lisp/calendar/cal-coptic.el

   1 ;;; cal-coptic.el --- calendar functions for the Coptic/Ethiopic calendars
   2
   3 ;; Copyright (C) 1995, 1997, 2001-2012  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 <http://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 (define-obsolete-function-alias 'calendar-absolute-from-coptic
  79   'calendar-coptic-to-absolute "23.1")
  80
  81 (defun calendar-coptic-from-absolute (date)
  82   "Compute the Coptic equivalent for absolute date DATE.
  83 The result is a list of the form (MONTH DAY YEAR).
  84 The absolute date is the number of days elapsed since the imaginary
  85 Gregorian date Sunday, December 31, 1 BC."
  86   (if (< date calendar-coptic-epoch)
  87       (list 0 0 0)                      ; pre-Coptic date
  88     (let* ((approx (/ (- date calendar-coptic-epoch)
  89                       366))    ; approximation from below
  90            (year               ; search forward from the approximation
  91             (+ approx
  92                (calendar-sum y approx
  93                              (>= date (calendar-coptic-to-absolute
  94                                        (list 1 1 (1+ y))))
  95                              1)))
  96            (month                       ; search forward from Tot
  97             (1+ (calendar-sum m 1
  98                               (> date
  99                                  (calendar-coptic-to-absolute
 100                                   (list m
 101                                         (calendar-coptic-last-day-of-month m
 102                                                                            year)
 103                                         year)))
 104                               1)))
 105            (day                     ; calculate the day by subtraction
 106             (- date
 107                (1- (calendar-coptic-to-absolute (list month 1 year))))))
 108       (list month day year))))
 109
 110 ;;;###cal-autoload
 111 (defun calendar-coptic-date-string (&optional date)
 112   "String of Coptic date of Gregorian DATE.
 113 Returns the empty string if DATE is pre-Coptic calendar.
 114 Defaults to today's date if DATE is not given."
 115   (let* ((coptic-date (calendar-coptic-from-absolute
 116                        (calendar-absolute-from-gregorian
 117                         (or date (calendar-current-date)))))
 118          (y (calendar-extract-year coptic-date))
 119          (m (calendar-extract-month coptic-date)))
 120     (if (< y 1)
 121         ""
 122       (let ((monthname (aref calendar-coptic-month-name-array (1- m)))
 123             (day (number-to-string (calendar-extract-day coptic-date)))
 124             (dayname nil)
 125             (month (number-to-string m))
 126             (year (number-to-string y)))
 127         (mapconcat 'eval calendar-date-display-form "")))))
 128
 129 ;;;###cal-autoload
 130 (defun calendar-coptic-print-date ()
 131   "Show the Coptic calendar equivalent of the selected date."
 132   (interactive)
 133   (let ((f (calendar-coptic-date-string (calendar-cursor-to-date t))))
 134     (if (string-equal f "")
 135         (message "Date is pre-%s calendar" calendar-coptic-name)
 136       (message "%s date: %s" calendar-coptic-name f))))
 137
 138 (define-obsolete-function-alias 'calendar-print-coptic-date
 139   'calendar-coptic-print-date "23.1")
 140
 141 (defun calendar-coptic-read-date ()
 142   "Interactively read the arguments for a Coptic date command.
 143 Reads a year, month, and day."
 144   (let* ((today (calendar-current-date))
 145          (year (calendar-read
 146                 (format "%s calendar year (>0): " calendar-coptic-name)
 147                 (lambda (x) (> x 0))
 148                 (number-to-string
 149                  (calendar-extract-year
 150                   (calendar-coptic-from-absolute
 151                    (calendar-absolute-from-gregorian today))))))
 152          (completion-ignore-case t)
 153          (month (cdr (assoc-string
 154                       (completing-read
 155                        (format "%s calendar month name: " calendar-coptic-name)
 156                        (mapcar 'list
 157                                (append calendar-coptic-month-name-array nil))
 158                        nil t)
 159                       (calendar-make-alist calendar-coptic-month-name-array
 160                                            1) t)))
 161          (last (calendar-coptic-last-day-of-month month year))
 162          (day (calendar-read
 163                (format "%s calendar day (1-%d): " calendar-coptic-name last)
 164                (lambda (x) (and (< 0 x) (<= x last))))))
 165     (list (list month day year))))
 166
 167 (define-obsolete-function-alias 'coptic-prompt-for-date
 168   'calendar-coptic-read-date "23.1")
 169
 170 ;;;###cal-autoload
 171 (defun calendar-coptic-goto-date (date &optional noecho)
 172   "Move cursor to Coptic date DATE.
 173 Echo Coptic date unless NOECHO is t."
 174   (interactive (calendar-coptic-read-date))
 175   (calendar-goto-date (calendar-gregorian-from-absolute
 176                        (calendar-coptic-to-absolute date)))
 177   (or noecho (calendar-coptic-print-date)))
 178
 179 (define-obsolete-function-alias 'calendar-goto-coptic-date
 180   'calendar-coptic-goto-date "23.1")
 181
 182 (defvar date)
 183
 184 ;; To be called from diary-list-sexp-entries, where DATE is bound.
 185 ;;;###diary-autoload
 186 (defun diary-coptic-date ()
 187   "Coptic calendar equivalent of date diary entry."
 188   (let ((f (calendar-coptic-date-string date)))
 189     (if (string-equal f "")
 190         (format "Date is pre-%s calendar" calendar-coptic-name)
 191       (format "%s date: %s" calendar-coptic-name f))))
 192
 193 (defconst calendar-ethiopic-month-name-array
 194   ["Maskaram" "Teqemt" "Khedar" "Takhsas" "Ter" "Yakatit" "Magabit" "Miyazya"
 195    "Genbot" "Sane" "Hamle" "Nahas" "Paguem"]
 196   "Array of the month names in the Ethiopic calendar.")
 197
 198 (defconst calendar-ethiopic-epoch 2796
 199   "Absolute date of start of Ethiopic calendar = August 29, 8 C.E. (Julian).")
 200
 201 (defconst calendar-ethiopic-name "Ethiopic"
 202   "Used in some message strings.")
 203
 204 (defun calendar-ethiopic-to-absolute (date)
 205   "Compute absolute date from Ethiopic date DATE.
 206 The absolute date is the number of days elapsed since the (imaginary)
 207 Gregorian date Sunday, December 31, 1 BC."
 208   (let ((calendar-coptic-epoch calendar-ethiopic-epoch))
 209     (calendar-coptic-to-absolute date)))
 210
 211 (define-obsolete-function-alias 'calendar-absolute-from-ethiopic
 212   'calendar-ethiopic-to-absolute "23.1")
 213
 214 (defun calendar-ethiopic-from-absolute (date)
 215   "Compute the Ethiopic equivalent for absolute date DATE.
 216 The result is a list of the form (MONTH DAY YEAR).
 217 The absolute date is the number of days elapsed since the imaginary
 218 Gregorian date Sunday, December 31, 1 BC."
 219   (let ((calendar-coptic-epoch calendar-ethiopic-epoch))
 220     (calendar-coptic-from-absolute date)))
 221
 222 ;;;###cal-autoload
 223 (defun calendar-ethiopic-date-string (&optional date)
 224   "String of Ethiopic date of Gregorian DATE.
 225 Returns the empty string if DATE is pre-Ethiopic calendar.
 226 Defaults to today's date if DATE is not given."
 227   (let ((calendar-coptic-epoch calendar-ethiopic-epoch)
 228         (calendar-coptic-name calendar-ethiopic-name)
 229         (calendar-coptic-month-name-array calendar-ethiopic-month-name-array))
 230     (calendar-coptic-date-string date)))
 231
 232 ;;;###cal-autoload
 233 (defun calendar-ethiopic-print-date ()
 234   "Show the Ethiopic calendar equivalent of the selected date."
 235   (interactive)
 236   (let ((calendar-coptic-epoch calendar-ethiopic-epoch)
 237         (calendar-coptic-name calendar-ethiopic-name)
 238         (calendar-coptic-month-name-array calendar-ethiopic-month-name-array))
 239     (call-interactively 'calendar-coptic-print-date)))
 240
 241 (define-obsolete-function-alias 'calendar-print-ethiopic-date
 242   'calendar-ethiopic-print-date "23.1")
 243
 244 ;;;###cal-autoload
 245 (defun calendar-ethiopic-goto-date (date &optional noecho)
 246   "Move cursor to Ethiopic date DATE.
 247 Echo Ethiopic date unless NOECHO is t."
 248   (interactive
 249    (let ((calendar-coptic-epoch calendar-ethiopic-epoch)
 250          (calendar-coptic-name calendar-ethiopic-name)
 251          (calendar-coptic-month-name-array calendar-ethiopic-month-name-array))
 252      (calendar-coptic-read-date)))
 253   (calendar-goto-date (calendar-gregorian-from-absolute
 254                        (calendar-ethiopic-to-absolute date)))
 255   (or noecho (calendar-ethiopic-print-date)))
 256
 257 (define-obsolete-function-alias 'calendar-goto-ethiopic-date
 258   'calendar-ethiopic-goto-date "23.1")
 259
 260 ;; To be called from diary-list-sexp-entries, where DATE is bound.
 261 ;;;###diary-autoload
 262 (defun diary-ethiopic-date ()
 263   "Ethiopic calendar equivalent of date diary entry."
 264   (let ((calendar-coptic-epoch calendar-ethiopic-epoch)
 265         (calendar-coptic-name calendar-ethiopic-name)
 266         (calendar-coptic-month-name-array calendar-ethiopic-month-name-array))
 267     (diary-coptic-date)))
 268
 269 (provide 'cal-coptic)
 270
 271 ;;; cal-coptic.el ends here