|What is the complement of context free language? firstname.lastname@example.org (jianhua li) (2007-06-04)|
|Re: What is the complement of context free language? email@example.com (Roberto Bagnara) (2007-06-09)|
|Re: What is the complement of context free language? firstname.lastname@example.org (Tomasz Kowaltowski) (2007-06-09)|
|Re: What is the complement of context free language? email@example.com (Mustafa Elsheikh) (2007-06-09)|
|From:||Mustafa Elsheikh <firstname.lastname@example.org>|
|Date:||Sat, 09 Jun 2007 08:28:43 -0700|
|Posted-Date:||09 Jun 2007 18:30:48 EDT|
On Jun 3, 8:31 pm, jianhua li <lijh...@yahoo.com.cn> wrote:
> In many text books, they say that the complememt of context free
> language us not context free language . But they do not say the
> complemet of CFL is context sensitive language or Recursively
> enumerable language ? So what is the language of the complement of
> context free language?
Complement of CFL could possibly be CFL but not necessarily is.
Complement of CFL is both recursive (R) and recursively enumerable
(RE). Why? All CFLs are both R and RE. R languages are closed under
complement (but RE are not). In that context, complement of CFL is R
which is inherently RE.
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