[antlr-interest] Syntactic predicates elude me

[Terence Parr]

New AW starts with a warning dialog.
Ter
On Jun 29, 2008, at 7:40 AM, Raphael Reitzig wrote:

> For backtracking is done through implicitly placed predicates for all
> rules, no.
>
> However, I found the debug mode to be satisfying. It is not as  
> responsive
> as the interpreteter, for you have to generate and compile code, but  
> it can
> show you the produced AST as well as the parse tree.
>
> I understand your feeling, I had the same ;) Though I spent only  
> days, not
> weeks, confusing a bunch of fellow students as well :D
>
> Raphael
>
> On Sun, 29 Jun 2008 11:31:24 +0100, "Artemus Ward"
> <coddbotherer at googlemail.com> wrote:
>> 2008/6/28 Raphael Reitzig <r_reitzi at cs.uni-kl.de>:
>>> Hi!
>>>
>>> I had a similar problem. ANTLRWorks' interpreter cannot evaluate
>>> predicates. Try debugging it. The Debugger actually works with the
>> created
>>> and compiled classes and thus is able to work with predicates.
>>
>> Hell.  I have wasted two weeks because I felt it was arrogant to  
>> think
>> the problem wasn't just my own lack of understanding. I am not happy.
>> What about backtracking?  Does ANTLRWorks support that?
>>
>> Art
>>
>>> On Sat, 28 Jun 2008 21:43:30 +0100, "Artemus Ward"
>>> <coddbotherer at googlemail.com> wrote:
>>>> I am a newbie and for a couple of weeks I've been banging my head  
>>>> on
>>>> something simple that I'm just not getting.
>>>>
>>>> I just cannot figure out how to write a syntactic predicate.  I'm
>>>> testing in ANTLRWorks and I always get an error reported like:
>>>> FailedPredicateException(rulename,{synpredN}?).
>>>>
>>>> What puzzles me is that the predicate that is reported is always  
>>>> the
>>>> one I expected would succeed based on the input I provide.  If I
>>>> provide an input that should match (say) the third predicate it  
>>>> will
>>>> report the third predicate as the error.
>>>>
>>>> I'm using ANTLR 3.0.1 and ANTLRWorks 1.1.7.
>>>>
>>>> Art
>>>
>>>
>