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

[Terence Parr]

hi.  can u resend w/o all the stars?
Ter
On May 23, 2010, at 6:29 AM, Sameh W. Zaky wrote:

> 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_recognizer.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
> 
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