[antlr-interest] catching an exception in the parser and continuing - will this work?

[davidjpenton2002 <djplists at arrowsash.com>]

I am handling "include files" in my lexer, as in the java example 
provided with antlr.  This means that fact the lexer is in an 
included file is transparent to the parser.

However, it turns out that I want the parser to be made aware of the 
fact that the lexer is in an included file. (Kindly assume that I 
have a sound design reason for this ;-) Given the amount of lookahead 
that may occur, I am sure that the only safe way to do this is by 
putting the correct "notification" on the stream of tokens passed to 
the parser.

Is it possible to have the lexer pass a back a "bad" token (i.e. one 
that the parser can never recognize), catch a resultant exception, 
and then (here's the important part) force the parser to take up 
right where is was when it got the "bad" token?  It would amount to 
skipping over the "bad" token, except that the exception handling 
code would set a flag or two that would be available later to parser 
semantic actions.

I have looked at the exception handling documentation, and sifted 
through my generated parser.  It is not clear to me if my strategy 
will work.

BTW, I am still using antlr 2.7.1 - I want to try to finish what I am 
doing before trying the switch to 2.7.2.

Thanks.

- Dave Penton -


 

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