From: Emanuel Berg <embe8573@student.uu.se>
To: help-gnu-emacs@gnu.org
Subject: `append' vs. `nconc' (was: Re: Error: Setting the shell in sh-mode via a local variable does not work)
Date: Wed, 30 Dec 2015 16:41:51 +0100 [thread overview]
Message-ID: <87a8osrlj4.fsf_-_@debian.uxu> (raw)
In-Reply-To: 87si2kezg1.fsf@mithlond.arda
Teemu Likonen <tlikonen@iki.fi> writes:
> There you create a list MODES and then APPEND copies
> the whole list and joins it to AUTO-MODE-ALIST.
> The original list is discarded. No problem, it's
> just a configuration code. But in some other
> situation it might be good idea to construct the
> list only once and use NCONC which only traverses
> the lists through and modifies last conses to join
> it to the next list:
>
> (let ((modes (list '(a . b) ;; ... ))) (setq
> auto-mode-alist (nconc modes auto-mode-alist)))
So what you are saying, if `append' is replaced by
`nconc', the same thing happens, only one less list
has to be created?
I have several appends in my source, is there
a rule-of-thumb when to use `append' and when to use
`nconc'?
> The PROGN is redundant because LAMBDA has an implicit
> PROGN
OK, cool.
--
underground experts united
http://user.it.uu.se/~embe8573
next prev parent reply other threads:[~2015-12-30 15:41 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-28 16:35 Error: Setting the shell in sh-mode via a local variable does not work Johannes Kastl
2015-12-29 1:32 ` Emanuel Berg
2015-12-29 18:33 ` Johannes Kastl
2015-12-30 14:53 ` Emanuel Berg
2015-12-30 15:15 ` Robert Thorpe
2015-12-30 15:30 ` Emanuel Berg
2015-12-30 17:42 ` Johannes Kastl
2015-12-30 15:19 ` Teemu Likonen
2015-12-30 15:41 ` Emanuel Berg [this message]
2015-12-30 16:37 ` `append' vs. `nconc' Teemu Likonen
2015-12-31 3:37 ` Emanuel Berg
[not found] ` <mailman.1400.1451533083.843.help-gnu-emacs@gnu.org>
2015-12-31 3:45 ` Pascal J. Bourguignon
2015-12-31 4:00 ` Emanuel Berg
2015-12-31 9:22 ` tomas
2015-12-31 18:48 ` Emanuel Berg
[not found] ` <mailman.1402.1451534421.843.help-gnu-emacs@gnu.org>
2015-12-31 5:36 ` Pascal J. Bourguignon
2015-12-31 3:50 ` Emanuel Berg
[not found] ` <mailman.1401.1451533833.843.help-gnu-emacs@gnu.org>
2015-12-31 5:37 ` Pascal J. Bourguignon
2015-12-31 7:13 ` Emanuel Berg
2015-12-31 9:30 ` tomas
2015-12-31 17:56 ` side effects, list sharing [was: `append' vs. `nconc'] Drew Adams
2015-12-31 19:00 ` Emanuel Berg
2015-12-31 19:15 ` Drew Adams
2016-01-01 13:20 ` Emanuel Berg
2015-12-31 18:51 ` `append' vs. `nconc' Emanuel Berg
[not found] ` <mailman.1440.1451588113.843.help-gnu-emacs@gnu.org>
2016-01-01 2:53 ` Barry Margolin
2016-01-01 13:26 ` Emanuel Berg
[not found] ` <mailman.1406.1451546036.843.help-gnu-emacs@gnu.org>
2015-12-31 8:54 ` Pascal J. Bourguignon
2015-12-31 7:31 ` Teemu Likonen
2015-12-31 18:35 ` Emanuel Berg
2015-12-31 20:04 ` Teemu Likonen
2016-01-01 13:23 ` Emanuel Berg
2016-01-01 14:02 ` Teemu Likonen
2016-01-01 18:31 ` Emanuel Berg
[not found] ` <mailman.1438.1451586967.843.help-gnu-emacs@gnu.org>
2016-01-01 6:25 ` Pascal J. Bourguignon
2016-01-01 13:31 ` Emanuel Berg
2016-01-01 15:04 ` Drew Adams
[not found] ` <mailman.1353.1451490125.843.help-gnu-emacs@gnu.org>
2015-12-30 16:18 ` Pascal J. Bourguignon
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