From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Overlays as an AA-tree Date: Wed, 21 Sep 2016 12:24:30 -0400 Message-ID: References: <87d1jylv43.fsf@fastmail.com> <83k2e5fdmo.fsf@gnu.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1474475195 32368 195.159.176.226 (21 Sep 2016 16:26:35 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 21 Sep 2016 16:26:35 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux) Cc: emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Wed Sep 21 18:26:32 2016 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 1bmkLd-00061p-L5 for ged-emacs-devel@m.gmane.org; Wed, 21 Sep 2016 18:26:13 +0200 Original-Received: from localhost ([::1]:43720 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bmkLc-000231-0P for ged-emacs-devel@m.gmane.org; Wed, 21 Sep 2016 12:26:12 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:57914) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bmkK6-0000mY-OJ for emacs-devel@gnu.org; Wed, 21 Sep 2016 12:24:39 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bmkK4-0008Ms-Nv for emacs-devel@gnu.org; Wed, 21 Sep 2016 12:24:37 -0400 Original-Received: from ironport2-out.teksavvy.com ([206.248.154.181]:2574) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bmkJz-0008LB-P1; Wed, 21 Sep 2016 12:24:31 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: A0CaBgALW9BX/xfxd0tdHAEBBAEBgy0BAQEBAR6ETYVQsXmGFgQCAoFpPRABAgEBAQEBAQFeJ4RiAQEDAScvIxALNBIUGA0kiFUIvFUBAQEHAiWKfYocAQSZWZkNhguPDYE+NR+CaBuBaSCGCgEBAQ X-IPAS-Result: A0CaBgALW9BX/xfxd0tdHAEBBAEBgy0BAQEBAR6ETYVQsXmGFgQCAoFpPRABAgEBAQEBAQFeJ4RiAQEDAScvIxALNBIUGA0kiFUIvFUBAQEHAiWKfYocAQSZWZkNhguPDYE+NR+CaBuBaSCGCgEBAQ X-IronPort-AV: E=Sophos;i="5.30,296,1470715200"; d="scan'208";a="273150136" Original-Received: from 75-119-241-23.dsl.teksavvy.com (HELO pastel.home) ([75.119.241.23]) by smtp.teksavvy.com with ESMTP; 21 Sep 2016 12:24:30 -0400 Original-Received: by pastel.home (Postfix, from userid 20848) id AB75B605D7; Wed, 21 Sep 2016 12:24:30 -0400 (EDT) In-Reply-To: <83k2e5fdmo.fsf@gnu.org> (Eli Zaretskii's message of "Wed, 21 Sep 2016 18:58:55 +0300") X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 206.248.154.181 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:207665 Archived-At: >> > Speaking of which, is the byte position stored in a marker of any >> > significance in an overlay? Otherwise I could at least get rid of >> > those. >> AFAIK, the byte-position of markers is used, but the byte-position of >> overlays isn't, so you should be able to get rid of them. > Why bother? AFAIK there'd be no benefit at all until/unless you add extra code to try and use those byte-positions somewhere. I know of two cases where we use such byte-positions, currently: - in goto-char, but that never receives an overlay as argument. - when converting charpos <-> bytepos (where we use the table of markers as a kind of cache of existing translations) The second use would probably better be served by a separate table: - This hack of (ab)using markers can occasionally lead to bad performance because it makes the charpos<->bytepos conversion O(N) in the worst case where N is the number of markers which can get very large). - It can also lead to bad performance in the other case: lack of markers around the "destination" makes the conversion O(N) in the worst case where N is the size of the displacement. Stefan