[antlr-interest] Repost: ANTLRworks: Why do these rules behave differently in the embedded interpreter?

Terence Parr parrt at cs.usfca.edu
Fri Jan 1 16:28:35 PST 2010

yeah, the interp has never been quite right...just haven't had time to  
fix. now that book is done (printed just about now I guess) I can get  
back to ANTLR.
On Jan 1, 2010, at 1:58 PM, Kyle Ferrio wrote:

> Thanks, folks.
> David-Sarah makes a good point, which I would make perhaps just a bit
> differently, and this is I see the interpreter as a kind of learning
> tool, a crutch if you will.  If it goes wonky in a way that makes it
> obvious to a knave that it's at fault, fine.  But if it goes wonky in
> a way which causes the student to wonder, "Is this me, or is this the
> tool?" then learning is impeded at a critical juncture, even if the
> ultimate resolution (assuming a persistent student) does produce
> deeper insight.
> Note: I manage a commercial software development group serving highly
> specialized engineering customers.  More than one customer has told me
> that he or she would rather have "a tool that fails in an obvious way"
> more often than "a tool which fails in an ambiguous way less often."
> {Quotes added to assist parsing.  :) }  It's not about being right or
> wrong.  It's about knowing when you can trust your tools, and when you
> shouldn't.
> Kyle
> On Fri, Jan 1, 2010 at 1:31 PM, Terence Parr <parrt at cs.usfca.edu>  
> wrote:
>> On Jan 1, 2010, at 11:45 AM, David-Sarah Hopwood wrote:
>>> Jim Idle wrote:
>>>> The interpreter is just a quick testing device and is easily  
>>>> fooled by grammar rules, use the debugger and not the interpreter  
>>>> and all will be fine.
>>> Yes, but what Kyle pointed out seems like an obvious bug in the
>>> interpreter in a case that it is supposed to be able to handle.
>>> Either bugs like this should be fixed, or there is no point in  
>>> having
>>> the interpreter and all and it should be removed, with its  
>>> functionality
>>> being replaced by the debugger.
>> yup. it's on my to-do list.
>> T
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