Path: csiph.com!x330-a1.tempe.blueboxinc.net!newsfeed.hal-mli.net!feeder3.hal-mli.net!newsfeed.hal-mli.net!feeder1.hal-mli.net!border3.nntp.dca.giganews.com!border1.nntp.dca.giganews.com!nntp.giganews.com!news.iecc.com!nerds-end
From: Borneq <a.moderacja@gmail.com>
Newsgroups: comp.compilers
Subject: How detect cycle in grammar ?
Date: Sun, 20 Nov 2011 08:48:47 -0800 (PST)
Organization: Compilers Central
Lines: 15
Sender: news@iecc.com
Approved: comp.compilers@iecc.com
Message-ID: <11-11-041@comp.compilers>
NNTP-Posting-Host: news.iecc.com
X-Trace: leila.iecc.com 1321891701 80510 64.57.183.58 (21 Nov 2011 16:08:21 GMT)
X-Complaints-To: abuse@iecc.com
NNTP-Posting-Date: Mon, 21 Nov 2011 16:08:21 +0000 (UTC)
Keywords: parse, question
Posted-Date: 21 Nov 2011 11:08:21 EST
X-submission-address: compilers@iecc.com
X-moderator-address: compilers-request@iecc.com
X-FAQ-and-archives: http://compilers.iecc.com
Xref: x330-a1.tempe.blueboxinc.net comp.compilers:343

A->B
B->B
This grammar is not correct, B is looped.

A->B
B->C
C->A
This another grammar, cycle can be arbitrarily long.
Is cycle when First(Nonterminal) not contain any terminal, even not
epsilon?

A->B
B->   (=B->epsilon)
in first A and B is epsilon