From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Code for cond* Date: Mon, 12 Feb 2024 19:41:12 -0500 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="11200"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Cc: emacs-devel@gnu.org To: Richard Stallman Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Tue Feb 13 01:42:17 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 1rZgsK-0002fg-V5 for ged-emacs-devel@m.gmane-mx.org; Tue, 13 Feb 2024 01:42:17 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rZgra-0003Rr-B9; Mon, 12 Feb 2024 19:41:30 -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 1rZgrY-0003Rh-9m for emacs-devel@gnu.org; Mon, 12 Feb 2024 19:41:28 -0500 Original-Received: from mailscanner.iro.umontreal.ca ([132.204.25.50]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rZgrM-0008W1-IE; Mon, 12 Feb 2024 19:41:28 -0500 Original-Received: from pmg1.iro.umontreal.ca (localhost.localdomain [127.0.0.1]) by pmg1.iro.umontreal.ca (Proxmox) with ESMTP id 7D27910007D; Mon, 12 Feb 2024 19:41:14 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=iro.umontreal.ca; s=mail; t=1707784873; bh=VelFGiXj2sG0Zp5BZfX8zFKmqMWh6a8brHE3x4CoPE8=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=HqcCcheMpLgz4g6tg0ab2giu2JyBsFuL2eLVZ5PnLEj4bTSGLHySxfJyvgtoVs9TY +qZNcIhp6oVmHIZj3O4laV6k7wF5TYvp8gF1s/c6Thg/2OJ/istQdqzINfUyDZRnoE c5o4G/ipoYq+rQbjZJEmm3jhmVek7uR+Vm+s7RtADvSZTF2z132Vdnh3Fbo9x3yjGh L5pgr3AVqSaLD/+9OMPHE7gfav55cU+khvPm2DYAEssE6ZESBidg4VptTzY8vAke5R N+JjL1jzd4PqF6Oa2aN0wUxdt3hF1kFcb8lV9srAG1R0JUYFdT5tQFZBAy1upGS7/I gQwrfrSDJz12g== Original-Received: from mail01.iro.umontreal.ca (unknown [172.31.2.1]) by pmg1.iro.umontreal.ca (Proxmox) with ESMTP id 7AB4910004C; Mon, 12 Feb 2024 19:41:13 -0500 (EST) Original-Received: from pastel (unknown [104.247.238.113]) by mail01.iro.umontreal.ca (Postfix) with ESMTPSA id 56AC2120306; Mon, 12 Feb 2024 19:41:13 -0500 (EST) In-Reply-To: (Richard Stallman's message of "Tue, 30 Jan 2024 22:32:42 -0500") Received-SPF: pass client-ip=132.204.25.50; envelope-from=monnier@iro.umontreal.ca; helo=mailscanner.iro.umontreal.ca X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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:316154 Archived-At: > With the cond* syntax for simple constrained variables, > that ordering is natural. the variable to be bound > goes in the same spot as its value will be passed to the predicate. > > (< x 15) as a pattern means, conceptually, bind x and evaluate (< x 15). > > So the question is whether to use > > (pred < x 15) > > or just > > (< x 15) > > I prefer the latter because it is more concise. > The equivalent (and (pred...) car) is used often in pcase > so other forms ofit will be used often also. As mentioned in an email I had sent before, I agree that it'd be nice for `pred` to be able to bind a variable, since indeed when that's needed the `(and (pred ...) VAR)` form is rather inconveniently verbose. Your syntax (FUN VAR ARGS...) has two disadvantages in my view: - It fixes the argument to be checked as the first argument. - It does not syntactically distinguish the VAR from the normal arguments, making a bit too magical for my taste. Maybe a good alternative is to annotate the special arg with a comma: (pred (FUN ,VAR ARGS...)) this way we can trivially support other placements: (pred (FUN ARG1 ARG2 ,VAR ARGS...)) Of course, there remains the question whether this usage should be the one that gets the privilege of not needing a dedicated "keyword", i.e. to allowing using it without the surrounding `pred`: (FUN ,VAR ARGS...) Until now, in `pcase` I refrained from eating this huge chunk of the namespace. Stefan