true_comparison_range
int true_comparison_range(struct data_range *left, int comparison, struct data_range *right);
if (true_comparison_range(&tmp_left, expr->op, &tmp_right))
return true_comparison_range(var, comparison, val);
return true_comparison_range(val, comparison, var);
if (true_comparison_range(tmp_left, comparison, tmp_right))
if (true_comparison_range(left_tmp, comparison, right_tmp))