From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier via Users list for the GNU Emacs text editor Newsgroups: gmane.emacs.help Subject: Mutation - do you understand it really? (was: Closures - do you understand them well?) Date: Sat, 10 Dec 2022 11:28:43 -0500 Message-ID: References: <87lenh7vrn.fsf@web.de> <87tu25d77o.fsf@gnu.org> <87h6y5pt8k.fsf@web.de> <87bkodpqnk.fsf@web.de> <87k030tlfh.fsf@web.de> <87ilikxgkd.fsf@web.de> <87y1rf1txv.fsf@gnu.org> Reply-To: Stefan Monnier Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="9915"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) To: help-gnu-emacs@gnu.org Cancel-Lock: sha1:UtyZzNUfvFtd07DL6wuwhK/LRYo= Original-X-From: help-gnu-emacs-bounces+geh-help-gnu-emacs=m.gmane-mx.org@gnu.org Sat Dec 10 17:29:26 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 1p42j7-0002SH-L2 for geh-help-gnu-emacs@m.gmane-mx.org; Sat, 10 Dec 2022 17:29:25 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1p42ib-0005CB-Ox; Sat, 10 Dec 2022 11:28:53 -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 1p42iZ-0005Bm-Su for help-gnu-emacs@gnu.org; Sat, 10 Dec 2022 11:28:51 -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 1p42iY-0005iP-FG for help-gnu-emacs@gnu.org; Sat, 10 Dec 2022 11:28:51 -0500 Original-Received: from list by ciao.gmane.io with local (Exim 4.92) (envelope-from ) id 1p42iW-0001jD-Rr for help-gnu-emacs@gnu.org; Sat, 10 Dec 2022 17:28:48 +0100 X-Injected-Via-Gmane: http://gmane.org/ 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-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:141584 Archived-At: Tassilo Horn [2022-12-10 10:34:24] wrote: > Michael Heerdegen writes: >>> Write an expression that returns a list of 100 functions accepting >>> zero arguments. `funcall'ing the Nth function must return N. Use a >>> `while' loop or whatever you like but please not `dolist' or any >>> tool that already handles this "problem" specifically. >> >> Would this be a valid solution? >> >> #+begin_src emacs-lisp >> (let ((i 0) (funs)) >> (while (<= (cl-incf i) 100) >> (push (apply-partially #'identity i) funs)) >> (nreverse funs)) >> #+end_src > > Apparently it works although I don't see why. BTW, for those people here who find this all confusing. I'll point out that the culprit is not "closures" but `setq` (here hidden within `cl-incf`). Immutable variables are just a lot better behaved (and easier to work with for the compiler, which is why GCC/LLVM/... use an SSA conversion to replace those nasty mutable variables with immutable ones). Stefan