 store the input column names and the new columns to add in separate variables and provide them to <code>.SDcols</code> and for <code>LHS</code> (for better readability).</p></li>
<li><p>Note that since we allow assignment by reference without quoting column names when there is only one column as explained in <a href="#delete-convenience">Section 2c</a>, we can not do <code>out_cols := lapply(.SD, max)</code>. That would result in adding one new column named <code>out_col</code>. Instead we should do either