[antlr-interest] Context-Sensitive Follow Sets.. Bug?

[Terence Parr]

could be. ANTLR v4 also reports something wacky; was coincidentally working on itnow
T
On May 23, 2010, at 10:33 AM, Jim Idle wrote:

> Perhaps this is another instance of not clearing the cached set?
> 
> Jim
> 
>> -----Original Message-----
>> From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
>> bounces at antlr.org] On Behalf Of Terence Parr
>> Sent: Sunday, May 23, 2010 10:13 AM
>> To: Sameh W. Zaky
>> Cc: antlr-interest at antlr.org
>> Subject: Re: [antlr-interest] Context-Sensitive Follow Sets.. Bug?
>> 
>> oh. it includes AND (not THE).  That *is* weird.
>> 
>> I'll look.
>> Ter
>> On May 23, 2010, at 10:06 AM, Sameh W. Zaky wrote:
>> 
>>> Here is the same message without formatting:
>>> 
>>> ---------- Forwarded message ----------
>>> From: Sameh W. Zaky <sameh.wz at gmail.com>
>>> Date: Sun, May 23, 2010 at 3:29 PM
>>> Subject: [antlr-interest] Context-Sensitive Follow Sets.. Bug?
>>> To: antlr-interest at antlr.org
>>> 
>>> 
>>> Hello everyone..
>>> After reading the wiki article
>>> 
>> http://www.antlr.org/wiki/display/ANTLR3/Custom+Syntax+Error+Recovery,
>>> (thanks to Jim Idle, "Yes, you def. deserve a Masters too" ;-)) I
>> went on
>>> with developing my own example to test the
>>> method: computeContextSensitiveRuleFOLLOW() (described here:
>>> 
>> http://www.antlr.org/api/Java/classorg_1_1antlr_1_1runtime_1_1_base_rec
>> ognizer.html#2b566e00e5d771f66dd4e29a4a27a1c4
>>> )
>>> The method works perfectly in all cases except in the case of zero or
>> one,
>>> Consider the following simple grammar:
>>> 
>>> 
>> =======================================================================
>> ======================
>>> 
>>> start : animal (AND acClass)? service EOF;
>>> 
>>> animal : (DOG | CAT );
>>> service : (HARDWARE | SOFTWARE) ;
>>> AND : 'and';
>>> DOG : 'dog';
>>> CAT : 'cat';
>>> HARDWARE: 'hardware';
>>> SOFTWARE: 'software';
>>> 
>>> acClass
>>> @init
>>> {
>> System.out.println(computeContextSensitiveRuleFOLLOW().toString());}
>>>   :     ;
>>> 
>> =======================================================================
>> ==============
>>> 
>>> Testing this grammar, with let's say input:
>>> "dog and software",
>>> the result in the console is:
>>> "{4, 7, 8}" (which stands for tokens {THE, HARDWARE, SOFTWARE}),
>>> although it is supposed to be:
>>> "{7,8}" (which stand for tokens {HARDWARE, SOFTWARE} only).. Because
>> after
>>> acClass in start rule, if we get "the" as next token this will make
>> the
>>> input invalid..
>>> 
>>> Any idea why this happens? Or how we can overcome it?
>>> Thanks a bunch..
>>> --
>>> Sameh W. Zaky
>>> 
>>> 
>>> Regards
>>> --
>>> Sameh W. Zaky
>>> 
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> 
> 
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