Hello , the question below is from concepts of programming languages book by Robert sebasta , Q) Write an attribute grammar whose BNF basis is that of Example 3.6 inSection 3.4.5 but whose language rules are as follows: Data types cannotbe mixed in expressions, but assignment statements need not have thesame types on both sides of the assignment operator.Example 3.6 is attached as image . P.S : please explain the answer to me as I have shared the question twice today but the answer didn't convince me. EXAMPLE 3.6An Attribute Grammar for Simple Assignment Statements1. Syntax rule: → = Semantic rule: .expected_type ← .actual_type2. Syntax rule: → [2] + [3]Semantic rule: .actual_type ←if ([2].actual_type = int) and([3].actual_type = int)then intelse realend ifPredicate:.actual_type.expected_type3. Syntax rule: → Semantic rule: .actual_type ← .actual_typePredicate:.actual_type.expected_type====4. Syntax rule: → A | B | CSemantic rule: .actual_type ← look-up (.string)The look-up function looks up a given variable name in the symbol table andreturns the variable's type.

Write an attribute grammar for the given BNF with the same semantic rules as the given attribute…

Answered: EXAMPLE 3.6 An Attribute Grammar for…

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Author:James Kurose, Keith Ross

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Hello ,

the question below is from concepts of programming languages book by Robert sebasta ,

Q) Write an attribute grammar whose BNF basis is that of Example 3.6 in
Section 3.4.5 but whose language rules are as follows: Data types cannot
be mixed in expressions, but assignment statements need not have the
same types on both sides of the assignment operator.

Example 3.6 is attached as image .

P.S : please explain the answer to me as I have shared the question twice today but the answer didn't convince me.

EXAMPLE 3.6
An Attribute Grammar for Simple Assignment Statements
1. Syntax rule: <assign> → <var> = <expr>
Semantic rule: <expr>.expected_type ← <var>.actual_type
2. Syntax rule: <expr> → <var>[2] + <var>[3]
Semantic rule: <expr>.actual_type ←
if (<var>[2].actual_type = int) and
(<var>[3].actual_type = int)
then int
else real
end if
Predicate:
<expr>.actual_type
<expr>.expected_type
3. Syntax rule:
<expr> → <var>
Semantic rule: <expr>.actual_type ← <var>.actual_type
Predicate:
<expr>.actual_type
<expr>.expected_type
==
==
4. Syntax rule: <var> → A | B | C
Semantic rule: <var>.actual_type ← look-up (<var>.string)
The look-up function looks up a given variable name in the symbol table and
returns the variable's type.

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I am so sorry but the answer is wrong. the question is "follow the same BNF as the photo but Data types cannot be mixed in expressions", so we need to modify the grammar rules in order to prevent that mix . please explain how this can happen with your solution "or" another updated solution. thank you

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