Chapter 3, Problem 9PS

Explanation of Solution

Consider the following grammar in BNF:

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

<id> —> A|B|C

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

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

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

The grammar of Example 3.4 to add a unary minus operator that has higher precedence than either + or * are as follows:

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

<id> —> A|B|C

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

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

...