From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Helmut Eller Newsgroups: gmane.emacs.help Subject: Re: Replacement for Common Lisp's GENSYM in Emacs Lisp Date: Mon, 08 Mar 2010 08:01:15 +0100 Message-ID: References: <87tysssj78.fsf@rapttech.com.au> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: dough.gmane.org 1272990722 7516 80.91.229.12 (4 May 2010 16:32:02 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Tue, 4 May 2010 16:32:02 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Tue May 04 18:32:00 2010 connect(): No such file or directory Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1O9L2O-0002Dd-1w for geh-help-gnu-emacs@m.gmane.org; Tue, 04 May 2010 18:32:00 +0200 Original-Received: from localhost ([127.0.0.1]:39338 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1O9L2N-0005oE-In for geh-help-gnu-emacs@m.gmane.org; Tue, 04 May 2010 12:31:59 -0400 Original-Path: usenet.stanford.edu!news.glorb.com!news2.glorb.com!Xl.tags.giganews.com!border1.nntp.dca.giganews.com!nntp.giganews.com!local2.nntp.dca.giganews.com!nntp.kpnqwest.it!news.kpnqwest.it.POSTED!not-for-mail Original-NNTP-Posting-Date: Mon, 08 Mar 2010 01:01:15 -0600 Original-Newsgroups: gnu.emacs.help User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1.50 (gnu/linux) Cancel-Lock: sha1:22r5bTtMto2Who1DtEqo3/x7G1E= Original-Lines: 32 X-Usenet-Provider: http://www.giganews.com Original-NNTP-Posting-Host: 212.46.183.205 Original-X-Trace: sv3-BoaIX/MS4wO45ZIqj7Vtrsmz8nvzNKIFt1rNX9daNEN7F7AdqoBtcLnLoUjCcE5ZXbboGfE9i7WC4OL!OnDt/e3DdpzeyWuyLj9qVN/rlqHJklcBejnobtg7JM13ibZSxF8U7pjyn9ck1F4= X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 Original-Xref: usenet.stanford.edu gnu.emacs.help:177400 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:72932 Archived-At: * Stefan Monnier [2010-03-08 05:55+0100] writes: >>> (defmacro dotimes (xl e) >>> (let ((x (car xl)) >>> (l (cadr xl))) >>> `(let ((body (lambda (,x) ,e)) >>> (list ,l)) >>> (while (consp list) >>> (funcall body (car list)) >>> (setq list (cdr list)))))) >>> >>> Notice how the expressions `l' and `e' are evaluated in a context where >>> neither of `body', nor `list' exist. No need for gensym. > >> What makes you think that body and list aren't bound in e? > > Nothing, but luckily it doesn't make any difference whether they are > or not. Your "dotimes" macro produces: (let ((list '(1)) (result ())) (dotimes (i '(1 2 3)) (push list result)) result) => ((3) (2 3) (1 2 3)) While a version which doesn't shadow "list" produces this: (let ((list '(1)) (result ())) (dolist (i '(1 2 3)) (push list result)) result) => ((1) (1) (1)) Helmut