Ambiguous non-terminal in GLR

Maxim Reznik <reznikmm@front.ru>
Mon, 01 Apr 2013 11:16:51 +0300

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Ambiguous non-terminal in GLR reznikmm@front.ru (Maxim Reznik) (2013-04-01)
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From: Maxim Reznik <reznikmm@front.ru>
Newsgroups: comp.compilers
Date: Mon, 01 Apr 2013 11:16:51 +0300
Organization: Aioe.org NNTP Server
Keywords: parse, question
Posted-Date: 02 Apr 2013 13:02:28 EDT

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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