 first character of
<code>letters</code>, modifying the accumulating value by setting <code>1</code> for the key
<code>&quot;a&quot;</code>.</li>
<li>The closure is called again repeatedly with the updated accumulating
value and each element of the sequence.</li>
<li>When the sequence is exhausted, the accumulating value is returned to
the caller.</li>
</ol>
<p>If the sequence has no elements, <code>updateAccumulatingResult</code> is never
executed and <code>initialResult</code> is the result of the call to