[Emacs-diffs] Changes to emacs/lisp/calendar/cal-persia.el [lexbind]

[Miles Bader]

Index: emacs/lisp/calendar/cal-persia.el
diff -c /dev/null emacs/lisp/calendar/cal-persia.el:1.7.8.1
*** /dev/null   Tue Oct 14 19:42:18 2003
--- emacs/lisp/calendar/cal-persia.el   Tue Oct 14 19:42:13 2003
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+ ;;; cal-persia.el --- calendar functions for the Persian calendar
+ 
+ ;; Copyright (C) 1996, 1997 Free Software Foundation, Inc.
+ 
+ ;; Author: Edward M. Reingold <address@hidden>
+ ;; 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
+ ;;  address@hidden             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
+                        (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))))
+          (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)
+ 
+ ;;; arch-tag: 2832383c-e4b4-4dc2-8ee9-cfbdd53e5e2d
+ ;;; cal-persia.el ends here