Anyone have generic sed-like filter setup for yacc and lex?

I've programmed on UNIX for years and this is something I've wanted for
a long time but never found. Very often I have a lex scanner and a Yacc
grammar. I need to take valid grammar inputs and essentially stream
filter them, transforming certain constructs, or outputing only a small
part of the input that matches to particular constructs. The filtering
is too complex for sed and I want compiled performance and so don't wish
to use awk or perl.


Unfortunately, yacc provides no real support for stream filtering, yet
the problem fits well into a framework that could use yacc and lex as a
base, where one builds up a parse tree that includes the input tokens
from lex and then calls a single function within Yacc rules to output
the entire portion of the input stream that matches one of the current
production symbols, whether terminal or non-terminal. It doesn't seem
like a very hard problem, but I've never taken the time to build such a
thing and would rather not reinvent a wheel.


If anyone can provide me with or point me to such a set up I would be
quite appreciative. Please reply directly as I don't commonly read
these groups.


Bob
--
Bob Weiner rsw@cs.brown.edu
--

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