1 ;;; cal-iso.el --- calendar functions for the ISO calendar
3 ;; Copyright (C) 1995, 1997, 2001-2015 Free Software Foundation, Inc.
5 ;; Author: Edward M. Reingold <reingold@cs.uiuc.edu>
6 ;; Maintainer: Glenn Morris <rgm@gnu.org>
8 ;; Human-Keywords: ISO calendar, calendar, diary
11 ;; This file is part of GNU Emacs.
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15 ;; the Free Software Foundation, either version 3 of the License, or
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20 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
21 ;; GNU General Public License for more details.
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34 (defun calendar-iso-to-absolute (date)
35 "The number of days elapsed between the Gregorian date 12/31/1 BC and DATE.
36 The `ISO year' corresponds approximately to the Gregorian year, but
37 weeks start on Monday and end on Sunday. The first week of the ISO year is
38 the first such week in which at least 4 days are in a year. The ISO
39 commercial DATE has the form (week day year) in which week is in the range
40 1..52 and day is in the range 0..6 (1 = Monday, 2 = Tuesday, ..., 0 =
41 Sunday). The Gregorian date Sunday, December 31, 1 BC is imaginary."
42 (let ((day (calendar-extract-day date
)))
43 (+ (calendar-dayname-on-or-before
44 1 (+ 3 (calendar-absolute-from-gregorian
45 (list 1 1 (calendar-extract-year date
)))))
46 ;; ISO date is (week day year); normally (month day year).
47 (* 7 (1- (calendar-extract-month date
)))
48 (if (zerop day
) 6 (1- day
)))))
50 (define-obsolete-function-alias 'calendar-absolute-from-iso
51 'calendar-iso-to-absolute
"23.1")
54 (defun calendar-iso-from-absolute (date)
55 "Compute the `ISO commercial date' corresponding to the absolute DATE.
56 The ISO year corresponds approximately to the Gregorian year, but weeks
57 start on Monday and end on Sunday. The first week of the ISO year is the
58 first such week in which at least 4 days are in a year. The ISO commercial
59 date has the form (week day year) in which week is in the range 1..52 and
60 day is in the range 0..6 (1 = Monday, 2 = Tuesday, ..., 0 = Sunday). The
61 absolute date is the number of days elapsed since the (imaginary) Gregorian
62 date Sunday, December 31, 1 BC."
63 (let* ((approx (calendar-extract-year
64 (calendar-gregorian-from-absolute (- date
3))))
66 (calendar-sum y approx
67 (>= date
(calendar-iso-to-absolute
71 (1+ (/ (- date
(calendar-iso-to-absolute (list 1 1 year
))) 7))
76 (defun calendar-iso-date-string (&optional date
)
77 "String of ISO date of Gregorian DATE, default today."
78 (let* ((d (calendar-absolute-from-gregorian
79 (or date
(calendar-current-date))))
81 (iso-date (calendar-iso-from-absolute d
)))
82 (format "Day %s of week %d of %d"
83 (if (zerop day
) 7 day
)
84 (calendar-extract-month iso-date
)
85 (calendar-extract-year iso-date
))))
88 (defun calendar-iso-print-date ()
89 "Show equivalent ISO date for the date under the cursor."
91 (message "ISO date: %s"
92 (calendar-iso-date-string (calendar-cursor-to-date t
))))
94 (define-obsolete-function-alias 'calendar-print-iso-date
95 'calendar-iso-print-date
"23.1")
97 (defun calendar-iso-read-date (&optional dayflag
)
98 "Interactively read the arguments for an ISO date command.
99 Reads a year and week, and if DAYFLAG is non-nil a day (otherwise
101 (let* ((year (calendar-read
102 "ISO calendar year (>0): "
104 (number-to-string (calendar-extract-year
105 (calendar-current-date)))))
106 (no-weeks (calendar-extract-month
107 (calendar-iso-from-absolute
109 (calendar-dayname-on-or-before
110 1 (calendar-absolute-from-gregorian
111 (list 1 4 (1+ year
))))))))
113 (format "ISO calendar week (1-%d): " no-weeks
)
114 (lambda (x) (and (> x
0) (<= x no-weeks
)))))
115 (day (if dayflag
(calendar-read
117 (lambda (x) (and (<= 1 x
) (<= x
7))))
119 (list (list week day year
))))
121 (define-obsolete-function-alias 'calendar-iso-read-args
122 'calendar-iso-read-date
"23.1")
125 (defun calendar-iso-goto-date (date &optional noecho
)
126 "Move cursor to ISO DATE; echo ISO date unless NOECHO is non-nil."
127 (interactive (calendar-iso-read-date t
))
128 (calendar-goto-date (calendar-gregorian-from-absolute
129 (calendar-iso-to-absolute date
)))
130 (or noecho
(calendar-iso-print-date)))
132 (define-obsolete-function-alias 'calendar-goto-iso-date
133 'calendar-iso-goto-date
"23.1")
136 (defun calendar-iso-goto-week (date &optional noecho
)
137 "Move cursor to ISO DATE; echo ISO date unless NOECHO is non-nil.
138 Interactively, goes to the first day of the specified week."
139 (interactive (calendar-iso-read-date))
140 (calendar-goto-date (calendar-gregorian-from-absolute
141 (calendar-iso-to-absolute date
)))
142 (or noecho
(calendar-iso-print-date)))
144 (define-obsolete-function-alias 'calendar-goto-iso-week
145 'calendar-iso-goto-week
"23.1")
149 ;; To be called from diary-list-sexp-entries, where DATE is bound.
151 (defun diary-iso-date ()
152 "ISO calendar equivalent of date diary entry."
153 (format "ISO date: %s" (calendar-iso-date-string date
)))
157 ;;; cal-iso.el ends here