[antlr-interest] Default error handler, generated _token_set_n

Terence Parr parrt at cs.usfca.edu
Sun Aug 15 15:04:06 PDT 2004


On Aug 15, 2004, at 5:06 PM, Ingo Maier wrote:

>
> Hi,
>
> the default parser error handler seems to catch RecognitionExceptions
> and then calls consumeUntil() with an auto generated BitSet as argument
> (_token_set_n). I guess these BitSets contain some hint to 
> synchronizing
> tokens?  But how exactly? I couldn't fiddle out by myself nor found it
> in the docs.

Hi :)

It's the FOLLOW(r) where r is the rule you are in.  For example, if the 
FOLLOW(expr) is {',', ';', '}'} then that is a could list of tokens to 
look for in order to resynch after an error in an expression. :)  
Simplest reasonable strategy, but it works wonders. ;)

Terence
--
CS Professor & Grad Director, University of San Francisco
Creator, ANTLR Parser Generator, http://www.antlr.org
Cofounder, http://www.jguru.com
Cofounder, http://www.knowspam.net enjoy email again!





 
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