invert_op
int invert_op(int op);
*left_p = binop_expression(left, invert_op(right->op), right->right);
*left_p = binop_expression(left, invert_op(right->op), right->left);
*left_p = binop_expression(left, invert_op(right->op), right->right);
*right_p = binop_expression(right, invert_op(left->op), left->right);
*right_p = binop_expression(right, invert_op(left->op), left->left);
*right_p = binop_expression(right, invert_op(left->op), left->right);
if (sval_cmp(left, sval_binop(max, invert_op(op), right)) > 0)