Re: Reguar expression - what with *


Helmut Richter napisal(a):
On Wed, 8 Nov 2006, pgn@xxxxxxxxx wrote:

1. I have a regular expr. like this: (( a+b )a* )* and I'm trying to
describe it, and it's like this in my opinion: at the very beginning
language generated by this regular expr. has 'a' or 'b' and then
multiple of 'a' (empty, a, aa...). And now my question what about the
last '*' sign? How to write it down?

Take any string over the alphabet {a, b}, e.g.

baabbababaabbbababbbabab

Now cut it into pieces just before each occurrence of b:

baa b ba ba baa b b ba ba b b ba ba b

Which of the pieces does not belong to the language (a+b)a* ?
What can be concluded for the language ((a+b)a*)* ?

All of the pieces belongs to the language, I think. Because at the
beggining we have b (a+b means a or b - so that is correct) and then we
can have zero or more times a.
So for the language ((a+b)a*)* we can have: a or b then zero or more
times a and all of this zero or more times.
Am I right?

Regards,
Pi

.

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