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3afbc435 | 1 | ;;; cal-coptic.el --- calendar functions for the Coptic/Ethiopic calendars |
0808d911 | 2 | |
a96a5fca | 3 | ;; Copyright (C) 1995, 1997 Free Software Foundation, Inc. |
0808d911 ER |
4 | |
5 | ;; Author: Edward M. Reingold <reingold@cs.uiuc.edu> | |
6 | ;; Keywords: calendar | |
7 | ;; Human-Keywords: Coptic calendar, Ethiopic calendar, calendar, diary | |
8 | ||
9 | ;; This file is part of GNU Emacs. | |
10 | ||
11 | ;; GNU Emacs is free software; you can redistribute it and/or modify | |
12 | ;; it under the terms of the GNU General Public License as published by | |
13 | ;; the Free Software Foundation; either version 2, or (at your option) | |
14 | ;; any later version. | |
15 | ||
16 | ;; GNU Emacs is distributed in the hope that it will be useful, | |
17 | ;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
18 | ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
19 | ;; GNU General Public License for more details. | |
20 | ||
21 | ;; You should have received a copy of the GNU General Public License | |
b578f267 EN |
22 | ;; along with GNU Emacs; see the file COPYING. If not, write to the |
23 | ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
24 | ;; Boston, MA 02111-1307, USA. | |
0808d911 ER |
25 | |
26 | ;;; Commentary: | |
27 | ||
28 | ;; This collection of functions implements the features of calendar.el and | |
29 | ;; diary.el that deal with the Coptic and Ethiopic calendars. | |
30 | ||
a96a5fca PE |
31 | ;; Technical details of all the calendrical calculations can be found in |
32 | ;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold, | |
33 | ;; Cambridge University Press (1997). | |
34 | ||
0808d911 ER |
35 | ;; Comments, corrections, and improvements should be sent to |
36 | ;; Edward M. Reingold Department of Computer Science | |
37 | ;; (217) 333-6733 University of Illinois at Urbana-Champaign | |
38 | ;; reingold@cs.uiuc.edu 1304 West Springfield Avenue | |
39 | ;; Urbana, Illinois 61801 | |
40 | ||
41 | ;;; Code: | |
42 | ||
43 | (require 'cal-julian) | |
44 | ||
45 | (defvar coptic-calendar-month-name-array | |
179bd1b3 ER |
46 | ["Tut" "Babah" "Hatur" "Kiyahk" "Tubah" "Amshir" "Baramhat" "Barmundah" |
47 | "Bashans" "Baunah" "Abib" "Misra" "al-Nasi"]) | |
0808d911 ER |
48 | |
49 | (defvar coptic-calendar-epoch (calendar-absolute-from-julian '(8 29 284)) | |
50 | "Absolute date of start of Coptic calendar = August 29, 284 A.D. (Julian).") | |
51 | ||
52 | (defconst coptic-name "Coptic") | |
53 | ||
54 | (defun coptic-calendar-leap-year-p (year) | |
55 | "True if YEAR is a leap year on the Coptic calendar." | |
56 | (zerop (mod (1+ year) 4))) | |
57 | ||
58 | (defun coptic-calendar-last-day-of-month (month year) | |
59 | "Return last day of MONTH, YEAR on the Coptic calendar. | |
60 | The 13th month is not really a month, but the 5 (6 in leap years) day period of | |
61 | Nisi (Kebus) at the end of the year." | |
62 | (if (< month 13) | |
63 | 30 | |
64 | (if (coptic-calendar-leap-year-p year) | |
65 | 6 | |
66 | 5))) | |
67 | ||
68 | (defun calendar-absolute-from-coptic (date) | |
69 | "Compute absolute date from Coptic date DATE. | |
70 | The absolute date is the number of days elapsed since the (imaginary) | |
71 | Gregorian date Sunday, December 31, 1 BC." | |
72 | (let ((month (extract-calendar-month date)) | |
73 | (day (extract-calendar-day date)) | |
74 | (year (extract-calendar-year date))) | |
75 | (+ (1- coptic-calendar-epoch);; Days before start of calendar | |
76 | (* 365 (1- year)) ;; Days in prior years | |
77 | (/ year 4) ;; Leap days in prior years | |
78 | (* 30 (1- month)) ;; Days in prior months this year | |
79 | day))) ;; Days so far this month | |
a1506d29 | 80 | |
0808d911 ER |
81 | |
82 | (defun calendar-coptic-from-absolute (date) | |
83 | "Compute the Coptic equivalent for absolute date DATE. | |
84 | The result is a list of the form (MONTH DAY YEAR). | |
85 | The absolute date is the number of days elapsed since the imaginary | |
86 | Gregorian date Sunday, December 31, 1 BC." | |
87 | (if (< date coptic-calendar-epoch) | |
88 | (list 0 0 0);; pre-Coptic date | |
89 | (let* ((approx (/ (- date coptic-calendar-epoch) | |
90 | 366)) ;; Approximation from below. | |
91 | (year ;; Search forward from the approximation. | |
92 | (+ approx | |
93 | (calendar-sum y approx | |
94 | (>= date (calendar-absolute-from-coptic (list 1 1 (1+ y)))) | |
95 | 1))) | |
96 | (month ;; Search forward from Tot. | |
97 | (1+ (calendar-sum m 1 | |
98 | (> date | |
99 | (calendar-absolute-from-coptic | |
100 | (list m | |
101 | (coptic-calendar-last-day-of-month m year) | |
102 | year))) | |
103 | 1))) | |
104 | (day ;; Calculate the day by subtraction. | |
105 | (- date | |
106 | (1- (calendar-absolute-from-coptic (list month 1 year)))))) | |
107 | (list month day year)))) | |
108 | ||
109 | (defun calendar-coptic-date-string (&optional date) | |
110 | "String of Coptic date of Gregorian DATE. | |
111 | Returns the empty string if DATE is pre-Coptic calendar. | |
112 | Defaults to today's date if DATE is not given." | |
113 | (let* ((coptic-date (calendar-coptic-from-absolute | |
114 | (calendar-absolute-from-gregorian | |
115 | (or date (calendar-current-date))))) | |
116 | (y (extract-calendar-year coptic-date)) | |
117 | (m (extract-calendar-month coptic-date))) | |
118 | (if (< y 1) | |
119 | "" | |
120 | (let ((monthname (aref coptic-calendar-month-name-array (1- m))) | |
121 | (day (int-to-string (extract-calendar-day coptic-date))) | |
122 | (dayname nil) | |
123 | (month (int-to-string m)) | |
124 | (year (int-to-string y))) | |
125 | (mapconcat 'eval calendar-date-display-form ""))))) | |
126 | ||
127 | (defun calendar-print-coptic-date () | |
128 | "Show the Coptic calendar equivalent of the selected date." | |
129 | (interactive) | |
130 | (let ((f (calendar-coptic-date-string (calendar-cursor-to-date t)))) | |
131 | (if (string-equal f "") | |
132 | (message "Date is pre-%s calendar" coptic-name) | |
ed8fcefb | 133 | (message "%s date: %s" coptic-name f)))) |
0808d911 ER |
134 | |
135 | (defun calendar-goto-coptic-date (date &optional noecho) | |
136 | "Move cursor to Coptic date DATE. | |
137 | Echo Coptic date unless NOECHO is t." | |
138 | (interactive (coptic-prompt-for-date)) | |
139 | (calendar-goto-date (calendar-gregorian-from-absolute | |
140 | (calendar-absolute-from-coptic date))) | |
141 | (or noecho (calendar-print-coptic-date))) | |
142 | ||
143 | (defun coptic-prompt-for-date () | |
144 | "Ask for a Coptic date." | |
145 | (let* ((today (calendar-current-date)) | |
146 | (year (calendar-read | |
147 | (format "%s calendar year (>0): " coptic-name) | |
148 | '(lambda (x) (> x 0)) | |
149 | (int-to-string | |
150 | (extract-calendar-year | |
151 | (calendar-coptic-from-absolute | |
152 | (calendar-absolute-from-gregorian today)))))) | |
153 | (completion-ignore-case t) | |
50830fad RS |
154 | (month (cdr (assoc-ignore-case |
155 | (completing-read | |
156 | (format "%s calendar month name: " coptic-name) | |
157 | (mapcar 'list | |
158 | (append coptic-calendar-month-name-array nil)) | |
159 | nil t) | |
0808d911 | 160 | (calendar-make-alist coptic-calendar-month-name-array |
50830fad | 161 | 1)))) |
0808d911 ER |
162 | (last (coptic-calendar-last-day-of-month month year)) |
163 | (day (calendar-read | |
164 | (format "%s calendar day (1-%d): " coptic-name last) | |
165 | '(lambda (x) (and (< 0 x) (<= x last)))))) | |
166 | (list (list month day year)))) | |
167 | ||
168 | (defun diary-coptic-date () | |
169 | "Coptic calendar equivalent of date diary entry." | |
7801463c | 170 | (let ((f (calendar-coptic-date-string date))) |
0808d911 ER |
171 | (if (string-equal f "") |
172 | (format "Date is pre-%s calendar" coptic-name) | |
7801463c | 173 | (format "%s date: %s" coptic-name f)))) |
0808d911 ER |
174 | |
175 | (defconst ethiopic-calendar-month-name-array | |
179bd1b3 ER |
176 | ["Maskaram" "Teqemt" "Khedar" "Takhsas" "Ter" "Yakatit" "Magabit" "Miyazya" |
177 | "Genbot" "Sane" "Hamle" "Nahas" "Paguem"]) | |
0808d911 | 178 | |
d5824b35 KH |
179 | (defconst ethiopic-calendar-epoch 2796 |
180 | "Absolute date of start of Ethiopic calendar = August 29, 8 C.E. (Julian).") | |
0808d911 ER |
181 | |
182 | (defconst ethiopic-name "Ethiopic") | |
183 | ||
184 | (defun calendar-absolute-from-ethiopic (date) | |
185 | "Compute absolute date from Ethiopic date DATE. | |
186 | The absolute date is the number of days elapsed since the (imaginary) | |
187 | Gregorian date Sunday, December 31, 1 BC." | |
188 | (let ((coptic-calendar-epoch ethiopic-calendar-epoch)) | |
189 | (calendar-absolute-from-coptic date))) | |
190 | ||
191 | (defun calendar-ethiopic-from-absolute (date) | |
192 | "Compute the Ethiopic equivalent for absolute date DATE. | |
193 | The result is a list of the form (MONTH DAY YEAR). | |
194 | The absolute date is the number of days elapsed since the imaginary | |
195 | Gregorian date Sunday, December 31, 1 BC." | |
196 | (let ((coptic-calendar-epoch ethiopic-calendar-epoch)) | |
197 | (calendar-coptic-from-absolute date))) | |
198 | ||
199 | (defun calendar-ethiopic-date-string (&optional date) | |
200 | "String of Ethiopic date of Gregorian DATE. | |
201 | Returns the empty string if DATE is pre-Ethiopic calendar. | |
202 | Defaults to today's date if DATE is not given." | |
203 | (let ((coptic-calendar-epoch ethiopic-calendar-epoch) | |
204 | (coptic-name ethiopic-name) | |
205 | (coptic-calendar-month-name-array ethiopic-calendar-month-name-array)) | |
206 | (calendar-coptic-date-string date))) | |
207 | ||
208 | (defun calendar-print-ethiopic-date () | |
209 | "Show the Ethiopic calendar equivalent of the selected date." | |
210 | (interactive) | |
211 | (let ((coptic-calendar-epoch ethiopic-calendar-epoch) | |
212 | (coptic-name ethiopic-name) | |
213 | (coptic-calendar-month-name-array ethiopic-calendar-month-name-array)) | |
214 | (call-interactively 'calendar-print-coptic-date))) | |
215 | ||
216 | (defun calendar-goto-ethiopic-date (date &optional noecho) | |
217 | "Move cursor to Ethiopic date DATE. | |
218 | Echo Ethiopic date unless NOECHO is t." | |
219 | (interactive | |
220 | (let ((coptic-calendar-epoch ethiopic-calendar-epoch) | |
221 | (coptic-name ethiopic-name) | |
222 | (coptic-calendar-month-name-array ethiopic-calendar-month-name-array)) | |
223 | (coptic-prompt-for-date))) | |
224 | (calendar-goto-date (calendar-gregorian-from-absolute | |
225 | (calendar-absolute-from-ethiopic date))) | |
226 | (or noecho (calendar-print-ethiopic-date))) | |
227 | ||
228 | (defun diary-ethiopic-date () | |
229 | "Ethiopic calendar equivalent of date diary entry." | |
230 | (let ((coptic-calendar-epoch ethiopic-calendar-epoch) | |
231 | (coptic-name ethiopic-name) | |
232 | (coptic-calendar-month-name-array ethiopic-calendar-month-name-array)) | |
233 | (diary-coptic-date))) | |
234 | ||
235 | (provide 'cal-coptic) | |
236 | ||
237 | ;;; cal-coptic.el ends here |