From: Barry Margolin <barmar@alum.mit.edu>
To: help-gnu-emacs@gnu.org
Subject: Re: Working with constansts
Date: Wed, 13 May 2009 00:59:58 -0400 [thread overview]
Message-ID: <barmar-113174.00595813052009@mara100-84.onlink.net> (raw)
In-Reply-To: mailman.7052.1242121473.31690.help-gnu-emacs@gnu.org
In article <mailman.7052.1242121473.31690.help-gnu-emacs@gnu.org>,
Nikolaj Schumacher <me@nschum.de> wrote:
> Richard Riley <rileyrgdev@googlemail.com> wrote:
>
> >> Because this would incur overhead on every assignment, as it would have
> >> to check whether the variable being assigned was declared as a constant.
> >> Since this is so rarely the case, this overhead could be seen as mostly
> >> wasted and unnecessary.
> >
> > I don't know enough about Lisp than I can only assume that in this case
> > it can not be detected at compile time IF you compile to byte/p code.
>
> "Thanks" to dynamic scoping it cannot be caught at compile time.
It could at least generate a warning.
> (defconst xxx nil)
>
> (defun change-xxx ()
> (setx xxx t)) ;; const or variable?
>
> (let ((xxx nil))
> (change-xxx))
This should also warn about binding a constant.
--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***
next prev parent reply other threads:[~2009-05-13 4:59 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-10 15:25 Working with constansts Decebal
2009-05-10 16:19 ` Pascal J. Bourguignon
2009-05-10 16:20 ` Richard Riley
2009-05-10 16:33 ` Pascal J. Bourguignon
2009-05-12 10:34 ` Nikolaj Schumacher
2009-05-10 17:02 ` Drew Adams
2009-05-10 17:28 ` Richard Riley
2009-05-11 7:39 ` Tassilo Horn
[not found] ` <mailman.6953.1241976532.31690.help-gnu-emacs@gnu.org>
2009-05-10 18:17 ` Pascal J. Bourguignon
2009-05-11 1:36 ` Richard Riley
2009-05-11 6:29 ` Pascal J. Bourguignon
2009-05-12 10:06 ` Nikolaj Schumacher
[not found] ` <mailman.7056.1242122790.31690.help-gnu-emacs@gnu.org>
2009-05-12 11:54 ` Pascal J. Bourguignon
2009-05-18 10:55 ` Nikolaj Schumacher
[not found] ` <7ceiuuczad.fsf@pbourguignon.informatimago.com>
[not found] ` <mailman.7379.1242644154.31690.help-gnu-emacs@gnu.org>
2009-05-18 12:20 ` Pascal J. Bourguignon
2009-05-18 19:19 ` Nikolaj Schumacher
2009-05-10 18:59 ` Barry Margolin
2009-05-11 1:38 ` Richard Riley
2009-05-12 9:44 ` Nikolaj Schumacher
[not found] ` <mailman.7052.1242121473.31690.help-gnu-emacs@gnu.org>
2009-05-12 11:43 ` Pascal J. Bourguignon
2009-05-13 4:59 ` Barry Margolin [this message]
2009-05-13 13:41 ` Ralf Wachinger
2009-05-13 21:23 ` Barry Margolin
2009-05-11 9:58 ` Thien-Thi Nguyen
[not found] ` <mailman.6988.1242036217.31690.help-gnu-emacs@gnu.org>
2009-05-12 1:31 ` Barry Margolin
2009-05-11 8:27 ` Decebal
2009-05-12 9:46 ` Nikolaj Schumacher
2009-05-10 16:31 ` Drew Adams
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