Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!usenet.blueworldhosting.com!feeder01.blueworldhosting.com!border2.nntp.dca1.giganews.com!nntp.giganews.com!news.iecc.com!.POSTED!nerds-end From: wclodius@earthlink.net (William Clodius) Newsgroups: comp.compilers Subject: Re: LR(1) Parsing : Error Handling & Recovery Date: Sun, 20 Jul 2014 21:43:37 -0600 Organization: Compilers Central Lines: 19 Sender: news@iecc.com Approved: comp.compilers@iecc.com Message-ID: <14-07-045@comp.compilers> References: <14-07-023@comp.compilers> <14-07-024@comp.compilers> <14-07-030@comp.compilers> <14-07-031@comp.compilers> <14-07-041@comp.compilers> NNTP-Posting-Host: news.iecc.com X-Trace: miucha.iecc.com 1405951720 13290 2001:470:1f07:1126:0:676f:7373:6970 (21 Jul 2014 14:08:40 GMT) X-Complaints-To: abuse@iecc.com NNTP-Posting-Date: Mon, 21 Jul 2014 14:08:40 +0000 (UTC) Keywords: parse, theory,question Posted-Date: 21 Jul 2014 10:08:40 EDT X-submission-address: compilers@iecc.com X-moderator-address: compilers-request@iecc.com X-FAQ-and-archives: http://compilers.iecc.com Xref: csiph.com comp.compilers:1335 George Neuner wrote: > On Fri, 18 Jul 2014 13:41:53 -0600, wclodius@earthlink.net (William > Clodius) wrote: > > >I have memories that an LR(k) grammar can in principle be refactored > >to LR(1), but that in general an LL(k) grammar cannot be refactored to > >LL(1). > > LL(k) always can be refactored to single token lookahead, but it > causes an explosion of grammar states. E.g., given a single LL(3) > rule, an equivalent set of LL(1) rules must match every valid > combination of tokens at +1, +2 and +3. Rosenkerantz and Stearns appeared to show otherwise, Do you know of a problem with their proof? See