From: Eric Abrahamsen <eric@ericabrahamsen.net>
To: help-gnu-emacs@gnu.org
Subject: Re: replace element in list
Date: Wed, 21 Nov 2018 22:04:35 -0800 [thread overview]
Message-ID: <87va4py7f0.fsf@ericabrahamsen.net> (raw)
In-Reply-To: 45a3b5b6-2985-4eab-bb2c-2ad9b4459018@default
Drew Adams <drew.adams@oracle.com> writes:
>> > (defun my-list-replace (obj orig new)
>> > "Replaces an element in a list with something else"
>> > (let* ((pos (cl-position orig obj :test 'equal))
>> > (pos (if pos pos 0))
>> > (objlen (length obj))
>> > (head (butlast obj (- objlen pos)))
>> > (trail (nthcdr (+ 1 pos) obj)))
>> > (append head (append new trail))))
>>
>> (let ((orig '(("a" . "b") ("c" "d")))
>> (obj '("c" "d"))
>> (new '(":)")))
>> (setf (nth (cl-position obj orig :test #'equal) orig) new)
>> orig)
>
> (defun toto (xs old new)
> (let ((ms (member old xs)))
> (unless ms (error "%S is not in %S" old xs))
> (setcar ms new)
> xs))
Old school, and proper :)
next prev parent reply other threads:[~2018-11-22 6:04 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-22 4:42 replace element in list edgar
2018-11-22 5:18 ` Eric Abrahamsen
2018-11-22 5:39 ` Drew Adams
2018-11-22 6:04 ` Eric Abrahamsen [this message]
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
-- strict thread matches above, loose matches on Subject: below --
2019-09-02 9:44 Replace " 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
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
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