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: named-let Date: Mon, 11 Jan 2021 18:57:36 -0500 Message-ID: References: <87im86kub6.fsf@logand.com> <86zh1g62zx.fsf@163.com> <875z4385yd.fsf@logand.com> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="6185"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) Cc: Zhu Zihao , Tomas Hlavaty , emacs-devel@gnu.org To: Andrea Corallo Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Tue Jan 12 00:59:04 2021 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 1kz75U-0001UP-BS for ged-emacs-devel@m.gmane-mx.org; Tue, 12 Jan 2021 00:59:04 +0100 Original-Received: from localhost ([::1]:54454 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kz75T-0006uP-77 for ged-emacs-devel@m.gmane-mx.org; Mon, 11 Jan 2021 18:59:03 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:33658) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kz74B-0005K3-8N for emacs-devel@gnu.org; Mon, 11 Jan 2021 18:57:43 -0500 Original-Received: from mailscanner.iro.umontreal.ca ([132.204.25.50]:44721) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kz748-0003Uk-L4 for emacs-devel@gnu.org; Mon, 11 Jan 2021 18:57:42 -0500 Original-Received: from pmg2.iro.umontreal.ca (localhost.localdomain [127.0.0.1]) by pmg2.iro.umontreal.ca (Proxmox) with ESMTP id 99381808C6; Mon, 11 Jan 2021 18:57:38 -0500 (EST) Original-Received: from mail01.iro.umontreal.ca (unknown [172.31.2.1]) by pmg2.iro.umontreal.ca (Proxmox) with ESMTP id 4546D8021A; Mon, 11 Jan 2021 18:57:37 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=iro.umontreal.ca; s=mail; t=1610409457; bh=DB3SdXOEQ3LVqcmkVZdNtRWdNT05LBSaIwh1H22+Uic=; h=From:To:Cc:Subject:References:Date:In-Reply-To:From; b=kBU3pscGG+UnnF6jY+N+mvdo2m0bvV0GzNB3spGz8hzWpZG8EqhSFiXPxLRMzk6KL quNQmBN5b8GmshWehuzQG1Nv8tZVR0a9dHAtFckxUjxk/Fm0rTbKywCvvHkLdOO7HP m3Xavi2ahcWJJZKjP9iE1mEI3mZ04j+ydMsYCOVT6QNSoffVGSOZ2fj6nsqC78QnMH qPicBehNJOrzAUGqWI3DU/foj1MyP8GOBu9itCRCN0FkbiTXOaGdABq6yqs07eXTyD hGv8RH5MFHTTqdbllGqnqVUYSo+PmoTDPLcZl8aGEgbchCeI894nkauZ8hIJYWAPyH yyjWy5entqy+w== Original-Received: from alfajor (unknown [45.72.224.181]) by mail01.iro.umontreal.ca (Postfix) with ESMTPSA id 0811312037A; Mon, 11 Jan 2021 18:57:37 -0500 (EST) In-Reply-To: (Andrea Corallo's message of "Mon, 11 Jan 2021 23:28:08 +0000") 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 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.23 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" Xref: news.gmane.io gmane.emacs.devel:262951 Archived-At: >> [ TCO has also undesirable interactions with debugging/tracing, but >> I think that would be a secondary concern which should be >> manageable somehow. ] > > It's also a change in semantic as one must assume that `bar' is not > redefining `foo'. > > (defun foo () > (bar) > (foo)) I think there's a bit of confusion: you can have TCO without having to pay any attention to whether `bar` changes `foo`. True TCO will also avoid eating up stack space when you have code like (defun foo (x) (baz (1+ x))) or (defun foo (x) (funcall (if (something) #'bar #'foo) (1+ x))) or (defun foo (x) (let ((k (lambda (y) (foo (1+ x))))) (k 5))) or ... and that doesn't depend on analyzing the code at all. IOW, it shouldn't matter whether it's a recursive call or whether it's a call to "self": all calls in tail position would conceptually pop their stack frame before jumping to the destination function. Stefan