[PDF] THEORY OF COMPUTATION MCQ SET 1 targatenetcom

Are recursive languages closed under Union?

Recursive languages are closed under union. (b.) Recursive languages are closed under complementation. (c.) If a language and its complement are both regular then the language must be recursive. (d.)

What is the intersection of recursively enumerable languages?

the intersection . Note that recursively enumerable languages are not closed under set difference or complementation. The set difference L - P may or may not be recursively enumerable. If L is recursively enumerable, then the complement of L is recursively enumerable if and only if L is also recursive.

Is halting a recursive enumerable language?

The contradiction implies that H cannot exist, that is, that the halting problem is undecidable. The simplicity with which the halting problem can be obtained from Theorem 11.5 is a consequence of the fact that the halting problem and the membership problem for recursively enumerable languages are nearly identical.

Is-L recursively enumerable?

If wkdoes not belong to L, then it belongs to -L and is accepted by Tk. But since Tkaccepts wk, wkmust belong to L. Again, ar contradiction. We have now defined a recursively enumerable language L and shown by contradiction thatr-L is not recursively enumerable.