From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Lars Ingebrigtsen Newsgroups: gmane.emacs.devel Subject: Re: encode-time vs decode-time Date: Wed, 31 Jul 2019 21:03:07 +0200 Message-ID: <87v9viuivo.fsf@mouse.gnus.org> References: <502b23f8-58ed-38ff-ae50-fae391129a10@cs.ucla.edu> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="35928"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) Cc: Andy Moreton , emacs-devel@gnu.org To: Paul Eggert Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Wed Jul 31 21:03:23 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 (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hstsg-0009Br-Md for ged-emacs-devel@m.gmane.org; Wed, 31 Jul 2019 21:03:22 +0200 Original-Received: from localhost ([::1]:43780 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hstsf-0001QT-2B for ged-emacs-devel@m.gmane.org; Wed, 31 Jul 2019 15:03:21 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:34005) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hstsZ-0001QL-1w for emacs-devel@gnu.org; Wed, 31 Jul 2019 15:03:16 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hstsX-0006iA-Kj for emacs-devel@gnu.org; Wed, 31 Jul 2019 15:03:15 -0400 Original-Received: from quimby.gnus.org ([80.91.231.51]:48452) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hstsX-0006hb-DK for emacs-devel@gnu.org; Wed, 31 Jul 2019 15:03:13 -0400 Original-Received: from 77.18.62.220.tmi.telenormobil.no ([77.18.62.220] helo=sandy) by quimby.gnus.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hstsS-00080D-1W; Wed, 31 Jul 2019 21:03:10 +0200 In-Reply-To: <502b23f8-58ed-38ff-ae50-fae391129a10@cs.ucla.edu> (Paul Eggert's message of "Tue, 30 Jul 2019 12:54:21 -0500") X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 80.91.231.51 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.23 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:239056 Archived-At: Paul Eggert writes: >> this is very confusing indeed > To some extent the confusion is inherent: there are a lot of useful > ways to represent and manipulate times, and people unfamiliar with the > issues will find this complexity confusing. That being said, it would > be good to simplify the Emacs API for time without significantly > hurting functionality or compatibility. > > So, how about this idea. First we go along the lines of your > suggestion, and change decode-time to return a ninth slot with a > numerator-denominator pair that preserves all the precision of its > argument. Second, we change (encode-time TIME t) so that it also > preserves all the precision of its argument. This will cause > (encode-time (decode-time TIME) t) to return a value equivalent to > TIME, which will simplify roundtripping. I think this sounds workable, but I think it would be even better to introduce some new functions instead of overloading our poor encode-time function. When you did the major sanitation in this area last year (which was overall a very good thing), you did stuff like - (now (string-to-number (format-time-string "%s"))) + (now (encode-time nil 'integer)) and - (now (float-time)) + (now (encode-time nil 'integer)) and many similar transforms. The new code is definitely better than the old code, and it's not more cryptic than it used to be, really. However, I think it would have been even better to introduce a new function to enable people who are unfamiliar with how this all works to just read the code and understand what it's doing. So I think the things up above there should really be calls to a new function `get-current-time', that returns the same thing as `(encode-time nil 'integer)'. It should default to `integer', but can have an optional argument that says what form of "internal second time format" to return (i.e., `list', `t'). And then, finally, I think there should be a function to convert between these "internal second time" formats. Like... `convert-time-format', which would be like `(encode-time time 'list)' (etc). And then leave encode-time/decode-time a simple pair that would do nothing but convert between "internal second time format" and "decoded time format". -- (domestic pets only, the antidote for overdose, milk.) bloggy blog: http://lars.ingebrigtsen.no