From: Drew Adams <drew.adams@oracle.com>
To: Michael Heerdegen <michael_heerdegen@web.de>, help-gnu-emacs@gnu.org
Subject: RE: alist-get in Emacs 24?
Date: Thu, 8 Oct 2015 08:53:55 -0700 (PDT) [thread overview]
Message-ID: <fcc233e7-0e38-458c-8eaf-12efa985d8ed@default> (raw)
In-Reply-To: <87egh5g48f.fsf@web.de>
> Second, yes, you could modify the list structure, but this can't be
> done if the alist is empty, because the empty (a)list is not a cons.
> At least in this case, your setter would still have to receive a symbol.
I don't see it that way. How is this different from defining
`delete' or any of the other structure potentially-modifying
functions? None of those functions require you to pass a symbol
argument. The only function I can think of offhand that does
that is `add-to-list'. Its more common (and generally more useful)
cousins, `push' and `pushnew' don't do that.
Yes, with such (destructive) functions, if you have a variable
pointing to the list (empty or not), you do need to re-set it
to the result returned by the function. But that's all, AFAIK.
As I said (examples):
(setq THE-VAR (my-set-alist-value key alist value))
(setq foo (delete 42 foo))
next prev parent reply other threads:[~2015-10-08 15:53 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-02 6:32 alist-get in Emacs 24? Marcin Borkowski
2015-10-02 6:39 ` Dmitry Gutov
2015-10-02 6:54 ` Marcin Borkowski
2015-10-02 7:34 ` Michael Heerdegen
2015-10-02 8:49 ` Marcin Borkowski
2015-10-03 3:05 ` Michael Heerdegen
2015-10-02 13:37 ` Stefan Monnier
2015-10-07 19:15 ` Marcin Borkowski
2015-10-07 20:45 ` Drew Adams
2015-10-08 8:21 ` Michael Heerdegen
2015-10-08 15:53 ` Drew Adams [this message]
2015-10-08 16:14 ` Michael Heerdegen
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