[antlr-interest] a new paper on ANTLR style grammars

Arnar Birgisson arnarb at oddi.is
Thu Nov 20 10:05:41 PST 2003


Hello there..

Am I correct in the assumption that the "|" operator in ANTLR is not
ordered, i.e. it has the same meaning as in BNF? If so, wouldn't the "/"
operator as defined in the paper be useful? I don't have much
perspective on this as I am yet a beginner, but wouldn't it at least
save us from inserting "options {greedy=true}:" and syntactic predicates
here and there?

Arnar

> -----Original Message-----
> From: Terence Parr [mailto:parrt at cs.usfca.edu] 
> Sent: 18. nóvember 2003 19:31
> To: antlr-interest at yahoogroups.com
> Subject: [antlr-interest] a new paper on ANTLR style grammars
> 
> 
> Folks,
> 
> Here is an upcoming paper to a conference that formally defines 
> grammars that operate like antlr: where alternatives have an implied 
> order.  Nicely formalizes the strategy of predicated parsing etc...
> 
http://www.brynosaurus.com//pub/lang/peg.pdf

Just as we have the syntactic predicate that says what the lookahead 
context must be, he has a "not predicate" that says what the lookahead 
cannot be.  This is very useful for such things as saying "match this 
rule, but only if not following in context by this next thing."  Really 
powerful.  moreover, he has a parser that demonstrates linear 
backtracking parsing by use of dynamic programming.  I will be studying 
his technique very closely before code gen for ANTLR. :)

Ter
--
Professor Comp. Sci., University of San Francisco
Creator, ANTLR Parser Generator, http://www.antlr.org
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