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b76a84cd86
(calendar-iso-read-args): New function, for old interactive spec from calendar-goto-iso-date. (calendar-goto-iso-date): Use it. (calendar-goto-iso-week): New function. Suggested by Emilio C. Lopes <eclig@gmx.net>.
145 lines
6.0 KiB
EmacsLisp
145 lines
6.0 KiB
EmacsLisp
;;; cal-iso.el --- calendar functions for the ISO calendar
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;; Copyright (C) 1995, 1997, 2004 Free Software Foundation, Inc.
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;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
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;; Maintainer: Glenn Morris <gmorris@ast.cam.ac.uk>
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;; Keywords: calendar
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;; Human-Keywords: ISO calendar, calendar, diary
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software; you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation; either version 2, or (at your option)
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;; any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs; see the file COPYING. If not, write to the
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;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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;; Boston, MA 02111-1307, USA.
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;;; Commentary:
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;; This collection of functions implements the features of calendar.el and
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;; diary.el that deal with the ISO calendar.
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;; Technical details of all the calendrical calculations can be found in
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;; ``Calendrical Calculations'' by Nachum Dershowitz and Edward M. Reingold,
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;; Cambridge University Press (1997).
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;; Comments, corrections, and improvements should be sent to
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;; Edward M. Reingold Department of Computer Science
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;; (217) 333-6733 University of Illinois at Urbana-Champaign
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;; reingold@cs.uiuc.edu 1304 West Springfield Avenue
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;; Urbana, Illinois 61801
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;;; Code:
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(require 'calendar)
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(defun calendar-absolute-from-iso (date)
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"The number of days elapsed between the Gregorian date 12/31/1 BC and DATE.
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The `ISO year' corresponds approximately to the Gregorian year, but
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weeks start on Monday and end on Sunday. The first week of the ISO year is
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the first such week in which at least 4 days are in a year. The ISO
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commercial DATE has the form (week day year) in which week is in the range
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1..52 and day is in the range 0..6 (1 = Monday, 2 = Tuesday, ..., 0 =
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Sunday). The Gregorian date Sunday, December 31, 1 BC is imaginary."
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(let* ((week (extract-calendar-month date))
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(day (extract-calendar-day date))
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(year (extract-calendar-year date)))
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(+ (calendar-dayname-on-or-before
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1 (+ 3 (calendar-absolute-from-gregorian (list 1 1 year))))
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(* 7 (1- week))
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(if (= day 0) 6 (1- day)))))
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(defun calendar-iso-from-absolute (date)
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"Compute the `ISO commercial date' corresponding to the absolute DATE.
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The ISO year corresponds approximately to the Gregorian year, but weeks
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start on Monday and end on Sunday. The first week of the ISO year is the
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first such week in which at least 4 days are in a year. The ISO commercial
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date has the form (week day year) in which week is in the range 1..52 and
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day is in the range 0..6 (1 = Monday, 2 = Tuesday, ..., 0 = Sunday). The
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absolute date is the number of days elapsed since the (imaginary) Gregorian
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date Sunday, December 31, 1 BC."
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(let* ((approx (extract-calendar-year
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(calendar-gregorian-from-absolute (- date 3))))
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(year (+ approx
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(calendar-sum y approx
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(>= date (calendar-absolute-from-iso (list 1 1 (1+ y))))
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1))))
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(list
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(1+ (/ (- date (calendar-absolute-from-iso (list 1 1 year))) 7))
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(% date 7)
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year)))
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(defun calendar-iso-date-string (&optional date)
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"String of ISO date of Gregorian DATE.
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Defaults to today's date if DATE is not given."
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(let* ((d (calendar-absolute-from-gregorian
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(or date (calendar-current-date))))
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(day (% d 7))
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(iso-date (calendar-iso-from-absolute d)))
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(format "Day %s of week %d of %d"
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(if (zerop day) 7 day)
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(extract-calendar-month iso-date)
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(extract-calendar-year iso-date))))
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(defun calendar-print-iso-date ()
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"Show equivalent ISO date for the date under the cursor."
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(interactive)
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(message "ISO date: %s"
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(calendar-iso-date-string (calendar-cursor-to-date t))))
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(defun calendar-iso-read-args (&optional dayflag)
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"Interactively read the arguments for an iso date command."
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(let* ((today (calendar-current-date))
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(year (calendar-read
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"ISO calendar year (>0): "
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'(lambda (x) (> x 0))
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(int-to-string (extract-calendar-year today))))
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(no-weeks (extract-calendar-month
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(calendar-iso-from-absolute
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(1-
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(calendar-dayname-on-or-before
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1 (calendar-absolute-from-gregorian
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(list 1 4 (1+ year))))))))
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(week (calendar-read
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(format "ISO calendar week (1-%d): " no-weeks)
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'(lambda (x) (and (> x 0) (<= x no-weeks)))))
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(day (if dayflag (calendar-read
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"ISO day (1-7): "
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'(lambda (x) (and (<= 1 x) (<= x 7))))
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1)))
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(list (list week day year))))
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(defun calendar-goto-iso-date (date &optional noecho)
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"Move cursor to ISO DATE; echo ISO date unless NOECHO is t."
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(interactive (calendar-iso-read-args t))
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(calendar-goto-date (calendar-gregorian-from-absolute
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(calendar-absolute-from-iso date)))
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(or noecho (calendar-print-iso-date)))
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(defun calendar-goto-iso-week (date &optional noecho)
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"Move cursor to ISO DATE; echo ISO date unless NOECHO is t.
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Interactively, goes to the first day of the specified week."
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(interactive (calendar-iso-read-args))
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(calendar-goto-date (calendar-gregorian-from-absolute
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(calendar-absolute-from-iso date)))
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(or noecho (calendar-print-iso-date)))
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(defun diary-iso-date ()
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"ISO calendar equivalent of date diary entry."
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(format "ISO date: %s" (calendar-iso-date-string date)))
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(provide 'cal-iso)
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;;; arch-tag: 3c0154cc-d30f-4981-9f60-42bdf7a468f6
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;;; cal-iso.el ends here
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