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All questions of Syntax Directed Translation for Computer Science Engineering (CSE) Exam
A translation scheme is shown as-
Output for 3 * 2 + 4 is ______.
Correct answer is '18'. Can you explain this answer?
A translation scheme is shown as-
Output for 3 * 2 + 4 is ______.
Output for 3 * 2 + 4 is ______.
|
Sudhir Patel answered |
Given grammar, is
is an ambiguous grammar.
Therefore two outputs are possible for single input i.e. 3 * 2 + 4.
Like: output 1 = 10
output 2 = 18
This problem is resolved by YACC Tool. So, according to rule of YACC Tool:
(1) S-R conflict is resolved by ‘S’
(2) Ri – Rj conflict is resolved by Ri where i < j.
So, scanning input from left to right
is an ambiguous grammar.Therefore two outputs are possible for single input i.e. 3 * 2 + 4.
Like: output 1 = 10
output 2 = 18
This problem is resolved by YACC Tool. So, according to rule of YACC Tool:
(1) S-R conflict is resolved by ‘S’
(2) Ri – Rj conflict is resolved by Ri where i < j.
So, scanning input from left to right
Consider the syntax-directed transition scheme given below with non-terminals {A, B, C} and terminals {a, b, c}
S → AC {print*} | aB{print ***}
A → Sb {print **}
B → c {print *}
C → S {print *}
Using the above SDT, calculate the total number of * that are going to be printed in the output for the input acbac.
Correct answer is '12'. Can you explain this answer?
Consider the syntax-directed transition scheme given below with non-terminals {A, B, C} and terminals {a, b, c}
S → AC {print*} | aB{print ***}
A → Sb {print **}
B → c {print *}
C → S {print *}
Using the above SDT, calculate the total number of * that are going to be printed in the output for the input acbac.
S → AC {print*} | aB{print ***}
A → Sb {print **}
B → c {print *}
C → S {print *}
Using the above SDT, calculate the total number of * that are going to be printed in the output for the input acbac.
|
|
Sudhir Patel answered |
Input: a c b a c
(1) Construct the syntax tree for the given input.
(1) Construct the syntax tree for the given input.
Consider the following grammar (that admits a series of declarations, followed by expressions) and the associated syntax directed translation (SDT) actions, given as pseudo-code:
P → D* E*
D → int ID {record that ID.lexeme is of type int}
D → bool ID { record that ID.lexeme is of type bool}
E → E1 + E2 {check that E1.type = E2.type = int; set E.type := int}
E → !E1 {check that E1.type = bool; set E.type := bool}
E → ID {set E.type := int}
With respect to the above grammar; which one of the following choices is correct?- a)The actions will lead to infinite loop.
- b)The actions can be used to correctly type-check any syntactically correct program.
- c)The actions can be used to type-check syntactically correct boolean variable declarations and boolean expressions.
- d)The actions can be used to type-check syntactically correct integer variable declarations and integer expressions.
Correct answer is option 'D'. Can you explain this answer?
Consider the following grammar (that admits a series of declarations, followed by expressions) and the associated syntax directed translation (SDT) actions, given as pseudo-code:
P → D* E*
D → int ID {record that ID.lexeme is of type int}
D → bool ID { record that ID.lexeme is of type bool}
E → E1 + E2 {check that E1.type = E2.type = int; set E.type := int}
E → !E1 {check that E1.type = bool; set E.type := bool}
E → ID {set E.type := int}
With respect to the above grammar; which one of the following choices is correct?
P → D* E*
D → int ID {record that ID.lexeme is of type int}
D → bool ID { record that ID.lexeme is of type bool}
E → E1 + E2 {check that E1.type = E2.type = int; set E.type := int}
E → !E1 {check that E1.type = bool; set E.type := bool}
E → ID {set E.type := int}
With respect to the above grammar; which one of the following choices is correct?
a)
The actions will lead to infinite loop.
b)
The actions can be used to correctly type-check any syntactically correct program.
c)
The actions can be used to type-check syntactically correct boolean variable declarations and boolean expressions.
d)
The actions can be used to type-check syntactically correct integer variable declarations and integer expressions.
|
Ankita Bose answered |
Understanding the Grammar and Actions
The provided grammar allows for a series of variable declarations followed by expressions, specifically for integer and boolean types. Each production rule is coupled with syntax-directed translation (SDT) actions which help in type-checking.
Type Declarations
- The rules for declarations are:
- D → int ID: Records that ID is of type int.
- D → bool ID: Records that ID is of type bool.
These rules imply that the grammar can handle both integer and boolean variable declarations.
Type Checking for Expressions
- The expression rules are:
- E → E1 + E2: Requires both operands to be of type int.
- E → !E1: Requires E1 to be of type bool.
- E → ID: For integers, it sets the type based on the ID's declaration.
The actions effectively enforce type correctness for integer expressions but have no provisions for handling boolean expressions.
Analysis of the Options
- Option A: Infinite Loop
- The grammar and actions are well-defined, and there is no recursion that could lead to an infinite loop.
- Option B: Correct Type-Check for Any Program
- The grammar does not support the type-checking of boolean expressions, so this option is incorrect.
- Option C: Type-Check Boolean Declarations and Expressions
- While boolean declarations are supported, boolean expressions are not adequately handled in the rules provided, making this option incorrect.
- Option D: Type-Check Integer Declarations and Expressions
- This is correct. The grammar and actions effectively handle integer declarations and ensure type consistency for integer expressions, making it the most suitable choice.
Conclusion
The correct answer is option D, as the grammar and SDT actions successfully manage integer type declarations and expressions, ensuring type safety in those contexts.
The provided grammar allows for a series of variable declarations followed by expressions, specifically for integer and boolean types. Each production rule is coupled with syntax-directed translation (SDT) actions which help in type-checking.
Type Declarations
- The rules for declarations are:
- D → int ID: Records that ID is of type int.
- D → bool ID: Records that ID is of type bool.
These rules imply that the grammar can handle both integer and boolean variable declarations.
Type Checking for Expressions
- The expression rules are:
- E → E1 + E2: Requires both operands to be of type int.
- E → !E1: Requires E1 to be of type bool.
- E → ID: For integers, it sets the type based on the ID's declaration.
The actions effectively enforce type correctness for integer expressions but have no provisions for handling boolean expressions.
Analysis of the Options
- Option A: Infinite Loop
- The grammar and actions are well-defined, and there is no recursion that could lead to an infinite loop.
- Option B: Correct Type-Check for Any Program
- The grammar does not support the type-checking of boolean expressions, so this option is incorrect.
- Option C: Type-Check Boolean Declarations and Expressions
- While boolean declarations are supported, boolean expressions are not adequately handled in the rules provided, making this option incorrect.
- Option D: Type-Check Integer Declarations and Expressions
- This is correct. The grammar and actions effectively handle integer declarations and ensure type consistency for integer expressions, making it the most suitable choice.
Conclusion
The correct answer is option D, as the grammar and SDT actions successfully manage integer type declarations and expressions, ensuring type safety in those contexts.
COMPILER is used to?- a)convert low level into high level language
- b)convert high level into low level language
- c)translate assembly language into machine language
- d)none of these
Correct answer is option 'B'. Can you explain this answer?
COMPILER is used to?
a)
convert low level into high level language
b)
convert high level into low level language
c)
translate assembly language into machine language
d)
none of these
|
|
Sudhir Patel answered |
Compiler is a translator which converts high level language (source program) into low level language (machine program).
Convert the pre-fix expression to in-fix
--*+ABC*DE+FG- a)(A - B)*C+(D*E)-(F+G)
- b)(A+B)*C-(D-E)*(F-G)
- c)(A+B-C)*(D-E)*(F+G)
- d)(A+B)*C - (D*E)-(F+G)
Correct answer is option 'D'. Can you explain this answer?
Convert the pre-fix expression to in-fix
--*+ABC*DE+FG
--*+ABC*DE+FG
a)
(A - B)*C+(D*E)-(F+G)
b)
(A+B)*C-(D-E)*(F-G)
c)
(A+B-C)*(D-E)*(F+G)
d)
(A+B)*C - (D*E)-(F+G)
|
|
Sudhir Patel answered |
(A+B)*C - (D*E)-(F+G)
+AB*C - (D*E)-(F+G)
+AB*C - *DE - (F+G)
+AB*C - *DE - +FG
*+ABC - *DE - +FG
-*+ABC*DE - +FG
--*+ABC*DE+FG
+AB*C - (D*E)-(F+G)
+AB*C - *DE - (F+G)
+AB*C - *DE - +FG
*+ABC - *DE - +FG
-*+ABC*DE - +FG
--*+ABC*DE+FG
_____ is done by attaching rules or algorithms or program fragments to productions in a grammar.- a)Syntax-directed translation
- b)Lexical analysis
- c)Execution
- d)Loading
Correct answer is option 'A'. Can you explain this answer?
_____ is done by attaching rules or algorithms or program fragments to productions in a grammar.
a)
Syntax-directed translation
b)
Lexical analysis
c)
Execution
d)
Loading
|
|
Sudhir Patel answered |
Syntax Directed Translation is done by attaching augmented rules to the grammar that facilitate semantic analysis. It involves passing information top bottom and/or bottom up the parse tree in form of attributes attached to the nodes. Syntax directed translation rules use the following
- lexical values of nodes
- constants
- attributes associated to the non-terminals in their definitions.
Consider the following grammar along with translation rules.
Here # and % are operators and id is a token that represents an integer and id•val represents the corresponding integer value. The set of non-terminals is {S, T, R, P} and a subscripted non-terminal indicates an instance of the non-terminal.
Using this translation scheme, the computed value of S•val for root of the parse tree for the expression 20#10%5#8%2%2 is ______.
Correct answer is '80'. Can you explain this answer?
Consider the following grammar along with translation rules.
Here # and % are operators and id is a token that represents an integer and id•val represents the corresponding integer value. The set of non-terminals is {S, T, R, P} and a subscripted non-terminal indicates an instance of the non-terminal.
Using this translation scheme, the computed value of S•val for root of the parse tree for the expression 20#10%5#8%2%2 is ______.
Here # and % are operators and id is a token that represents an integer and id•val represents the corresponding integer value. The set of non-terminals is {S, T, R, P} and a subscripted non-terminal indicates an instance of the non-terminal.
Using this translation scheme, the computed value of S•val for root of the parse tree for the expression 20#10%5#8%2%2 is ______.
|
|
Sudhir Patel answered |
Concept:
The given grammar along with translation rules is,
The given string is= 20#10%5#8%2%2
Rule 1:
In the given SDT, % has more precedence than # and % because it is away from starting symbol.
Rule 2:
Both % and * are left-associative because the left non-terminal is present left most on the right side grammar.
The given string is= 20#10%5#8%2%2
The given string is= 20x10÷5 x 8÷2÷2
The given string is= 20 x2x4÷2
The given string is= 20 x2x2
The given string is= 40 x2
The given string is= 80
Hence the correct answer is 80.
The given grammar along with translation rules is,
The given string is= 20#10%5#8%2%2
Rule 1:
In the given SDT, % has more precedence than # and % because it is away from starting symbol.
Rule 2:
Both % and * are left-associative because the left non-terminal is present left most on the right side grammar.
The given string is= 20#10%5#8%2%2
The given string is= 20x10÷5 x 8÷2÷2
The given string is= 20 x2x4÷2
The given string is= 20 x2x2
The given string is= 40 x2
The given string is= 80
Hence the correct answer is 80.
Which of the following phase of the compiler is Syntax Analysis?- a)Second
- b)Third
- c)First
- d)All of the mentioned
Correct answer is option 'A'. Can you explain this answer?
Which of the following phase of the compiler is Syntax Analysis?
a)
Second
b)
Third
c)
First
d)
All of the mentioned
|
|
Sudhir Patel answered |
It is the Second Phase of the Compiler after Lexical Analyzer. It is also called Hierarchical Analysis or Parsing.
The below mentioned picture shows the:
- a)Conceptual view of lexical analysis
- b)Conceptual view of syntax analysis
- c)Conceptual view of syntax directed translation
- d)Conceptual view of top-down parsing
Correct answer is option 'C'. Can you explain this answer?
The below mentioned picture shows the:
a)
Conceptual view of lexical analysis
b)
Conceptual view of syntax analysis
c)
Conceptual view of syntax directed translation
d)
Conceptual view of top-down parsing
|
|
Sudhir Patel answered |
Concept:
Basic idea of syntax directed translation:
Syntax-Directed Constructing a parse tree or syntax tree and computing the values of attributes at the nodes of the tree by visiting them in some order is the definition of translation. In many circumstances, translation can be done without creating an explicit tree during parsing.
Basic idea of syntax directed translation:
Syntax-Directed Constructing a parse tree or syntax tree and computing the values of attributes at the nodes of the tree by visiting them in some order is the definition of translation. In many circumstances, translation can be done without creating an explicit tree during parsing.
Evaluation Orders for syntax directed translation:
- Dependency Graphs.
- Ordering the Evaluation of Attributes.
- S-Attributed Definitions.
- L-Attributed Definitions.
- Semantic Rules
Note:
- Evaluation of the semantic rules may generate code, save information in a symbol table, issue error messages, or perform any other activities.
- Special cases of syntax-directed definitions can be implemented in a single pass by evaluating semantic rules during parsing, without explicitly constructing a parse tree or a graph showing dependencies between attributes.
Hence the correct answer is the Conceptual view of syntax-directed translation.
Consider the following grammar and the semantic actions to support the inherited type declaration attributes. Let X1, X2, X3, X4, X5 and X6 be the placeholders for the non-terminals D, T, L or L1 in the following table:
Which one of the following are the appropriate choices for X1, X2, X3 and X4?- a)X1 = L, X2 = T, X3 = L1, X4 = L
- b)X1 = T, X2 = L, X3 = L1, X4 = T
- c)X1 = L, X2 = L, X3 = L1, X4 = T
- d)X1 = T, X2 = L, X3 = T, X4 = L1
Correct answer is option 'A'. Can you explain this answer?
Consider the following grammar and the semantic actions to support the inherited type declaration attributes. Let X1, X2, X3, X4, X5 and X6 be the placeholders for the non-terminals D, T, L or L1 in the following table:
Which one of the following are the appropriate choices for X1, X2, X3 and X4?
a)
X1 = L, X2 = T, X3 = L1, X4 = L
b)
X1 = T, X2 = L, X3 = L1, X4 = T
c)
X1 = L, X2 = L, X3 = L1, X4 = T
d)
X1 = T, X2 = L, X3 = T, X4 = L1
|
|
Sudhir Patel answered |
Concepts:
Synthesized attributes:
A Synthesized attribute is an attribute of the non-terminal on the left-hand side of a production. Synthesized attributes represent information that is being passed up the parse tree. The attribute can take value only from its children.
S-attributed SDT
If an SDT uses only synthesized attributes, it is called as S-attributed SDT.
Synthesized attributes:
A Synthesized attribute is an attribute of the non-terminal on the left-hand side of a production. Synthesized attributes represent information that is being passed up the parse tree. The attribute can take value only from its children.
S-attributed SDT
If an SDT uses only synthesized attributes, it is called as S-attributed SDT.
Inherited attributes:
An attribute of a nonterminal on the right-hand side of a production is called an inherited attribute. The attribute can take value either from its parent or from its siblings.
An attribute of a nonterminal on the right-hand side of a production is called an inherited attribute. The attribute can take value either from its parent or from its siblings.
L-attributed SDT
If an SDT uses both synthesized attributes and inherited attributes with a restriction that inherited attribute can inherit values from left siblings only, it is called as L-attributed SDT.
If an SDT uses both synthesized attributes and inherited attributes with a restriction that inherited attribute can inherit values from left siblings only, it is called as L-attributed SDT.
In SDT:
D → T L {X1.type = X2.type}
L.type = T.type (Inherited attributed)
∴ X1 = L and X2 = T
T can be int or float
In SDT:
L → L1, id {X3.type = X4.type}
L1.type = L.type (Inherited attributed)
∴ X3 = L1 and X4 = L
Hence option 1 is correct.
D → T L {X1.type = X2.type}
L.type = T.type (Inherited attributed)
∴ X1 = L and X2 = T
T can be int or float
In SDT:
L → L1, id {X3.type = X4.type}
L1.type = L.type (Inherited attributed)
∴ X3 = L1 and X4 = L
Hence option 1 is correct.
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