 given closure
over the sequence's elements.</p>
<p>In this example, <code>map</code> is used first to convert the names in the array
to lowercase strings and then to count their characters.</p>
<pre><code class="language-swift">let cast = [&quot;Vivien&quot;, &quot;Marlon&quot;, &quot;Kim&quot;, &quot;Karl&quot;]
let lowercaseNames = cast.map { $0.lowercased() }
// 'lowercaseNames' == [&quot;vivien&quot;, &quot;marlon&quot;, &quot;kim&quot;, &quot;karl&quot;]
let letterCounts = cast.map { $0.count }
// 'le