Which of the following statements is false?
2001
Which of the following statements is false?
Answer: A. An unambiguous grammar has the same leftmost and rightmost derivation — The correct answer is Option A. In an unambiguous grammar, every valid string has exactly one parse tree. Equivalently, it has a unique leftmost derivation…
- A.
An unambiguous grammar has the same leftmost and rightmost derivation
- B.
An LL(1) parser is a top-down parser
- C.
LALR parsing is more powerful than SLR parsing
- D.
An ambiguous grammar can never be LR(k) for any k
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Correct answer: A
The correct answer is Option A. In an unambiguous grammar, every valid string has exactly one parse tree. Equivalently, it has a unique leftmost derivation and a unique rightmost derivation. This does not mean that the leftmost derivation and the rightmost derivation are the same sequence of steps; they usually expand non-terminals in different orders. The other statements are true: LL(1) is a top-down parser, LALR is more powerful than SLR, and an LR(k) grammar must be unambiguous.
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