From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.bugs Subject: bug#19670: 24.4; pcase-let bug? Date: Mon, 26 Jan 2015 17:59:09 -0500 Message-ID: References: NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1422313216 5298 80.91.229.3 (26 Jan 2015 23:00:16 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Mon, 26 Jan 2015 23:00:16 +0000 (UTC) Cc: 19670@debbugs.gnu.org To: Leo Liu Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Tue Jan 27 00:00:15 2015 Return-path: Envelope-to: geb-bug-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 1YFsdi-00006l-43 for geb-bug-gnu-emacs@m.gmane.org; Tue, 27 Jan 2015 00:00:14 +0100 Original-Received: from localhost ([::1]:44485 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YFsdh-0005h7-Kj for geb-bug-gnu-emacs@m.gmane.org; Mon, 26 Jan 2015 18:00:13 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:34134) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YFsdc-0005e5-DQ for bug-gnu-emacs@gnu.org; Mon, 26 Jan 2015 18:00:09 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YFsdY-0002r3-BL for bug-gnu-emacs@gnu.org; Mon, 26 Jan 2015 18:00:08 -0500 Original-Received: from debbugs.gnu.org ([140.186.70.43]:38678) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YFsdY-0002qX-9C for bug-gnu-emacs@gnu.org; Mon, 26 Jan 2015 18:00:04 -0500 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.80) (envelope-from ) id 1YFsdX-0001L3-Gy for bug-gnu-emacs@gnu.org; Mon, 26 Jan 2015 18:00:03 -0500 X-Loop: help-debbugs@gnu.org Resent-From: Stefan Monnier Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Mon, 26 Jan 2015 23:00:03 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 19670 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: notabug Original-Received: via spool by 19670-submit@debbugs.gnu.org id=B19670.14223131535053 (code B ref 19670); Mon, 26 Jan 2015 23:00:03 +0000 Original-Received: (at 19670) by debbugs.gnu.org; 26 Jan 2015 22:59:13 +0000 Original-Received: from localhost ([127.0.0.1]:57370 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from ) id 1YFscj-0001JR-HQ for submit@debbugs.gnu.org; Mon, 26 Jan 2015 17:59:13 -0500 Original-Received: from chene.dit.umontreal.ca ([132.204.246.20]:53164) by debbugs.gnu.org with esmtp (Exim 4.80) (envelope-from ) id 1YFscg-0001JG-SQ for 19670@debbugs.gnu.org; Mon, 26 Jan 2015 17:59:11 -0500 Original-Received: from ceviche.home (lechon.iro.umontreal.ca [132.204.27.242]) by chene.dit.umontreal.ca (8.14.1/8.14.1) with ESMTP id t0QMx9bV007647; Mon, 26 Jan 2015 17:59:09 -0500 Original-Received: by ceviche.home (Postfix, from userid 20848) id 495AB66135; Mon, 26 Jan 2015 17:59:09 -0500 (EST) In-Reply-To: (Leo Liu's message of "Mon, 26 Jan 2015 22:27:20 +0800") User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux) X-NAI-Spam-Flag: NO X-NAI-Spam-Threshold: 5 X-NAI-Spam-Score: 0 X-NAI-Spam-Rules: 1 Rules triggered RV5198=0 X-NAI-Spam-Version: 2.3.0.9393 : core <5198> : inlines <1959> : streams <1379952> : uri <1843937> X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.15 Precedence: list X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 140.186.70.43 X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Original-Sender: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.bugs:98772 Archived-At: > It seems to make more sense for pcase-let to signal an error or bind X > to nil. WDYT? Signaling an error would be fine. But it significantly increases the macro-expanded code size (i.e. it's a lot less efficient). Defaulting to binding all vars to nil in case of match failure seems like an even more surprising behavior than what we have now. The current pcase-let (and pcase-dolist) is meant as a "destructuring" operation: it doesn't *check* anything, it just accesses subelements of a structure. Stefan