From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Madhu Newsgroups: gmane.emacs.devel Subject: Re: Code for cond* Date: Thu, 25 Jan 2024 08:46:51 +0530 Message-ID: References: <1AD5807F-91F7-4B92-BCB0-D0FEA904A75D@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="32988"; mail-complaints-to="usenet@ciao.gmane.io" To: emacs-devel@gnu.org Cancel-Lock: sha1:Tnh8UfErrid/LbPk7kXKMIWrDFI= Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Thu Jan 25 08:08:03 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 1rStqF-0008TF-4w for ged-emacs-devel@m.gmane-mx.org; Thu, 25 Jan 2024 08:08:03 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rStpR-0004i6-6Z; Thu, 25 Jan 2024 02:07:13 -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 1rSqEd-0006ns-F1 for emacs-devel@gnu.org; Wed, 24 Jan 2024 22:16:59 -0500 Original-Received: from ciao.gmane.io ([116.202.254.214]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rSqEb-000509-W0 for emacs-devel@gnu.org; Wed, 24 Jan 2024 22:16:59 -0500 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1rSqEZ-0000cW-1C for emacs-devel@gnu.org; Thu, 25 Jan 2024 04:16:55 +0100 X-Injected-Via-Gmane: http://gmane.org/ Received-SPF: pass client-ip=116.202.254.214; envelope-from=ged-emacs-devel@m.gmane-mx.org; helo=ciao.gmane.io X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.249, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Thu, 25 Jan 2024 02:07:08 -0500 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:315337 Archived-At: * JD Smith <1AD5807F-91F7-4B92-BCB0-D0FEA904A75D @gmail.com> : Wrote on Tue, 23 Jan 2024 23:49:06 -0500: > In general I’ve always felt cond by itself was missing some > functionality and could really use the ability to make bindings — a > cond-let if you will. [Using an example from another thread] ``` (t (let ((temp (cadr whatsis))) (cond ((eq temp 'foo)) ... ``` The idiom i've seen from 80s code is to explicitly pull the bindings to the outermost scope (like cl loop does when expanded) ``` (let (temp) (cond ((eq (setq temp (cadr whatsis)) 'foo)) ... ``` This solves one indentation problem and creates another. > Even making and testing bindings local to each > cond clause would be a real advance[1]. Pattern matching adds another > level of complexity I hadn’t considered, but overall I'm supportive of > efforts to improve cond. [...] > [1] I regularly convince myself that it’s such low hanging fruit, there must in fact already BE a cond-let, and I go hunting for it. The obvious interface seems like such a straightforward extension of if/when-let, that there would be absolutely nothing new to learn: > > (cond-let > (((var value) > (dvar (derived-from var)) > ((has-the-right-stuff-p dvar))) > (cons 'correct dvar)) > > (((foo value2) > (bar (1- foo)) > ((< bar 0))) > (cons 'incorrect bar)) > > (t nil))