mirror of
https://git.savannah.gnu.org/git/emacs.git
synced 2024-12-15 09:47:20 +00:00
211 lines
8.5 KiB
EmacsLisp
211 lines
8.5 KiB
EmacsLisp
;;; cal-persia.el --- calendar functions for the Persian calendar.
|
|
|
|
;; Copyright (C) 1996, 1997 Free Software Foundation, Inc.
|
|
|
|
;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
|
|
;; Keywords: calendar
|
|
;; Human-Keywords: Persian calendar, calendar, diary
|
|
|
|
;; This file is part of GNU Emacs.
|
|
|
|
;; 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.
|
|
|
|
;; GNU Emacs is distributed in the hope that it will be useful,
|
|
;; 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
|
|
;; 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.
|
|
|
|
;;; Commentary:
|
|
|
|
;; This collection of functions implements the features of calendar.el and
|
|
;; diary.el that deal with the Persian calendar.
|
|
|
|
;; Technical details of all the calendrical calculations can be found in
|
|
;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
|
|
;; Cambridge University Press (1997).
|
|
|
|
;; 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 'cal-julian)
|
|
|
|
(defvar persian-calendar-month-name-array
|
|
["Farvardin" "Ordibehest" "Xordad" "Tir" "Mordad" "Sahrivar" "Mehr" "Aban"
|
|
"Azar" "Dey" "Bahman" "Esfand"])
|
|
|
|
(defvar persian-calendar-epoch (calendar-absolute-from-julian '(3 19 622))
|
|
"Absolute date of start of Persian calendar = March 19, 622 A.D. (Julian).")
|
|
|
|
(defun persian-calendar-leap-year-p (year)
|
|
"True if YEAR is a leap year on the Persian calendar."
|
|
(< (mod (* (mod (mod (if (<= 0 year)
|
|
; No year zero
|
|
(+ year 2346)
|
|
(+ year 2347))
|
|
2820)
|
|
768)
|
|
683)
|
|
2820)
|
|
683))
|
|
|
|
(defun persian-calendar-last-day-of-month (month year)
|
|
"Return last day of MONTH, YEAR on the Persian calendar."
|
|
(cond
|
|
((< month 7) 31)
|
|
((or (< month 12) (persian-calendar-leap-year-p year)) 30)
|
|
(t 29)))
|
|
|
|
(defun calendar-absolute-from-persian (date)
|
|
"Compute absolute date from Persian date DATE.
|
|
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)))
|
|
(if (< year 0)
|
|
(+ (calendar-absolute-from-persian
|
|
(list month day (1+ (mod year 2820))))
|
|
(* 1029983 (floor year 2820)))
|
|
(+ (1- persian-calendar-epoch); Days before epoch
|
|
(* 365 (1- year)) ; Days in prior years.
|
|
(* 683 ; Leap days in prior 2820-year cycles
|
|
(floor (+ year 2345) 2820))
|
|
(* 186 ; Leap days in prior 768 year cycles
|
|
(floor (mod (+ year 2345) 2820) 768))
|
|
(floor; Leap years in current 768 or 516 year cycle
|
|
(* 683 (mod (mod (+ year 2345) 2820) 768))
|
|
2820)
|
|
-568 ; Leap years in Persian years -2345...-1
|
|
(calendar-sum ; Days in prior months this year.
|
|
m 1 (< m month)
|
|
(persian-calendar-last-day-of-month m year))
|
|
day)))) ; Days so far this month.
|
|
|
|
(defun calendar-persian-year-from-absolute (date)
|
|
"Persian year corresponding to the absolute DATE."
|
|
(let* ((d0 ; Prior days since start of 2820 cycles
|
|
(- date (calendar-absolute-from-persian (list 1 1 -2345))))
|
|
(n2820 ; Completed 2820-year cycles
|
|
(floor d0 1029983))
|
|
(d1 ; Prior days not in n2820
|
|
(mod d0 1029983))
|
|
(n768 ; 768-year cycles not in n2820
|
|
(floor d1 280506))
|
|
(d2 ; Prior days not in n2820 or n768
|
|
(mod d1 280506))
|
|
(n1 ; Years not in n2820 or n768
|
|
; we want is
|
|
; (floor (+ (* 2820 d2) (* 2820 366)) 1029983))
|
|
; but that causes overflow, so we use
|
|
(let ((a (floor d2 366)); we use 366 as the divisor because
|
|
; (2820*366 mod 1029983) is small
|
|
(b (mod d2 366)))
|
|
(+ 1 a (floor (+ (* 2137 a) (* 2820 b) 2137) 1029983))))
|
|
(year (+ (* 2820 n2820); Complete 2820 year cycles
|
|
(* 768 n768) ; Complete 768 year cycles
|
|
(if ; Remaining years
|
|
; Last day of 2820 year cycle
|
|
(= d1 1029617)
|
|
(1- n1)
|
|
n1)
|
|
-2345))) ; Years before year 1
|
|
(if (< year 1)
|
|
(1- year); No year zero
|
|
year)))
|
|
|
|
(defun calendar-persian-from-absolute (date)
|
|
"Compute the Persian 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 imaginary
|
|
Gregorian date Sunday, December 31, 1 BC."
|
|
(let* ((year (calendar-persian-year-from-absolute date))
|
|
(month ; Search forward from Farvardin
|
|
(1+ (calendar-sum m 1
|
|
(> date
|
|
(calendar-absolute-from-persian
|
|
(list
|
|
m
|
|
(persian-calendar-last-day-of-month m year)
|
|
year)))
|
|
1)))
|
|
(day ; Calculate the day by subtraction
|
|
(- date (1- (calendar-absolute-from-persian
|
|
(list month 1 year))))))
|
|
(list month day year)))
|
|
|
|
(defun calendar-persian-date-string (&optional date)
|
|
"String of Persian date of Gregorian DATE.
|
|
Defaults to today's date if DATE is not given."
|
|
(let* ((persian-date (calendar-persian-from-absolute
|
|
(calendar-absolute-from-gregorian
|
|
(or date (calendar-current-date)))))
|
|
(y (extract-calendar-year persian-date))
|
|
(m (extract-calendar-month persian-date)))
|
|
(let ((monthname (aref persian-calendar-month-name-array (1- m)))
|
|
(day (int-to-string (extract-calendar-day persian-date)))
|
|
(dayname nil)
|
|
(month (int-to-string m))
|
|
(year (int-to-string y)))
|
|
(mapconcat 'eval calendar-date-display-form ""))))
|
|
|
|
(defun calendar-print-persian-date ()
|
|
"Show the Persian calendar equivalent of the selected date."
|
|
(interactive)
|
|
(message "Persian date: %s"
|
|
(calendar-persian-date-string (calendar-cursor-to-date t))))
|
|
|
|
(defun calendar-goto-persian-date (date &optional noecho)
|
|
"Move cursor to Persian date DATE.
|
|
Echo Persian date unless NOECHO is t."
|
|
(interactive (persian-prompt-for-date))
|
|
(calendar-goto-date (calendar-gregorian-from-absolute
|
|
(calendar-absolute-from-persian date)))
|
|
(or noecho (calendar-print-persian-date)))
|
|
|
|
(defun persian-prompt-for-date ()
|
|
"Ask for a Persian date."
|
|
(let* ((today (calendar-current-date))
|
|
(year (calendar-read
|
|
"Persian calendar year (not 0): "
|
|
'(lambda (x) (/= x 0))
|
|
(int-to-string
|
|
(extract-calendar-year
|
|
(calendar-persian-from-absolute
|
|
(calendar-absolute-from-gregorian today))))))
|
|
(completion-ignore-case t)
|
|
(month (cdr (assoc
|
|
(capitalize
|
|
(completing-read
|
|
"Persian calendar month name: "
|
|
(mapcar 'list
|
|
(append persian-calendar-month-name-array nil))
|
|
nil t))
|
|
(calendar-make-alist persian-calendar-month-name-array
|
|
1 'capitalize))))
|
|
(last (persian-calendar-last-day-of-month month year))
|
|
(day (calendar-read
|
|
(format "Persian calendar day (1-%d): " last)
|
|
'(lambda (x) (and (< 0 x) (<= x last))))))
|
|
(list (list month day year))))
|
|
|
|
(defun diary-persian-date ()
|
|
"Persian calendar equivalent of date diary entry."
|
|
(format "Persian date: %s" (calendar-persian-date-string date)))
|
|
|
|
(provide 'cal-persia)
|
|
|
|
;;; cal-persia.el ends here
|