From: Juanma Barranquero <lekktu@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: assoc-delete-all
Date: Sun, 3 Jul 2005 02:52:34 +0200 [thread overview]
Message-ID: <f7ccd24b05070217522c17a52@mail.gmail.com> (raw)
In-Reply-To: <42C7300C.8050104@student.lu.se>
> There is an assq-delete-all, but I am missing assoc-delete-all ... or,
> am I missing something (else)?
If I had to guess, I'd say that is because `assq-delete-all' has only
one reasonable behavior, i.e., as it modifies the structure, you
usually are going to do
(setq alist (assq-delete-all 'my-key alist))
or directly construct the alist, filter it through `assq-delete-all'
and then discard it.
With `assoc-delete-all' you have to decide whether you want a shallow
or a deep copy, for example:
(defun assoc-delete-all (key alist)
(let (l)
(while alist
(unless (and (consp (car alist))
(eq key (caar alist)))
(setq l (cons (car alist) l)))
(setq alist (cdr alist)))
(nreverse l)))
will do what you want, but it will still share conses with the
original list. Other implementations can use `copy-tree' or
`copy-alist', but really, there's no one answer that is good for every
situation. Kent M. Pitman did a wonderful article about this issue (he
was speaking of copy) a long time ago: "The Best of Intentions: EQUAL
Rights--and Wrongs--in Lisp",
http://www.nhplace.com/kent/PS/EQUAL.html
--
/L/e/k/t/u
next prev parent reply other threads:[~2005-07-03 0:52 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-07-03 0:23 assoc-delete-all Lennart Borgman
2005-07-03 0:52 ` Juanma Barranquero [this message]
2005-07-03 7:30 ` assoc-delete-all Lennart Borgman
2005-07-03 10:24 ` assoc-delete-all Lute Kamstra
2005-07-03 10:51 ` assoc-delete-all Lennart Borgman
2005-07-03 10:58 ` assoc-delete-all Lennart Borgman
2005-07-03 20:43 ` assoc-delete-all Richard M. Stallman
2005-07-04 0:16 ` assoc-delete-all Juri Linkov
2005-07-04 9:00 ` assoc-delete-all Juanma Barranquero
2005-07-05 5:33 ` assoc-delete-all Juri Linkov
2005-07-05 4:35 ` assoc-delete-all Richard M. Stallman
2005-07-05 5:27 ` assoc-delete-all Juri Linkov
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