Unformatted text preview: L 1 ⊕ L 2 is inﬁnite and L 1 ∩ L 2 is context-free. 4. Consider the type of automaton that you obtain by replacing the stack in a PDA by a queue. Let us call this type of machine a FIFO-automaton. For simplicity, assume FIFO-automata accept by accepting state only. • Brieﬂy explain how a FIFO automaton can implement “PUSH(X,Q)” (add X to the front of Q ), “TAIL(Q)” (read the tail element in Q ), and “REMOVE-TAIL(Q)” (remove the tail element in Q ). • Does there exist a non-context free language L that is accepted by a FIFO-automaton? Justify your answer. 1...
View Full Document
This note was uploaded on 06/09/2011 for the course COT 4210 taught by Professor Staff during the Spring '08 term at University of Central Florida.
- Spring '08
- Computer Science