Question

Add a unary minus operator that has higher precedence than either + or *, to the following the grammar (below):

<assign> -> <id> = <expr>

<id> -> A | B | C

<expr> -> <expr> + < term> | <term>

<term> -> <term> * <factor> | <factor>

<factor> -> ( <expr> ) | <id>

please dont copy and paste

Answer 1

To add an operator of higher precedence always add it in lower level of grammer so that it is evaluated first(as grammer is left recursive). In the answer 1 that's the ereason -<id> is below <term> which consists of *. so always -will be evaluated first. Same is the case with answer 2.

Answer1:

< assign > ==> < id > = < expr >

<id> ==> A | B | C

< expr > ==> < expr > + < term > | < term >

< term > ==> < term > * < factor > | < factor >

< factor > ==> ( <expr> ) | +<id> | – <id>

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Answer 2:

< assign > ==> < id> = <expr>

< id > ==> A | B | C

< expr > ==> < expr > + <term> | <term> | - <factor>

<term> ==> <term> * <factor> | <factor>

<factor> ==> (<expr>) | <id>