Marlon&quot;, &quot;Kim&quot;, &quot;Karl&quot;]
let lowercaseNames = cast.map { $0.lowercaseString }
// &#39;lowercaseNames&#39; == [&quot;vivien&quot;, &quot;marlon&quot;, &quot;kim&quot;, &quot;karl&quot;]
let letterCounts = cast.map { $0.characters.count }
// &#39;letterCounts&#39; == [6, 6, 3, 4]</code></pre>

<p><strong><code>transform</code>:</strong>  A mapping closure. <code>transform</code> accepts an
  element of this sequence as its parameter and returns a transformed
  value of the same or of a