Formal Language - 22



- G is not a type 1 grammar because the production rule C violates the condition of type 1 grammar.

So G is a type 0 grammar (structural grammar). 1b) G = (N, T, P, S); in which:

N = {S, A, B, C, D} ; T = {a, b};

P ={S ABC; AB aADb; Dab bDb; DbC BaC; aB Ba; AB ; C };

S = S.

2a) - G is not a type 3 grammar because the production rule DF B violates the condition of type 3 grammar;

- G is not a type 2 grammar because the production rule DF B violates the condition of type 2 grammar;

- G is not a type 1 grammar because the production rule DF B violates the condition of type 1 grammar.

So G is a type 0 grammar (constructive grammar).

2b) G = (N, T, P, S); in which:

N = {S, A, B, C, D, E, F} ; T = {a, b};

P = {S ABaDF; BD DCB; BC bB; AD AAE; EC AE; EB BE; EF BBDF; DF B | };

S = S.

3a) - G is not a type 3 grammar because the production rule S SS violates the condition of type 3 grammar;

- G is a type 2 grammar (context-free grammar) because all of its productions satisfy the conditions of type 2 grammar.

3b) G = (N, T, P, S) with: N = {S};

T = {a, b};

P = {S SS; S aSb; S bSa; S ab; S ba}.


S = S.

4a) G is a type 3 grammar (regular grammar) because all its productions satisfy the conditions of a right linear grammar.

4b) G = (N, T, P, S) with: N = {S};

T = {a};

P = {S aS; S a; A abB | B| }; S = S.

1.18. 1) - G is a type 3 grammar (left linear grammar) because all of its productions satisfy the conditions of left linear grammar.

- G = (N, T, P, S) with:

N = {S, A};

T = {a, b};

P = {S Sab; S Aa; A Sa; A Abba; A a; S  }; S = S.

2) - G is a type 1 grammar (context-sensitive grammar) because:

+ G is not a type 3 grammar because the production rule AB BA violates the condition of type 3 grammar;

+ G is not a type 2 grammar because the production rule AB BA violates the condition of type 2 grammar;

+ All of its productions satisfy the conditions of type 1 grammar.

- G = (N, T, P, S) with:

N = {S, A, B};

T = {a, b};

P = {S AB; AB BA; A aA; B Bb; A a; B b}; S = S.

3) - G is a type 1 grammar (context-sensitive grammar) because:

+ G is not a type 3 grammar because the production rule Bb Abb violates the condition of type 3 grammar;



+ G is not a type 2 grammar because the production rule Bb Abb violates the condition of type 2 grammar;

+ All of its productions satisfy the conditions of type 1 grammar.

- G = (N, T, P, S) with:

N = {S, A, B};

T = {a, b};

P = {S A; S AAB; Aa Aba; A aa; Bb Abb; AB

ABB; B b};


S = S.

1.19. 1) - G is a type 3 grammar (left linear grammar) because all of its productions satisfy the conditions of left linear grammar.

- G = (N, T, P, S) with:

N = {S};

T = {a};

P = {S Sa; S a; S  }; S = S.

2) - w = .

Applying the production law S , we have the one-step derivation S .

- w = a.

Applying the production rule S a, we have a one-step derivation S a.

Or

Applying the production rule S Sa, then applying the production rule S  , we have the two-step derivation S

Saa.

- w = aa.

S Sa Saa aa or S Sa aa.

- w = a i ; with i N.

Applying i-1 times the production rule S Sa and once the production rule S a, we have S i a i . Or applying i times the production rule S Sa and once the production rule S  , we have S i+1 a i .

3) L(G) = {a i i N}.


1.20. 1) - G is a type 3 grammar (right linear grammar) because all of its productions satisfy the conditions of right linear grammar.

- G = (N, T, P, S) with:

N = {S, A, B};

T = {a, b};

P = {S aA; A aA; A aB; B bB; B b}; S = S.

2) - w = aab.

S aA aaB aab.

- w = aaaaabb.

S aA aaA aaaA aaaaA aaaaaB aaaaabB aaaaabb.

- w = a i b j ; with i, j N + ; i 2.

Apply the production rule S aA once

Applying i-2 times the production rule A aA and once the production rule A aB, we have S i a i B. Applying j-1 times the production rule B bB and once the production rule B b, we have S i+j a i b j .

3) L(G) = {a i b j ; with i, j N + ; i 2}.

1.21. 1) - G is a type 2 grammar.

- G = (N, T, P, S) with:

N = {S};

T = {a, b};

P = {S bSa; S  }; S = S.

2) - w = .

S .

- w = three.

S bSa ba.

- w = b i a i ; with i N.

Applying the production rule S  bSa i-1 times and the production rule S once , we have S i b i a i .

3) L(G) = {b i a i ; with i N}.



1.22. 1) - G is a type 2 grammar.

- G = (N, T, P, S) with:

N = {S, A};

T = {a, b};

P = {S aAb; S  ; A aAb; A  }; S = S.

2) - w = .

S .

- w = ab.

S aSb ab.

- w = aaaabbbb.

S aAb aaAbb aaaAbbb aaaaAbbbb aaaabbbb.

- w = b i a i ; with i N.

Applying the production rule S once , we have S . Applying the production rule S aAb once

Applying the production rule A  aAb i -1 times and the production rule A once , we have S i+1

a i b i with i N + .

3) L(G) = {a i b i ; with i N}.

1.23. 1) - G is a type 2 grammar.

- G = (N, T, P, S) with:

N = {S, A, B};

T = {a, b};

P = {S AB; A aA; A a; B aB; B b}; S = S.

2) - w = aab.

S AB aAB aaB aab.

- w = aaaaab.

S AB aAB aaAB aaaAB aaaaB aaaaaB aaaaab.

- w = a i b; with i N + .


Apply the production law S AB once.

Applying the production rule A  aA i-1 times and the production rule B aB once , we have S i+1 a i b. Applying B b once , we have S i+2 a i b.

3) L(G) = {a i b; with i N + }.

1.24. 1) S aA; A aA|b|c.

2) S Aab; A aA|b|c.

3) S Aba; A aA|b|c.

4) S Abcd; A aA|b|c. 1.25. 1) S A1; A A0|0.

2) S 0A; A 0A|1.

3) S 0A1; A 0A|0.

Or S AB; A 0A|0; B 1

1.26. 1) S A1; A A1|B; B C000; C .

2) S 000A; A 1A|1.

3) S 000AB; A 1A|1; B .

Or S AB; A 000; B 1B|1.

1.27. S AB; A 0A1|01; B 2B3 | .

1.28. S AB; A aAb| ab; B cB| .

1.29. 1) S abA; A abA| B; B cB|c;

2) S Ac; A Ac| B; B Bab| ab;

3) S abAB; A abA| ; B cB|c. Or S AB; A abA|ab; B cB|c.

1.30. 1) S A2; A A2|B; B B1|C; C 000.

2) S 000A; A 1A| B; B 2B| 2.

3) S 000AB; A 1A|1; B 2B|2.

1.31. 1) S S2| A; A A1|C; C C0| .

2) S 0S|A; A 1A|B; B 2B| .

3) S ABC; A 0A| ; B 1B| ; C 2C| .

1.32. 1) S S3|A; A A2|B; B B1|C; C C0| .


2) S 0S|A; A 1A|B; B 2B|C;C 3C| .

3) S ABCD; A 0A| ; B 1B| ; C 2C| ; D 1D| .

2. Chapter 2 exercises

2.16. 1) Representation of M

a) Tabular form:

- q 0 = A ;

- F = C, E ;

- :


Q

a

b

A

A

B

B

D

E

C

E

D

D

C

E

E

E


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Formal Language - 22


b) Graph form: a a

b a

Start A b B

C b D b E a

a

2) Automat M is a deterministic finite automaton; since q Q and a , we have:

(q, a)1

3) - (A, aaabbaaaa)

+ (A, a) = A; (A, a) = A; (A, a) = A;

+ (A, b) = B;

+ (B, b) = E;

+ (E, a) = E; (E, a) = E; (E, a) = E; (E, a) = E

(A, aaabbaaaa) = E.

- (B, aaaabbaa);

+ (B, a) = D;


+ (D, a) = C;

+ (C, a) = E;

+ (E, a) = E;

+ (E, b) = ;

+ ( , b) = ;

+ ( , a) = .

+ ( , a) = .

(B, aaaabbaa) =.

4) - w = aabaaaaa$

We present the algorithm using a single deterministic automaton to obtain w in the following table:


Step

q

c

initialize

A

a

1

A

a

2

A

b

3

B

a

4

D

a

5

C

a

6

E

a

7

E

a

8

E

$

We have q = E F. So the above automaton guesses that it gets from w = aabaaaaa.

- w = aaaababbb$


Step

q

c

initialize

A

a

1

A

a

2

A

a

3

A

a

4

A

b

5

B

a

6

D

b

7

E

b

8

b

9

$

We have q = F. So the above automaton cannot guess from w = aaaababbb.

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