From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: "Garreau\, Alexandre" Newsgroups: gmane.emacs.devel Subject: Re: Why is there no `until' in elisp? Date: Fri, 19 Oct 2018 20:08:07 +0200 Message-ID: <87k1mdn720.fsf@portable.galex-713.eu> References: <87murdu6to.fsf@portable.galex-713.eu> <87y3axjusi.fsf@portable.galex-713.eu> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1539972381 31582 195.159.176.226 (19 Oct 2018 18:06:21 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 19 Oct 2018 18:06:21 +0000 (UTC) User-Agent: Gnus (5.13), GNU Emacs 25.1.1 (i686-pc-linux-gnu) Cc: emacs-devel@gnu.org To: Stefan Monnier Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Fri Oct 19 20:06:17 2018 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1gDZA7-000834-SV for ged-emacs-devel@m.gmane.org; Fri, 19 Oct 2018 20:06:15 +0200 Original-Received: from localhost ([::1]:52116 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gDZCE-0003Bx-6L for ged-emacs-devel@m.gmane.org; Fri, 19 Oct 2018 14:08:26 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:44080) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gDZC7-0003Bk-FX for emacs-devel@gnu.org; Fri, 19 Oct 2018 14:08:20 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gDZC4-000838-QS for emacs-devel@gnu.org; Fri, 19 Oct 2018 14:08:17 -0400 Original-Received: from portable.galex-713.eu ([2a00:5884:8305::1]:37466) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gDZC4-0007rc-IT for emacs-devel@gnu.org; Fri, 19 Oct 2018 14:08:16 -0400 Original-Received: from localhost ([::1] helo=portable.galex-713.eu) by portable.galex-713.eu with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1gDZBw-00028P-8G; Fri, 19 Oct 2018 20:08:08 +0200 X-GPG-FINGERPRINT: E109 9988 4197 D7CB B0BC 5C23 8DEB 24BA 867D 3F7F X-Accept-Language: fr, en, it, eo In-Reply-To: (Stefan Monnier's message of "Fri, 19 Oct 2018 11:34:01 -0400") X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2a00:5884:8305::1 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 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.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:230502 Archived-At: On 2018-10-19 at 11:34, Stefan Monnier wrote: >> think `until' should refer to the version I gave because this is >> probably the one which is going to be implemented naively by most >> people, > > BTW, this is only true if those people have to implement it on top of > the pre-existing `while`. Once you go down to implementing it as > a sequence of byte-codes, then the `until` you proposed is no simpler > than the one I proposed. > > So reversing your argument, if Elisp had my `until` and you wanted to > define `while` would you define it to return nil or to return t? > IOW would you define it as > > (defmacro while (test &rest body) > `(until (not ,test) ,@body)) > or > (defmacro while (test &rest body) > `(progn (until (not ,test) ,@body) nil)) > > ? The former, you=E2=80=99re right. What I was saying was mainly to keep consistence, only then I was finding that, for me, returning the body of a loop looks more logical than returning its condition (as you said, this only makes sense for until). But now I saw the working of `while' match the semantics you gave, I believe your version is better to be implemented, in elisp.