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Re: using setq to create lists based on other lists...
From: |
Jean-Christophe Helary |
Subject: |
Re: using setq to create lists based on other lists... |
Date: |
Mon, 3 Dec 2018 01:23:25 +0900 |
> On Dec 3, 2018, at 1:05, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>
>> When I check "Modifying Existing List Structure" the only things I find of
>> any use in my case are setcar/setcdr.
>
> That's because "modifying" is the wrong way to think about it.
>
> That section should start by telling the user that most likely what they
> really want to do is something else (i.e. get a similar list structure
> with some differences).
I see. Eventually I used copy-tree instead to initialize the new lists and then
modified them separately with setcar.
>> I would certainly have considered that if I had known that setq was
>> linking the lists :)
>
> Clearly, "linking the lists" means something to you, but it means
> nothing to me, so the manual can't really say something like that.
I think somebody used that term in the thread. I didn't even have that concept
before the discussion started :)
Just out of curiosity, let me post what I did. There are probably better ways
to do it, but that's the best I could come up with today. I'd love to be able
to think in terms closer to what elisp allows though.
Jean-Christophe Helary
-----------------------------------------------
http://mac4translators.blogspot.com @brandelune
;; The function takes a date d and returns a (d m y) list where (d m y) is the
closest day to today
;; For ex, today is 2018/12/3
;; d=1 -> (1 12 2018)
;; d=30 -> (30 11 2018)
;; d=15 -> (15 12 2018)
;; I use the function in a template for a blog that I write one page a day.
;; When I launch the template for a given day, it creates links for the
previous day and the next day
;; I used the "closest" assumption because I'm either writing the blog late, or
outputing future days templates for preparation.
(defun getMyDate (myDay)
(interactive)
(if (or (> 1 myDay) (< 32 myDay))
(setq myDay (nth 3 (decode-time))))
(setq now (decode-time (float-time))
myDateLastMonth (copy-tree now)
myDateThisMonth (copy-tree now)
myDateNextMonth (copy-tree now)
now (encode-time now 'integer))
;; need to create "last month", "next month", "last year", "next year"
;; 1 day is 84600 seconds
;; 1 month is approximately 2,592,000 seconds
;; 1 year is approximately 31,536,000 seconds
(setq yesterDay (nth 3 (decode-time (- (float-time) 84600))) ;; not used in
the function
toMorrow (nth 3 (decode-time (+ (float-time) 84600))) ;; not used in
the function
lastMonth (nth 4 (decode-time (- (float-time) 2592000)))
thisMonth (nth 4 (decode-time)) ;; not used in the function
nextMonth (nth 4 (decode-time (+ (float-time) 2592000)))
lastYear (nth 5 (decode-time (- (float-time) 31536000)))
thisYear (nth 5 (decode-time)) ;; not used in the function
nextYear (nth 5 (decode-time (+ (float-time) 31536000))))
;; create the data for last month
(setcar (cdr (cdr (cdr myDateLastMonth))) myDay)
(setcar (cdr (cdr (cdr (cdr myDateLastMonth)))) lastMonth)
(if (= lastMonth 12)
(setcar (cdr (cdr (cdr (cdr (cdr myDateLastMonth))))) lastYear))
;; create the data for this month
(setcar (cdr (cdr (cdr myDateThisMonth))) myDay)
;; create the data for next month
(setcar (cdr (cdr (cdr myDateNextMonth))) myDay)
(setcar (cdr (cdr (cdr (cdr myDateNextMonth)))) nextMonth)
(if (= nextMonth 1)
(setcar (cdr (cdr (cdr (cdr (cdr myDateNextMonth))))) nextYear))
;; compare the dates to find the closest
(setq a (abs (- now (encode-time myDateLastMonth 'integer)))
b (abs (- now (encode-time myDateThisMonth 'integer)))
c (abs (- (encode-time myDateNextMonth 'integer))))
(if (and (< a b) (< b c))
(setq myMonth (nth 4 myDateLastMonth)
myYear (nth 5 myDateLastMonth))
(if (and (< b a) (< b c))
(setq myMonth (nth 4 myDateThisMonth)
myYear (nth 5 myDateThisMonth))
(setq myMonth (nth 4 myDateNextMonth)
myYear (nth 5 myDateNextMonth))))
;; et voilĂ
(list myDay myMonth myYear))
(getMyDate 30)
- using setq to create lists based on other lists..., Jean-Christophe Helary, 2018/12/02
- Re: using setq to create lists based on other lists..., Stefan Monnier, 2018/12/02
- Re: using setq to create lists based on other lists..., Jean-Christophe Helary, 2018/12/02
- Re: using setq to create lists based on other lists..., Stefan Monnier, 2018/12/02
- Re: using setq to create lists based on other lists...,
Jean-Christophe Helary <=
- Re: using setq to create lists based on other lists..., Stefan Monnier, 2018/12/02
- Re: using setq to create lists based on other lists..., Jean-Christophe Helary, 2018/12/02
- Re: using setq to create lists based on other lists..., Robert Thorpe, 2018/12/02
- Re: using setq to create lists based on other lists..., Jean-Christophe Helary, 2018/12/02
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