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(holiday-float): Rewritten to fix bug when base date

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of holiday and holiday date are in different months.
This commit is contained in:
Richard M. Stallman 1997-05-20 05:17:49 +00:00
parent 4abfba1faa
commit 151eeaa7c4
1 changed files with 44 additions and 7 deletions
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51
lisp/calendar/holidays.el
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@ -310,20 +310,57 @@ STRING)). Returns nil if it is not visible in the current calendar window."
(list (list (list month day y) string)))))
(defun holiday-float (month dayname n string &optional day)
"Holiday on MONTH, DAYNAME (Nth occurrence, Gregorian) called STRING.
"Holiday on MONTH, DAYNAME (Nth occurrence) called STRING.
If the Nth DAYNAME in MONTH is visible, the value returned is the list
\(((MONTH DAY year) STRING)).
If N<0, count backward from the end of MONTH.
An optional parameter DAY means the Nth DAYNAME after/before MONTH DAY.
An optional parameter DAY means the Nth DAYNAME on or after/before MONTH DAY.
Returns nil if it is not visible in the current calendar window."
(let ((m displayed-month)
(y displayed-year))
(increment-calendar-month m y (- 11 month))
(if (> m 9)
(list (list (calendar-nth-named-day n dayname month y day) string)))))
;; This is messy because the holiday may be visible, while the date on which
;; it is based is not. For example, the first Monday after December 30 may be
;; visible when January is not. For large values of |n| the problem is more
;; grotesque. If we didn't have to worry about such cases, we could just use
;; (let ((m displayed-month)
;; (y displayed-year))
;; (increment-calendar-month m y (- 11 month))
;; (if (> m 9); month in year y is visible
;; (list (list (calendar-nth-named-day n dayname month y day) string)))))
;; which is the way the function was originally written.
(let* ((m1 displayed-month)
(y1 displayed-year)
(m2 m1)
(y2 y1))
(increment-calendar-month m1 y1 -1)
(increment-calendar-month m2 y2 1)
(let* ((d1; first possible base date for holiday
(+ (calendar-nth-named-absday 1 dayname m1 y1)
(* -7 n)
(if (> n 0) 1 -7)))
(d2; last possible base date for holiday
(+ (calendar-nth-named-absday -1 dayname m2 y2)
(* -7 n)
(if (> n 0) 7 -1)))
(y1 (extract-calendar-year (calendar-gregorian-from-absolute d1)))
(y2 (extract-calendar-year (calendar-gregorian-from-absolute d2)))
(y; year of base date
(if (or (= y1 y2) (> month 9))
y1
y2))
(d; day of base date
(or day (if (> n 0)
1
(calendar-last-day-of-month month y))))
(date; base date for holiday
(calendar-absolute-from-gregorian (list month d y))))
(if (and (<= d1 date) (<= date d2))
(list (list (calendar-nth-named-day n dayname month y d)
string))))))
(defun holiday-sexp (sexp string)
"Sexp holiday for dates in the calendar window.