Understanding map in Scala : <p>Please help me understand what map(_(0)) means here:</p>

<pre><code>scala&gt; a.collect
res97: Array[org.apache.spark.sql.Row] = Array([1039], [1010], [1002], [926])

scala&gt; a.collect.map(_(0))
res98: Array[Any] = Array(1039, 1010, 1002, 926)
</code></pre>
