Computer Science Engineering (CSE) Exam > Computer Science Engineering (CSE) Questions > Consider the following two sets of LR(1) item...
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Consider the following two sets of LR(1) items of an LR(1) grammar.
X -> c.X, c/d
X -> .cX, c/d
X -> .d, c/d
X -> c.X, $
X -> .cX, $
X -> .d, $
X -> c.X, c/d
X -> .cX, c/d
X -> .d, c/d
X -> c.X, $
X -> .cX, $
X -> .d, $
Q. Which of the following statements related to merging of the two sets in the corresponding LALR parser is/are FALSE?
1. Cannot be merged since look aheads are different.
2. Can be merged but will result in S-R conflict.
3. Can be merged but will result in R-R conflict.
4. Cannot be merged since goto on c will lead to two different sets.
2. Can be merged but will result in S-R conflict.
3. Can be merged but will result in R-R conflict.
4. Cannot be merged since goto on c will lead to two different sets.
- a)1 only
- b)2 only
- c)1 and 4 only
- d)1, 2, 3, and 4
Correct answer is option 'D'. Can you explain this answer?
Verified Answer
Consider the following two sets of LR(1) items of an LR(1) grammar.X -...
The given two LR(1) set of items are :
X -> c.X, c/d
X -> .cX, c/d
X -> .d, c/d
and
X -> c.X, $
X -> .cX, $
X -> .d, $
X -> c.X, c/d
X -> .cX, c/d
X -> .d, c/d
and
X -> c.X, $
X -> .cX, $
X -> .d, $
The symbols/terminals after the comma are Look-Ahead symbols. These are the sets of LR(1) (LR(1) is also called CLR(1)) items. The LALR(1) parser combines those set of LR(1) items which are identical with respect to their 1st component but different with respect to their 2nd component. In a production rule of a LR(1) set of items, (A -> B , c) , A->B is the 1st component , and the Look-Ahead set of symbols, which is c here, is the second component. Now we can see that in the sets given, 1st component of the corresponding production rule is identical in both sets, and they only differ in 2nd component (i.e. their look-ahead symbols) hence we can combine these sets to make a a single set which would be :
X -> c.X, c/d/$
X -> .cX, c/d/$
X -> .d, c/d/$
X -> .cX, c/d/$
X -> .d, c/d/$
This is done to reduce the total number of parser states. Now we can check the statements given. Statement 1 : The statement is false, as merging has been done because 2nd components i.e. look-ahead were different. Statement 2 : In the merged set, we can't see any Shift-Reduce conflict ( because no reduction even possible, reduction would be possible when a production of form P -> q. is present) Statement 3 : In the merged set, we can't see any Reduce-Reduce conflict ( same reason as above, no reduction even possible, so no chances of R-R conflict ) Statement 4: This statement is also wrong, because goto is carried on Non-Terminals symbols, not on terminal symbols, and c is a terminal symbol. Thus, all statements are wrong, hence option D.
Most Upvoted Answer
Consider the following two sets of LR(1) items of an LR(1) grammar.X -...
Explanation:
1. Cannot be merged since lookaheads are different:
- In LALR parser construction, sets can be merged even if the lookaheads are different as long as the core LR(1) items are the same.
2. Can be merged but will result in S-R conflict:
- If merging the two sets results in a shift-reduce conflict, it means that there is a transition in the DFA where both a shift and a reduce action are possible. This conflict can be resolved through precedence or associativity rules.
3. Can be merged but will result in R-R conflict:
- If merging the two sets results in a reduce-reduce conflict, it means that there are two different reduce actions possible at the same state. This conflict can be resolved by modifying the grammar to remove ambiguity.
4. Cannot be merged since goto on c will lead to two different sets:
- This statement is false because the fact that goto on the same symbol leads to different sets does not prevent the sets from being merged in the LALR parser construction process.
Therefore, options 1, 2, 3, and 4 are all false in the context of merging sets in an LALR parser.
1. Cannot be merged since lookaheads are different:
- In LALR parser construction, sets can be merged even if the lookaheads are different as long as the core LR(1) items are the same.
2. Can be merged but will result in S-R conflict:
- If merging the two sets results in a shift-reduce conflict, it means that there is a transition in the DFA where both a shift and a reduce action are possible. This conflict can be resolved through precedence or associativity rules.
3. Can be merged but will result in R-R conflict:
- If merging the two sets results in a reduce-reduce conflict, it means that there are two different reduce actions possible at the same state. This conflict can be resolved by modifying the grammar to remove ambiguity.
4. Cannot be merged since goto on c will lead to two different sets:
- This statement is false because the fact that goto on the same symbol leads to different sets does not prevent the sets from being merged in the LALR parser construction process.
Therefore, options 1, 2, 3, and 4 are all false in the context of merging sets in an LALR parser.
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Consider the following two sets of LR(1) items of an LR(1) grammar.X -> c.X, c/dX -> .cX, c/dX -> .d, c/dX -> c.X, $X -> .cX, $X -> .d, $Q. Which of the following statements related to merging of the two sets in the corresponding LALR parser is/are FALSE?1. Cannot be merged since look aheads are different.2. Can be merged but will result in S-R conflict.3. Can be merged but will result in R-R conflict.4. Cannot be merged since goto on c will lead to two different sets.a)1 onlyb)2 onlyc)1 and 4 onlyd)1, 2, 3, and 4Correct answer is option 'D'. Can you explain this answer? for Computer Science Engineering (CSE) 2025 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 two sets of LR(1) items of an LR(1) grammar.X -> c.X, c/dX -> .cX, c/dX -> .d, c/dX -> c.X, $X -> .cX, $X -> .d, $Q. Which of the following statements related to merging of the two sets in the corresponding LALR parser is/are FALSE?1. Cannot be merged since look aheads are different.2. Can be merged but will result in S-R conflict.3. Can be merged but will result in R-R conflict.4. Cannot be merged since goto on c will lead to two different sets.a)1 onlyb)2 onlyc)1 and 4 onlyd)1, 2, 3, and 4Correct answer is option 'D'. Can you explain this answer? covers all topics & solutions for Computer Science Engineering (CSE) 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Consider the following two sets of LR(1) items of an LR(1) grammar.X -> c.X, c/dX -> .cX, c/dX -> .d, c/dX -> c.X, $X -> .cX, $X -> .d, $Q. Which of the following statements related to merging of the two sets in the corresponding LALR parser is/are FALSE?1. Cannot be merged since look aheads are different.2. Can be merged but will result in S-R conflict.3. Can be merged but will result in R-R conflict.4. Cannot be merged since goto on c will lead to two different sets.a)1 onlyb)2 onlyc)1 and 4 onlyd)1, 2, 3, and 4Correct answer is option 'D'. Can you explain this answer?.
Consider the following two sets of LR(1) items of an LR(1) grammar.X -> c.X, c/dX -> .cX, c/dX -> .d, c/dX -> c.X, $X -> .cX, $X -> .d, $Q. Which of the following statements related to merging of the two sets in the corresponding LALR parser is/are FALSE?1. Cannot be merged since look aheads are different.2. Can be merged but will result in S-R conflict.3. Can be merged but will result in R-R conflict.4. Cannot be merged since goto on c will lead to two different sets.a)1 onlyb)2 onlyc)1 and 4 onlyd)1, 2, 3, and 4Correct answer is option 'D'. Can you explain this answer? for Computer Science Engineering (CSE) 2025 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 two sets of LR(1) items of an LR(1) grammar.X -> c.X, c/dX -> .cX, c/dX -> .d, c/dX -> c.X, $X -> .cX, $X -> .d, $Q. Which of the following statements related to merging of the two sets in the corresponding LALR parser is/are FALSE?1. Cannot be merged since look aheads are different.2. Can be merged but will result in S-R conflict.3. Can be merged but will result in R-R conflict.4. Cannot be merged since goto on c will lead to two different sets.a)1 onlyb)2 onlyc)1 and 4 onlyd)1, 2, 3, and 4Correct answer is option 'D'. Can you explain this answer? covers all topics & solutions for Computer Science Engineering (CSE) 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Consider the following two sets of LR(1) items of an LR(1) grammar.X -> c.X, c/dX -> .cX, c/dX -> .d, c/dX -> c.X, $X -> .cX, $X -> .d, $Q. Which of the following statements related to merging of the two sets in the corresponding LALR parser is/are FALSE?1. Cannot be merged since look aheads are different.2. Can be merged but will result in S-R conflict.3. Can be merged but will result in R-R conflict.4. Cannot be merged since goto on c will lead to two different sets.a)1 onlyb)2 onlyc)1 and 4 onlyd)1, 2, 3, and 4Correct answer is option 'D'. Can you explain this answer?.
Solutions for Consider the following two sets of LR(1) items of an LR(1) grammar.X -> c.X, c/dX -> .cX, c/dX -> .d, c/dX -> c.X, $X -> .cX, $X -> .d, $Q. Which of the following statements related to merging of the two sets in the corresponding LALR parser is/are FALSE?1. Cannot be merged since look aheads are different.2. Can be merged but will result in S-R conflict.3. Can be merged but will result in R-R conflict.4. Cannot be merged since goto on c will lead to two different sets.a)1 onlyb)2 onlyc)1 and 4 onlyd)1, 2, 3, and 4Correct answer is option 'D'. Can you explain this answer? in English & in Hindi are available as part of our courses for Computer Science Engineering (CSE).
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Consider the following two sets of LR(1) items of an LR(1) grammar.X -> c.X, c/dX -> .cX, c/dX -> .d, c/dX -> c.X, $X -> .cX, $X -> .d, $Q. Which of the following statements related to merging of the two sets in the corresponding LALR parser is/are FALSE?1. Cannot be merged since look aheads are different.2. Can be merged but will result in S-R conflict.3. Can be merged but will result in R-R conflict.4. Cannot be merged since goto on c will lead to two different sets.a)1 onlyb)2 onlyc)1 and 4 onlyd)1, 2, 3, and 4Correct answer is option 'D'. Can you explain this answer?, a detailed solution for Consider the following two sets of LR(1) items of an LR(1) grammar.X -> c.X, c/dX -> .cX, c/dX -> .d, c/dX -> c.X, $X -> .cX, $X -> .d, $Q. Which of the following statements related to merging of the two sets in the corresponding LALR parser is/are FALSE?1. Cannot be merged since look aheads are different.2. Can be merged but will result in S-R conflict.3. Can be merged but will result in R-R conflict.4. Cannot be merged since goto on c will lead to two different sets.a)1 onlyb)2 onlyc)1 and 4 onlyd)1, 2, 3, and 4Correct answer is option 'D'. Can you explain this answer? has been provided alongside types of Consider the following two sets of LR(1) items of an LR(1) grammar.X -> c.X, c/dX -> .cX, c/dX -> .d, c/dX -> c.X, $X -> .cX, $X -> .d, $Q. Which of the following statements related to merging of the two sets in the corresponding LALR parser is/are FALSE?1. Cannot be merged since look aheads are different.2. Can be merged but will result in S-R conflict.3. Can be merged but will result in R-R conflict.4. Cannot be merged since goto on c will lead to two different sets.a)1 onlyb)2 onlyc)1 and 4 onlyd)1, 2, 3, and 4Correct answer is option 'D'. Can you explain this answer? theory, EduRev gives you an
ample number of questions to practice Consider the following two sets of LR(1) items of an LR(1) grammar.X -> c.X, c/dX -> .cX, c/dX -> .d, c/dX -> c.X, $X -> .cX, $X -> .d, $Q. Which of the following statements related to merging of the two sets in the corresponding LALR parser is/are FALSE?1. Cannot be merged since look aheads are different.2. Can be merged but will result in S-R conflict.3. Can be merged but will result in R-R conflict.4. Cannot be merged since goto on c will lead to two different sets.a)1 onlyb)2 onlyc)1 and 4 onlyd)1, 2, 3, and 4Correct answer is option 'D'. Can you explain this answer? tests, examples and also practice Computer Science Engineering (CSE) tests.
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