September 13

September 13 - CSCI 2670 Introduction to Theory of...

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CSCI 2670 Introduction to Theory of Computing September 13, 2005
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Announcement Homework due next Tuesday 9/20 Use the pumping lemma to prove the following  language is not regular A = {ww R  | w   {a,b} * } 1.54, 2.1 c & d, 2.4 c & e, 2.6 b & d Note in 2.6 d, it is possible that i = j
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Agenda Last week Proved correspondence between regular languages and  regular expressions This week Learn how to prove a language is not regular Introduce a new class of language Introduce a new type of state machine
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Nonregular languages So far, we have explored several ways to identify  regular languages DFA’s, NFA’s, GNFA’s, RE’s There are many nonregular languages {0 n 1 n  | n   0} {101,101001,1010010001,…} {w | w has the same number of 0s and 1s} How can we tell if a language is  not  regular?
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Property of regular languages All regular languages can be generated by  finite   automata States must be reused if the length of a string is  greater than the number of states If states are reused, there will be  repetition  
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September 13 - CSCI 2670 Introduction to Theory of...

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