From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Andy Moreton Newsgroups: gmane.emacs.devel Subject: Re: Replace trivial pcase occurrences in the Emacs sources Date: Tue, 30 Oct 2018 14:16:59 +0000 Message-ID: References: <83tvlcsnee.fsf@gnu.org> <86mur137n8.fsf@gmail.com> <20181029130132.GB4195@ACM> <20181029134722.GC4195@ACM> <83r2g8klf9.fsf@gnu.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1540908973 9909 195.159.176.226 (30 Oct 2018 14:16:13 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Tue, 30 Oct 2018 14:16:13 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (windows-nt) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Tue Oct 30 15:16:09 2018 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1gHUoT-0002Ur-4J for ged-emacs-devel@m.gmane.org; Tue, 30 Oct 2018 15:16:09 +0100 Original-Received: from localhost ([::1]:53520 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gHUqZ-000716-Lw for ged-emacs-devel@m.gmane.org; Tue, 30 Oct 2018 10:18:19 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:39174) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gHUph-00070y-AU for emacs-devel@gnu.org; Tue, 30 Oct 2018 10:17:25 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gHUpb-00017n-Lo for emacs-devel@gnu.org; Tue, 30 Oct 2018 10:17:24 -0400 Original-Received: from [195.159.176.226] (port=54584 helo=blaine.gmane.org) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1gHUpb-00014N-Cy for emacs-devel@gnu.org; Tue, 30 Oct 2018 10:17:19 -0400 Original-Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1gHUnL-0001Db-HI for emacs-devel@gnu.org; Tue, 30 Oct 2018 15:14:59 +0100 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 21 Original-X-Complaints-To: usenet@blaine.gmane.org Cancel-Lock: sha1:jF8MOWDak5TttR3qZHSWx4ImmeM= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 195.159.176.226 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:230827 Archived-At: On Tue 30 Oct 2018, Stefan Monnier wrote: >> I think the doc string should be (more) independent, at least in the >> pcase-dolist case, because the semantics of executing BODY with >> PATTERN matched against a LIST element is significantly different from >> that of executing the dolist BODY with a VAR binding. > > Hmm... I really don't see what difference you're thinking of. > > Maybe a simpler way to document it is to show its definition: > > (dolist (x LIST) (pcase-let ((PATTERN x)) BODY)) So this also fails randomly if the pattern does not match, like `pcase-let', and this should be documented. How are users meant to write reliable code using such constructs ? Why are there not versions of these constructs that have deterministic behaviour on pattern match failure ? AndyM