[antlr-interest] how to deal with optional parameters in ast

Dave Cramer davec at postgresintl.com
Tue Mar 27 12:51:02 PDT 2007

On 27-Mar-07, at 3:36 PM, Gavin Lambert wrote:

> At 02:56 28/03/2007, Dave Cramer wrote:
>> I have a rule which is
>> WAKEUP expr*NEWLINE-> ^(WAKEUP expr*)
>> if the input is
>> the ast will just be ^ WAKEUP
>> What's the right way to deal with this ?
> That seems correct to me.  What were you wanting it to do instead?
> If WAKEUP is always supposed to have a parameter, then you should  
> change * to + in both places.  If it's allowed to have no  
> parameters, then what you have already seems like the best option  
> (assuming your description is correct).
OK, then in the treewalker I am going to eventually call a function  
called wakeUp(int seconds) where if the optional seconds is not  
provided I will default it to something. The question really is how  
to write the treewalker with two possibililties; one with the param,  
one without ?


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