I fully agree. As I pointed out in my paper, PEG is not good at
specifying
lexical structures. But, if I need an ad hoc parser, I would prefer
to skip
a separate lexer. So, my question is: how could one modify PEG
to facilitate this, and at the same time have a decent speed?
Rats! performs a number of optimizations that are specifically
designed to reduce the overhead when recognizing lexical syntax. For
my experiments with Java, the overall result is performance pretty
close to ANTLR 2.7.5. So, I'm not worried about using PEGs for
lexical syntax.
Furthermore, once you combine both lexical and hierarchical syntax,
i.e., rely on scannerless parsing, you can do strictly more. Martin
Hirzel and I have combined the complete Java and C languages into a
new language (called Jeannie) to substantially simplify Jave Native
Interface programming. The syntactic composition of the existing
grammars for Java and C was trivial thanks in part to scannerless
parsing. Several papers by Eelco Visser make a similar case for other
language extensions, only they are building on a scannerless GLR
parser generator.
Robert
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