms of the GNU General Public License as published by
15 ;; the Free Software Foundation; either version 2, or (at your option)
18 ;; GNU Emacs is distributed in the hope that it will be useful,
19 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
20 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
21 ;; GNU General Public License for more details.
23 ;; You should have received a copy of the GNU General Public License
24 ;; along with GNU Emacs; see the file COPYING. If not, write to the
25 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
26 ;; Boston, MA 02110-1301, USA.
30 ;; This collection of functions implements the features of calendar.el and
31 ;; diary.el that deal with the Islamic calendar.
33 ;; Technical details of all the calendrical calculations can be found in
34 ;; ``Calendrical Calculations: The Millennium Edition'' by Edward M. Reingold
35 ;; and Nachum Dershowitz, Cambridge University Press (2001).
37 ;; Comments, corrections, and improvements should be sent to
38 ;; Edward M. Reingold Department of Computer Science
39 ;; (217) 333-6733 University of Illinois at Urbana-Champaign
40 ;; reingold@cs.uiuc.edu 1304 West Springfield Avenue
41 ;; Urbana, Illinois 61801
46 (defvar displayed-month)
47 (defvar displayed-year)
49 (defvar original-date)
53 (defvar calendar-islamic-month-name-array
54 ["Muharram" "Safar" "Rabi I" "Rabi II" "Jumada I" "Jumada II"
55 "Rajab" "Sha'ban" "Ramadan" "Shawwal" "Dhu al-Qada" "Dhu al-Hijjah"]
56 "Array of strings giving the names of the Islamic months.")
58 (defvar calendar-islamic-epoch (calendar-absolute-from-julian '(7 16 622))
59 "Absolute date of start of Islamic calendar = August 29, 284 A.D. (Julian).")
61 (defun islamic-calendar-leap-year-p (year)
62 "Returns t if YEAR is a leap year on the Islamic calendar."
64 (list 2 5 7 10 13 16 18 21 24 26 29)))
66 (defun islamic-calendar-last-day-of-month (month year)
67 "The last day in MONTH during YEAR on the Islamic calendar."
69 ((memq month (list 1 3 5 7 9 11)) 30)
70 ((memq month (list 2 4 6 8 10)) 29)
71 (t (if (islamic-calendar-leap-year-p year) 30 29))))
73 (defun islamic-calendar-day-number (date)
74 "Return the day number within the year of the Islamic date DATE."
75 (let* ((month (extract-calendar-month date))
76 (day (extract-calendar-day date)))
78 (* 29 (/ (1- month) 2))
81 (defun calendar-absolute-from-islamic (date)
82 "Absolute date of Islamic DATE.
83 The absolute date is the number of days elapsed since the (imaginary)
84 Gregorian date Sunday, December 31, 1 BC."
85 (let* ((month (extract-calendar-month date))
86 (day (extract-calendar-day date))
87 (year (extract-calendar-year date))
91 ((< y 3) 0) ((< y 6) 1) ((< y 8) 2) ((< y 11) 3) ((< y 14) 4)
92 ((< y 17) 5) ((< y 19) 6) ((< y 22) 7) ((< y 25) 8) ((< y 27) 9)
94 (+ (islamic-calendar-day-number date);; days so far this year
95 (* (1- year) 354) ;; days in all non-leap years
96 (* 11 (/ year 30)) ;; leap days in complete cycles
97 leap-years-in-cycle ;; leap days this cycle
98 (1- calendar-islamic-epoch)))) ;; days before start of calendar
100 (defun calendar-islamic-from-absolute (date)
101 "Compute the Islamic date (month day year) corresponding to absolute DATE.
102 The absolute date is the number of days elapsed since the (imaginary)
103 Gregorian date Sunday, December 31, 1 BC."
104 (if (< date calendar-islamic-epoch)
105 (list 0 0 0);; pre-Islamic date
106 (let* ((approx (/ (- date calendar-islamic-epoch)
107 355));; Approximation from below.
108 (year ;; Search forward from the approximation.
110 (calendar-sum y approx
111 (>= date (calendar-absolute-from-islamic
114 (month ;; Search forward from Muharram.
115 (1+ (calendar-sum m 1
117 (calendar-absolute-from-islamic
119 (islamic-calendar-last-day-of-month
123 (day ;; Calculate the day by subtraction.
125 (1- (calendar-absolute-from-islamic (list month 1 year))))))
126 (list month day year))))
128 (defun calendar-islamic-date-string (&optional date)
129 "String of Islamic date before sunset of Gregorian DATE.
130 Returns the empty string if DATE is pre-Islamic.
131 Defaults to today's date if DATE is not given.
132 Driven by the variable `calendar-date-display-form'."
133 (let ((calendar-month-name-array calendar-islamic-month-name-array)
134 (islamic-date (calendar-islamic-from-absolute
135 (calendar-absolute-from-gregorian
136 (or date (calendar-current-date))))))
137 (if (< (extract-calendar-year islamic-date) 1)
139 (calendar-date-string islamic-date nil t))))
141 (defun calendar-print-islamic-date ()
142 "Show the Islamic calendar equivalent of the date under the cursor."
144 (let ((i (calendar-islamic-date-string (calendar-cursor-to-date t))))
145 (if (string-equal i "")
146 (message "Date is pre-Islamic")
147 (message "Islamic date (until sunset): %s" i))))
149 (defun calendar-goto-islamic-date (date &optional noecho)
150 "Move cursor to Islamic DATE; echo Islamic date unless NOECHO is t."
152 (let* ((today (calendar-current-date))
154 "Islamic calendar year (>0): "
155 '(lambda (x) (> x 0))
157 (extract-calendar-year
158 (calendar-islamic-from-absolute
159 (calendar-absolute-from-gregorian today))))))
160 (month-array calendar-islamic-month-name-array)
161 (completion-ignore-case t)
162 (month (cdr (assoc-string
164 "Islamic calendar month name: "
165 (mapcar 'list (append month-array nil))
167 (calendar-make-alist month-array 1) t)))
168 (last (islamic-calendar-last-day-of-month month year))
170 (format "Islamic calendar day (1-%d): " last)
171 '(lambda (x) (and (< 0 x) (<= x last))))))
172 (list (list month day year))))
173 (calendar-goto-date (calendar-gregorian-from-absolute
174 (calendar-absolute-from-islamic date)))
175 (or noecho (calendar-print-islamic-date)))
177 (defun diary-islamic-date ()
178 "Islamic calendar equivalent of date diary entry."
179 (let ((i (calendar-islamic-date-string date)))
180 (if (string-equal i "")
181 "Date is pre-Islamic"
182 (format "Islamic date (until sunset): %s" i))))
184 (defun holiday-islamic (month day string)
185 "Holiday on MONTH, DAY (Islamic) called STRING.
186 If MONTH, DAY (Islamic) is visible, the value returned is corresponding
187 Gregorian date in the form of the list (((month day year) STRING)). Returns
188 nil if it is not visible in the current calendar window."
189 (let* ((islamic-date (calendar-islamic-from-absolute
190 (calendar-absolute-from-gregorian
191 (list displayed-month 15 displayed-year))))
192 (m (extract-calendar-month islamic-date))
193 (y (extract-calendar-year islamic-date))
196 nil;; Islamic calendar doesn't apply.
197 (increment-calendar-month m y (- 10 month))
198 (if (> m 7);; Islamic date might be visible
199 (let ((date (calendar-gregorian-from-absolute
200 (calendar-absolute-from-islamic (list month day y)))))
201 (if (calendar-date-is-visible-p date)
202 (list (list date string))))))))
204 (defun list-islamic-diary-entries ()
205 "Add any Islamic date entries from the diary file to `diary-entries-list'.
206 Islamic date diary entries must be prefaced by an `islamic-diary-entry-symbol'
207 \(normally an `I'). The same diary date forms govern the style of the Islamic
208 calendar entries, except that the Islamic month names must be spelled in full.
209 The Islamic months are numbered from 1 to 12 with Muharram being 1 and 12 being
210 Dhu al-Hijjah. If an Islamic date diary entry begins with a
211 `diary-nonmarking-symbol', the entry will appear in the diary listing, but will
212 not be marked in the calendar. This function is provided for use with the
213 `nongregorian-diary-listing-hook'."
215 (let ((buffer-read-only nil)
216 (diary-modified (buffer-modified-p))
217 (gdate original-date)
218 (mark (regexp-quote diary-nonmarking-symbol)))
219 (calendar-for-loop i from 1 to number do
220 (let* ((d diary-date-forms)
221 (idate (calendar-islamic-from-absolute
222 (calendar-absolute-from-gregorian gdate)))
223 (month (extract-calendar-month idate))
224 (day (extract-calendar-day idate))
225 (year (extract-calendar-year idate)))
228 ((date-form (if (equal (car (car d)) 'backup)
231 (backup (equal (car (car d)) 'backup))
233 (format "%s\\|%s\\.?"
234 (calendar-day-name gdate)
235 (calendar-day-name gdate 'abbrev)))
236 (calendar-month-name-array
237 calendar-islamic-month-name-array)
241 (calendar-month-name month)))
242 (month (concat "\\*\\|0*" (int-to-string month)))
243 (day (concat "\\*\\|0*" (int-to-string day)))
246 "\\*\\|0*" (int-to-string year)
247 (if abbreviated-calendar-year
248 (concat "\\|" (int-to-string (% year 100)))
252 "\\(\\`\\|\^M\\|\n\\)" mark "?"
253 (regexp-quote islamic-diary-entry-symbol)
255 (mapconcat 'eval date-form "\\)\\(")
257 (case-fold-search t))
258 (goto-char (point-min))
259 (while (re-search-forward regexp nil t)
260 (if backup (re-search-backward "\\<" nil t))
261 (if (and (or (char-equal (preceding-char) ?\^M)
262 (char-equal (preceding-char) ?\n))
263 (not (looking-at " \\|\^I")))
264 ;; Diary entry that consists only of date.
266 ;; Found a nonempty diary entry--make it visible and
267 ;; add it to the list.
268 (let ((entry-start (point))
270 (re-search-backward "\^M\\|\n\\|\\`")
271 (setq date-start (point))
272 (re-search-forward "\^M\\|\n" nil t 2)
273 (while (looking-at " \\|\^I")
274 (re-search-forward "\^M\\|\n" nil t))
276 (subst-char-in-region date-start (point) ?\^M ?\n t)
279 (buffer-substring-no-properties entry-start (point))
280 (buffer-substring-no-properties
281 (1+ date-start) (1- entry-start))
282 (copy-marker entry-start))))))
285 (calendar-gregorian-from-absolute
286 (1+ (calendar-absolute-from-gregorian gdate)))))
287 (set-buffer-modified-p diary-modified))
288 (goto-char (point-min))))
290 (defun mark-islamic-diary-entries ()
291 "Mark days in the calendar window that have Islamic date diary entries.
292 Each entry in diary-file (or included files) visible in the calendar window
293 is marked. Islamic date entries are prefaced by a islamic-diary-entry-symbol
294 \(normally an `I'). The same diary-date-forms govern the style of the Islamic
295 calendar entries, except that the Islamic month names must be spelled in full.
296 The Islamic months are numbered from 1 to 12 with Muharram being 1 and 12 being
297 Dhu al-Hijjah. Islamic date diary entries that begin with a
298 diary-nonmarking-symbol will not be marked in the calendar. This function is
299 provided for use as part of the nongregorian-diary-marking-hook."
300 (let ((d diary-date-forms))
303 ((date-form (if (equal (car (car d)) 'backup)
305 (car d)));; ignore 'backup directive
306 (dayname (diary-name-pattern calendar-day-name-array
307 calendar-day-abbrev-array))
310 (diary-name-pattern calendar-islamic-month-name-array)))
311 (month "[0-9]+\\|\\*")
313 (year "[0-9]+\\|\\*")
314 (l (length date-form))
315 (d-name-pos (- l (length (memq 'dayname date-form))))
316 (d-name-pos (if (/= l d-name-pos) (+ 2 d-name-pos)))
317 (m-name-pos (- l (length (memq 'monthname date-form))))
318 (m-name-pos (if (/= l m-name-pos) (+ 2 m-name-pos)))
319 (d-pos (- l (length (memq 'day date-form))))
320 (d-pos (if (/= l d-pos) (+ 2 d-pos)))
321 (m-pos (- l (length (memq 'month date-form))))
322 (m-pos (if (/= l m-pos) (+ 2 m-pos)))
323 (y-pos (- l (length (memq 'year date-form))))
324 (y-pos (if (/= l y-pos) (+ 2 y-pos)))
327 "\\(\\`\\|\^M\\|\n\\)"
328 (regexp-quote islamic-diary-entry-symbol)
330 (mapconcat 'eval date-form "\\)\\(")
332 (case-fold-search t))
333 (goto-char (point-min))
334 (while (re-search-forward regexp nil t)
338 (match-beginning d-name-pos)
339 (match-end d-name-pos))))
343 (match-beginning m-name-pos)
344 (match-end m-name-pos))))
345 (mm (string-to-number
348 (match-beginning m-pos)
351 (dd (string-to-number
354 (match-beginning d-pos)
359 (match-beginning y-pos)
363 (if (and (= (length y-str) 2)
364 abbreviated-calendar-year)
366 (extract-calendar-year
367 (calendar-islamic-from-absolute
368 (calendar-absolute-from-gregorian
369 (calendar-current-date)))))
370 (y (+ (string-to-number y-str)
371 (* 100 (/ current-y 100)))))
372 (if (> (- y current-y) 50)
374 (if (> (- current-y y) 50)
377 (string-to-number y-str)))))
379 (mark-calendar-days-named
380 (cdr (assoc-string dd-name
382 calendar-day-name-array
383 0 nil calendar-day-abbrev-array) t)))
385 (setq mm (if (string-equal mm-name "*") 0
389 calendar-islamic-month-name-array) t)))))
390 (mark-islamic-calendar-date-pattern mm dd yy)))))
393 (defun mark-islamic-calendar-date-pattern (month day year)
394 "Mark dates in calendar window that conform to Islamic date MONTH/DAY/YEAR.
395 A value of 0 in any position is a wildcard."
397 (set-buffer calendar-buffer)
398 (if (and (/= 0 month) (/= 0 day))
400 ;; Fully specified Islamic date.
401 (let ((date (calendar-gregorian-from-absolute
402 (calendar-absolute-from-islamic
403 (list month day year)))))
404 (if (calendar-date-is-visible-p date)
405 (mark-visible-calendar-date date)))
406 ;; Month and day in any year--this taken from the holiday stuff.
407 (let* ((islamic-date (calendar-islamic-from-absolute
408 (calendar-absolute-from-gregorian
409 (list displayed-month 15 displayed-year))))
410 (m (extract-calendar-month islamic-date))
411 (y (extract-calendar-year islamic-date))
414 nil;; Islamic calendar doesn't apply.
415 (increment-calendar-month m y (- 10 month))
416 (if (> m 7);; Islamic date might be visible
417 (let ((date (calendar-gregorian-from-absolute
418 (calendar-absolute-from-islamic
419 (list month day y)))))
420 (if (calendar-date-is-visible-p date)
421 (mark-visible-calendar-date date)))))))
422 ;; Not one of the simple cases--check all visible dates for match.
423 ;; Actually, the following code takes care of ALL of the cases, but
424 ;; it's much too slow to be used for the simple (common) cases.
425 (let ((m displayed-month)
429 (increment-calendar-month m y -1)
431 (calendar-absolute-from-gregorian
433 (increment-calendar-month m y 2)
435 (calendar-absolute-from-gregorian
436 (list m (calendar-last-day-of-month m y) y)))
437 (calendar-for-loop date from first-date to last-date do
438 (let* ((i-date (calendar-islamic-from-absolute date))
439 (i-month (extract-calendar-month i-date))
440 (i-day (extract-calendar-day i-date))
441 (i-year (extract-calendar-year i-date)))
442 (and (or (zerop month)
448 (mark-visible-calendar-date
449 (calendar-gregorian-from-absolute date)))))))))
451 (defun insert-islamic-diary-entry (arg)
452 "Insert a diary entry.
453 For the Islamic date corresponding to the date indicated by point.
454 Prefix arg will make the entry nonmarking."
456 (let* ((calendar-month-name-array calendar-islamic-month-name-array))
459 islamic-diary-entry-symbol
460 (calendar-date-string
461 (calendar-islamic-from-absolute
462 (calendar-absolute-from-gregorian
463 (calendar-cursor-to-date t)))
467 (defun insert-monthly-islamic-diary-entry (arg)
468 "Insert a monthly diary entry.
469 For the day of the Islamic month corresponding to the date indicated by point.
470 Prefix arg will make the entry nonmarking."
472 (let* ((calendar-date-display-form
473 (if european-calendar-style '(day " * ") '("* " day )))
474 (calendar-month-name-array calendar-islamic-month-name-array))
477 islamic-diary-entry-symbol
478 (calendar-date-string
479 (calendar-islamic-from-absolute
480 (calendar-absolute-from-gregorian
481 (calendar-cursor-to-date t)))))
484 (defun insert-yearly-islamic-diary-entry (arg)
485 "Insert an annual diary entry.
486 For the day of the Islamic year corresponding to the date indicated by point.
487 Prefix arg will make the entry nonmarking."
489 (let* ((calendar-date-display-form
490 (if european-calendar-style
492 '(monthname " " day)))
493 (calendar-month-name-array calendar-islamic-month-name-array))
496 islamic-diary-entry-symbol
497 (calendar-date-string
498 (calendar-islamic-from-absolute
499 (calendar-absolute-from-gregorian
500 (calendar-cursor-to-date t)))))
505 ;;; arch-tag: a951b6c1-6f47-48d5-bac3-1b505cd719f7
506 ;;; cal-islam.el ends here