assign_op: ASSIGN | ASSIGN_ADD | ASSIGN_SUBTRACT;
cond_op: AND | OR;
eq_op: EQUALS | NOT_EQUALS;
rel_op: LESS_THAN | LESS_THAN_OR_EQUAL_TO | GREATER_THAN_OR_EQUAL_TO | GREATER_THAN;
arith_op: MULTIPLY | DIVIDE | MOD | ADD | SUBTRACT;
bin_op: arith_op | rel_op | eq_op | cond_op;