UGC NET CSE | December 2014 | Part 2 | Question: 31

Question

Shift-Reduce parsers perform the following : 

• A. Shift step that advances in the input stream by $K(K > 1)$ symbols and Reduce step that applies a completed grammar rule to some recent parse trees, joining them together as one tree with a new root symbol. 
• B. Shift step that advances in the input stream by one symbol and Reduce step that applies a completed grammar rule to some recent parse trees, joining them together as one tree with a new root symbol. 
• C. Shift step that advances in the input stream by $K(K = 2)$ symbols and Reduce step that applies a completed grammar rule to form a single tree. 
• D. Shift step that does not advance in the input stream and Reduce step that applies a completed grammar rule to form a single tree. 

Answer 1

Ans: B

• A Shift step advances in the input stream by one symbol. That shifted symbol becomes a new single-node parse tree.
• A Reduce step applies a completed grammar rule to some of the recent parse trees, joining them together as one tree with a new root symbol.

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