[antlr-interest] [SPAM] [SPAM] Re: [SPAM] [SPAM] Optional expression rule alternative
Justin Murray
jmurray at aerotech.com
Fri Feb 11 10:33:25 PST 2011
These are called Semantic Predicates. Section 12.1 in TDAR.
Specifically, look at page 295 of the PDF. If the predicate evaluates to
false, the alternative is effectively switched off.
- Justin
On 2/11/2011 1:04 PM, Olivier Lefevre wrote:
> Great! Not to abuse but would you know in which section of
> "The Definitive ANTLR Reference" this mentioned? I couldn't
> find it. What is this syntax called?
>
> But in my real-world problem it was actually not a choice
> between rule1 and rule2 but a question of whether to allow
> an extra alternative in the z case without too much
> verbatim repetition, i.e. (again in pseudo-code):
>
> rule[boolean z] :
> rule1 | rule2 | ... | rule23 | (z ? rule24 : nothing) ;
>
> That is, allow rule24 if z otherwise stop at rule23.
>
> Thanks again,
>
> -- O.L.
>
>
> List: http://www.antlr.org/mailman/listinfo/antlr-interest
> Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address
More information about the antlr-interest
mailing list