LL(1) Parser Properties Analysis
This question asks to identify the true statement(s) regarding LL(1) parsers and grammars.
Statement Analysis
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Statement 1: LL(1) parser uses backtracking
This statement is false. LL(1) parsers are predictive parsers. They use a parse table to deterministically choose the next production rule based on the current non-terminal and the next input token. They do not backtrack.
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Statement 2: For a grammar to be LL(1), it must be left-recursive
This statement is false. LL(1) grammars explicitly require the *absence* of left-recursion (e.g., A -> Aα). Left-recursive rules prevent the construction of a predictive parsing table and cause infinite loops in recursive descent parsing.
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Statement 3: For a grammar to be LL(1), it must be left-factored
This statement is true. Left-factoring is a grammar transformation technique used to eliminate sequences of productions that start with the same common prefix. This ensures that for any non-terminal, the productions having the same starting symbol can be uniquely determined from the next input token, which is a prerequisite for a grammar to be LL(1).
Example: If a rule is P -> αβ | αγ, it must be left-factored to P -> αP' and P' -> β | γ.
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Statement 4: The LL(1) parsers are more powerful than the SLR parsers
This statement is false. LL(1) parsers can handle a more restricted set of context-free grammars compared to LR parsers, including SLR (Simple LR). SLR parsers are generally considered more powerful because they can parse a larger class of grammars than LL(1) parsers.
Conclusion
Based on the analysis, only the third statement is true. A grammar must be left-factored to be considered LL(1).
Important Questions from Parser
Consider the following statements:
Statement I: LALR parser is more powerful than canonical LR Parser.
Statement II: SLR parser is more powerful than LALR
Which of the following is correct?
Given below are two statements
Statement I : LL(1) and LR are examples of Bottom‐up parsers.
Statement II : Recursive descent parser and SLR are examples of Top‐down parsers
In light of the above statements, choose the correct answer from the options given below
Consider the following Grammar G:
S ➝ A | B
A➝ a | c
B➝ b | c
Where {S, A, B} is the set of non-terminals, {a, b, c} is the set of terminals.
Which of the following statement(s) is/are correct?
S 1 : LR(1) can parse all strings that are generated using grammar G.
S 2 : LL(1) can parse all strings that are generated using grammar G.The grammar S → SS | (S)| ϵ is not suitable for predictive parsing because the grammar is:
- Arrange the following parsers in increasing order of their power of handling grammars i.e. from the least powerful parser to the most powerful parser.
A. LR(0)
B. LR(1)
C. LALR(1)
D. LL(0)
E. SLR
Choose the correct answer from the options given below:
