GATE CSE 2019 | Question: 3

Question

Which one of the following kinds of derivation is used by LR parsers?

• A. Leftmost
• B. Leftmost in reverse
• C. Rightmost
• D. Rightmost in reverse

Comments

D is the correct answer.

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D. produces a rightmost derivation in reverse

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Isn't LR leftmost in reverse?

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No. 'L' for left-to-right scan and 'R' for rightmost derivation. 

https://gateoverflow.in/299818/go-compiler1-parsing-6

Answer 1

A bottom-up parser traces a rightmost derivation in reverse. Answer (D).

Answer 2

Bottom Up parser – Rightmost derivation in reverse

Top Down parser – Leftmost Derivation 

Answer 3

LR parser are type of bottom up parser and LR(Left-to-right, Rightmost derivation in reverse)  uses rightmost in reverse.

https://en.wikipedia.org/wiki/LR_parser

Answer 4

LR parsers have Rightmost derivation in reverse.