Computer Science Engineering (CSE) Exam > Computer Science Engineering (CSE) Questions > Consider the following expression grammar. Th...
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Consider the following expression grammar. The semantic rules for expression calculation are stated next to each grammar production.
E → number E.val = number. val
| E '+' E E(1).val = E(2).val + E(3).val
| E '×' E E(1).val = E(2).val × E(3).val
| E '+' E E(1).val = E(2).val + E(3).val
| E '×' E E(1).val = E(2).val × E(3).val
Q. 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
Correct answer is option 'C'. Can you explain this answer?
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Verified Answer
Consider the following expression grammar. The semantic rules fo...
E→ number |E '+'E|E'x' E
Shift reduce conflict and resolves the conflict in favor of a shift over a reduce action.
Consider the following configuration where shift-reduce conflict occurs.
Stack Input ...
E+Ex E..$
Most Upvoted Answer
Consider the following expression grammar. The semantic rules fo...
Explanation:
The given grammar and semantic rules are fed to a yacc tool, which is an LALR(1) parser generator. Let's analyze the action of yacc for the given grammar.
Shift-Reduce Conflict:
A shift-reduce conflict occurs when the parser is unsure whether to shift (read the next input symbol and push it onto the stack) or reduce (apply a production rule and replace a set of symbols on top of the stack with a non-terminal).
In the given grammar, there are two instances of shift-reduce conflict:
1. Shift-Reduce Conflict in Production E → E E (1) E.val = E(2).val E(3).val:
- When the parser sees the first E in E E, it can either shift (read the next input symbol) or reduce (apply the production rule E → E E (1) E.val = E(2).val E(3).val).
- The parser cannot decide whether to shift or reduce solely based on the current input symbol and the symbols on top of the stack.
- In this case, yacc resolves the conflict in favor of a shift over a reduce action. This means that the parser will shift and read the next input symbol.
2. Shift-Reduce Conflict in Production E → E E (1) E.val = E(2).val E(3).val:
- When the parser sees the second E in E E, it can either shift or reduce.
- Again, the parser cannot decide whether to shift or reduce based on the current input symbol and the symbols on top of the stack.
- Yacc resolves this conflict in favor of a shift over a reduce action. The parser will shift and read the next input symbol.
Resolution of Shift-Reduce Conflict:
The resolution of shift-reduce conflicts in yacc is based on the principle of "precedence and associativity". Precedence and associativity rules are used to determine whether to shift or reduce when there is a conflict.
In the case of the given grammar, the shift-reduce conflicts are resolved in favor of a shift over a reduce action. This means that the parser will always shift and read the next input symbol when it encounters a conflict.
Therefore, the correct answer is option C: yacc detects shift-reduce conflicts and resolves the conflict in favor of a shift over a reduce action.
The given grammar and semantic rules are fed to a yacc tool, which is an LALR(1) parser generator. Let's analyze the action of yacc for the given grammar.
Shift-Reduce Conflict:
A shift-reduce conflict occurs when the parser is unsure whether to shift (read the next input symbol and push it onto the stack) or reduce (apply a production rule and replace a set of symbols on top of the stack with a non-terminal).
In the given grammar, there are two instances of shift-reduce conflict:
1. Shift-Reduce Conflict in Production E → E E (1) E.val = E(2).val E(3).val:
- When the parser sees the first E in E E, it can either shift (read the next input symbol) or reduce (apply the production rule E → E E (1) E.val = E(2).val E(3).val).
- The parser cannot decide whether to shift or reduce solely based on the current input symbol and the symbols on top of the stack.
- In this case, yacc resolves the conflict in favor of a shift over a reduce action. This means that the parser will shift and read the next input symbol.
2. Shift-Reduce Conflict in Production E → E E (1) E.val = E(2).val E(3).val:
- When the parser sees the second E in E E, it can either shift or reduce.
- Again, the parser cannot decide whether to shift or reduce based on the current input symbol and the symbols on top of the stack.
- Yacc resolves this conflict in favor of a shift over a reduce action. The parser will shift and read the next input symbol.
Resolution of Shift-Reduce Conflict:
The resolution of shift-reduce conflicts in yacc is based on the principle of "precedence and associativity". Precedence and associativity rules are used to determine whether to shift or reduce when there is a conflict.
In the case of the given grammar, the shift-reduce conflicts are resolved in favor of a shift over a reduce action. This means that the parser will always shift and read the next input symbol when it encounters a conflict.
Therefore, the correct answer is option C: yacc detects shift-reduce conflicts and resolves the conflict in favor of a shift over a reduce action.
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Consider the following expression grammar. The semantic rules for expression calculation are stated next to each grammar production.E → number E.val = number. val| E '+' E E(1).val = E(2).val + E(3).val| E '×' E E(1).val = E(2).val × E(3).valQ.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 recursionb)It detects reduce-reduce conflict, and resolvesc)It detects shift-reduce conflict, and resolves the conflict in favor of a shift over a reduce actiond)It detects shift-reduce conflict, and resolves the conflict in favor of a reduce over a shift actionCorrect answer is option 'C'. Can you explain this answer?
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Consider the following expression grammar. The semantic rules for expression calculation are stated next to each grammar production.E → number E.val = number. val| E '+' E E(1).val = E(2).val + E(3).val| E '×' E E(1).val = E(2).val × E(3).valQ.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 recursionb)It detects reduce-reduce conflict, and resolvesc)It detects shift-reduce conflict, and resolves the conflict in favor of a shift over a reduce actiond)It detects shift-reduce conflict, and resolves the conflict in favor of a reduce over a shift actionCorrect answer is option 'C'. Can you explain this answer? for Computer Science Engineering (CSE) 2024 is part of Computer Science Engineering (CSE) preparation. The Question and answers have been prepared according to the Computer Science Engineering (CSE) exam syllabus. Information about Consider the following expression grammar. The semantic rules for expression calculation are stated next to each grammar production.E → number E.val = number. val| E '+' E E(1).val = E(2).val + E(3).val| E '×' E E(1).val = E(2).val × E(3).valQ.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 recursionb)It detects reduce-reduce conflict, and resolvesc)It detects shift-reduce conflict, and resolves the conflict in favor of a shift over a reduce actiond)It detects shift-reduce conflict, and resolves the conflict in favor of a reduce over a shift actionCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for Computer Science Engineering (CSE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Consider the following expression grammar. The semantic rules for expression calculation are stated next to each grammar production.E → number E.val = number. val| E '+' E E(1).val = E(2).val + E(3).val| E '×' E E(1).val = E(2).val × E(3).valQ.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 recursionb)It detects reduce-reduce conflict, and resolvesc)It detects shift-reduce conflict, and resolves the conflict in favor of a shift over a reduce actiond)It detects shift-reduce conflict, and resolves the conflict in favor of a reduce over a shift actionCorrect answer is option 'C'. Can you explain this answer?.
Consider the following expression grammar. The semantic rules for expression calculation are stated next to each grammar production.E → number E.val = number. val| E '+' E E(1).val = E(2).val + E(3).val| E '×' E E(1).val = E(2).val × E(3).valQ.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 recursionb)It detects reduce-reduce conflict, and resolvesc)It detects shift-reduce conflict, and resolves the conflict in favor of a shift over a reduce actiond)It detects shift-reduce conflict, and resolves the conflict in favor of a reduce over a shift actionCorrect answer is option 'C'. Can you explain this answer? for Computer Science Engineering (CSE) 2024 is part of Computer Science Engineering (CSE) preparation. The Question and answers have been prepared according to the Computer Science Engineering (CSE) exam syllabus. Information about Consider the following expression grammar. The semantic rules for expression calculation are stated next to each grammar production.E → number E.val = number. val| E '+' E E(1).val = E(2).val + E(3).val| E '×' E E(1).val = E(2).val × E(3).valQ.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 recursionb)It detects reduce-reduce conflict, and resolvesc)It detects shift-reduce conflict, and resolves the conflict in favor of a shift over a reduce actiond)It detects shift-reduce conflict, and resolves the conflict in favor of a reduce over a shift actionCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for Computer Science Engineering (CSE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Consider the following expression grammar. The semantic rules for expression calculation are stated next to each grammar production.E → number E.val = number. val| E '+' E E(1).val = E(2).val + E(3).val| E '×' E E(1).val = E(2).val × E(3).valQ.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 recursionb)It detects reduce-reduce conflict, and resolvesc)It detects shift-reduce conflict, and resolves the conflict in favor of a shift over a reduce actiond)It detects shift-reduce conflict, and resolves the conflict in favor of a reduce over a shift actionCorrect answer is option 'C'. Can you explain this answer?.
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