Ambiguous non-terminal in GLR

From	Maxim Reznik <reznikmm@front.ru>
Newsgroups	comp.compilers
Subject	Ambiguous non-terminal in GLR
Date	2013-04-01 11:16 +0300
Organization	Aioe.org NNTP Server
Message-ID	<13-04-002@comp.compilers> (permalink)

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Hi, all

I'm playing with GLR and have a question.

When GLR parser reduces some text to the same non-terminal in two or
more ways it merges parse subtrees. Rekers uses 'symbol nodes' for this.

I this not each non-terminal could cause a merge. Knowing in advance
what non-terminals never merge will greatly simplify parse tree
construction.

For instance in Elkhound Technical Report the author implemented C++
grammar for GLR parser. He describes it:

    The grammar currently has 37 shift/reduce conflicts, 47
reduce/reduce conflicts and 8 ambiguous nonterminal.

How can I separate ambiguous and unambiguous nonterminal for a given
CFG? Where can I read about this?


Thank you
--
Maxim Reznik

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Ambiguous non-terminal in GLR Maxim Reznik <reznikmm@front.ru> - 2013-04-01 11:16 +0300

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