From: "Andreas Röhler" <andreas.roehler@easy-emacs.de>
To: help-gnu-emacs@gnu.org
Subject: Re: Replace element in list
Date: Mon, 2 Sep 2019 16:00:30 +0200 [thread overview]
Message-ID: <fe022e54-9c09-60a9-af05-95e2be169e9a@easy-emacs.de> (raw)
In-Reply-To: <20190902134342.GG1466@tuxteam.de>
Am 02.09.19 um 15:43 schrieb tomas@tuxteam.de:
> On Mon, Sep 02, 2019 at 09:29:39AM -0400, Stefan Monnier wrote:
>>> is there a recommended way to replace element x at index i of somelist
>>> y by newelement?
>> What Thomas is hinting at with his "copy-list" and "functional sector"
>> is that if you need to do that, there's a problem upstream.
>> E.g. could you use a struct instead of a list?
> Thanks for putting my mumbling into civilised words :-)
>
> Cheers
> -- t
Hmm, what means struct here?
Tried a little program to answer a quiz in
https://www.futurelearn.com/courses/how-computers-work/4/steps/551852/questions/3:
;; If the head is in state A at the position shown below, what would the
final output of this Turing machine be?
;; |0|0|0|0|1|1|0|0|0|
;; ^
Started that way:
[leaving out here z_B - z_E]
(defun z_A (zeichen pos)
;; Char: 1 (49, #o61, #x31)
(when (eq 49 (aref zeichen pos))
(aset zeichen pos 48)
(z_B zeichen (1- pos))))
(defun zeichenmachine ()
(interactive)
(let ((zeichen "000011000")
(pos 5))
(message "%s" zeichen)
(z_A zeichen pos)))
But that was easier to read:
[leaving out here state_B - state_E]
(defun state_A (elist pos)
(if (eq 1 (nth pos elist))
(progn
(setf (nth pos elist) 0)
(state_B elist (1- pos)))
(message "Fertig %s" elist)))
(defun statemachine ()
(interactive)
(let ((elist (list 0 0 0 0 1 1 0 0 0))
(pos 5))
(state_A elist pos)))
next prev parent reply other threads:[~2019-09-02 14:00 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-02 9:44 Replace element in list Andreas Röhler
2019-09-02 10:37 ` tomas
2019-09-02 10:41 ` tomas
2019-09-02 10:46 ` tomas
2019-09-02 11:03 ` Michael Heerdegen
2019-09-02 11:05 ` tomas
2019-09-02 13:38 ` Andreas Röhler
2019-09-02 13:29 ` Stefan Monnier
2019-09-02 13:43 ` tomas
2019-09-02 14:00 ` Andreas Röhler [this message]
2019-09-02 14:57 ` Stefan Monnier
2019-09-02 20:29 ` Andreas Röhler
2019-09-02 21:32 ` Stefan Monnier
2019-09-03 5:37 ` Andreas Röhler
-- strict thread matches above, loose matches on Subject: below --
2018-11-22 4:42 replace " edgar
2018-11-22 5:18 ` Eric Abrahamsen
2018-11-22 5:39 ` Drew Adams
2018-11-22 6:04 ` Eric Abrahamsen
2018-11-22 13:19 ` Stefan Monnier
[not found] ` <mailman.4442.1542892802.1284.help-gnu-emacs@gnu.org>
2018-11-23 12:05 ` Robert Munyer
2018-11-24 3:01 ` edgar
2018-11-24 5:27 ` Drew Adams
2018-11-24 7:22 ` edgar
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