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Give a counterexample to show that the following construction fails to prove Theorem 1.49, the closure of the class of regular languages under the star operationLet N1=Q1,Σ,δ1,q1,F1 recognize . Construct N=Q1,Σ,δ,q1,F as follows. Nis supposed to recognize A*1.

a. The states of Nare the states of N1.

b. The start state ofN is the same as the start state ofN1 .

c. . F=q1∪F1.The accept states are the old accept states plus its start state.

d. Defineδso that for any and any a∈Σε, δq,a=(δ1q,aq6∈F1ora6=εδ1q,a∪q1q∈F1anda=ε

Short Answer

Expert verified
  1. States of Nare the states of N1 .
  2. The start state of Nis same as start state of N1 .
  3. F=q1∪F1.The accept states for Fare the accept states of F1including the start state.
  4. Define the transitionδnforanyq∈Q1andanya∈∑∈ by using the following transition:

Step by step solution

01

To Apply the Theorem

Theorem 1.49 states that “The class of regular languages is closed under the star operation."

Consider the data,

A language A is recognized by the automataN1=Q1,∑,n1,q1,F1

Assume N is the non-deterministic finite automaton that recognizes the language A1*.

02

To Explain the finite state

We can start step 2 with an example to easily understand. So, let’s see the below example.

Example

Assume a language A1=00*1 .

The finite state automataN1, which recognizes the languageA1is as follows:

03

To Simplify the States

The following procedure is used to construct the finite state automata N, which recognizes the language A1*:

a. States of N are the states of N1.

States of N1are 1,2,3 .

So, States of N are 1,2,3 .

b. The start state of localid="1663213421606" Nis same as start state of localid="1663213414314" N1.

Start state of localid="1663213426131" N1is localid="1663213431322" 1.

So, Start state of localid="1663213439797" Nis localid="1663213435395" 1

c. . localid="1663213443717" F=q1∪F1The accept states for are the accept states of including the start state. So, the accept state for are 1and 3.

d. Define the transition localid="1663213448158" δforanyq∈Q1andanya∈∑∈ by using the following transition:

localid="1663213453268" δ(q,a)=δ1(q,a)   q∉F1  and  a≠ ∈δ1(q,a) ∪{q1}   q∈F1  and  a= ∈

localid="1663213457964" δ(1,∈)=δ1(1,∈)∪{1}                =∅∪{1}                ={1}

localid="1663213462341" δ(3,∈)=δ1(3,∈)∪{1}                =∅∪{1}                ={1}

localid="1663213468584" δ(1,0)=δ1(1,0)                =2δ(1,1)=δ1(1,1)                =3δ(2,0)=δ1(2,0)                 =1δ(2,1)=δ1(2,1)                 =∅δ(3,0)=δ1(3,0)                 =∅δ(3,1)=δ1(3,1)                 =∅

The state diagram for the Finite State Automata is as follows:

Its beginning state is added to the set of accept states in the aforementioned finite automata, as well as some more undesirable strings and the recognised language. The automaton does not get a new beginning state that is also an accept state. As a result, the new state is not added to the automata, resulting in automata that are distinct from either the original automata.

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Most popular questions from this chapter

Question: Each of the following languages is the intersection of two simpler languages. In each part, construct DFAs for the simpler languages, then combine them using the construction discussed in footnote 3 (page 46) to give the state diagram of a DFA for the language given. In all parts,∑=a,b.

a.{w|w\kern1pt has  at  least  three  a's  and  at  least  two  b's}b.w|w\kern1pt has  exactly  two  a's  and  at  least  two  b'sc.w|w\kern1pt has  even number  of  a's  and  one or  two  b'sd.{w|w\kern1pt has  even number  of  a's  and eachais followed by at least  one b}e.w|w\kern1pt starts  with  an  a  and  has at most one  bf.w|w\kern1pt has an odd number ofa's  and ends with a  bg.w|w\kern1pt has even length and an odd number ofa's

Use the construction in the proof of Theorem 1.45 to give the state diagrams of NFAs recognizing the union of the languages described in

a. Exercises 1.6a and 1.6b.

b. Exercises 1.6c and 1.6f

Give informal English descriptions of PDAs for the languages in Exercise 2.6

Give context-free grammars generating the following languages.

a. The set of strings over the alphabet a,bwith more a's than b's

b. The complement of the language anbnn≥0.

c. w#xwRis a substring of x for w,x ∈0,1*

d. localid="1662105288591" x1#x2#...#xkk≥1,each xilocalid="1662105304877" ∈a,b*,and for some i and j ,localid="1662105320570" xi=xjR

Use the construction in the proof of Theorem 1.49 to give the state diagrams of NFAs recognizing the star of the languages described in

a. Exercise 1.6b

b. Exercise 1.6 j

c. Exercise 1.6m

THEOREM1.49

The class of regular languages is closed under the star operation.

Write formal descriptions of the following sets.

  1. The set containing the numbers1,10, and100
  2. The set containing all integers that are greater than5
  3. The set containing all natural numbers that are less than5
  4. The set containing the string aba
  5. The set containing the empty string
  6. The set containing nothing at all
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