COMPUTER SCIENCE AND ENGINEERING
THEORY OF COMPUTATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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union
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concatenation
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kleene
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All of the mentioned
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Detailed explanation-1: -A regular language over an alphabet ∑ is one that cannot be obtained from the basic languages using the operation. A.
Detailed explanation-2: -How many languages are over the alphabet R? Explanation: A language over an alphabet R is a set of strings over A which is uncountable and infinite.
Detailed explanation-3: -Which of the following regular expression corresponds to the language of all strings over the alphabet a, b that do not end with ab? a)(a + b)* (aa + ba + bb)b)(a + b)* (aa + ba + bb) + a + b + ∈c)b* ab* ad)b* aa b*Correct answer is option ‘B’.
Detailed explanation-4: -Definition: A regular expression over the alphabet is an expression derived from the following rules: , ∅, and a, where a ∈ , are all regular expressions. if E is a regular expression then (E)* is a regular expression. if E1 and E2 are regular expressions then (E1)(E2) and (E1)|(E2) are regular expressions.
Detailed explanation-5: -To prove a language is regular: construct a DFA, NFA or RE that recognizes it. To prove a language is not regular: show that recognizing it requires keeping track of infinite state (hard to be completely convincing in most cases) or use the pumping lemma to get a contradiction.