I have the following grammar for expressions involving binary operators (| ^ & << >> + - * /):
expression : expression BITWISE_OR xor_expression
| xor_expression
xor_expression : xor_expression BITWISE_XOR and_expression
| and_expression
and_expression : and_expression BITWISE_AND shift_expression
| shift_expression
shift_expression : shift_expression LEFT_SHIFT arith_expression
| shift_expression RIGHT_SHIFT arith_expression
| arith_expression
arith_expression : arith_expression PLUS term
| arith_expression MINUS term
| term
term : term TIMES factor
| term DIVIDE factor
| factor
factor : NUMBER
| LPAREN expression RPAREN
This seems to work fine, but doesn't quite match my needs because it allows outer parentheses e.g. ((3 + 4) * 2).
How can I change the grammar to disallow outer parentheses, while still allowing them within expressions e.g. (3 + 4) * 2, even redundantly e.g. (3 * 4) + 2?