Q: <fail>, and context-aware rules

[Patrick R. Michaud]

On Mon, Aug 03, 2009 at 12:48:34PM -0400, Austin Hastings wrote:
> Vasily Chekalkin wrote:
>> Austin Hastings wrote:
>>
>>> I'm trying to solve "the typedef problem" in Close. Specifically, a  
>>> variable declaration may include a "typedef" as part of the type  
>>> specifier. But I need to know what's a typedef, and what's not a  
>>> typedef, because the only rule for typedef is that it's a valid name.
>>>
>> [[ ... ]]
>>
>> So, you probably need something like
>>
>> token typedef_name {
>>     <identifier> <?{ is_a_typedef(~$0) }>
>> }
>>
>
> Yeah, except it would be <?{{ ... pir ... }}>, and I'd prefer to code it  
> in NQP if possible. 

My expectation is that NQP will be embeddable within regexes in the
very near future.  Then it would be

    <?{ is_a_typedef(~$0) }>

Beyond that, I'm not aware of any way for an action method to easily
signal a <fail> to the outer regex.

Pm