September 6

September 6 - CSCI 2670 Introduction to Theory of Computing...

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CSCI 2670 Introduction to Theory of Computing September 6, 2005
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Announcements • Homework due next Tuesday (9/13) – 1.7(d,h), 1.16b, 1.21b (show the GNFA steps),1.19a, 1.46c, 1.55(c,f,j) • Old text numbers 1.5(d,g), 1.12b, 1.16b, 1.14a, 1.23d, 1.38(same instructions on (001 0 * 1 * , ε , and Σ * ) • If you ask me a question on a homework problem by email, please email me the problem in question • Quiz tomorrow – Section 1.2 & Formal definition of RE
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Agenda • Last week –Sect ion 1 .2 –NFA ’s – Regular expression intro (Section 1.3) •Today – Continue regular expressions • This week – Sections 1.3 and 1.4
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RE inductive definition R is a regular expression if R is 1. af o r s om e a ∈ Σ 2. ε 3. 4. R 1 R 2 where R 1 and R 2 are both regular expressions 5. R 1 ° R 2 where R 1 and R 2 are both regular expressions 6. (R 1 * ) where R 1 is a regular expression Abuse of notation. These should be sets!
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RE’s and regular languages Theorem: A language is regular if and only if some regular expression describes it. – i.e., every regular expression has a corresponding DFA and vice versa
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RE’s and regular languages Lemma: If a language is described by a regular expression, then it is regular.
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This note was uploaded on 02/07/2011 for the course CS 501 taught by Professor Sm during the Spring '11 term at Indiana.

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September 6 - CSCI 2670 Introduction to Theory of Computing...

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