From mboxrd@z Thu Jan 1 00:00:00 1970 Path: main.gmane.org!not-for-mail From: Lars Brinkhoff Newsgroups: gmane.emacs.help Subject: Re: Object identity Date: 21 Oct 2003 21:49:13 +0200 Organization: nocrew Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Message-ID: <851xt69xs6.fsf@junk.nocrew.org> References: NNTP-Posting-Host: deer.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: sea.gmane.org 1066765848 19866 80.91.224.253 (21 Oct 2003 19:50:48 GMT) X-Complaints-To: usenet@sea.gmane.org NNTP-Posting-Date: Tue, 21 Oct 2003 19:50:48 +0000 (UTC) Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Tue Oct 21 21:50:45 2003 Return-path: Original-Received: from monty-python.gnu.org ([199.232.76.173]) by deer.gmane.org with esmtp (Exim 3.35 #1 (Debian)) id 1AC2Wj-0005f5-00 for ; Tue, 21 Oct 2003 21:50:45 +0200 Original-Received: from localhost ([127.0.0.1] helo=monty-python.gnu.org) by monty-python.gnu.org with esmtp (Exim 4.24) id 1AC2WK-0004ql-Ua for geh-help-gnu-emacs@m.gmane.org; Tue, 21 Oct 2003 15:50:20 -0400 Original-Received: from list by monty-python.gnu.org with tmda-scanned (Exim 4.24) id 1AC2Vo-0004ll-VQ for help-gnu-emacs@gnu.org; Tue, 21 Oct 2003 15:49:48 -0400 Original-Received: from mail by monty-python.gnu.org with spam-scanned (Exim 4.24) id 1AC2VI-0004ZX-N4 for help-gnu-emacs@gnu.org; Tue, 21 Oct 2003 15:49:47 -0400 Original-Received: from [80.91.224.249] (helo=main.gmane.org) by monty-python.gnu.org with esmtp (Exim 4.24) id 1AC2VH-0004Yq-9k for help-gnu-emacs@gnu.org; Tue, 21 Oct 2003 15:49:15 -0400 Original-Received: from list by main.gmane.org with local (Exim 3.35 #1 (Debian)) id 1AC2VG-0004aE-00 for ; Tue, 21 Oct 2003 21:49:14 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-To: help-gnu-emacs@gnu.org Original-Received: from sea.gmane.org ([80.91.224.252]) by main.gmane.org with esmtp (Exim 3.35 #1 (Debian)) id 1AC2VF-0004a6-00 for ; Tue, 21 Oct 2003 21:49:13 +0200 Original-Received: from news by sea.gmane.org with local (Exim 3.35 #1 (Debian)) id 1AC2VF-000578-00 for ; Tue, 21 Oct 2003 21:49:13 +0200 Original-Lines: 28 Original-X-Complaints-To: usenet@sea.gmane.org User-Agent: Gnus/5.0808 (Gnus v5.8.8) Emacs/20.7 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.2 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: main.gmane.org gmane.emacs.help:13434 X-Report-Spam: http://spam.gmane.org/gmane.emacs.help:13434 Barry Margolin writes: > In article , > Lars Brinkhoff wrote: > >Stefan Monnier writes: > >> > Is there a function, say object-identity, in Emacs Lisp that maps an > >> > object to a unique value (other than the object itself)? > >> I'm wondering what you want it for. > >In the implementation of Common Lisp's print-unreadable-object when > >:identity t is supplied. > AFAIK, there's no guarantee that the same object will print identically > over time. Most implementations just display the object's current address; > if the GC moves it, the next time it's printed it will be different. Excellent, then the functionality I would need shouldn't that hard to implement. > Anyway, there's a reason why Common Lisp requires that > PRINT-UNREADABLE-OBJECT be built into the implementation. We didn't > want to expose an interface to getting these not-quite-unique > identifiers. They're not much use for anything other than this one > function; if we provided the API, users would undoubtedly misuse it. I have no desire to get the not-quite-unique identifiers in Common Lisp. I want to implement PRINT-UNREADABLE-OBJECT in Emacs Lisp. -- Lars Brinkhoff, Services for Unix, Linux, GCC, HTTP Brinkhoff Consulting http://www.brinkhoff.se/