From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Ihor Radchenko Newsgroups: gmane.emacs.devel Subject: Re: Instead of pcase Date: Sat, 06 Jan 2024 13:04:44 +0000 Message-ID: <874jfqwr2r.fsf@localhost> References: <878r5inysw.fsf@localhost> <878r5ewk81.fsf@localhost> <87h6jxm8d4.fsf@localhost> <87a5pm762w.fsf@localhost> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="33082"; mail-complaints-to="usenet@ciao.gmane.io" Cc: emacs-devel@gnu.org To: rms@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sat Jan 06 14:02:42 2024 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1rM6K1-0008OK-2s for ged-emacs-devel@m.gmane-mx.org; Sat, 06 Jan 2024 14:02:41 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rM6J4-0007Se-7O; Sat, 06 Jan 2024 08:01:42 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rM6J2-0007ST-Ia for emacs-devel@gnu.org; Sat, 06 Jan 2024 08:01:40 -0500 Original-Received: from mout02.posteo.de ([185.67.36.66]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rM6Iz-0000lN-50 for emacs-devel@gnu.org; Sat, 06 Jan 2024 08:01:40 -0500 Original-Received: from submission (posteo.de [185.67.36.169]) by mout02.posteo.de (Postfix) with ESMTPS id 937CF240101 for ; Sat, 6 Jan 2024 14:01:34 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.net; s=2017; t=1704546094; bh=P/6HI4N7R5WwYyl8ly5KKfBQHa+HyZn2YvS2T2+jefY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:From; b=VobnNP34Qgap/HJpZEIOSTzc4WQjocHoCG9YdE0HumJljRtN+z9djmqg0wYx+yaIC UEsKQBV01kyTOz0q9GHritsCFMeOhbCIvqCtSfOrbRZl5SVXrPXXAApRA4GvFP/CB3 bXVIDJ29/+V7ID8pOMjje4wHKdhzb4tK5kpldGG21eKl4wqeXTcGrDsUmZRc+uZWEb q7unmQJhiUkm0DBVBrczlzgt8ahfs3/RCqSRHwWSQMobFdGrLDj5Ny5nfzt/k0l8it yBZijXdqLXXWdFY+kcsEF5DawMPLno4PoafORXcMjBjqev679mdT/cW8E6QiddFWLf ubBSuo7mS1G4Q== Original-Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4T6gSY6gKtz6txp; Sat, 6 Jan 2024 14:01:33 +0100 (CET) In-Reply-To: Received-SPF: pass client-ip=185.67.36.66; envelope-from=yantar92@posteo.net; helo=mout02.posteo.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 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-mx.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:314616 Archived-At: Richard Stallman writes: > > Consider another example: > > > (match* (xor (not var) t) t) > > Anyway, I suppose the best response is to say that such counterintuitive > constrained variables are best avoided. Or else specifically disallow > `xor' as PRED in a constrained variable. My point is not about `xor' in particular. What I am trying to demonstrate is that (foo (bar var) arg) looks like a normal Elisp call - `foo' called with two arguments: (bar var) and arg. Yet, it has completely different meaning inside match*. So, it is very easy to confuse match* clause result with return value of the equivalent normal Elisp expression. In contrast, a more explicit (match* (constrain var (and (bar var) (foo var arg))) ...) (match* (constrain var (and (not var) (xor var t)) t) ...) is much more natural and avoids confusion. > ... > I wonder why people defined `xor'. It can't be used > as a conditional, like `and' and `or', so what is the point of it? `xor' can be used as conditional, and it also comes handy at time (we have 7 functions using `xor' in Org mode, for example). But that's off-topic to `pcase' discussion. -- Ihor Radchenko // yantar92, Org mode contributor, Learn more about Org mode at . Support Org development at , or support my work at