Consider 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

Q. Consider 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:

Production rule	Semantic action
D → T L	𝑋1.type = 𝑋2.type
T → int	T.type = int
T → float	T.type = float
L → L1 , id	𝑋3.type = 𝑋4.type addType(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?

(A) 𝑋1 = 𝐿 , 𝑋2 = 𝑇, 𝑋3 = 𝐿1, 𝑋4 = 𝐿	(B) 𝑋1 = 𝑇 , 𝑋2 = 𝐿, 𝑋3 = 𝐿1, 𝑋4 = 𝑇
(C) 𝑋1 = 𝐿 , 𝑋2 = 𝐿, 𝑋3 = 𝐿1, 𝑋4 = 𝑇	(D) 𝑋1 = 𝑇 , 𝑋2 = 𝐿, 𝑋3 = 𝑇, 𝑋4 = 𝐿1

Solution:

The correct answer is X₁ = L, X₂ = T, X₃ = L₁, X₄ = L

According to Inherited attribute definition, an attribute is inherited if the attribute value of a parse-tree node is determined from attribute values of its parent and siblings.

So, semantic rules should be as following below:

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)