lisp/calendar/cal-coptic.el

   1 ;;; cal-coptic.el --- calendar functions for the Coptic/Ethiopic calendars
   2
   3 ;; Copyright (C) 1995, 1997, 2001-2017 Free Software Foundation, Inc.
   4
   5 ;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
   6 ;; Maintainer: Glenn Morris <rgm@gnu.org>
   7 ;; Keywords: calendar
   8 ;; Human-Keywords: Coptic calendar, Ethiopic calendar, calendar, diary
   9 ;; Package: calendar
  10
  11 ;; This file is part of GNU Emacs.
  12
  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 3 of the License, or
  16 ;; (at your option) any later version.
  17
  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.
  22
  23 ;; You should have received a copy of the GNU General Public License
  24 ;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
  25
  26 ;;; Commentary:
  27
  28 ;; See calendar.el.
  29
  30 ;;; Code:
  31
  32 (require 'calendar)
  33
  34 ;; Not constants because they get let-bound.
  35
  36 (defvar calendar-coptic-month-name-array
  37   ["Tut" "Babah" "Hatur" "Kiyahk" "Tubah" "Amshir" "Baramhat" "Barmundah"
  38    "Bashans" "Baunah" "Abib" "Misra" "al-Nasi"]
  39   "Array of the month names in the Coptic calendar.")
  40
  41 (eval-and-compile
  42   (autoload 'calendar-julian-to-absolute "cal-julian"))
  43
  44 (defvar calendar-coptic-epoch
  45   (eval-when-compile (calendar-julian-to-absolute '(8 29 284)))
  46   "Absolute date of start of Coptic calendar = August 29, 284 AD (Julian).")
  47
  48 (defvar calendar-coptic-name "Coptic"
  49   "Used in some message strings.")
  50
  51 (defun calendar-coptic-leap-year-p (year)
  52   "True if YEAR is a leap year on the Coptic calendar."
  53   (zerop (mod (1+ year) 4)))
  54
  55 (defun calendar-coptic-last-day-of-month (month year)
  56   "Return last day of MONTH, YEAR on the Coptic calendar.
  57 The 13th month is not really a month, but the 5 (6 in leap years) day period of
  58 Nisi (Kebus) at the end of the year."
  59   (if (< month 13)
  60       30
  61     (if (calendar-coptic-leap-year-p year)
  62         6
  63       5)))
  64
  65 (defun calendar-coptic-to-absolute (date)
  66   "Compute absolute date from Coptic date DATE.
  67 The absolute date is the number of days elapsed since the (imaginary)
  68 Gregorian date Sunday, December 31, 1 BC."
  69   (let ((month (calendar-extract-month date))
  70         (day (calendar-extract-day date))
  71         (year (calendar-extract-year date)))
  72     (+ (1- calendar-coptic-epoch)     ; days before start of calendar
  73        (* 365 (1- year))              ; days in prior years
  74        (/ year 4)                     ; leap days in prior years
  75        (* 30 (1- month))              ; days in prior months this year
  76        day)))                         ; days so far this month
  77
  78 (defun calendar-coptic-from-absolute (date)
  79   "Compute the Coptic equivalent for absolute date DATE.
  80 The result is a list of the form (MONTH DAY YEAR).
  81 The absolute date is the number of days elapsed since the imaginary
  82 Gregorian date Sunday, December 31, 1 BC."
  83   (if (< date calendar-coptic-epoch)
  84       (list 0 0 0)                      ; pre-Coptic date
  85     (let* ((approx (/ (- date calendar-coptic-epoch)
  86                       366))    ; approximation from below
  87            (year               ; search forward from the approximation
  88             (+ approx
  89                (calendar-sum y approx
  90                              (>= date (calendar-coptic-to-absolute
  91                                        (list 1 1 (1+ y))))
  92                              1)))
  93            (month                       ; search forward from Tot
  94             (1+ (calendar-sum m 1
  95                               (> date
  96                                  (calendar-coptic-to-absolute
  97                                   (list m
  98                                         (calendar-coptic-last-day-of-month m
  99                                                                            year)
 100                                         year)))
 101                               1)))
 102            (day                     ; calculate the day by subtraction
 103             (- date
 104                (1- (calendar-coptic-to-absolute (list month 1 year))))))
 105       (list month day year))))
 106
 107 ;;;###cal-autoload
 108 (defun calendar-coptic-date-string (&optional date)
 109   "String of Coptic date of Gregorian DATE.
 110 Returns the empty string if DATE is pre-Coptic calendar.
 111 Defaults to today's date if DATE is not given."
 112   (let* ((coptic-date (calendar-coptic-from-absolute
 113                        (calendar-absolute-from-gregorian
 114                         (or date (calendar-current-date)))))
 115          (y (calendar-extract-year coptic-date))
 116          (m (calendar-extract-month coptic-date)))
 117     (if (< y 1)
 118         ""
 119       (let ((monthname (aref calendar-coptic-month-name-array (1- m)))
 120             (day (number-to-string (calendar-extract-day coptic-date)))
 121             (dayname nil)
 122             (month (number-to-string m))
 123             (year (number-to-string y)))
 124         (mapconcat 'eval calendar-date-display-form "")))))
 125
 126 ;;;###cal-autoload
 127 (defun calendar-coptic-print-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" calendar-coptic-name)
 133       (message "%s date: %s" calendar-coptic-name f))))
 134
 135 (defun calendar-coptic-read-date ()
 136   "Interactively read the arguments for a Coptic date command.
 137 Reads a year, month, and day."
 138   (let* ((today (calendar-current-date))
 139          (year (calendar-read
 140                 (format "%s calendar year (>0): " calendar-coptic-name)
 141                 (lambda (x) (> x 0))
 142                 (number-to-string
 143                  (calendar-extract-year
 144                   (calendar-coptic-from-absolute
 145                    (calendar-absolute-from-gregorian today))))))
 146          (completion-ignore-case t)
 147          (month (cdr (assoc-string
 148                       (completing-read
 149                        (format "%s calendar month name: " calendar-coptic-name)
 150                        (mapcar 'list
 151                                (append calendar-coptic-month-name-array nil))
 152                        nil t)
 153                       (calendar-make-alist calendar-coptic-month-name-array
 154                                            1) t)))
 155          (last (calendar-coptic-last-day-of-month month year))
 156          (day (calendar-read
 157                (format "%s calendar day (1-%d): " calendar-coptic-name last)
 158                (lambda (x) (and (< 0 x) (<= x last))))))
 159     (list (list month day year))))
 160
 161 ;;;###cal-autoload
 162 (defun calendar-coptic-goto-date (date &optional noecho)
 163   "Move cursor to Coptic date DATE.
 164 Echo Coptic date unless NOECHO is t."
 165   (interactive (calendar-coptic-read-date))
 166   (calendar-goto-date (calendar-gregorian-from-absolute
 167                        (calendar-coptic-to-absolute date)))
 168   (or noecho (calendar-coptic-print-date)))
 169
 170
 171 (defvar date)
 172
 173 ;; To be called from diary-list-sexp-entries, where DATE is bound.
 174 ;;;###diary-autoload
 175 (defun diary-coptic-date ()
 176   "Coptic calendar equivalent of date diary entry."
 177   (let ((f (calendar-coptic-date-string date)))
 178     (if (string-equal f "")
 179         (format "Date is pre-%s calendar" calendar-coptic-name)
 180       (format "%s date: %s" calendar-coptic-name f))))
 181
 182 (defconst calendar-ethiopic-month-name-array
 183   ["Maskaram" "Teqemt" "Khedar" "Takhsas" "Ter" "Yakatit" "Magabit" "Miyazya"
 184    "Genbot" "Sane" "Hamle" "Nahas" "Paguem"]
 185   "Array of the month names in the Ethiopic calendar.")
 186
 187 (defconst calendar-ethiopic-epoch 2796
 188   "Absolute date of start of Ethiopic calendar = August 29, 8 C.E. (Julian).")
 189
 190 (defconst calendar-ethiopic-name "Ethiopic"
 191   "Used in some message strings.")
 192
 193 (defun calendar-ethiopic-to-absolute (date)
 194   "Compute absolute date from Ethiopic date DATE.
 195 The absolute date is the number of days elapsed since the (imaginary)
 196 Gregorian date Sunday, December 31, 1 BC."
 197   (let ((calendar-coptic-epoch calendar-ethiopic-epoch))
 198     (calendar-coptic-to-absolute date)))
 199
 200 (defun calendar-ethiopic-from-absolute (date)
 201   "Compute the Ethiopic equivalent for absolute date DATE.
 202 The result is a list of the form (MONTH DAY YEAR).
 203 The absolute date is the number of days elapsed since the imaginary
 204 Gregorian date Sunday, December 31, 1 BC."
 205   (let ((calendar-coptic-epoch calendar-ethiopic-epoch))
 206     (calendar-coptic-from-absolute date)))
 207
 208 ;;;###cal-autoload
 209 (defun calendar-ethiopic-date-string (&optional date)
 210   "String of Ethiopic date of Gregorian DATE.
 211 Returns the empty string if DATE is pre-Ethiopic calendar.
 212 Defaults to today's date if DATE is not given."
 213   (let ((calendar-coptic-epoch calendar-ethiopic-epoch)
 214         (calendar-coptic-name calendar-ethiopic-name)
 215         (calendar-coptic-month-name-array calendar-ethiopic-month-name-array))
 216     (calendar-coptic-date-string date)))
 217
 218 ;;;###cal-autoload
 219 (defun calendar-ethiopic-print-date ()
 220   "Show the Ethiopic calendar equivalent of the selected date."
 221   (interactive)
 222   (let ((calendar-coptic-epoch calendar-ethiopic-epoch)
 223         (calendar-coptic-name calendar-ethiopic-name)
 224         (calendar-coptic-month-name-array calendar-ethiopic-month-name-array))
 225     (call-interactively 'calendar-coptic-print-date)))
 226
 227 ;;;###cal-autoload
 228 (defun calendar-ethiopic-goto-date (date &optional noecho)
 229   "Move cursor to Ethiopic date DATE.
 230 Echo Ethiopic date unless NOECHO is t."
 231   (interactive
 232    (let ((calendar-coptic-epoch calendar-ethiopic-epoch)
 233          (calendar-coptic-name calendar-ethiopic-name)
 234          (calendar-coptic-month-name-array calendar-ethiopic-month-name-array))
 235      (calendar-coptic-read-date)))
 236   (calendar-goto-date (calendar-gregorian-from-absolute
 237                        (calendar-ethiopic-to-absolute date)))
 238   (or noecho (calendar-ethiopic-print-date)))
 239
 240 ;; To be called from diary-list-sexp-entries, where DATE is bound.
 241 ;;;###diary-autoload
 242 (defun diary-ethiopic-date ()
 243   "Ethiopic calendar equivalent of date diary entry."
 244   (let ((calendar-coptic-epoch calendar-ethiopic-epoch)
 245         (calendar-coptic-name calendar-ethiopic-name)
 246         (calendar-coptic-month-name-array calendar-ethiopic-month-name-array))
 247     (diary-coptic-date)))
 248
 249 (provide 'cal-coptic)
 250
 251 ;;; cal-coptic.el ends here