Closure properties of recognizable languages, Theory of Computation

Assignment Help:

We got the class LT by taking the class SL and closing it under Boolean operations. We have observed that LT ⊆ Recog, so certainly any Boolean combination of LT languages will also be recognizable. But what about the class of recognizable languages as a whole? Are Boolean combinations of recognizable (not just LT) languages also recognizable. In answering we can use the same methodology we use to show that any language is recognizable: consider what we need to keep track of in scanning a string in order to determine if it belongs to the language or not and then use that information to build our state set.

Suppose, then, that L = L1 ∩ L2, where L1 and L2 are both recognizable. A string w will be in L iff it is in both L1 and L2. Since they are recognizable there exist DFAs A1 and A2 for which L1 = L(A1) and L2 = L(A2). We can tell if the string is in L1 or L2 simply by keeping track of the state of the corresponding automaton. We can tell if it is in both by keeping track of both states simultaneously.


Related Discussions:- Closure properties of recognizable languages

Finiteness problem for regular languages, The fact that the Recognition Pro...

The fact that the Recognition Problem is decidable gives us another algorithm for deciding Emptiness. The pumping lemma tells us that if every string x ∈ L(A) which has length grea

Mapping reducibility, (c) Can you say that B is decidable? (d) If you someh...

(c) Can you say that B is decidable? (d) If you somehow know that A is decidable, what can you say about B?

Turing machine, prove following function is turing computable? f(m)={m-2,if...

prove following function is turing computable? f(m)={m-2,if m>2, {1,if

Finiteness of languages is decidable, To see this, note that if there are a...

To see this, note that if there are any cycles in the Myhill graph of A then L(A) will be infinite, since any such cycle can be repeated arbitrarily many times. Conversely, if the

Boolean operations - class of recognizable languages, Theorem The class of ...

Theorem The class of recognizable languages is closed under Boolean operations. The construction of the proof of Lemma 3 gives us a DFA that keeps track of whether or not a give

Powerset construction, As de?ned the powerset construction builds a DFA wit...

As de?ned the powerset construction builds a DFA with many states that can never be reached from Q′ 0 . Since they cannot be reached from Q′ 0 there is no path from Q′ 0 to a sta

Shell script, shell script to print table in given range

shell script to print table in given range

Finite-state automaton, Paths leading to regions B, C and E are paths which...

Paths leading to regions B, C and E are paths which have not yet seen aa. Those leading to region B and E end in a, with those leading to E having seen ba and those leading to B no

Automaton theory, let G=(V,T,S,P) where V={a,b,A,B,S}, T={a,b},S the start ...

let G=(V,T,S,P) where V={a,b,A,B,S}, T={a,b},S the start symbol and P={S->Aba, A->BB, B->ab,AB->b} 1.show the derivation sentence for the string ababba 2. find a sentential form

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd