From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: "Pascal J. Bourguignon" Newsgroups: gmane.emacs.help Subject: Re: About `catch' and `throw' Date: Sat, 22 Dec 2012 21:33:54 +0100 Organization: Informatimago Message-ID: <87mwx5zv0t.fsf@kuiper.lan.informatimago.com> References: <20121221200001.891d30e881f25580089bbc5b@gmail.com> <6EB1418B063C4F8CAFA179007459A7A5@us.oracle.com> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1356208512 20337 80.91.229.3 (22 Dec 2012 20:35:12 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 22 Dec 2012 20:35:12 +0000 (UTC) To: help-gnu-emacs@gnu.org Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Sat Dec 22 21:35:27 2012 Return-path: Envelope-to: geh-help-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1TmVn4-0003ro-I9 for geh-help-gnu-emacs@m.gmane.org; Sat, 22 Dec 2012 21:35:26 +0100 Original-Received: from localhost ([::1]:38763 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TmVmq-0001cR-Hm for geh-help-gnu-emacs@m.gmane.org; Sat, 22 Dec 2012 15:35:12 -0500 Original-Path: usenet.stanford.edu!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail Original-Newsgroups: gnu.emacs.help Original-Lines: 41 Original-X-Trace: individual.net 0+525F7eQImM3uqtMqjiMANnPw0J2Ek3rYsqGRiBgaGBccHStLx38Ohyr2LoMsQvFs Cancel-Lock: sha1:MmU2ZGNjOGNkNTA4MTIxZGVjMGMzMGNlYzFlMmY5NWMxNmZhYmRiMA== sha1:l5/3Pyzrw0DljssKYQ8kLmQpIFI= Face: iVBORw0KGgoAAAANSUhEUgAAADAAAAAwAQMAAABtzGvEAAAABlBMVEUAAAD///+l2Z/dAAAA oElEQVR4nK3OsRHCMAwF0O8YQufUNIQRGIAja9CxSA55AxZgFO4coMgYrEDDQZWPIlNAjwq9 033pbOBPtbXuB6PKNBn5gZkhGa86Z4x2wE67O+06WxGD/HCOGR0deY3f9Ijwwt7rNGNf6Oac l/GuZTF1wFGKiYYHKSFAkjIo1b6sCYS1sVmFhhhahKQssRjRT90ITWUk6vvK3RsPGs+M1RuR mV+hO/VvFAAAAABJRU5ErkJggg== X-Accept-Language: fr, es, en User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.2 (gnu/linux) Original-Xref: usenet.stanford.edu gnu.emacs.help:195978 X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.14 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 Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.help:88293 Archived-At: Stefan Monnier writes: >> During the evaluation of code that is lexically inside the `catch', >> a `throw' that is evaluated throws back to that `catch'. > > Usually, but not always. > >> And if there is more than one `catch' with the same label then it >> throws to the one that is lexically nearest (i.e., innermost, outside >> the `throw'), which is also the most recent. > > Usually, but not always: > > (catch 'foo > (let ((f (lambda () (throw 'foo)))) > ... > (catch 'foo > (funcall f)) > ...)) > > will throw to the inner catch, not the outer one. Again, because it does not matter WHERE the catch is: it's not because it's _placed_ _inner_ or _outer_. What matter is WHEN the catch is: it is because it is the most recently established catch 'foo, that it will catch the throw 'foo. Conversely with: (catch 'foo (funcall (catch 'foo (lambda () (throw 'foo))))) it is the first catch 'foo which is the most RECENTLY established catch 'foo, WHEN throw 'foo is called, because the second catch 'foo at that TIME has been already disestablished. -- __Pascal Bourguignon__ http://www.informatimago.com/ A bad day in () is better than a good day in {}.