From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Pascal Bourguignon Newsgroups: gmane.emacs.help Subject: Re: A macro and an unwanted containing list in the resulting form Date: Thu, 24 May 2007 01:48:12 +0200 Organization: Informatimago Message-ID: <874pm3umo3.fsf@thalassa.lan.informatimago.com> References: <87ejl7vj8a.fsf@thalassa.lan.informatimago.com> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: sea.gmane.org 1179967242 16425 80.91.229.12 (24 May 2007 00:40:42 GMT) X-Complaints-To: usenet@sea.gmane.org NNTP-Posting-Date: Thu, 24 May 2007 00:40:42 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Thu May 24 02:40:34 2007 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 4.50) id 1Hr1NZ-0003Zg-LK for geh-help-gnu-emacs@m.gmane.org; Thu, 24 May 2007 02:40:33 +0200 Original-Received: from localhost ([127.0.0.1] helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Hr1Nb-0000J4-V1 for geh-help-gnu-emacs@m.gmane.org; Wed, 23 May 2007 20:40:35 -0400 Original-Path: shelby.stanford.edu!newsfeed.stanford.edu!news.tele.dk!news.tele.dk!small.news.tele.dk!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail Original-Newsgroups: gnu.emacs.help Original-Lines: 55 Original-X-Trace: individual.net WIgq3FGBGg8+DPE0DFvp8QyE8WK3CYCQPxrGPtt97to00fpvpE Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwAQMAAABtzGvEAAAABlBMVEUAAAD///+l2Z/dAAAA oElEQVR4nK3OsRHCMAwF0O8YQufUNIQRGIAja9CxSA55AxZgFO4coMgYrEDDQZWPIlNAjwq9 033pbOBPtbXuB6PKNBn5gZkhGa86Z4x2wE67O+06WxGD/HCOGR0deY3f9Ijwwt7rNGNf6Oac l/GuZTF1wFGKiYYHKSFAkjIo1b6sCYS1sVmFhhhahKQssRjRT90ITWUk6vvK3RsPGs+M1RuR mV+hO/VvFAAAAABJRU5ErkJggg== X-Accept-Language: fr, es, en X-Disabled: X-No-Archive: no User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/22.0.99 (gnu/linux) Cancel-Lock: sha1:ZGViMTE3ZjUyYjU0MDgyZGMxNDliYmUzODY1YzdmMDJkYWM5NDExNw== Original-Xref: shelby.stanford.edu gnu.emacs.help:148767 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:44358 Archived-At: Sebastian Tennant writes: >> And finally, it would be better if we could have several forms in each >> branches, and if we lost the dot: > > "lost the dot" = "do without cons cells" -----+ > | > +-------- > | > \/ >> (defmacro string-case (strexpr &rest alist) >> (let ((var-name (gensym))) >> `(let ((,var-name ,strexpr)) >> (cond ,@(mapcar (lambda (each) >> `((equal ,var-name ,(car each)) ,@(cdr each))) >> alist))))) ^ > | > I see. ----------------------------------------------------+--+ > | >> (macroexpand '(string-case (aref my-strings (incf i)) | >> ("hello" (message "hi") (message "ho")) | >> ("goodbye" (message "bye")))) | > | > Unique variable name created by (gensym) ---+ | > | | > ---------------------------------+ | > | | > \/ | >> (let ((G42298 (aref my-strings (incf i)))) | >> (cond | >> ((equal G42298 "hello") | >> (message "hi") (message "ho")) <--+---------------------+ >> ((equal G42298 "goodbye") | >> (message "bye")))) | > | > "several forms in each branch" ----------+ > > Well Pascal, thank you for an excellent crash-course in macro > expansion! > > I hope my annotations are correct, and not out of place, although > people not reading this in a fixed-with font will no doubt wonder what > on earth is going on, not to mention the other nasty things > line-wrapping news-manglers are inclined to do! They're correct. -- __Pascal Bourguignon__ http://www.informatimago.com/ NOTE: The most fundamental particles in this product are held together by a "gluing" force about which little is currently known and whose adhesive power can therefore not be permanently guaranteed.