Convincing an LR parser to emit fragments?
Tue, 26 May 1992 18:18:22 GMT

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Newsgroups: comp.compilers
Keywords: parse, LALR
Organization: Compilers Central
Date: Tue, 26 May 1992 18:18:22 GMT

Hello all,

My work is connected with parsing natural language and in particular with
dealing with undergeneration. That is, what happens when we have some
sentence l that is not in L(g), where g is a grammar attempting to account
for some natural language.

My query concerns the use of LR parsers for dealing with undergeneration.
A chart parser will produce a chart showing the set of partial derivation
sequences that it has constructed. Would it be possible to convince an LR
parser to do likewise? I know that the correct prefix property means that
an LR parser will stop as soon as the sentence extends out of the
language, but this is not what I want: I want the parser to be able to
emit the fragments. I would like to use an LR parser but if I can't
convince it to produce the fragments then I'll have to fall back onto
chart parsing, which is what I would like to avoid.


[There's always Earley's algorithm which carries along all of the possible
parses even for ambiguous input. -John]

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