[antlr-interest] ANTLR Kudos...

[Foust]

>
> How do you turn on backtracking on a per rule basis?  
>

The name of the backtracking option is "backtrack".

	options {backtrack=true;}

As noted, per-rule options go before the colon

	rule		options {backtrack=true; memoize=true;}	
			: <rule pattern>
			;

Brent

> -----Original Message-----
> From: antlr-interest-bounces at antlr.org [mailto:antlr-interest- 
> bounces at antlr.org] On Behalf Of Johannes Luber
> Sent: Friday, August 15, 2008 5:15 AM
> To: Ian Kaplan
> Cc: antlr-interest at antlr.org
> Subject: Re: [antlr-interest] ANTLR Kudos...
> 
> Ian Kaplan schrieb:
> >
> >
> >     /
> >     Performance is not bad with backtracking and memoization; linear
> >     time cost.  Still better to let ANTLR predict with a simple DFA
> >     rather than backtracking.  Also can set backtracking per rule./
> >
> >
> >
> >        Only a part of my grammar requires more than two symbols of
> look
> > a head.  How do you turn on backtracking on a per rule basis?  I've
> got
> > it set globally and it may not need to be.
> 
> You can put an options block into a rule definition like so (didn't 
> test it, so syntax may be a bit off):
> 
> rule
> options {
> backtracking=true;
> memoize=true;
> }
> : otherRule;
> 
> Johannes
> 
> >
> >   Thanks,
> >
> >   Ian
> >