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: Thu, 25 Jan 2024 08:57:36 -0500 Message-ID: References: <1AD5807F-91F7-4B92-BCB0-D0FEA904A75D@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="29795"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Cc: emacs-devel@gnu.org To: Madhu Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Thu Jan 25 14:58:24 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 1rT0FL-0007YE-Ho for ged-emacs-devel@m.gmane-mx.org; Thu, 25 Jan 2024 14:58:23 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rT0Ek-0001DR-UO; Thu, 25 Jan 2024 08:57:46 -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 1rT0Eh-0001AX-Dy for emacs-devel@gnu.org; Thu, 25 Jan 2024 08:57:44 -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 1rT0Ef-0007Hb-4K for emacs-devel@gnu.org; Thu, 25 Jan 2024 08:57:42 -0500 Original-Received: from pmg3.iro.umontreal.ca (localhost [127.0.0.1]) by pmg3.iro.umontreal.ca (Proxmox) with ESMTP id 19B38441542; Thu, 25 Jan 2024 08:57:39 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=iro.umontreal.ca; s=mail; t=1706191057; bh=70KOM28F6gb3MyOEuL5eaMCCguiAv0IbyXM2uYfwr4g=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=TEmL40agnnUpP89lp8MYq0EjOeCcRCZ3g1cI9bt6QVwNDW8JCQy0yNZUyZVClr1Q8 WL98uetSkI6/0ERJUdCyR6w47z2rlEWP8dePPEuElDCJmnNR5A0DaKJtxuS7jeI241 8khqu98T21FfCzVNiLOHspJQ2yxEx4MZ5pT7sCbR0lI0f6+XLTz3uJZ6xL06/sOrsp ZFL3ii59knbhS0ev9v9AkmiXo+mEPldDQBJBwBf6OFVQyut/Pa+YjIU5Ff2hsDOm+c Tt44ERhqssSMOEbgGHJ/XHiex99lR6RUXoFR0bT0RoMpEX8GZW7yczLfq4RIPSrMRD wF2dWoK5pg0ZQ== Original-Received: from mail01.iro.umontreal.ca (unknown [172.31.2.1]) by pmg3.iro.umontreal.ca (Proxmox) with ESMTP id B84E84422A7; Thu, 25 Jan 2024 08:57:37 -0500 (EST) Original-Received: from pastel (unknown [45.72.206.68]) by mail01.iro.umontreal.ca (Postfix) with ESMTPSA id 9928F120C5A; Thu, 25 Jan 2024 08:57:37 -0500 (EST) In-Reply-To: (Madhu's message of "Thu, 25 Jan 2024 08:46:51 +0530") 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:315356 Archived-At: >> [1] I regularly convince myself that it=E2=80=99s 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)) Nice. Would `var` and `dvar` scope over just the first branch or also the other ones? Technically, there is no reason for them not to be visible in the other branches, so that's what I would go for. Personally, I was thinking of a syntax like (my-cond (:let var value) (:let dvar (derived-from var)) ((has-the-right-stuff-p dvar) (cons 'correct dvar)) (:let foo value2) (:let bar (1- foo)) ((< bar 0) (cons 'incorrect bar)) (t nil)) with the intention of replacing `cond` without introducing any incompatibility. Stefan