Regular Expressions Questions

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1.

The grammar defined by regular expressions is known as?

A

regular language

B

regular grammar

C

regular notations

D

regular operation

Correct Answer: B

The grammar defined by regular expressions is known as regular grammar

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2.

The language defined by regular grammar is known as?

A

regular language

B

regular grammar

C

regular notations

D

regular operation

Correct Answer: A

The language defined by regular grammar is known as regular language.

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3.

Union of two languages L and M is written as?

A

LM = {st | s is in L and t is in M}

B

L+M

C

L*M

D

L U M = {s | s is in L or s is in M}

Correct Answer: D

Union of two languages L and M is written as L U M = {s | s is in L or s is in M}

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4.

Concatenation (.) has the ________ highest precedence

A

first

B

second

C

third

D

fourth

Correct Answer: B

Concatenation (.) has the second highest precedence

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5.

Which of them are not left associative ?

A

*

B

|

C

plus(+)

D

.

Correct Answer: C

*, concatenation (.), and | (pipe sign) are left associative

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6.

The RE in which any number of 0?s is followed by any number of 1?s followed by any number of 2?s is?

A

(0+1+2)*

B

0*1*2*

C

0* + 1 + 2

D

(0+1)*2*

Correct Answer: B

The order for the desired string is 012 and for any number of 0s we write 0* for any number of 1s we denote it by 1* and similarly for 2*.Thus 0*1*2*.

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7.

Which of the following is NOT the set of regular expression R = (ab + abb)* bbab?

A

ababbbbab

B

abbbab

C

ababbabbbab

D

abababab

Correct Answer: A

ab followed by abb which is followed by bbab.

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8.

Consider the production of the grammar S->AA A->aa A->bb Describe the language specified by the production grammar.

A

L = {aaaa,aabb,bbaa,bbbb}

B

L = {abab,abaa,aaab,baaa}

C

L = {aaab,baba,bbaa,bbbb}

D

L = {aaaa,abab,bbaa,aaab}

Correct Answer: A

Explanation: S->AA (substitute A->aa) S->aaaa S->AA (substitute A->aa ) S->aaA (substitute A->bb) S->aabb S->AA (substitute A->bb the A->aa) S->bbaa S->AA (substitute A->bb) S->bbbb.

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9.

If R is regular language and Q is any language (regular/ non regular), then Pref (Q in R) is _____________

A

Non-regular

B

Equal

C

Infinite

D

Regular

Correct Answer: D

So says the definition of Regular Grammar

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10.

The non terminal that gives null will said to have a null production

A

TRUE

B

FALSE

C

Can be true or false

D

Can not say

Correct Answer: A

True, The non terminal that gives null will said to have a null production.

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