Parsing Questions

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21.

Which of the following grammar rules violate the requirements of an operator grammar?
(i) P -> QR
(ii) P -> QsR
(iii) P -> ?
(iV) P -> QtRr

A

(i) only

B

(i) and (iii) only

C

(ii) and (iii) only

D

(iii) and (iv) only

Correct Answer: B

An operator precedence parser is a bottom-up parser that interprets an operator-precedence grammar. Consider the grammar with the following translation rules and E as the start symbol. A -> A1 #B {A.value = A1.value * B.value} | B {A.value = B.value} B-> B1 & F {B.value = B1.value + C.value} |C {B.value= C.value } C -> num {C.value = num.value}.

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22.

Compute E.value for the root of the parse tree for the expression:2 # 3 & 5 # 6 &4.

A

200

B

180

C

160

D

40

Correct Answer: C

Higher precedence operator will never produce an expression with operator with lower precedence.&># in terms of precedence order.

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23.

Given the following expression grammar:

E -> E * F | F+E | F
F -> F-F | id

which of the following is true?

A

* has higher precedence than +

C

+ and

D

+ has higher precedence than *

Correct Answer: B

Precedence is that a higher precedence operator will never produce an expression with operator with lower precedence. In the given grammar MINUS has higher precedence than ASTERIX.

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24.

Consider a program P that consists of two source modules M1(contains reference to a function defined in M2) and M2 contained in two different files.

A

Edit time

B

Compile time

C

Link time

D

Load time

Correct Answer: C

Compiler transforms source code into the machine language which is in binary. Kinds of object codes: i. Defined symbols, which allow it to be called by other modules, ii. Undefined symbols, which call the other modules where these symbols are defined, and iii. Symbols which are used internally within object file for relocation.

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25.

Which of the following suffices to convert an arbitrary CFG to an LL(1) grammar?

A

Removing left recursion only

B

Factoring the grammar alone

C

Factoring & left recursion removal

D

None of the mentioned

Correct Answer: D

Factoring as well as left recursion removal do not suffice to convert an arbitrary CFG to LL(1) grammar.

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26.

Assume that the SLR parser for a grammar G has n1 states and the LALR parser for G has n2 states.

A

n1 is necessarily less than n2

B

n1 is necessarily equal to n2

C

n1 is necessarily greater than n2

D

none of the mentioned

Correct Answer: B

SLR parser has less range of context free languages than LALR but still both n1 & n2 are same for SLR & LALR respectively.

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27.

Match the following.

P. Regular expression        1. Syntax analysis
Q. Pushdown automata         2. Code generation
R. Dataflow analysis         3. Lexical analysis
S. Register allocation       4. Code optimization

A

P-4. Q-1, R-2, S-3

B

P-3, Q-1, R-4, S-2

C

P-3, Q-4, R-1, S-2

D

P-2, Q-1, R-4, S-3

Correct Answer: B

Syntax analysis has Regular expressions. The code optimization goes hand in hand with data flow analysis. Whereas CFG is related to PDA which is related to syntax analysis Register allocation is used in reference with code generation.

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28.

Find the TRUE statement?

I.  There exist parsing algorithms for some programming languages which has O(3) complexity.
II.  A programming language which allows recursion can be implemented with static storage allocation.
III. No L-attributed definition can be evaluated in The framework of bottom-up parsing.
IV. Code improving transformations can be performed at both intermediate code level and source Language.

A

I and II

B

I and IV

C

III and IV

D

I III and IV

Correct Answer: B

In recursion, space used but recursive call can

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29.

Which of the following describes a handle (as applicable to LR-parsing) appropriately?

A

Position where next reduce or shift operation will occur

B

The next step has use of Non-terminal for reduction

C

Used for reduction in a coming-up step along with a position in the sentential form where the next shift or reduce operation will occur

D

Used in the next step for reduction along with a position in the sentential form where the right hand side of the production may be found

Correct Answer: D

the next step in LR parsing shall have a Reduction.

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30.

Which one of the following is a top-down parser?

A

Recursive descent parser

B

Operator precedence parser

C

An LR(k) parser

D

An LALR(k) parser

Correct Answer: A

Recursive Descent also known as top down parsing also known to be LL(1). Consider the following two statements: P: Every regular grammar is LL(1) Q: Regular is LR(1) grammar.

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