From lojban+bncCLr6ktCfBBCrn7DnBBoEFC2IUQ@googlegroups.com Tue Nov 23 11:02:21 2010 Received: from mail-qy0-f189.google.com ([209.85.216.189]) by chain.digitalkingdom.org with esmtp (Exim 4.72) (envelope-from ) id 1PKy87-0006mB-09; Tue, 23 Nov 2010 11:02:21 -0800 Received: by qyk1 with SMTP id 1sf16199748qyk.16 for ; Tue, 23 Nov 2010 11:02:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlegroups.com; s=beta; h=domainkey-signature:received:x-beenthere:received:received:received :received:received-spf:received:received:received:date:from:to :subject:message-id:mail-followup-to:references:mime-version :in-reply-to:x-original-sender:x-original-authentication-results :reply-to:precedence:mailing-list:list-id:list-post:list-help :list-archive:sender:list-subscribe:list-unsubscribe:content-type :content-disposition; bh=HnLDn3KbDDnn/S+jaljqOmHKGTtrZDS9B23iL9vuI7k=; b=6xuveIe+cCBY1UusCuDdTYFk/HlSmq4YAwJ6SDVGtSkAuUWJhdgMwD98d2yS2C8Ii3 wncjVkG//O26h8FRelSTRdyKAPfsvVsTHOiJF6juoz/yDHFuHapBlA5AcmB2VOQKrD1n fpnjkC9M+VjUPe2QTEN2fUjLkZY7z8HUwxJ8E= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlegroups.com; s=beta; h=x-beenthere:received-spf:date:from:to:subject:message-id :mail-followup-to:references:mime-version:in-reply-to :x-original-sender:x-original-authentication-results:reply-to :precedence:mailing-list:list-id:list-post:list-help:list-archive :sender:list-subscribe:list-unsubscribe:content-type :content-disposition; b=x7OeZgvDJ56FAumdH1Elw3Zvzb8VsCtnoR0OsZncS31HlWmmj4yQzPv0+EO/DyMh3H a+ZIZ1Mms0/sOc3rbO/ZhOdv7BIa/zczlKbMcAxYKHG0IImPFy5x+q4OWxdmySntlUZx uvgYqrWKuli5nYXQnJfzrSI/8uq8Cj1GMwQpc= Received: by 10.229.43.68 with SMTP id v4mr823446qce.40.1290538923426; Tue, 23 Nov 2010 11:02:03 -0800 (PST) X-BeenThere: lojban@googlegroups.com Received: by 10.224.136.206 with SMTP id s14ls1451801qat.0.p; Tue, 23 Nov 2010 11:02:02 -0800 (PST) Received: by 10.224.67.146 with SMTP id r18mr725196qai.13.1290538922817; Tue, 23 Nov 2010 11:02:02 -0800 (PST) Received: by 10.224.67.146 with SMTP id r18mr725195qai.13.1290538922796; Tue, 23 Nov 2010 11:02:02 -0800 (PST) Received: from mail-qy0-f178.google.com (mail-qy0-f178.google.com [209.85.216.178]) by gmr-mx.google.com with ESMTP id e24si220677qcg.5.2010.11.23.11.02.02; Tue, 23 Nov 2010 11:02:02 -0800 (PST) Received-SPF: neutral (google.com: 209.85.216.178 is neither permitted nor denied by best guess record for domain of alanpost@sunflowerriver.org) client-ip=209.85.216.178; Received: by mail-qy0-f178.google.com with SMTP id 33so3846599qyk.16 for ; Tue, 23 Nov 2010 11:02:02 -0800 (PST) Received: by 10.224.2.76 with SMTP id 12mr5901107qai.89.1290538922665; Tue, 23 Nov 2010 11:02:02 -0800 (PST) Received: from sunflowerriver.org (c-68-35-167-179.hsd1.nm.comcast.net [68.35.167.179]) by mx.google.com with ESMTPS id nb14sm3816327qcb.12.2010.11.23.11.02.00 (version=TLSv1/SSLv3 cipher=RC4-MD5); Tue, 23 Nov 2010 11:02:01 -0800 (PST) Date: Tue, 23 Nov 2010 12:01:57 -0700 From: ".alyn.post." To: lojban@googlegroups.com Subject: Re: [lojban] rp-expression-tail ordered choice with empty grouping Message-ID: <20101123190157.GG10838@alice.local> Mail-Followup-To: lojban@googlegroups.com References: <20101123184352.GE10838@alice.local> <20101123185211.GU9301@digitalkingdom.org> Mime-Version: 1.0 In-Reply-To: <20101123185211.GU9301@digitalkingdom.org> X-Original-Sender: alyn.post@lodockikumazvati.org X-Original-Authentication-Results: gmr-mx.google.com; spf=neutral (google.com: 209.85.216.178 is neither permitted nor denied by best guess record for domain of alanpost@sunflowerriver.org) smtp.mail=alanpost@sunflowerriver.org Reply-To: lojban@googlegroups.com Precedence: list Mailing-list: list lojban@googlegroups.com; contact lojban+owners@googlegroups.com List-ID: List-Post: , List-Help: , List-Archive: Sender: lojban@googlegroups.com List-Subscribe: , List-Unsubscribe: , Content-Type: text/plain; charset=ISO-8859-1 Content-Disposition: inline On Tue, Nov 23, 2010 at 10:52:11AM -0800, Robin Lee Powell wrote: > On Tue, Nov 23, 2010 at 11:43:52AM -0700, .alyn.post. wrote: > > What does the following production in the lojban grammar mean?: > > > > rp-expression-tail <- rp-expression operator rp-expression-tail / > > () > > > > Do I understand that to mean 'the sequence of rp-expression, > > operator, and rp-expression-tail OR nothing?' Could the above > > also be expressed: > > > > rp-expression-tail <- (rp-expression operator rp-expression-tail)? > > > > And if so, why the odd way of specifying it? I'm weak on pitfalls > > of recursive behavior in grammars, am I looking at a workaround > > related to that? > > Yes, and it mostly doesn't work. Lojban's RPN (which, if I have my > druthers, the next version of the language will not have, by the > way) is left-recursive, which is problematic. See the peg mailing > list for various solutions, but IMO since a number of PEG parser > generators handle this on their own, I think we should just have it > be left-recursive and say that people have to use such a generator. > > If you can figure out how to fix it in in the rules so the right > behaviour pops out, though, *please* do so. There are links to > papers on the peg mailing list; it came up just last week; "*[1]* > *Packrat Parsers Can Support Left Recursion*, Alessandro Warth, > James R. Douglass, and Todd Millstein (2008)" is the citation I'm > seeing at a brief glance. > Great. I saw that thread and ignored it as not being relevant in the moment, but I'm happy to read it and play with it when I get to that point. I've downloaded the paper and cached it with this problem, as I'm a bit ahead of myself with it. -Alan -- .i ko djuno fi le do sevzi -- You received this message because you are subscribed to the Google Groups "lojban" group. To post to this group, send email to lojban@googlegroups.com. To unsubscribe from this group, send email to lojban+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/lojban?hl=en.