Take the 2-minute tour ×  Are the languages generated by the
regular expressions $(a + b)^*$ and $(b^*a^*)^*$ the same
language?  The solution for this problem is yes, but I couldn't
figure out why it is true. The first regular expression $(a +
b)^*$ generate all strings over alphabet $\{a, b\}$, it makes
sense to me. On the other hand, how does the second regular
expression generate, say, the string $abbb$? From my
understanding, the order of the concatenation of $b$ and $a$
does affect the result of *. Any idea? Thank you.  share|improve
this question $(b^*a^*)^* \to (b^*a^*)(b^*a^*) \to (\epsilon
a)(bbb \epsilon) \to abbb$. –  Rahul Aug 16 '11 at 14:50 @Rahul
Narain: Grea thanks ;)! Would you mind writing it as an answer
so that I can accept it. –  Chan Aug 16 '11 at 14:52 In my view,
Dave Radcliffe's post already answers the question; my comment
just applies it to one example. –  Rahul Aug 16 '11 at 14:55 add
comment  3 Answers  up vote 5 down vote accepted  The Kleene
star * allows zero or more repetitio