Unformatted text preview: mentation. 3. Let A = {h R,S i R and S are regular expressions and L ( R ) ⊆ L ( S ) } . Show that A is decidable. (Hint: regular languages are closed under complementation, intersection, and union). 4. Prove that EQ DFA is decidable by testing the two D±As on all strings up to a certain size. Calculate a size that works. 5. A language is prefxFree iF no member is a proper prefx oF another member. Let PF REX = {h R i R is a regular expression where L ( R ) is prefxFree } . Show hat PF REX is decidable. 1...
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 Spring '11
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 Formal language, Regular expression, doubly infinite tape

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