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259 lines
10 KiB
EmacsLisp
259 lines
10 KiB
EmacsLisp
;;; cal-french.el --- calendar functions for the French Revolutionary calendar
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;; Copyright (C) 1988, 89, 92, 94, 95, 1997 Free Software Foundation, Inc.
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;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
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;; Keywords: calendar
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;; Human-Keywords: French Revolutionary calendar, calendar, diary
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software; you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation; either version 2, or (at your option)
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;; any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs; see the file COPYING. If not, write to the
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;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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;; Boston, MA 02111-1307, USA.
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;;; Commentary:
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;; This collection of functions implements the features of calendar.el and
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;; diary.el that deal with the French Revolutionary calendar.
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;; Technical details of the French Revolutionary calendar can be found in
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;; ``Calendrical Calculations: The Millennium Edition'' by Edward M. Reingold
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;; and Nachum Dershowitz, Cambridge University Press (2001), and in
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;; ``Calendrical Calculations, Part II: Three Historical Calendars'' by
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;; E. M. Reingold, N. Dershowitz, and S. M. Clamen, Software--Practice and
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;; Experience, Volume 23, Number 4 (April, 1993), pages 383-404.
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;; Comments, corrections, and improvements should be sent to
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;; Edward M. Reingold Department of Computer Science
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;; (217) 333-6733 University of Illinois at Urbana-Champaign
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;; reingold@cs.uiuc.edu 1304 West Springfield Avenue
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;; Urbana, Illinois 61801
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;;; Code:
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(require 'calendar)
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(defun french-calendar-accents ()
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"True if diacritical marks are available."
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(and (or window-system
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(terminal-coding-system))
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(or enable-multibyte-characters
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(and (char-table-p standard-display-table)
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(equal (aref standard-display-table 161) [161])))))
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(defconst french-calendar-epoch (calendar-absolute-from-gregorian '(9 22 1792))
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"Absolute date of start of French Revolutionary calendar = September 22, 1792.")
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(defconst french-calendar-month-name-array
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["Vende'miaire" "Brumaire" "Frimaire" "Nivo^se" "Pluvio^se" "Vento^se"
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"Germinal" "Flore'al" "Prairial" "Messidor" "Thermidor" "Fructidor"])
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(defconst french-calendar-multibyte-month-name-array
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["Vend<EFBFBD>miaire" "Brumaire" "Frimaire" "Niv<EFBFBD>se" "Pluvi<EFBFBD>se" "Vent<EFBFBD>se"
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"Germinal" "Flor<EFBFBD>al" "Prairial" "Messidor" "Thermidor" "Fructidor"])
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(defconst french-calendar-day-name-array
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["Primidi" "Duodi" "Tridi" "Quartidi" "Quintidi" "Sextidi" "Septidi"
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"Octidi" "Nonidi" "Decadi"])
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(defconst french-calendar-multibyte-special-days-array
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["de la Vertu" "du G<>nie" "du Travail" "de la Raison" "des R<>compenses"
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"de la R<>volution"])
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(defconst french-calendar-special-days-array
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["de la Vertu" "du Ge'nie" "du Travail" "de la Raison" "des Re'compenses"
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"de la Re'volution"])
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(defun french-calendar-month-name-array ()
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(if (french-calendar-accents)
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french-calendar-multibyte-month-name-array
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french-calendar-month-name-array))
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(defun french-calendar-day-name-array ()
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french-calendar-day-name-array)
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(defun french-calendar-special-days-array ()
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(if (french-calendar-accents)
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french-calendar-multibyte-special-days-array
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french-calendar-special-days-array))
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(defun french-calendar-leap-year-p (year)
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"True if YEAR is a leap year on the French Revolutionary calendar.
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For Gregorian years 1793 to 1805, the years of actual operation of the
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calendar, follows historical practice based on equinoxes (years 3, 7,
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and 11 were leap years; 15 and 20 would have been leap years). For later
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years uses the proposed rule of Romme (never adopted)--leap years fall every
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four years except century years not divisible 400 and century years that are
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multiples of 4000."
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(or (memq year '(3 7 11));; Actual practice--based on equinoxes
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(memq year '(15 20)) ;; Anticipated practice--based on equinoxes
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(and (> year 20) ;; Romme's proposal--never adopted
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(zerop (% year 4))
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(not (memq (% year 400) '(100 200 300)))
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(not (zerop (% year 4000))))))
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(defun french-calendar-last-day-of-month (month year)
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"Return last day of MONTH, YEAR on the French Revolutionary calendar.
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The 13th month is not really a month, but the 5 (6 in leap years) day period of
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`sansculottides' at the end of the year."
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(if (< month 13)
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30
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(if (french-calendar-leap-year-p year)
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6
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5)))
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(defun calendar-absolute-from-french (date)
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"Compute absolute date from French Revolutionary date DATE.
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The absolute date is the number of days elapsed since the (imaginary)
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Gregorian date Sunday, December 31, 1 BC."
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(let ((month (extract-calendar-month date))
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(day (extract-calendar-day date))
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(year (extract-calendar-year date)))
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(+ (* 365 (1- year));; Days in prior years
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;; Leap days in prior years
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(if (< year 20)
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(/ year 4);; Actual and anticipated practice (years 3, 7, 11, 15)
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;; Romme's proposed rule (using the Principle of Inclusion/Exclusion)
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(+ (/ (1- year) 4);; Luckily, there were 4 leap years before year 20
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(- (/ (1- year) 100))
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(/ (1- year) 400)
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(- (/ (1- year) 4000))))
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(* 30 (1- month));; Days in prior months this year
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day;; Days so far this month
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(1- french-calendar-epoch))));; Days before start of calendar
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(defun calendar-french-from-absolute (date)
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"Compute the French Revolutionary equivalent for absolute date DATE.
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The result is a list of the form (MONTH DAY YEAR).
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The absolute date is the number of days elapsed since the
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\(imaginary) Gregorian date Sunday, December 31, 1 BC."
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(if (< date french-calendar-epoch)
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(list 0 0 0);; pre-French Revolutionary date
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(let* ((approx ;; Approximation from below.
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(/ (- date french-calendar-epoch) 366))
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(year ;; Search forward from the approximation.
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(+ approx
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(calendar-sum y approx
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(>= date (calendar-absolute-from-french (list 1 1 (1+ y))))
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1)))
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(month ;; Search forward from Vendemiaire.
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(1+ (calendar-sum m 1
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(> date
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(calendar-absolute-from-french
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(list m
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(french-calendar-last-day-of-month m year)
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year)))
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1)))
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(day ;; Calculate the day by subtraction.
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(- date
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(1- (calendar-absolute-from-french (list month 1 year))))))
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(list month day year))))
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(defun calendar-french-date-string (&optional date)
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"String of French Revolutionary date of Gregorian DATE.
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Returns the empty string if DATE is pre-French Revolutionary.
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Defaults to today's date if DATE is not given."
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(let* ((french-date (calendar-french-from-absolute
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(calendar-absolute-from-gregorian
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(or date (calendar-current-date)))))
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(y (extract-calendar-year french-date))
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(m (extract-calendar-month french-date))
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(d (extract-calendar-day french-date)))
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(cond
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((< y 1) "")
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((= m 13) (format (if (french-calendar-accents)
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"Jour %s de l'Ann<6E>e %d de la R<>volution"
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"Jour %s de l'Anne'e %d de la Re'volution")
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(aref (french-calendar-special-days-array) (1- d))
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y))
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(t (format
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(if (french-calendar-accents)
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"%d %s an %d de la R<>volution"
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"%d %s an %d de la Re'volution")
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d
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(aref (french-calendar-month-name-array) (1- m))
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y)))))
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(defun calendar-print-french-date ()
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"Show the French Revolutionary calendar equivalent of the selected date."
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(interactive)
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(let ((f (calendar-french-date-string (calendar-cursor-to-date t))))
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(if (string-equal f "")
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(message "Date is pre-French Revolution")
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(message "French Revolutionary date: %s" f))))
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(defun calendar-goto-french-date (date &optional noecho)
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"Move cursor to French Revolutionary date DATE.
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Echo French Revolutionary date unless NOECHO is t."
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(interactive
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(let ((accents (french-calendar-accents))
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(months (french-calendar-month-name-array))
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(special-days (french-calendar-special-days-array)))
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(let* ((year
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(progn
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(calendar-read
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(if accents
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"Ann<EFBFBD>e de la R<>volution (>0): "
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"Anne'e de la Re'volution (>0): ")
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'(lambda (x) (> x 0))
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(int-to-string
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(extract-calendar-year
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(calendar-french-from-absolute
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(calendar-absolute-from-gregorian
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(calendar-current-date))))))))
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(month-list
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(mapcar 'list
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(append months
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(if (french-calendar-leap-year-p year)
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(mapcar
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'(lambda (x) (concat "Jour " x))
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french-calendar-special-days-array)
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(reverse
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(cdr;; we don't want rev. day in a non-leap yr.
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(reverse
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(mapcar
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'(lambda (x)
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(concat "Jour " x))
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special-days))))))))
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(completion-ignore-case t)
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(month (cdr (assoc-string
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(completing-read
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"Mois ou Sansculottide: "
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month-list
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nil t)
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(calendar-make-alist month-list 1 'car) t)))
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(day (if (> month 12)
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(- month 12)
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(calendar-read
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"Jour (1-30): "
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'(lambda (x) (and (<= 1 x) (<= x 30))))))
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(month (if (> month 12) 13 month)))
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(list (list month day year)))))
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(calendar-goto-date (calendar-gregorian-from-absolute
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(calendar-absolute-from-french date)))
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(or noecho (calendar-print-french-date)))
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(defun diary-french-date ()
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"French calendar equivalent of date diary entry."
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(let ((f (calendar-french-date-string date)))
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(if (string-equal f "")
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"Date is pre-French Revolution"
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(format "French Revolutionary date: %s" f))))
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(provide 'cal-french)
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;;; arch-tag: 7e8045a3-8609-46b5-9cde-cf40ce541cf9
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;;; cal-french.el ends here
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