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: Effect of lexical binding upon function paramaters Date: Sat, 05 Nov 2022 17:25:24 +0100 Message-ID: <87h6zdfjwr.fsf@dataswamp.org> References: <87k04ci43r.fsf@dataswamp.org> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="3689"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:VnGv//tw0yaPSs2cm9ELE7azcxo= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Sun Nov 06 15:22:20 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 1orgXT-0000j7-Ph for geh-help-gnu-emacs@m.gmane-mx.org; Sun, 06 Nov 2022 15:22:19 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1orgWk-0004Ts-2B; Sun, 06 Nov 2022 09:21:34 -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 1orLzD-0006XT-HD for help-gnu-emacs@gnu.org; Sat, 05 Nov 2022 12:25:35 -0400 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 1orLzB-0000Hp-Rh for help-gnu-emacs@gnu.org; Sat, 05 Nov 2022 12:25:35 -0400 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1orLz9-00045K-OJ for help-gnu-emacs@gnu.org; Sat, 05 Nov 2022 17:25:31 +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: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.249, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Sun, 06 Nov 2022 09:21:33 -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: , Original-Sender: "help-gnu-emacs" Errors-To: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.help:140725 Archived-At: Heime wrote: >>> What I can see from this test below, formal parameters >>> ("arguments" in standard information interchange) are >>> always dynamic under dynabound, and always static under >>> lexical >> >> Yup. Same holds for the var bound by `condition-case`. >> The binding constructs that can be "either/or" are `let` >> and `let*` (via `lexical-let` for the dynbound dialect and >> via `defvar` for the lexbound dialect). > > So what are we to do Use lexbound, so far by adding this, as you know ;;; -*- lexical-binding: t -*- as the first line of every Elisp source file. Byte-compile the source, it will warn you for unused lexical variables for example. Avoid global lexical variables (created with `setq' in the absence of another variable with the same name), instead use let-closures for the 'persistent value' (state) and share-between-functions use cases. If you desire to create a global variable in the "option" sense, i.e. you want to introduce something like the `fill-column' variable, because you imagine it will be used across a range of functions and different settings (ha), even be used by future functions - then use `defvar'. Use `let'/`let*' for function-local variables to organize the code neatly and break up computations into smaller steps, this will be the number one use case, however let/let* can also be used in the "with-option-temporarily-as" sense, in that case that variable must already exist and be dynamic/special, so either it is an Emacs option already _or_ you have created it as described above, with `defvar'. Note that you can mix this up, let/let* handles it all for you transparently, just spell everything correctly, okay? In the example below, we see that `fill-column' is already a dynamic/special variable, i.e. a global option. In a lexbound `let', we create "a" and "b" and since they don't exist they default to lexical. `fill-column' OTOH is temporarily assigned a new value and remains dynamic/special. ;;; -*- lexical-binding: t -*- fill-column ; 62 (special-variable-p 'fill-column) ; t, i.e. dynamic/special (let ((a 1) ; lexical/static (b 2) ; lexical/static (fill-column 10) ) ; dynamic/special (fill-paragraph) ) ; eval me, then change `fill-column' to say 99 and retry fill-column ; 62 -- underground experts united https://dataswamp.org/~incal