19. Given the following parser table, state of the stack, and input string, if y

Question

19. Given the following parser table, state of the stack, and input string, if you were to readi symbol, what action would you take? Tip: Recall th the . represents what we have already read in, and everything AFTER the . represents what we at when representing how much of an input string we've read, everything BEFORE haven't seen yet. State Action Goto S1 2 3 1 R3 R3 R3 2 S4 acc 3 R2 R2 R2 4 Sl input: .id +id $ Stack: 0 A. Add id to the stack, advance the input string so that the . is after the first id symbol, and reduce B. Add id to the stack, advance the input string so that the is after the first id symbol, and C. Add id to the stack, add 1 to the stack, advance the input string so that the . is after the first id D. Add id to the stack, advance the input string so that the is after the first id symbol, reduce by by rule 3. transition to state 1. symbol, and transition to state 1. rule 3, and pop one pair of symbols off the stack.

Explanation / Answer

Explanation:

Stack: 0

Input: .id + id $

At this time the look ahead points to the first id. The . (dot) is on the left of the whole input string which means that the whole string has not been parsed. The top of the stack is 0.

Read id from look-ahead. 0 (top of the stack) on id is S1 which means push id and state number i.e. 1 to the stack.Read the next symbol + from the look-ahead. top of the stack is now 1. 1 on + is R3, i.e. reduce using rule 3.

Therefore the answer is C.

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