[antlr-interest] can antlr handle some ambiguity, specifically this one...
david shepherd
davidshepherd at rocketmail.com
Thu Aug 9 12:35:10 PDT 2007
I have really enjoyed using ANTLR and ANTLRWorks, but have run into
problems because of the LL parsing technology. I thought that
antlr should be able to parse:
ES -> CE | PE | E
CE -> PE E
PE -> n | PE n
E -> e
because it can lookahead k tokens and decide to reduce ES -> CE or ES -> PE.
In practice, I can't get anltr to handle the ambiguity in ES -> CE | PE | E .
It wants to always reduce to CE, even when PE is necessary. I thought
that the LL(*), or the * lookahead would allow it to parse 'n n e n',
but it cannot parse this.
Am I doing something wrong, or is this a consequence of LL grammars?
Thanks,
David Shepherd
Postdoctoral Fellow at UBC
PS-I
have gotten an LR parser to parse this example, but the antlr and
antlrworks environment is much preferred, if it can handle this issue.
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