Re: Several parsing questions

Joachim Durchholz <joachim_d@gmx.de>
17 Mar 2002 22:40:25 -0500

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Re: Several parsing questions joachim_d@gmx.de (Joachim Durchholz) (2002-03-17)
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From: Joachim Durchholz <joachim_d@gmx.de>
Newsgroups: comp.compilers
Date: 17 Mar 2002 22:40:25 -0500
Organization: Compilers Central
References: 02-03-034 02-03-056
Keywords: parse
Posted-Date: 17 Mar 2002 22:40:25 EST

jscid wrote:
>
> As of your 1st question there are several reasons that make a grammar
> ambigous one of them is left recursion. A production system is said to
> be left recursive if a nonterminal can be expanded into a string that
> begins with the same nonterminal. Due to this all the time the same
> nonterminal gets replaced and there is no end to this.


Sorry, this is wrong. A left-recursive grammar can be unambiguous (in
fact many LALR grammars are left-recursive). What you mean is that an LL
parser will get into an infinite loop if the grammar is left-recursive,
but that's different from grammar ambiguity.


Regards,
Joachim

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