Module34 - 2 are context-free? 5 CFLs not closed under...

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1 Module 34 Showing CFL’s not closed under set intersection and set complement
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2 Nonclosure Properties for CFL’s
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3 CFL’s not closed under set intersection How can we prove that CFL’s are not closed under set intersection?
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4 Counterexample • What is a possible L 1 intersect L 2 ? What non-CFL languages do we know? • What could L 1 and L 2 be? – L 1 = – L 2 = – How can we prove that L 1 and L
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Unformatted text preview: 2 are context-free? 5 CFLs not closed under complement How can we prove that CFLs are not closed under complement? Another way Use fact that any language class which is closed under union and complement must also be closed under intersection 6 Language class hierarchy All languages over alphabet RE REG H H Equal CFL REC Equal-3...
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This note was uploaded on 07/25/2008 for the course CSE 460 taught by Professor Torng during the Fall '07 term at Michigan State University.

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Module34 - 2 are context-free? 5 CFLs not closed under...

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