cal-french.el 10.9 KB
Newer Older
Jim Blandy's avatar
Jim Blandy committed
1 2
;;; cal-french.el --- calendar functions for the French Revolutionary calendar.

3
;; Copyright (C) 1988, 89, 92, 94, 95, 1997 Free Software Foundation, Inc.
Jim Blandy's avatar
Jim Blandy committed
4 5

;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
Eric S. Raymond's avatar
Eric S. Raymond committed
6 7
;; Keywords: calendar
;; Human-Keywords: French Revolutionary calendar, calendar, diary
Jim Blandy's avatar
Jim Blandy committed
8 9 10

;; This file is part of GNU Emacs.

11 12 13 14 15
;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

Jim Blandy's avatar
Jim Blandy committed
16
;; GNU Emacs is distributed in the hope that it will be useful,
17 18 19 20 21
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
Erik Naggum's avatar
Erik Naggum committed
22 23 24
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.
Jim Blandy's avatar
Jim Blandy committed
25 26 27 28 29 30

;;; Commentary:

;; This collection of functions implements the features of calendar.el and
;; diary.el that deal with the French Revolutionary calendar.

31
;; Technical details of the French Revolutionary calendar can be found in
32 33 34
;; ``Calendrical Calculations, Part II: Three Historical Calendars'' by
;; E. M. Reingold, N. Dershowitz, and S. M. Clamen, Software--Practice and
;; Experience, Volume 23, Number 4 (April, 1993), pages 383-404.
Jim Blandy's avatar
Jim Blandy committed
35 36 37 38 39 40 41 42 43 44 45

;; Comments, corrections, and improvements should be sent to
;;  Edward M. Reingold               Department of Computer Science
;;  (217) 333-6733                   University of Illinois at Urbana-Champaign
;;  reingold@cs.uiuc.edu             1304 West Springfield Avenue
;;                                   Urbana, Illinois 61801

;;; Code:

(require 'calendar)

46 47 48 49 50 51 52
(defun french-calendar-accents ()
  "True if diacritical marks are available."
  (and (or window-system
	   (terminal-coding-system))
       (or enable-multibyte-characters
	   (and (char-table-p standard-display-table)
		(equal (aref standard-display-table 161) [161])))))
53

Edward M. Reingold's avatar
Edward M. Reingold committed
54 55 56
(defconst french-calendar-epoch (calendar-absolute-from-gregorian '(9 22 1792))
  "Absolute date of start of French Revolutionary calendar = September 22, 1792.")

Jim Blandy's avatar
Jim Blandy committed
57
(defconst french-calendar-month-name-array
58 59 60 61 62 63
  ["Vende'miaire" "Brumaire" "Frimaire" "Nivo^se" "Pluvio^se" "Vento^se"
   "Germinal" "Flore'al" "Prairial" "Messidor" "Thermidor" "Fructidor"])

(defconst french-calendar-multibyte-month-name-array
  ["Vendmiaire" "Brumaire" "Frimaire" "Nivse" "Pluvise" "Ventse"
   "Germinal" "Floral" "Prairial" "Messidor" "Thermidor" "Fructidor"])
Jim Blandy's avatar
Jim Blandy committed
64 65 66 67 68

(defconst french-calendar-day-name-array
  ["Primidi" "Duodi" "Tridi" "Quartidi" "Quintidi" "Sextidi" "Septidi"
   "Octidi" "Nonidi" "Decadi"])

69 70 71 72 73 74 75 76 77 78
(defconst french-calendar-multibyte-special-days-array
  ["de la Vertu" "du Gnie" "du Labour" "de la Raison"
   "de la Rcompense" "de la Rvolution"])

(defun french-calendar-month-name-array ()
  (if (french-calendar-accents)
      french-calendar-multibyte-month-name-array
    french-calendar-month-name-array))

(defun french-calendar-day-name-array ()
Karl Heuer's avatar
Karl Heuer committed
79
  french-calendar-day-name-array)
80

Jim Blandy's avatar
Jim Blandy committed
81
(defconst french-calendar-special-days-array
82 83
  ["de la Vertu" "du Ge'nie" "du Labour" "de la Raison" "de la Re'compense"
   "de la Re'volution"])
Jim Blandy's avatar
Jim Blandy committed
84 85 86 87

(defun french-calendar-leap-year-p (year)
  "True if YEAR is a leap year on the French Revolutionary calendar.
For Gregorian years 1793 to 1805, the years of actual operation of the
88
calendar, follows historical practice based on equinoxes (years 3, 7,
Jim Blandy's avatar
Jim Blandy committed
89 90 91 92 93 94 95 96 97 98 99 100
and 11 were leap years; 15 and 20 would have been leap years).  For later
years uses the proposed rule of Romme (never adopted)--leap years fall every
four years except century years not divisible 400 and century years that are
multiples of 4000."
  (or (memq year '(3 7 11));; Actual practice--based on equinoxes
      (memq year '(15 20)) ;; Anticipated practice--based on equinoxes
      (and (> year 20)     ;; Romme's proposal--never adopted
           (zerop (% year 4))
           (not (memq (% year 400) '(100 200 300)))
           (not (zerop (% year 4000))))))

(defun french-calendar-last-day-of-month (month year)
Richard M. Stallman's avatar
Richard M. Stallman committed
101
  "Return last day of MONTH, YEAR on the French Revolutionary calendar.
Jim Blandy's avatar
Jim Blandy committed
102 103 104 105 106 107 108 109 110
The 13th month is not really a month, but the 5 (6 in leap years) day period of
`sansculottides' at the end of the year."
  (if (< month 13)
      30
    (if (french-calendar-leap-year-p year)
        6
      5)))

(defun calendar-absolute-from-french (date)
Richard M. Stallman's avatar
Richard M. Stallman committed
111
  "Compute absolute date from French Revolutionary date DATE.
Jim Blandy's avatar
Jim Blandy committed
112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127
The absolute date is the number of days elapsed since the (imaginary)
Gregorian date Sunday, December 31, 1 BC."
  (let ((month (extract-calendar-month date))
        (day (extract-calendar-day date))
        (year (extract-calendar-year date)))
    (+ (* 365 (1- year));; Days in prior years
       ;; Leap days in prior years
       (if (< year 20)
           (/ year 4);; Actual and anticipated practice (years 3, 7, 11, 15)
         ;; Romme's proposed rule (using the Principle of Inclusion/Exclusion)
         (+ (/ (1- year) 4);; Luckily, there were 4 leap years before year 20
            (- (/ (1- year) 100))
            (/ (1- year) 400)
            (- (/ (1- year) 4000))))
       (* 30 (1- month));; Days in prior months this year
       day;; Days so far this month
Edward M. Reingold's avatar
Edward M. Reingold committed
128
       (1- french-calendar-epoch))));; Days before start of calendar
Jim Blandy's avatar
Jim Blandy committed
129 130

(defun calendar-french-from-absolute (date)
Richard M. Stallman's avatar
Richard M. Stallman committed
131 132 133
  "Compute the French Revolutionary equivalent for absolute date DATE.
The result is a list of the form (MONTH DAY YEAR).
The absolute date is the number of days elapsed since the
Richard M. Stallman's avatar
Richard M. Stallman committed
134
\(imaginary) Gregorian date Sunday, December 31, 1 BC."
Edward M. Reingold's avatar
Edward M. Reingold committed
135
  (if (< date french-calendar-epoch)
Jim Blandy's avatar
Jim Blandy committed
136
      (list 0 0 0);; pre-French Revolutionary date
Edward M. Reingold's avatar
Edward M. Reingold committed
137 138
    (let* ((approx              ;; Approximation from below.
            (/ (- date french-calendar-epoch) 366))
Jim Blandy's avatar
Jim Blandy committed
139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156
           (year                ;; Search forward from the approximation.
            (+ approx
               (calendar-sum y approx
                 (>= date (calendar-absolute-from-french (list 1 1 (1+ y))))
                 1)))
           (month               ;; Search forward from Vendemiaire.
            (1+ (calendar-sum m 1
                  (> date
                     (calendar-absolute-from-french
                      (list m
                            (french-calendar-last-day-of-month m year)
                            year)))
                  1)))
           (day                   ;; Calculate the day by subtraction.
            (- date
               (1- (calendar-absolute-from-french (list month 1 year))))))
    (list month day year))))

157 158 159 160
(defun calendar-french-date-string (&optional date)
  "String of French Revolutionary date of Gregorian DATE.
Returns the empty string if DATE is pre-French Revolutionary.
Defaults to today's date if DATE is not given."
Jim Blandy's avatar
Jim Blandy committed
161 162
  (let* ((french-date (calendar-french-from-absolute
                       (calendar-absolute-from-gregorian
163
                        (or date (calendar-current-date)))))
Jim Blandy's avatar
Jim Blandy committed
164 165 166
         (y (extract-calendar-year french-date))
         (m (extract-calendar-month french-date))
         (d (extract-calendar-day french-date)))
167 168
    (cond
     ((< y 1) "")
169
     ((= m 13) (format (if (french-calendar-accents)
170 171
                           "Jour %s de l'Anne %d de la Rvolution"
                         "Jour %s de l'Anne'e %d de la Re'volution")
172 173
                       (aref french-calendar-special-days-array (1- d))
                       y))
174
     (t (format
175
         (if (french-calendar-accents)
176 177 178
             "Dcade %s, %s de %s de l'Anne %d de la Rvolution"
           "De'cade %s, %s de %s de l'Anne'e %d de la Re'volution")
         (make-string (1+ (/ (1- d) 10)) ?I)
179 180
         (aref (french-calendar-day-name-array) (% (1- d) 10))
         (aref (french-calendar-month-name-array) (1- m))
181
         y)))))
182 183 184 185

(defun calendar-print-french-date ()
  "Show the French Revolutionary calendar equivalent of the selected date."
  (interactive)
186 187
  (let ((f (calendar-french-date-string (calendar-cursor-to-date t)))
	(enable-multibyte-characters t))
188
    (if (string-equal f "")
Jim Blandy's avatar
Jim Blandy committed
189
        (message "Date is pre-French Revolution")
190
      (message "French Revolutionary date: %s" f))))
Jim Blandy's avatar
Jim Blandy committed
191 192

(defun calendar-goto-french-date (date &optional noecho)
Richard M. Stallman's avatar
Richard M. Stallman committed
193
  "Move cursor to French Revolutionary date DATE.
Jim Blandy's avatar
Jim Blandy committed
194 195
Echo French Revolutionary date unless NOECHO is t."
  (interactive
196 197 198 199 200 201 202 203 204 205 206 207 208 209 210
   (let* ((oldval enable-multibyte-characters)
	  (year (unwind-protect
		    (progn
		      (setq-default enable-multibyte-characters t)
		      (calendar-read
		       (if (french-calendar-accents)
			   "Anne de la Rvolution (>0): "
			 "Anne'e de la Re'volution (>0): ")
		       '(lambda (x) (> x 0))
		       (int-to-string
			(extract-calendar-year
			 (calendar-french-from-absolute
			  (calendar-absolute-from-gregorian
			   (calendar-current-date)))))))
		  (setq-default enable-multibyte-characters oldval)))
Jim Blandy's avatar
Jim Blandy committed
211 212
          (month-list
           (mapcar 'list
213
                   (append (french-calendar-month-name-array)
Jim Blandy's avatar
Jim Blandy committed
214 215 216 217
                           (if (french-calendar-leap-year-p year)
                               (mapcar
                                '(lambda (x) (concat "Jour " x))
                                french-calendar-special-days-array)
Edward M. Reingold's avatar
Edward M. Reingold committed
218
                             (reverse
Jim Blandy's avatar
Jim Blandy committed
219
                              (cdr;; we don't want rev. day in a non-leap yr.
Edward M. Reingold's avatar
Edward M. Reingold committed
220
                               (reverse
Jim Blandy's avatar
Jim Blandy committed
221 222
                                (mapcar
                                 '(lambda (x) (concat "Jour " x))
223
                                 french-calendar-special-days-array))))))))
Jim Blandy's avatar
Jim Blandy committed
224 225 226 227 228 229 230 231 232 233 234 235 236 237
          (completion-ignore-case t)
          (month (cdr (assoc
                       (capitalize
                        (completing-read
                         "Mois ou Sansculottide: "
                         month-list
                         nil t))
                       (calendar-make-alist
                        month-list
                        1
                        '(lambda (x) (capitalize (car x)))))))
          (decade (if (> month 12)
                      1
                    (calendar-read
238
                     (if (french-calendar-accents)
239 240
                         "Dcade (1-3): "
                       "De'cade (1-3): ")
Jim Blandy's avatar
Jim Blandy committed
241 242 243 244
                     '(lambda (x) (memq x '(1 2 3))))))
          (day (if (> month 12)
                   (- month 12)
                 (calendar-read
245
                  "Jour (1-10): "
Jim Blandy's avatar
Jim Blandy committed
246 247 248 249 250 251 252 253 254 255
                  '(lambda (x) (and (<= 1 x) (<= x 10))))))
          (month (if (> month 12) 13 month))
          (day (+ day (* 10 (1- decade)))))
     (list (list month day year))))
  (calendar-goto-date (calendar-gregorian-from-absolute
                       (calendar-absolute-from-french date)))
  (or noecho (calendar-print-french-date)))

(defun diary-french-date ()
  "French calendar equivalent of date diary entry."
256
  (let ((f (calendar-french-date-string date)))
257 258
    (if (string-equal f "")
        "Date is pre-French Revolution"
259
      (format "French Revolutionary date: %s" f))))
Jim Blandy's avatar
Jim Blandy committed
260 261 262 263

(provide 'cal-french)

;;; cal-french.el ends here