15-453 Formal Languages, Automata, and Computation
Lecture 12: Non-Context-Free Languages
We introduce a version of the pumping lemma for context-free languages which
allows us to show that various languages are not context
free. Because of the added expressive power of pushdown automata as compared
to finite automata, the pumping lemma and its application are more
complicated. As we will see later in this class, even more powerful models
such as Turing machine require an entirely new technique for showing that they
cannot recognize certain languages.
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Frank Pfenning
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