Unformatted text preview: b) The class of contextfree languages is closed under homomorphism. c) The class of contextfree languages is closed under inverse homomorphism. 5. Prove that the halting problem for Turing machines, }  ) , {( x input on halts M x M , is undecidable. 6. For each of the following conditions, give an example of a set or prove that no such set exists. a) Both the set and its complement are recursive. b) The set is recursive but its complement is not. c) The set is recursively enumerable and its complement is recursive. d) The set is recursively enumerable and its complement is also recursively enumerable. e) The set is recursively enumerable but its complement is not recursively enumerable. f) Neither the set nor its complement are recursively enumerable....
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 Fall '05
 HOPCROFT
 Formal language, Halting problem, Turing Machines, contextfree languages, Location Olin

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