1
GATE CSE 2006
MCQ (Single Correct Answer)
+2
-0.6

Which one of the following grammars generates the following language?

$$L = \left( {{a^i}{b^j}|i \ne j} \right)$$
A
$$\eqalign{ & S \to AC\,|\,CB \cr & C \to aCb\,|\,a\,|\,b \cr & A \to aA\,|\, \in \cr & B \to Bb\,|\, \in \cr} $$
B
$$S \to aS\,|\,Sb\,|\,a\,|\,b$$
C
$$\eqalign{ & S \to AC\,|\,CB \cr & C \to aCb\,|\, \in \cr & A \to aA\,|\, \in \cr & B \to Bb\,|\, \in \cr} $$
D
$$\eqalign{ & S \to AC\,|\,CB \cr & C \to aCb\,|\, \in \cr & A \to aA\,|\,a \cr & B \to Bb\,|\,b \cr} $$
2
GATE CSE 2005
MCQ (Single Correct Answer)
+2
-0.6

Consider the following expression grammar. The seman­tic rules for expression calculation are stated next to each grammar production.

$$\eqalign{ & E \to number\,\,\,\,\,E.val = number.val \cr & \,\,\,\,\,\,\,\,\,\,\,|E\,\,' + '\,\,E\,\,\,\,\,\,{E^{\left( 1 \right)}}.val = {E^{\left( 2 \right)}}.val + {E^{\left( 3 \right)}}.val \cr & \,\,\,\,\,\,\,\,\,\,\,|\,E\,\,' \times '\,\,E\,\,\,\,\,\,\,{E^{\left( 1 \right)}}.val = {E^{\left( 2 \right)}}.val \times {E^{\left( 3 \right)}}.val \cr} $$

Assume the conflicts in the previous question are resolved and an LALR(1) parser is generated for parsing arithmetic expressions as per the given grammar. Consider an expression
3 × 2 + 1.
What precedence and associativity properties does the generated parser realize?

A
Equal precedence and left associativity; ex­pression is evaluated to 7
B
Equal precedence and right associativity; ex­pression is evaluated to 9
C
Precedence of $$' \times '$$ is higher than that of ‘+’, and both operators are left associative; expression is evaluated to 7
D
Precedence of ‘+’ is higher than that of $$' \times '$$, and both operators are left associative; expression is evaluated to 9
3
GATE CSE 2005
MCQ (Single Correct Answer)
+2
-0.6

Consider the following expression grammar. The seman­tic rules for expression calculation are stated next to each grammar production.

$$\eqalign{ & E \to number\,\,\,\,\,E.val = number.val \cr & \,\,\,\,\,\,\,\,\,\,\,|E\,\,' + '\,\,E\,\,\,\,\,\,{E^{\left( 1 \right)}}.val = {E^{\left( 2 \right)}}.val + {E^{\left( 3 \right)}}.val \cr & \,\,\,\,\,\,\,\,\,\,\,|\,E\,\,' \times '\,\,E\,\,\,\,\,\,\,{E^{\left( 1 \right)}}.val = {E^{\left( 2 \right)}}.val \times {E^{\left( 3 \right)}}.val \cr} $$

The above grammar and the semantic rules are fed to a yacc tool (which is an LALR (1) parser generator) for parsing and evaluating arithmetic expressions. Which one of the following is true about the action of yacc for the given grammar?

A
It detects recursion and eliminates recursion
B
It detects reduce-reduce conflict, and resolves
C
It detects shift-reduce conflict, and resolves the conflict in favor of a shift over a reduce action
D
It detects shift-reduce conflict, and resolves the conflict in favor of a reduce over a shift action
4
GATE CSE 2005
MCQ (Single Correct Answer)
+2
-0.6

Consider the grammar

$$S \to \left( S \right)\,|\,a$$

Let the number of states in SLR(1), LR(1) and LALR(1) parsers for the grammar be n1, n2 and n3 respectively.

The following relationship holds good
A
n1 < n2 < n3
B
n1 = n3 < n2
C
n1 = n2 = n3
D
n1 ≥ n3 ≥ n2
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