From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: emacs-26 8f18d12: Improve documentation of decoding into a unibyte buffer Date: Tue, 28 May 2019 18:18:07 +0300 Message-ID: <83woiazjyo.fsf@gnu.org> References: <20190525191039.14136.23307@vcs0.savannah.gnu.org> <20190525191040.CCD6C207F5@vcs0.savannah.gnu.org> <88F01F35-BE24-4F6E-B832-64AFE28CD06B@gnu.org> Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="77869"; mail-complaints-to="usenet@blaine.gmane.org" Cc: emacs-devel@gnu.org To: Stefan Monnier Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Tue May 28 17:18:57 2019 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1hVdsO-000K5X-Sc for ged-emacs-devel@m.gmane.org; Tue, 28 May 2019 17:18:56 +0200 Original-Received: from localhost ([127.0.0.1]:36617 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hVdsN-0006Eh-U5 for ged-emacs-devel@m.gmane.org; Tue, 28 May 2019 11:18:55 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:60359) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hVdrb-0006EW-6x for emacs-devel@gnu.org; Tue, 28 May 2019 11:18:08 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]:32810) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hVdrZ-00054i-5n; Tue, 28 May 2019 11:18:05 -0400 Original-Received: from [176.228.60.248] (port=3802 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1hVdrU-0004Dc-HQ; Tue, 28 May 2019 11:18:02 -0400 In-reply-to: (message from Stefan Monnier on Tue, 28 May 2019 07:55:40 -0400) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] 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:237109 Archived-At: > From: Stefan Monnier > Cc: emacs-devel@gnu.org > Date: Tue, 28 May 2019 07:55:40 -0400 > > >> Hence according to my reading of the code, this call to > >> string-as-unibyte will always just return its argument unchanged. > > That's not entirely true, because encode-coding-char can return a multibyte > > string. > > That's weird. When would that happen? "Use the source, Luke!" (let* ((str1 (string-as-multibyte (string char))) (str2 (string-as-multibyte (string char char))) (found (find-coding-systems-string str1)) enc1 enc2 i1 i2) (if (and (consp found) (eq (car found) 'undecided)) str1 <<<<<<<<<<<<<<<<<<<<<<<<< If we return here, the value is str1, which is a multibyte string, see how it was calculated. The easiest use case is this: (multibyte-string-p (encode-coding-char ?a 'utf-8)) => t I didn't think enough about this to figure out if there can be less trivial use cases. If you can describe all the cases where find-coding-systems-string will return a list whose 'car' is 'undecided', my hat off to you.