From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Ihor Radchenko Newsgroups: gmane.emacs.devel Subject: Re: cond* Date: Sat, 03 Feb 2024 16:52:54 +0000 Message-ID: <87eddtjxqx.fsf@localhost> References: <87frzuae9n.fsf@posteo.net> <871qbatqc8.fsf@posteo.net> <87wmsz7lzn.fsf@posteo.net> <87edf1m7lq.fsf@localhost> <87cyui76l9.fsf@localhost> <871qauy1io.fsf@localhost> <87wmsjyi2h.fsf@localhost> <875xz86tgu.fsf@localhost> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="13365"; mail-complaints-to="usenet@ciao.gmane.io" Cc: emacs-devel@gnu.org To: rms@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sat Feb 03 17:50:36 2024 Return-path: Envelope-to: ged-emacs-devel@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 1rWJDw-0003GN-Aq for ged-emacs-devel@m.gmane-mx.org; Sat, 03 Feb 2024 17:50:36 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rWJD5-0003HW-2W; Sat, 03 Feb 2024 11:49:43 -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 1rWJD3-0003HJ-PO for emacs-devel@gnu.org; Sat, 03 Feb 2024 11:49:41 -0500 Original-Received: from mout01.posteo.de ([185.67.36.65]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rWJCs-0005BN-2z for emacs-devel@gnu.org; Sat, 03 Feb 2024 11:49:41 -0500 Original-Received: from submission (posteo.de [185.67.36.169]) by mout01.posteo.de (Postfix) with ESMTPS id 4CF99240028 for ; Sat, 3 Feb 2024 17:49:26 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.net; s=2017; t=1706978966; bh=wKNMEsq+812ziqTdLPqbEafbgaBGTzO1pX6whYXQHZM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type: From; b=WVgXSf5puiI6NUehwjizr87NtDk6a4WeQhFz/V+Yt/wA4oDnIPsY1ut1a4ejo2qHW XcbZU4CI0G4opQ+Zu6yUf9YiHEMsrplhS2hnlaeAMVre/ODou0RQgbfQNEI0Hi+z5S hSaZAkrbPg9Pjrz0djRlBRZJ1S8ccAtk4ZWAydJgy8ubgQtm4iFwMx+jI6R9vFrPVY 02u+p5hrjdLvmitAlNuZzZ7KYiy1r9NxbrbOXrcz2nZSpzwfFe9EUOKDp5wIq7efnC KG0HpHq38UtqlLUnKSMu+TsGjhnNRwhe0t5e1V0R8K8KPZp/hj/8VdT7pMsisGQH7K zJwlWX0C9lHRg== Original-Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4TRzBY1wKzz6vyt; Sat, 3 Feb 2024 17:49:24 +0100 (CET) In-Reply-To: Received-SPF: pass client-ip=185.67.36.65; envelope-from=yantar92@posteo.net; helo=mout01.posteo.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:315835 Archived-At: Richard Stallman writes: > > (let ((list-of-three '(1 2))) > > (cond* ((match* `(,x ,y ,z) list-of-three)) > > ((< 2 (+ x y z)) > > 'success))) ; => (wrong-type-argument number-or-marker-p nil) > > That is not exactly a bug, but it is an unclarity in the design. > ... I think that we are drifting away from the original topic I raised in this discussion branch. I originally pointed to a missing feature of cond* - inability to match against multiple values as in (defun yant/list-sum (list) (apply #'+ list)) (pcase '(1 2 3) ((and `(,x ,y ,z) (app yant/list-sum (and sum (guard (< 2 sum))))) (format "%d + %d + %d = %d; 2 is < %d" x y z sum sum))) ; => "1 + 2 + 3 = 6; 2 is < 6" You suggested how the same can be done with cond*. However, your example does not work, throwing wrong-type-argument, when the first match fails. So, I still view the above scenario as a missing feature in cond*. What I imagine as an addition to cond* is something like: (let ((list-of-three '(1 2))) (cond* ((and (match* `(,x ,y ,z) list-of-three) (match* (constrain x (< 2 x)) (yant/list-sum list-of-three))) 'success))) This way, multiple values can be matched against. > But it raises the question of what a non-exit match* clause should do > when it does not match. What do you think it should do? > > The idea that occurs to me is this: bind all those variables, > initializing by matching those that can match, and initializing the > rest to nil. I'd rather make cond* throw an error in such scenario. Otherwise, it will be impossible to distinguish between "no match" and something like (let ((list-of-three '(nil nil nil))) (cond* ((match* `(,x ,y ,z) list-of-three) ((and (null x) (null y) (null z)) "We matched '(nil nil nil), or did we?")))) (let ((list-of-three 'not-a-list)) (cond* ((match* `(,x ,y ,z) list-of-three) ((and (null x) (null y) (null z)) "We matched '(nil nil nil), or did we?")))) -- Ihor Radchenko // yantar92, Org mode contributor, Learn more about Org mode at . Support Org development at , or support my work at