[antlr-interest] Breaking a loop

[John Green]

The semantic predicate would be awful complex, since it would have to check for:
  (io_opt)* state_end
In other words, I'd have to hand-code a syntactic predicate into the semantic predicate.


Terence Parr wrote:
> Add a semantic predicate in front of alt(s) that says when to break :)
> Ter
> On Nov 4, 2005, at 10:43 AM, John Green wrote:
> 
>> I've got a pre-existing language with a requirement like this:
>>
>>    (    ( (io_opt)* state_end )=> (io_opt)* state_end {break;}
>>    |    .
>>    )*
>>
>> Hopefully my question is obvious from the example. I need to break the 
>> loop when I hit a certain production. Until that production is 
>> reached, arbitrary tokens are consumed by the ".". Assuming {break;} 
>> is a bad hack, what's a good way to do this in Antlr?
>>
>> Cheers,
>> john at joanju dot com
>>
> 
> 
>