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

Q. 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

Ans: Rightmost in reverse

Solution:

Parsing is classified into two categories, i.e. Top Down Parsing and Bottom-Up Parsing. Top-Down Parsing is based on Left Most Derivation whereas Bottom Up Parsing is dependent on Reverse Right Most Derivation. A general shift reduce parsing is LR parsing is bottom-up parsing where L stands for scanning the input from left to right and R stands for constructing a rightmost derivation in reverse.