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Unformatted text preview: L 1 L 2 is innite 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. Briey 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...
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- Spring '08
- Computer Science