title: How do you map over the values of Zip2?
body: <p>I have two arrays like <code>[1, 2, 3]</code> and <code>["a", "b", "c"]</code> and I want to map over the zipped values <code>(1, "a")</code>, <code>(2, "b")</code>, and <code>(3, "c")</code> using Zip2.</p>
  
  <p>If I do this:</p>
  
  <pre><code>let foo = map(Zip2([1, 2, 3], ["a", "b", "c"]).generate()) { $0.0 }
  </code></pre>
  
  <p>foo has the type <code>ZipGenerator2&lt;IndexingGenerator&lt;Array&lt;Int&gt;&gt;, IndexingGenerator&lt;Array&lt;String&gt;&gt;&gt;?</code>.</p>
  
  <p>Is there a way to make that an array?</p>