From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Kevin Rodgers Newsgroups: gmane.emacs.help Subject: Re: How to distinguish gobal and local variables in elisp? Date: Thu, 21 Sep 2006 13:51:13 -0600 Organization: IHS Message-ID: References: NNTP-Posting-Host: main.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Trace: sea.gmane.org 1158868753 25113 80.91.229.2 (21 Sep 2006 19:59:13 GMT) X-Complaints-To: usenet@sea.gmane.org NNTP-Posting-Date: Thu, 21 Sep 2006 19:59:13 +0000 (UTC) Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Thu Sep 21 21:59:11 2006 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by ciao.gmane.org with esmtp (Exim 4.43) id 1GQUgF-0005k8-Or for geh-help-gnu-emacs@m.gmane.org; Thu, 21 Sep 2006 21:57:56 +0200 Original-Received: from localhost ([127.0.0.1] helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1GQUgF-0004g0-9a for geh-help-gnu-emacs@m.gmane.org; Thu, 21 Sep 2006 15:57:55 -0400 Original-Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1GQUfB-0003zU-6R for help-gnu-emacs@gnu.org; Thu, 21 Sep 2006 15:56:49 -0400 Original-Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1GQUf9-0003yb-JD for help-gnu-emacs@gnu.org; Thu, 21 Sep 2006 15:56:48 -0400 Original-Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1GQUf8-0003yU-Nt for help-gnu-emacs@gnu.org; Thu, 21 Sep 2006 15:56:46 -0400 Original-Received: from [80.91.229.2] (helo=ciao.gmane.org) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA:32) (Exim 4.52) id 1GQUii-0000Kn-EQ for help-gnu-emacs@gnu.org; Thu, 21 Sep 2006 16:00:28 -0400 Original-Received: from list by ciao.gmane.org with local (Exim 4.43) id 1GQUcV-0004VE-EJ for help-gnu-emacs@gnu.org; Thu, 21 Sep 2006 21:54:04 +0200 Original-Received: from 207.167.42.206 ([207.167.42.206]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 21 Sep 2006 21:54:03 +0200 Original-Received: from ihs_4664 by 207.167.42.206 with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 21 Sep 2006 21:54:03 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-To: help-gnu-emacs@gnu.org Original-Lines: 31 Original-X-Complaints-To: usenet@sea.gmane.org X-Gmane-NNTP-Posting-Host: 207.167.42.206 User-Agent: Thunderbird 1.5.0.7 (Windows/20060909) In-Reply-To: X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:37550 Archived-At: jronald wrote: > The question comes from setq. > Usually, setq appears in a file without in any parentheses. > Does it mean that it awlays set the global varaible then? Or what's a local > variable in lisp? Emacs Lisp is dynamically scoped (like most older Lisp dialects, and unlike most newer dialects). That means that a variable may be referenced outside the lexical scope that declares it. For example: (setq foo 0) ;; At this point, foo has only a global binding, to 0. (defun bar () (setq foo 2)) ;; When bar is called, it will update foo's global binding, unless it is ;; shadowed by a local binding. (let ((foo 1)) ;; For the duration of the let form, foo also has a local binding. ;; At this point, its local value is 1. (bar) ;; Now foo's local value is 2, but its global value is still 0. ) ;; And now only the global binding exists, so foo's value is 0. -- Kevin