From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Emanuel Berg Newsgroups: gmane.emacs.help Subject: Re: curious why private variables are rare Date: Mon, 21 Nov 2022 13:48:50 +0100 Message-ID: <874jus3231.fsf@dataswamp.org> References: Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="31127"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:mUqVpsUXbCUF5PQDcpwZ61KBCSA= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Mon Nov 21 17:36:45 2022 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 1ox9mn-0007tX-Or for geh-help-gnu-emacs@m.gmane-mx.org; Mon, 21 Nov 2022 17:36:45 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ox9i9-0006fn-NR; Mon, 21 Nov 2022 11:32:00 -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 1ox6EQ-0007Lr-JF for help-gnu-emacs@gnu.org; Mon, 21 Nov 2022 07:49:03 -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 1ox6EO-0003tv-Kl for help-gnu-emacs@gnu.org; Mon, 21 Nov 2022 07:49:02 -0500 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1ox6EM-0006Xq-7o for help-gnu-emacs@gnu.org; Mon, 21 Nov 2022 13:48:58 +0100 X-Injected-Via-Gmane: http://gmane.org/ Mail-Followup-To: help-gnu-emacs@gnu.org Mail-Copies-To: never Received-SPF: pass client-ip=116.202.254.214; envelope-from=geh-help-gnu-emacs@m.gmane-mx.org; helo=ciao.gmane.io X-Spam_score_int: -15 X-Spam_score: -1.6 X-Spam_bar: - X-Spam_report: (-1.6 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.25, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Mon, 21 Nov 2022 11:31:48 -0500 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:141084 Archived-At: Samuel Wales wrote: > the usual thing is: > > (defvar var ...) > (defun fun ...) I hope not, as that introduces a global/dynamic/special variable ... > even when var is only used by fun. but you could do: > > (let ((var ...)) > (defun fun ...)) Yes, a lexical let-closure. Here [1] is an example of the two use cases I've found so far https://dataswamp.org/~incal/emacs-init/w3m/w3m-survivor.el The use-cases are (1) state variables that don't change between function calls (2) share variables between functions (The `declare-function' stuff is to shut up the byte-compiler.) > [at least, i /think/ you can do this with similar results from the > perspective of the function You think right! > the most obvious drawback of the latter would probably be > convenience in debugging/inspectability/discoverability. > re-using a variable name could be confusing. other than that > and extra indentation, i'm not sure if there are > big drawbacks. I don't think there are any drawbacks to closures, it's a good way, maybe the best way, to do (1) and (2). > it would limit scope so you don't pollute completion, > apropos, etc. you can eliminate prefix. no stomp on vars. If so, that's a problem for completion etc. [1] https://dataswamp.org/~incal/emacs-init/w3m/w3m-survivor.el -- underground experts united https://dataswamp.org/~incal