From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Heime Newsgroups: gmane.emacs.help Subject: Re: [External] : Use of an associated list with completing-read Date: Sat, 20 Apr 2024 06:14:13 +0000 Message-ID: References: <1ZznhcKDmGMQcjaA3pyQaBOnYG81YwX4pE1YSoGxi_Vj_UFqz_DzTcdhZ50XnL3lEDivoq5THtGr-ShAq1PMbkmNHxajYrXWeRmti6_BSD4=@protonmail.com> <6IDPPDE6NaK72davfT7rnK8S553m9H8sBdCDy8UqV81_uCoMjrGuIjErQYACxxx5LZjd2Np0R9S2RPCqIFanRLNpVZhEGvXNYfqBrYI0ahw=@protonmail.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="10077"; mail-complaints-to="usenet@ciao.gmane.io" Cc: help-gnu-emacs@gnu.org To: Stefan Monnier Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Sat Apr 20 08:15:04 2024 Return-path: Envelope-to: geh-help-gnu-emacs@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 1ry408-0002Px-4I for geh-help-gnu-emacs@m.gmane-mx.org; Sat, 20 Apr 2024 08:15:04 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ry3zc-0003mj-HJ; Sat, 20 Apr 2024 02:14:32 -0400 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 1ry3zZ-0003li-Ap for help-gnu-emacs@gnu.org; Sat, 20 Apr 2024 02:14:29 -0400 Original-Received: from mail-40137.protonmail.ch ([185.70.40.137]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ry3zW-0003P3-Dk for help-gnu-emacs@gnu.org; Sat, 20 Apr 2024 02:14:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.com; s=protonmail3; t=1713593659; x=1713852859; bh=VzMNkQCFZSqyYisWWr/RnOAhJ0h+e7ICkhTpz8mh+SI=; h=Date:To:From:Cc:Subject:Message-ID:In-Reply-To:References: Feedback-ID:From:To:Cc:Date:Subject:Reply-To:Feedback-ID: Message-ID:BIMI-Selector; b=O4m6skd3p3Eey7qtvzkOsRTUHL+6J6GAOZZEK1fEs3sDM+3MSXqqiCBmX6VmFOcbd oZCw4WX6cvqCUGmfsbtdWgA0v2J7aGjpFDzSCUEvU5ZHFpcZVAhs6rcPNP7tzYxXkn U7XTd8t+nuoQ2JLylcoDwb37UEddUJS2VlJUxYZw6dwHyPCti2G8Lkz9c+EQqD2goW UZ3VLMo7IkYPckDHvDT2+MG1kpqLgH1VTWGifETJcNqy0J3BtiTx2ETr/N5zPZ+JGI 2Ng7+qoOIdO66+p/T0wRsq6GS4JycJP1wSwqwX8oIRXk+004tgAwOBJRXML+RfrCbg sHn0tonHkKBxA== In-Reply-To: Feedback-ID: 57735886:user:proton X-Pm-Message-ID: 5002c93a2d9dfcc1ab7c7938dc64b09bee85319a Received-SPF: pass client-ip=185.70.40.137; envelope-from=heimeborgia@protonmail.com; helo=mail-40137.protonmail.ch X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, FREEMAIL_FROM=0.001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: help-gnu-emacs@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Users list for the GNU Emacs text editor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.help:146396 Archived-At: On Saturday, April 20th, 2024 at 1:52 PM, Stefan Monnier via Users list for= the GNU Emacs text editor wrote: > > > > (setq-local tema-lugar > > > > (append tema--lugar (list (cons lnum strg)))) > > >=20 > > > This is the classic recipe for poor scaling performance since the abo= ve > > > operation takes time proportional to the length of the list, so if yo= u > > > execute this N times (in a loop), the loop builds a list of length N > > > but takes time N=C2=B2 to do it. When N is small, noone notices, and = as it gets > > > large the performance starts to suck. > >=20 > > Heime: > >=20 > > One programming cliche for this is to > > (1) start with a list that you create > > (e.g., a let-binding to nil), so you > > don't modify any existing list that > > you might not want to mess with, (2) > > use `nconc' instead of` append', to > > append quickly (the list structure > > is modified - destructive), (3) being > > sure to set your list variable to the > > result of each modification. >=20 >=20 > While this is slightly better because it avoid the O(N=C2=B2) memory > allocation, it's still O(N=C2=B2) operations. >=20 > > An even more common cliche for doing > > the same thing is to do #1, then (2) > > cons instead of append, and (3) when > > finished adding list elements, do an > > `nreverse' of the list you created. > > That too is a destructive operation. >=20 >=20 > That's the usual solution, with the desired linear > (i.e. optimal) complexity, indeed. - Stefan How would the implementation be like exactly ?