Which of the following problems are decidable?
1) Does a given program ever produce an output?
2) If L is a context-free language, then is L' (complement of L) also context-free?
3) If L is a regular language, then is L' also regular?
4) If L is a recursive language, then, is L' also recursive?
A)1, 2, 3, 4
B)1, 2
C)2, 3, 4
D)3, 4

Question

Quizplus · Accepted Answer

3) The problem of determining if the complement of a regular language is regular is decidable because regular languages are closed under complementation. 4) The problem of determining if the complement of a recursive language is recursive is decidable because recursive languages are closed under complementation.

Which of the Following Problems Are Decidable