Are context-free languages closed?
Context-free languages are not closedunder intersection or complement. Thiswill be shown later. 1.5 Intersection with a regular language The intersection of a context-free language and a regular language is context-free (Theorem 3.5.2).
Is the intersection of a regular language and a context-free language?
Since A and B were arbitrary, we conclude that the intersection of a regular language and a context-free language is context-free. 10.4 Reverse We will now show that the context-free languages are closed under the operations reverse, pre?x, su?x, and substring.
What is the complement of a context-free language?
The complement of a context-free language can be context-free or not; the complement of a non-context free language can be context-free or not. Every regular language is context-free. Regular languages are closed under complement, so the complement of a regular language is regular.
Do two context-free grammars generate the same language?
Different context-free grammars can generate the same context-free language. It is important to distinguish the properties of the language (intrinsic properties) from the properties of a particular grammar (extrinsic properties). The language equality question (do two given context-free grammars generate the same language?) is undecidable .
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Prove Context Free languages not closed under difference?
Then the context-free languages would be equal to the languages accepted by Turing Machines: the languages of valid computations would be context-free, and from this we can find their prefixes or the accepted inputs of the TM. I do think that is a contradiction without the pumping lemma. lgo algo-sr relsrch lst richAlgo" data-ff8="645f5dcc57a97">cs.stackexchange.com › questions › 13701Prove Context Free languages not closed under difference? cs.stackexchange.com › questions › 13701 Cached