Assume the following rules of associativity and precedence for expressions: Prec

Question

Assume the following rules of associativity and precedence for expressions:

Precedence:     Highest                              *, /

                                                                   +, -

                                                                   =, /=, <, <=, >=, >

                                                                   and

                        Lowest                               or

Associativity: Left to right

Write a BNF description of the precedence and associativity rules defined above for the expressions. Assume the only operands are the names a, b, c, d, and e.

Explanation / Answer

Requirement

following rules of associativity and precedence for expressions:

Precedence:     Highest                              *, /

                                                                   +, -

                                                                   =, /=, <, <=, >=, >

                                                                   and

                        Lowest                               or

Associativity: Left to right

Write a BNF description of the precedence and associativity rules defined above for the expressions. Assume the only operands are the names a, b, c, d, and e.

Solution

<expression> <expression> or <or_exp> | <or_exp>

<or_exp> <or_exp> and <and_exp> | <and_exp>

< and_exp > <and_exp> = <expr> | <and_exp /= <expr> | <and_exp> < <expr> | <and_exp> <= <expr> | <and_exp> >= <expr> | <and_exp> > <expr> | <expr>

<expr> <expr> + <term> | <expr> – <term> | <term>

< term > < term > * < factor > | < term > / < factor > | < factor >

< factor > ( < expr > ) | <operand>

<operand> a | b | c | d | e

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