Q: <fail>, and context-aware rules

[Austin Hastings]

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. That's why I was wondering if there's a "fail from 
within" function available in the Action methods.

=Austin