GATE CS 2020 Set 1 — Question 43
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Compiler Design → Semantic Analysis → S- & L-Attributed Grammars
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Question
Consider the productions
Rule 2:
Which one of the following is TRUE?
A → PQ and A → XY. Each of the five non-terminals and has two attributes: is a synthesized attribute, and is an inherited attribute. Consider the following rules.Rule 1: Rule 2:
Which one of the following is TRUE?
Correct answer
(B) Only Rule 1 is L-attributed.
Solution
An L-attributed definition allows inherited attributes of a symbol on the RHS to depend only on:
1.Inherited attributes of the LHS symbol.
2.Attributes (synthesized or inherited) of symbols to the left of the symbol in the production.
Rule 1: A → PQ- : Depends on inherited attribute of LHS. OK.
- : Depends on (left of ) and (LHS). OK.
- : Synthesized attribute depends on RHS attributes. OK.
A → XY- : is the first symbol on RHS. Its inherited attribute depends on . is to the right of . This violates the L-attributed condition.
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