a. Explain why regex commonly used in text editors are not regular expressions.

b. Can the language { | 3} be accepted by a DFA? Justify your answer.

c. Construct a context-free grammars for each of the given regular expressions. The alphabet is {, }. Indicate terminals and non-terminals. i.

ii. (|)

iii. (|) (|) + ()

d. Explain in which logical phase, or phases, of a compiler context-free grammars can be useful.