de>.  <code>EnumerateGenerator</code>
wraps a <code>Base</code> <code>GeneratorType</code> and yields successive <code>Int</code> values,
starting at zero, along with the elements of the underlying
<code>Base</code>:</p>

<pre><code class="language-swift">var g = EnumerateGenerator([&quot;foo&quot;, &quot;bar&quot;].generate())
g.next() // (0, &quot;foo&quot;)
g.next() // (1, &quot;bar&quot;)
g.next() // nil</code></pre>

<p>Note:: idiomatic usage is to call <code>enumerate</code> instead of
constructing an