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Hi, I am having a doubt understanding the result of CFL – Regular:

Here’s my approach:

  1. CFL – Regular = CFL INTERSECTION Regular’ = CFL INTERSECTION Regular = CFL
  2. Suppose some CFL L1= {a^n b^n | n>=1} and some Regular R1= (a+b)* : 

Now if I do CFL – Reg = {ab,aabb,aaabbb, ….} – { epsilon, a, b, ab, aabb, aaabbb, …..} 

It gives { phi } which is Regular (hence also CFL)
 

So is it better to say CFL – Regular = Regular or CFL – Regular = CFL ? If both are separate options, which one should I go for? Thanks

 

in Theory of Computation by (39 points) | 50 views

1 Answer

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CFL. Because a regular language is also a context free language, as you can make a context free grammar from the D.F.A of the corresponding regular language.
by Active (2.3k points)

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