/em> now contains the two newly added columns. This is what we mean by <em>added by reference</em>.</p></li>
<li><p>We used the functional form so that we could add comments on the side to explain what the computation does. You can also see the <code>LHS := RHS</code> form (commented).</p></li>
</ul>
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<div id="ref-i-j" class="section level3">
<h3>b) Update some rows of columns by reference - <em>sub-assign</em> by reference</h3>
<p>Let’s take a look at all the <code>hours</code> available in 