I was wondering if there are any "table driven" PEG/packrat based
parsers.
In looking at the url
http://en.wikipedia.org/wiki/Comparison_of_parser_generators#Parsing_Expression_Grammars
I see that there are four implementation styles for a PEG parser:
Packrat, Recursive Descent, Parsing Machine and PEG parser interpreter.
As far as I know, all the Packrat and Recursive Descent varieties
generate
code. If I am wrong please correct me.
Parsing Machine seems to generate a byte code for a PEG virtual machine.
http://www.inf.puc-rio.br/~roberto/docs/ry08-4.pdf.
The PEG parser interpreter seems to just interpret the PEG directly
via a
set of recursive functions.
http://fdik.org/pyPEG/
Can one create a table driven PEG/packrat parser? What would such a
program
look like? Does this question even make sense?
I know Terrance Parr wrote in his "ANTLRWorks" draft paper:
ANTLR provides the power of a PEG with the semantic action
flexibility and low
overhead of a traditional LL-based parser. ANTLR not only supports
manual
backtracking via syntactic predicates, but supports an automatic
backtracking
option that tells ANTLR to backtrack at runtime if LL(*) static
analysis fails.
However, ANTLR generates code (aside from it not strictly being a
Packrat parser).
Perhaps there is no reason why it could not be made to generate a
table and
support code.
I am also aware of the paper by Roman R. Redziejowski titled
"Applying Classical Concepts to Parsing Expression Grammar", which
seems to
attempt to define the FIRST and FOLLOW sets for PEGs. (Caveat, as I
have not
read this paper yet.)
So, are there any "table driven" PEG based parsers?
One reason I am asking this question is that I was wondering how to
use PEGs in
a dynamic context. If you read in a grammar and generate a table, you
now have
a data driven process which can be used at runtime. Is there someway
to use PEGs
in a dynamic context, w/o having to generate code? (The Lua PEG
virtual machine
and the pyPeg mentioned above seem to be two approaches to this
problem.)
Thanks for your time.
_bernhard
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