S and L-attribute

Question

Answer 1

Ans C)

If a attribute taking valuefrom it's children, then it is called Synthesized Attribute. S attribute contains Synthesized Attribute.

Now, $E.val=E_{1}.val+T.val$

Here E is taking value from it's children.

$E.val=T.val$

Here E taking value from T, i.e. from it's children.

$T.val=id$

Same case here too.

So, this grammar is S attributed. If a grammar is S attributed, then it must be L attri buted. But if a grammar is L attributed, then it may or maynot be S attributed

Comments

@srestha How to check for L attributed if it is not S attributed ?

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L attribute uses inherited attribute + synthesized attribute whereas S attribute uses only synthesized attribute that is a parent can synthesis value from children. In L attribute it uses both inherited as well as a synthesized attribute in a restricted manner.   L is superset of S