From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Tomas Hlavaty Newsgroups: gmane.emacs.devel Subject: Re: combining cond and let, to replace pcase. Date: Tue, 28 Nov 2023 15:25:15 +0100 Message-ID: <87v89mymyc.fsf@neko.mail-host-address-is-not-set> References: <87v89t7y13.fsf@neko.mail-host-address-is-not-set> <87zfyz15w1.fsf@neko.mail-host-address-is-not-set> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="11289"; mail-complaints-to="usenet@ciao.gmane.io" Cc: rms@gnu.org, emacs-devel@gnu.org To: Yuri Khan Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Tue Nov 28 15:27:01 2023 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 1r7z3E-0002lE-EF for ged-emacs-devel@m.gmane-mx.org; Tue, 28 Nov 2023 15:27:00 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1r7z25-0002ue-ND; Tue, 28 Nov 2023 09:25:49 -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 1r7z1f-0002oH-74 for emacs-devel@gnu.org; Tue, 28 Nov 2023 09:25:27 -0500 Original-Received: from logand.com ([37.48.87.44]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1r7z1d-0001ms-5S; Tue, 28 Nov 2023 09:25:22 -0500 Original-Received: by logand.com (Postfix, from userid 1001) id CD7A219E77A; Tue, 28 Nov 2023 15:25:17 +0100 (CET) X-Mailer: emacs 28.2 (via feedmail 11-beta-1 I) In-Reply-To: Received-SPF: pass client-ip=37.48.87.44; envelope-from=tom@logand.com; helo=logand.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham 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:313320 Archived-At: On Tue 28 Nov 2023 at 00:59, Yuri Khan wrote: > So, for the intended effect of exiting the =E2=80=98or=E2=80=99 when a br= anch is > taken, one has to make sure to terminate that branch with a truthy > expression: > > (or > (when CONDITION > do-this-possibly-returning-nil > :break) > (let (BINDINGS) > do-something-else-possibly-returning-nil > :break) > =E2=80=A6more branches=E2=80=A6) > > Also, a =E2=80=98cond=E2=80=99 or a =E2=80=98pcase=E2=80=99 form will ret= urn the result of the branch > taken, which can be nil. An =E2=80=98or=E2=80=99 form will return the re= sult of the > branch taken, as long as it is not nil. A branch that returns nil will > result in evaluation of the next branch. same issue with cond: (cond ((let (bindings) 'do-something-else-possibly-returning-nil nil)) (t :default)) =3D> :default (cond ((let (bindings) 'do-something-else-possibly-returning-nil :break)) (t :default)) =3D> :break