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regular expressions/kleene closure (very basic, just need clarification) watch

1. (Original post by pissingMonkey)
hey..

on the attachment (lecture notes) it shows an example of kleene closure. it says that A = {a,b,c,d,1,2}

words on A: abba, b, 1ab2, ccc ...

so does this mean that the kleene closure of every set will have an infinite number of elements? for example if u can have ccc then u can also have ddd and a^infinity right?

if i was asked in an exam to write the kleene closure of {a, b}, how would i answer it?

{a, b}* = a, b, ab, ba, aa, bb, aabb, abab ...........

i'm probably missing something here. can somebody please clarify this concept for me? any help is much appreciated
Yes, as written it has an infinite number of elements (countably many, if the alphabet is finite). So to write out the Kleene closure of your example, you can't write it as a list of elements as you've figured out; you'll have to write it in the way given in your lecture notes.

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Updated: April 8, 2013
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