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Ass1 Q7 strategy

Posted by Anonymous User 
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Anonymous User
Ass1 Q7 strategy
March 28, 2008 08:54AM
Hey guys,

what strategy did you use to draw the PDA for this question? I just sort of "figured it out" and was wondering if there was a better way to do it.

I also have another question (it may be stupid tho) - what is the definition of a context-free language..i.e. what make a language context free rather than regular/non-context free etc?


Re: Ass1 Q7 strategy
March 30, 2008 12:19PM
For strategy, I also just 'drew it'. Can't say I have a strategy.

Contect-free languages are those that are (essentially) a collection of terminals and non-terminals, one of them being a starting non-terminal.

Regular languages are those that can be described by a regular expression.

So, when presented by a language, you can check whether it can be created by a regular expression or a set of productions, and in many cases, by both. They are not mutually exclusive. That, I think, is more or less the explanation that the textbook gives. Have a look at the circles on page 300.
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