From: Barry Margolin <barmar@alum.mit.edu>
To: help-gnu-emacs@gnu.org
Subject: Re: using setq to create lists based on other lists...
Date: Tue, 04 Dec 2018 04:00:32 -0500 [thread overview]
Message-ID: <barmar-2E240B.04003204122018@reader.eternal-september.org> (raw)
In-Reply-To: mailman.5026.1543764670.1284.help-gnu-emacs@gnu.org
In article <mailman.5026.1543764670.1284.help-gnu-emacs@gnu.org>,
Jean-Christophe Helary <brandelune@gmail.com> wrote:
> > On Dec 3, 2018, at 0:00, Stephen Berman <stephen.berman@gmx.net> wrote:
> >
> > I think your confusion may be due to not distinguishing the value
> > assigned by setq, which is a particular object, and the form of the
> > value, which may look the same but nevertheless be a different object.
>
> You are absolutely right.
>
> But I think the "not distinguishing" the difference between the two is
> partially caused by the way the Reference is written:
>
> Global Variables:
> > You specify a value for a symbol with setq. For example, (setq x '(a b))
> > gives the variable x the value (a b).
>
> This is not saying: gives the variable x a pointer to the object (a b)
There are no pointers in Lisp. There are just objects, the pointers are
in the implementation.
The important thing is that
(setq list1 list2)
doesn't make a copy of the value of list2 when assigning to list1. The
two variables refer to the same value when this is done.
--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
next prev parent reply other threads:[~2018-12-04 9:00 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.5010.1543748027.1284.help-gnu-emacs@gnu.org>
2018-12-02 11:21 ` using setq to create lists based on other lists Barry Margolin
2018-12-02 11:51 ` Stephen Berman
2018-12-02 12:22 ` Jean-Christophe Helary
2018-12-02 13:08 ` Stephen Berman
2018-12-02 13:28 ` Jean-Christophe Helary
2018-12-02 14:40 ` Michael Heerdegen
2018-12-02 15:34 ` Jean-Christophe Helary
2018-12-02 15:44 ` Michael Heerdegen
2018-12-02 15:57 ` Jean-Christophe Helary
2018-12-02 15:00 ` Stephen Berman
2018-12-02 15:30 ` Jean-Christophe Helary
[not found] ` <mailman.5026.1543764670.1284.help-gnu-emacs@gnu.org>
2018-12-04 9:00 ` Barry Margolin [this message]
2018-12-02 12:03 ` Jean-Christophe Helary
[not found] <mailman.5042.1543777897.1284.help-gnu-emacs@gnu.org>
2018-12-04 9:04 ` Barry Margolin
[not found] ` <(message>
[not found] ` <from>
[not found] ` <Barry>
[not found] ` <Margolin>
[not found] ` <on>
[not found] ` <Tue>
[not found] ` <04>
[not found] ` <Dec>
[not found] ` <2018>
[not found] ` <04:04:52>
2018-12-04 13:56 ` Stefan Monnier
2018-12-05 1:07 ` Robert Thorpe
2018-12-05 2:32 ` Drew Adams
2018-12-05 6:45 ` Jean-Christophe Helary
2018-12-05 8:00 ` Marcin Borkowski
2018-12-05 8:11 ` Jean-Christophe Helary
2018-12-05 14:57 ` Drew Adams
[not found] ` <mailman.5218.1544021892.1284.help-gnu-emacs@gnu.org>
2018-12-05 16:59 ` Barry Margolin
[not found] ` <mailman.5186.1543978155.1284.help-gnu-emacs@gnu.org>
2018-12-05 16:50 ` Barry Margolin
[not found] ` <mailman.5145.1543931778.1284.help-gnu-emacs@gnu.org>
2018-12-05 16:47 ` Barry Margolin
2018-12-02 10:53 Jean-Christophe Helary
2018-12-02 15:07 ` Stefan Monnier
2018-12-02 15:41 ` Jean-Christophe Helary
2018-12-02 16:05 ` Stefan Monnier
2018-12-02 16:23 ` Jean-Christophe Helary
2018-12-02 17:02 ` Stefan Monnier
2018-12-02 17:21 ` Jean-Christophe Helary
2018-12-02 19:11 ` Robert Thorpe
2018-12-02 23:44 ` Jean-Christophe Helary
[not found] ` <mailman.5028.1543765273.1284.help-gnu-emacs@gnu.org>
2018-12-03 13:43 ` Rusi
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