From: Giorgos Keramidas <keramida@ceid.upatras.gr>
Cc: emacs-devel@gnu.org
Subject: Re: Is this a bug of Emacs-Lisp?
Date: Fri, 17 Feb 2006 18:21:37 +0200 [thread overview]
Message-ID: <20060217162137.GA12962@flame.pc> (raw)
In-Reply-To: <87slqipmde.fsf@emacsfans.org>
On 2006-02-17 13:47, Zhang Wei <id.brep@gmail.com> wrote:
> (defun dummy () '(1 . 2))
>
> (dummy)
> => (1 . 2)
>
> (setcdr (dummy) 3)
>
> (dummy)
> => (1 . 3)
>
> Modify the return value of dummy changed it's defination. Is this
> a bug of Elisp? If it's not. How does this happen?
You are modifying a `literal' cons cell. It's not mandatory for the
LISP reader to create a new cons cell every time the (dummy) function
runs.
If you really want to create a new cons cell every time (dummy) runs,
you'll have to explicitly do that in the function:
(defun dummy ()
(copy-tree '(1 . 2)))
=> dummy
(setcdr (dummy) 3)
=> 3
(dummy)
=> '(1 . 2)
next prev parent reply other threads:[~2006-02-17 16:21 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-17 5:47 Is this a bug of Emacs-Lisp? Zhang Wei
2006-02-17 16:21 ` Giorgos Keramidas [this message]
2006-02-18 5:26 ` Drew Adams
2006-02-18 6:42 ` Drew Adams
2006-02-18 16:18 ` Andreas Schwab
2006-02-17 16:28 ` Andreas Schwab
2006-02-17 17:20 ` David Kastrup
2006-02-17 17:57 ` Luc Teirlinck
2006-02-17 18:18 ` Luc Teirlinck
2006-02-17 19:24 ` Alan Mackenzie
2006-02-17 19:29 ` Kevin Rodgers
2006-02-17 22:34 ` Sascha Wilde
2006-02-18 18:34 ` Richard M. Stallman
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