CSE355 Module 2: Quiz 8
The union of a CFL and a regular language is always a CFL
a. True
b. False - ANS-a. True
If L1 is a CFL and L2 is a CFL, then L1L2 is a CFL
a. True
b.False - ANS-a. True
Any NFA transition diagram can be converted to an equivalent PDA transition diagram by
rewriting every transition labeled with some character (or possibly ε) a to instead be labeled as
a, ε -> ε
a. True
b. False - ANS-a. True
Must it always be the case that the input alphabet, is a subset of the stack alphabet?
a. Yes
b. No - ANS-b. No
If a pushdown automaton recognizes some language, then it is context-free
a. True
b. False - ANS-a. True
The class of PDAs which do not utilize the stack (in other words, every transition is of form a, ε
-> ε, and a ∈ Σ) recognizes precisely the regular languages
a. True
b. False
c. False, there are some PDAs that don't use the stack that can recognize non-regular
languages - ANS-a. True
I have a PDA in which no transition pops the stack. What class of languages can such PDAs
recognize? (Choose the most specific answer)
a. Context-free Languages
b. Chomsky Normal Languages
c. Regular Languages
d. Finite Languages - ANS-c. Regular Languages
Suppose that M = (Q, Σ, 𝜞, δ, q0, F) is a PDA. Is it possible for Q, 𝜞, δ, and F to be empty?
(Choose the most specific answer)
a. Only F may be empty
b. None of them can be empty
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