[antlr-interest] executing actions during backtrack

[Jeff Barnes]

Martin sez:

Sorry, but that sounds a lot like implementing a database, but at all 
like implementing a parser generator, at least to me. And you didn't 
even start about all the concurrency issues with the log ;-)
 
Jeff sez:
Sounds like an undo stack to me. Yeah, some databases do it that way, Oracle in particular. But the GOF patterns (Command and Memento) are more general than that. 
 
The technical problem with this and the new ground that Ter is breaking, as I understand, is having a DFA-based LL(*) parser. Even more expressive and therefore difficult would be to implement NFA with an undo stack.
 
Just curious, why would there be concurrency issues? The issue to me would be solved at the same time as a concurrency issue with a shared input stream.
 
Regards,
Jeff