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vixie-time: Refactor 'interpolate-weekdays'

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* src/mcron/vixie-time.scm (interpolate-weekdays): Avoid mutation and
add 'range-wday' inner procedure.
This commit is contained in:
Mathieu Lirzin 2018-04-08 15:57:43 +02:00
commit 68be2dd2dd
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1 changed files with 11 additions and 18 deletions
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29
src/mcron/vixie-time.scm
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@ -122,27 +122,20 @@
(parse-vixie-subelement sub-element base limit))
(string-tokenize string (char-set-complement (char-set #\,))))))
;; Consider there are two lists, one of days in the month, the other of days in
;; the week. This procedure returns an augmented list of days in the month with
;; weekdays accounted for.
(define (interpolate-weekdays mday-list wday-list month year)
"Given a list of days in the month MDAY-LIST and a list of days in the week
WDAY-LIST, return an augmented list of days in the month with weekdays
accounted for."
(let ((t (localtime 0)))
(set-tm:mday t 1)
(set-tm:mon t month)
(set-tm:year t year)
(set-tm:mday t 1)
(set-tm:mon t month)
(set-tm:year t year)
(let ((first-day (tm:wday (cdr (mktime t)))))
(apply append
mday-list
(map (lambda (wday)
(let ((first (- wday first-day)))
(if (< first 0) (set! first (+ first 7)))
(range (+ 1 first) 32 7)))
wday-list)))))
(define (range-wday wday)
(let* ((first (- wday first-day))
(first* (if (negative? first) (+ 7 first) first)))
(range (1+ first*) 32 7)))
(apply append mday-list (map range-wday wday-list)))))
;; Return the number of days in a month. Fix up a tm object for the zero'th day
;; of the next month, rationalize the object and extract the day.