From: Jean-Christophe Helary <brandelune@gmail.com>
To: help-gnu-emacs <help-gnu-emacs@gnu.org>
Subject: Re: using setq to create lists based on other lists...
Date: Mon, 3 Dec 2018 01:23:25 +0900 [thread overview]
Message-ID: <6641A86F-1E33-44BA-8CEE-625F3213D9C4@gmail.com> (raw)
In-Reply-To: <jwvr2ezj4ur.fsf-monnier+gmane.emacs.help@gnu.org>
> 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 voilà
(list myDay myMonth myYear))
(getMyDate 30)
next prev parent reply other threads:[~2018-12-02 16:23 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-02 10:53 using setq to create lists based on other lists Jean-Christophe Helary
2018-12-02 15:07 ` Stefan Monnier
2018-12-02 15:41 ` Jean-Christophe Helary
2018-12-02 16:05 ` Stefan Monnier
2018-12-02 16:23 ` Jean-Christophe Helary [this message]
2018-12-02 17:02 ` Stefan Monnier
2018-12-02 17:21 ` Jean-Christophe Helary
2018-12-02 19:11 ` Robert Thorpe
2018-12-02 23:44 ` Jean-Christophe Helary
[not found] ` <mailman.5028.1543765273.1284.help-gnu-emacs@gnu.org>
2018-12-03 13:43 ` Rusi
[not found] <mailman.5010.1543748027.1284.help-gnu-emacs@gnu.org>
2018-12-02 11:21 ` Barry Margolin
2018-12-02 11:51 ` Stephen Berman
2018-12-02 12:22 ` Jean-Christophe Helary
2018-12-02 13:08 ` Stephen Berman
2018-12-02 13:28 ` Jean-Christophe Helary
2018-12-02 14:40 ` Michael Heerdegen
2018-12-02 15:34 ` Jean-Christophe Helary
2018-12-02 15:44 ` Michael Heerdegen
2018-12-02 15:57 ` Jean-Christophe Helary
2018-12-02 15:00 ` Stephen Berman
2018-12-02 15:30 ` Jean-Christophe Helary
[not found] ` <mailman.5026.1543764670.1284.help-gnu-emacs@gnu.org>
2018-12-04 9:00 ` Barry Margolin
2018-12-02 12:03 ` Jean-Christophe Helary
[not found] <mailman.5042.1543777897.1284.help-gnu-emacs@gnu.org>
2018-12-04 9:04 ` Barry Margolin
[not found] ` <(message>
[not found] ` <from>
[not found] ` <Barry>
[not found] ` <Margolin>
[not found] ` <on>
[not found] ` <Tue>
[not found] ` <04>
[not found] ` <Dec>
[not found] ` <2018>
[not found] ` <04:04:52>
2018-12-04 13:56 ` Stefan Monnier
2018-12-05 1:07 ` Robert Thorpe
2018-12-05 2:32 ` Drew Adams
2018-12-05 6:45 ` Jean-Christophe Helary
2018-12-05 8:00 ` Marcin Borkowski
2018-12-05 8:11 ` Jean-Christophe Helary
2018-12-05 14:57 ` Drew Adams
[not found] ` <mailman.5218.1544021892.1284.help-gnu-emacs@gnu.org>
2018-12-05 16:59 ` Barry Margolin
[not found] ` <mailman.5186.1543978155.1284.help-gnu-emacs@gnu.org>
2018-12-05 16:50 ` Barry Margolin
[not found] ` <mailman.5145.1543931778.1284.help-gnu-emacs@gnu.org>
2018-12-05 16:47 ` Barry Margolin
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