From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Hongyi Zhao Newsgroups: gmane.emacs.help Subject: Re: Closures in Emacs and their usage scenarios. Date: Tue, 28 Sep 2021 14:46:28 +0800 Message-ID: References: <87bl4do1ln.fsf@zoho.eu> 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="10194"; mail-complaints-to="usenet@ciao.gmane.io" To: Emanuel Berg , help-gnu-emacs Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Tue Sep 28 08:47:47 2021 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 1mV6u3-0002Ui-N2 for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 28 Sep 2021 08:47:47 +0200 Original-Received: from localhost ([::1]:55536 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mV6u2-00078X-Mn for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 28 Sep 2021 02:47:46 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:40608) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mV6t5-00078N-W2 for help-gnu-emacs@gnu.org; Tue, 28 Sep 2021 02:46:48 -0400 Original-Received: from mail-vs1-xe29.google.com ([2607:f8b0:4864:20::e29]:35666) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1mV6t0-0008CM-Hk for help-gnu-emacs@gnu.org; Tue, 28 Sep 2021 02:46:43 -0400 Original-Received: by mail-vs1-xe29.google.com with SMTP id f18so20958195vsp.2 for ; Mon, 27 Sep 2021 23:46:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :content-transfer-encoding; bh=vPcU6gDgl+7BWq45Mj1A2+ma4YJDOBtrnw84ZXa6JcM=; b=FprfjXDwBgVQ0trC6hKdG8Db9gKeuiFhu4B5se/NioY3oNG3phCe86UdePu+cZuPI4 MHdVhbtUPVNnCHyY5CZRsgBknHQPUVzsnLsv4JuHzBcPA5Lb7cQmEtznqqanQtgDnfrt 1p4+6O9GPes06yOrWPD7AQ8LOq2zZGn1t6t54gN+MPHIyvzOSb1SFGIDdeBIsJowK9o5 eogSDj24//NBWQUEq2ywDqhADFUX33JifPVdY6fgYK/Iif9yRkJGDKdbqSCOTPlAPIc3 dHlr67E9yyxK39QMAIrvP3ZU+dHJKDTVaMaPGa2cmbGu40vZYheX+fK7XLsF7KrwJonm vj+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:content-transfer-encoding; bh=vPcU6gDgl+7BWq45Mj1A2+ma4YJDOBtrnw84ZXa6JcM=; b=UDJRwzxFreqXRAJmFClUAo2sC6rwnLdnRQIBG5t/2Ly0XJwLFHXjj/RxX+5BWXZMIf hVebI3S89X6clAolF1j0YQ9M9XvCkqiTSt8mWdhDbh33RYydM6+G4NeSeF2ll2vDDr7W qHkpnAzZvrrj3TTy58BWyLr5fxr41WrWHGRqBabUJtm1Osd21y4IE1ENZ5HgGu7vtYSc gK8WKqqZByvuyjX0AmX7viHZmUpJJS9opl37uArvRgQC45W37cqsN+mNn5rSiVCxhOfg Z8U+U3VKVRVdTFlYSEjDQSdqksP6eHgcnbguSlgakPUFQYhTobeOQAbu68lGswkl4ns6 fMsQ== X-Gm-Message-State: AOAM530Rm7HcBzsrYSQTy0MrNn/ZlIZZEgRRrumqArGyDyiggW1Fcy2Y c5VNca0zjCKfRHH86VcCc8kGC+PrWOB+fDoVipM= X-Google-Smtp-Source: ABdhPJxPOYhgTUStfqPz/GwBlj4Q15oYSyVhCsXB5AQWAlbRlpDdtcIwJwGCwZ9k3DwanM2SGGvpcb2Ud66elWCBCrY= X-Received: by 2002:a05:6102:5f4:: with SMTP id w20mr3779801vsf.55.1632811600182; Mon, 27 Sep 2021 23:46:40 -0700 (PDT) In-Reply-To: <87bl4do1ln.fsf@zoho.eu> Received-SPF: pass client-ip=2607:f8b0:4864:20::e29; envelope-from=hongyi.zhao@gmail.com; helo=mail-vs1-xe29.google.com 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_DNSWL_NONE=-0.0001, SPF_HELO_NONE=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: 2.1.23 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" Xref: news.gmane.io gmane.emacs.help:133326 Archived-At: On Tue, Sep 28, 2021 at 10:50 AM Emanuel Berg via Users list for the GNU Emacs text editor wrote: > > Hongyi Zhao wrote: > > > I noticed the document on closure here [1] implemented in > > Emacs/Elisp currently. But it's only a very concise and > > short introduction, and I want to know more about the > > closures in Emacs and their usage scenarios. Any helpful > > tips are welcome. > > > > [1] https://www.gnu.org/software/emacs/manual/html_node/elisp/Closures.= html > > As a part of the language, or perhaps how the language is > implemented, I can't say I understand it, but from the > Joe Hacker perspective it is understandable enough, it can be > used so a function (or set of functions) will have a memory > and can use the variables that are part of that memory like > global variables, even tho they aren't and are protected from > outside interference, so that, for example, they wont be reset > between function calls ... > > Here is one example - note that the byte-compiler will warn > that "the function =E2=80=98align-from-left=E2=80=99 is not known to be > defined." Well, OK. > > There is a better/easier example, an example with a counter, > and then three functions within the `let' body, the let holds > the counter value and the functions are "increase", "decrease", > and "reset". Maybe one wants a "print" function as well? OK, > so four functions. > > ikr? smells like OO spirit ... What's the meaning of `OO spirit'? > > ;;; -*- lexical-binding: t -*- > ;;; > ;;; this file: > ;;; https://dataswamp.org/~incal/emacs-init/align-from-left.el > > (require 'cl-lib) > > (let ((alf-regexp)) > (defun align-from-left (&optional set-regexp) > (interactive "p") > (let ((default-regexp "^\\|[[:punct:]]\\|[[:space:]][[:alnum:]]")) > (unless (stringp set-regexp) > (cl-case set-regexp > ( 4 (setq alf-regexp (read-regexp "regexp: "))) > (16 (setq alf-regexp default-regexp)) > ( t (unless alf-regexp > (setq alf-regexp default-regexp) ))))) > (let ((beg (point)) > (re (or (and (stringp set-regexp) set-regexp) > alf-regexp) )) > (when (re-search-backward re (line-beginning-position) t) > (while (looking-at "[[:space:]]") > (forward-char 1) ) > (insert (make-string (- beg (point)) ?\s)) )))) > (defalias 'alf #'align-from-left) > > (provide 'align-from-left) > > -- > underground experts united > https://dataswamp.org/~incal > > --=20 Assoc. Prof. Hongyi Zhao Theory and Simulation of Materials Hebei Vocational University of Technology and Engineering No. 473, Quannan West Street, Xindu District, Xingtai, Hebei province