1 ;;; cal-iso.el --- calendar functions for the ISO calendar
3 ;; Copyright (C) 1995, 1997, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
4 ;; 2008, 2009, 2010 Free Software Foundation, Inc.
6 ;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
7 ;; Maintainer: Glenn Morris <rgm@gnu.org>
9 ;; Human-Keywords: ISO calendar, calendar, diary
12 ;; This file is part of GNU Emacs.
14 ;; GNU Emacs is free software: you can redistribute it and/or modify
15 ;; it under the terms of the GNU General Public License as published by
16 ;; the Free Software Foundation, either version 3 of the License, or
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20 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
21 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 ;; GNU General Public License for more details.
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25 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
35 (defun calendar-iso-to-absolute (date)
36 "The number of days elapsed between the Gregorian date 12/31/1 BC and DATE.
37 The `ISO year' corresponds approximately to the Gregorian year, but
38 weeks start on Monday and end on Sunday. The first week of the ISO year is
39 the first such week in which at least 4 days are in a year. The ISO
40 commercial DATE has the form (week day year) in which week is in the range
41 1..52 and day is in the range 0..6 (1 = Monday, 2 = Tuesday, ..., 0 =
42 Sunday). The Gregorian date Sunday, December 31, 1 BC is imaginary."
43 (let ((day (calendar-extract-day date
)))
44 (+ (calendar-dayname-on-or-before
45 1 (+ 3 (calendar-absolute-from-gregorian
46 (list 1 1 (calendar-extract-year date
)))))
47 ;; ISO date is (week day year); normally (month day year).
48 (* 7 (1- (calendar-extract-month date
)))
49 (if (zerop day
) 6 (1- day
)))))
51 (define-obsolete-function-alias 'calendar-absolute-from-iso
52 'calendar-iso-to-absolute
"23.1")
55 (defun calendar-iso-from-absolute (date)
56 "Compute the `ISO commercial date' corresponding to the absolute DATE.
57 The ISO year corresponds approximately to the Gregorian year, but weeks
58 start on Monday and end on Sunday. The first week of the ISO year is the
59 first such week in which at least 4 days are in a year. The ISO commercial
60 date has the form (week day year) in which week is in the range 1..52 and
61 day is in the range 0..6 (1 = Monday, 2 = Tuesday, ..., 0 = Sunday). The
62 absolute date is the number of days elapsed since the (imaginary) Gregorian
63 date Sunday, December 31, 1 BC."
64 (let* ((approx (calendar-extract-year
65 (calendar-gregorian-from-absolute (- date
3))))
67 (calendar-sum y approx
68 (>= date
(calendar-iso-to-absolute
72 (1+ (/ (- date
(calendar-iso-to-absolute (list 1 1 year
))) 7))
77 (defun calendar-iso-date-string (&optional date
)
78 "String of ISO date of Gregorian DATE, default today."
79 (let* ((d (calendar-absolute-from-gregorian
80 (or date
(calendar-current-date))))
82 (iso-date (calendar-iso-from-absolute d
)))
83 (format "Day %s of week %d of %d"
84 (if (zerop day
) 7 day
)
85 (calendar-extract-month iso-date
)
86 (calendar-extract-year iso-date
))))
89 (defun calendar-iso-print-date ()
90 "Show equivalent ISO date for the date under the cursor."
92 (message "ISO date: %s"
93 (calendar-iso-date-string (calendar-cursor-to-date t
))))
95 (define-obsolete-function-alias 'calendar-print-iso-date
96 'calendar-iso-print-date
"23.1")
98 (defun calendar-iso-read-date (&optional dayflag
)
99 "Interactively read the arguments for an ISO date command.
100 Reads a year and week, and if DAYFLAG is non-nil a day (otherwise
102 (let* ((year (calendar-read
103 "ISO calendar year (>0): "
105 (number-to-string (calendar-extract-year
106 (calendar-current-date)))))
107 (no-weeks (calendar-extract-month
108 (calendar-iso-from-absolute
110 (calendar-dayname-on-or-before
111 1 (calendar-absolute-from-gregorian
112 (list 1 4 (1+ year
))))))))
114 (format "ISO calendar week (1-%d): " no-weeks
)
115 (lambda (x) (and (> x
0) (<= x no-weeks
)))))
116 (day (if dayflag
(calendar-read
118 (lambda (x) (and (<= 1 x
) (<= x
7))))
120 (list (list week day year
))))
122 (define-obsolete-function-alias 'calendar-iso-read-args
123 'calendar-iso-read-date
"23.1")
126 (defun calendar-iso-goto-date (date &optional noecho
)
127 "Move cursor to ISO DATE; echo ISO date unless NOECHO is non-nil."
128 (interactive (calendar-iso-read-date t
))
129 (calendar-goto-date (calendar-gregorian-from-absolute
130 (calendar-iso-to-absolute date
)))
131 (or noecho
(calendar-iso-print-date)))
133 (define-obsolete-function-alias 'calendar-goto-iso-date
134 'calendar-iso-goto-date
"23.1")
137 (defun calendar-iso-goto-week (date &optional noecho
)
138 "Move cursor to ISO DATE; echo ISO date unless NOECHO is non-nil.
139 Interactively, goes to the first day of the specified week."
140 (interactive (calendar-iso-read-date))
141 (calendar-goto-date (calendar-gregorian-from-absolute
142 (calendar-iso-to-absolute date
)))
143 (or noecho
(calendar-iso-print-date)))
145 (define-obsolete-function-alias 'calendar-goto-iso-week
146 'calendar-iso-goto-week
"23.1")
150 ;; To be called from diary-list-sexp-entries, where DATE is bound.
152 (defun diary-iso-date ()
153 "ISO calendar equivalent of date diary entry."
154 (format "ISO date: %s" (calendar-iso-date-string date
)))
158 ;; arch-tag: 3c0154cc-d30f-4981-9f60-42bdf7a468f6
159 ;;; cal-iso.el ends here