February 3rd, 2012, 03:49 PM  #1 
Newbie Joined: Sep 2009 Posts: 9 Thanks: 0  Set Theory Definition
What does it mean when something is not a member of a*b*?

February 3rd, 2012, 08:15 PM  #2 
Global Moderator Joined: Nov 2006 From: UTC 5 Posts: 16,046 Thanks: 938 Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms  Re: Set Theory Definition
What are you using * to mean?

February 4th, 2012, 02:21 AM  #3 
Newbie Joined: Sep 2009 Posts: 9 Thanks: 0  Re: Set Theory Definition
sorry, it's the kleene star.

February 4th, 2012, 03:28 PM  #4  
Global Moderator Joined: May 2007 Posts: 6,852 Thanks: 743  Re: Set Theory Definition Quote:
What is a*b*?  
February 4th, 2012, 06:03 PM  #5 
Global Moderator Joined: Nov 2006 From: UTC 5 Posts: 16,046 Thanks: 938 Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms  Re: Set Theory Definition
OK, so you're looking for some word over an unspecified alphabet which does not match the regular expression a*b*. ba would be one example.


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