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: puzzle with string permutations [photo] Date: Tue, 07 Jun 2022 15:53:11 +0200 Message-ID: <87bkv4r35k.fsf@dataswamp.org> References: <87r141rn8n.fsf@dataswamp.org> <87wndtrlpg.fsf@mbork.pl> <87k09ssycf.fsf@dataswamp.org> <87fskgsy4c.fsf@dataswamp.org> <87bkv4sxnu.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="36837"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:QU7uTR6d8ckm6g/VyNHRjJUBZn4= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Tue Jun 07 15:54:09 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 1nyZer-0009Lw-3p for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 07 Jun 2022 15:54:09 +0200 Original-Received: from localhost ([::1]:45168 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nyZeq-0005ry-7y for geh-help-gnu-emacs@m.gmane-mx.org; Tue, 07 Jun 2022 09:54:08 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:40742) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nyZeI-0005q4-C8 for help-gnu-emacs@gnu.org; Tue, 07 Jun 2022 09:53:34 -0400 Original-Received: from ciao.gmane.io ([116.202.254.214]:44226) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nyZe9-0004lj-S5 for help-gnu-emacs@gnu.org; Tue, 07 Jun 2022 09:53:34 -0400 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1nyZe2-0007uf-O2 for help-gnu-emacs@gnu.org; Tue, 07 Jun 2022 15:53:18 +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, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=no 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" Xref: news.gmane.io gmane.emacs.help:137514 Archived-At: Emanuel Berg wrote: >>>> (calc-eval "fact(5)") => "120" >>>> (calc-eval "fact(10)") => "3628800" >>> >>> Indeed, however that isn't lispy either ... > > Perhaps better, as no recursion. > > (require 'cl-lib) > > (defun cl-faculty (n) > (cl-loop with prod = 1 > for i from 2 to n do > (setq prod (* i prod)) > finally return prod) ) > ;; (cl-faculty 5) ; 120 > ;; (cl-faculty 10) ; 3 628 800 Oh, that's right, we didn't think of duplicates. You can remove them with `cl-remove-duplicates' like this (cl-remove-duplicates (cl-remove-if-not (lambda (w) (spell-word w)) (string-perms str)) :test #'string=) ^^ ( Indeed, Lisp is a fun language! =) ) but to do it without counting I think the formula is n!/(n - r)! where n is the size of the set - here 26, as (length (alphabet t)) ; 26 [1] and r is the number of items to be picked and arranged, or here the length of the word. This field of mathematics is called combinatorics BTW, maybe because you combine a lot of stuff to solve it's problems LOL :) [1] https://dataswamp.org/~incal/emacs-init/abc.el https://www.youtube.com/watch?v=6M3Kg1_5xFw -- underground experts united https://dataswamp.org/~incal