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+16 votes

02. Choose the correct alternatives (more than one may be correct) and write the corresponding letters only:

(xix) Context-free languages are:

  1. closed under union
  2. closed under complementation
  3. closed under intersection
  4. closed under Kleene closure
in Theory of Computation by
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2 Answers

+19 votes
Best answer

Answer: a, d.

Context Free languages are not closed under intersection and complementation.

edited by
CFG are closed under Union , Kleen closure & Concatenation .

Also CFG are closed under Regular intersection

BUT , are CFG closed under Regular Union ?

I think yes...coz..every regular is CFG & CFG are closed under union ....

correct me if I am wrong
So take two regular language sigma* over {a,b} and other as {a}then their union is sigma* ,which is not cf.

Correct me if I am wrong.
+1 vote

According to the above table we can say , A and D is correct answer

wat is GSM mapping ??

Gsm mapping Short for generalized sequential machine mapping. A function that is the response function of a generalized sequential machine, and therefore generalizes the notion of sequential function. Without constraining the machine to have a finite state-set, generalized sequentiality is equivalent to the following property of initial subwords preservation

for all u,v in I*, f(uv) has the form f(u)w for some w in O*, where I* and O* are the sets of all input and output strings.

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