Gate2019 cs Q46

46Consider the following grammar and the semantic actions to support the inherited type declaration attributes. Let X₁, X₂, X₃, X₄, X₅ and X₆ be the placeholders for the non-terminals D, T, L or L₁ in the following table:

Productions rule	Semantic action
D → TL	X₁ .type = X₂ .type
T → int	T.type = int
T → float	T.type = float
L → L₁ , id	X₃ .type = X₄ .type add Type(id.entry, X₅ .type)
L → id	addType(id.entry, X₆ .type)

Which one of the following are the appropriate choices for 𝑋₁, 𝑋₂, 𝑋₃ and 𝑋₄?

Option : A
Explanation :
SDT for inserting type information in the symbol table
D → TL {L.idtype = T.stype}
T → int {T.stype = int}
T → float {T.stype = float}
L → L1, id {L₁.itype = L.itype}
addtype(id.entry, L.itype)
L → id addtype(id.entry, L.itype)

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