Re: Parsing Expression Grammar

"Oliver Wong" <owong@castortech.com>
3 Sep 2005 15:23:51 -0400

          From comp.compilers

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From: "Oliver Wong" <owong@castortech.com>
Newsgroups: comp.compilers
Date: 3 Sep 2005 15:23:51 -0400
Organization: GlobeTrotter
References: 05-08-115 05-09-013
Keywords: parse

"A Pietu Pohjalainen" <pohjalai@cc.helsinki.fi> wrote in message
> Uhm, using context free languages, it is always possible to write
> ambiguous grammars, and actually there are context free languages that
> are inherently ambiguous. So, you either have to deal with the
> ambiguousity in the CFG's (e.g. precedence, associativity), or not use
> context free languages.


        Sorry, I only know a bit about theory of computation, but I
thought ambiguity was a property of grammars, and not of
languages. Since a language is just a set of strings, how can a
language itself be ambiguous? I understand that perhaps there exists a
language which cannot be expressed by an unambiguous context free
grammar, but might there not exist another way (i.e. not using CFGs)
to express the language which is unambiguous?


        - Oliver


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