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: apply function Date: Mon, 07 Aug 2023 20:44:32 +0200 Message-ID: <878ramk7zj.fsf@dataswamp.org> References: <7bea436f-42ab-4fa4-9b28-e5fe34776691@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="18459"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:R5KjaL+kDfJqKjL5JP44Nyj726E= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Tue Aug 08 14:26:07 2023 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 1qTLmo-0004Xq-Vy for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 08 Aug 2023 14:26:06 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qTLme-0002Sv-LM; Tue, 08 Aug 2023 08:25:58 -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 1qT5Dw-00074N-1P for help-gnu-emacs@gnu.org; Mon, 07 Aug 2023 14:45:00 -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 1qT5Du-0007wK-Au for help-gnu-emacs@gnu.org; Mon, 07 Aug 2023 14:44:59 -0400 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1qT5Dh-0004k8-NK for help-gnu-emacs@gnu.org; Mon, 07 Aug 2023 20:44:45 +0200 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: Tue, 08 Aug 2023 08:25:38 -0400 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:144686 Archived-At: Karan Ahlawat wrote: >> What might be the reasons for doing so ? > > The most common use case I've seen for this is that apply > can take in a list as the arguments to the function, where > a list would not work, and then spread the elements of the > list as individual arguments. So > >     (+ (list 1 2 3)) > > doesn't work, but doing > >     (apply #'+ (list 1 2 3)) ; outputs 6 > > does work The other use case is when one has the function stored in a variable or provided as an argument, i.e. it is not known from the static code perspective what function will be executed. Observe: (require 'cl-lib) (defun test-final-line-f (fun pos-list) (cl-loop for p in pos-list do (goto-char p) (apply fun nil) )) Here is a better example, maybe, where the function is either `re-search-backward' or `re-search-forward' depending on the argument REV (as in "reverse"). ;;; -*- lexical-binding: t -*- ;; ;; this file: ;; https://dataswamp.org/~incal/emacs-init/regexp.el (require 'cl-lib) (require 'dwim) (defun replace-regexp-1 (re rep &optional beg end rev) (interactive `(,(read-string "regexp: ") ,(read-string "replace: ") ,@(use-region t) ,current-prefix-arg)) (or beg (setq beg (point-min))) (or end (setq end (point-max))) (pcase-let ((`(,start ,sfun ,stop) (if rev (list end #'re-search-backward beg) (list beg #'re-search-forward end) ))) (save-excursion (goto-char start) (let ((c 0)) (while (apply sfun re stop '(t)) (cl-incf c) (replace-match rep) ) (message "matches replaced: %d" c) )))) (defalias 'rr #'replace-regexp-1) (provide 'regexp) Source: https://dataswamp.org/~incal/emacs-init/dwim.el https://dataswamp.org/~incal/emacs-init/measure.el https://dataswamp.org/~incal/emacs-init/regexp.el -- underground experts united https://dataswamp.org/~incal