Re: OT: regular expression question
>>>>> "Rogerio" == Rogerio Brito <rbrito@iname.com> writes:
Rogerio> On Dec 08 2000, Hubert Chan wrote:
>> Oops. There should be a "| \epsilon" at the end of that (where \epsilon
>> is the empty string) if you count the empty string as a palindrome. If
>> not, then you should add "| aa | bb".
Rogerio> No, it's not the same thing. The former language generated by
Rogerio> the grammar with the production S -> \varepsilon has the empty
Rogerio> string, while, if you substitute it by S -> aa | bb, then your new
Rogerio> language does not contain \varepsilon.
Um, I never said that they were the same thing. In fact, I specifically said
that they different. If you read my post again (in fact, the very part that
you quoted), you will see that I said that which rule you add depends on
whether or not you count the empty string as a palindrome.
Hubert
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