title: Spark : what does "expr" mean?
body: <p>I'm learning Spark in Java, I noticed that to add a column we can use</p>
  <pre><code>dataset.withColumn(&quot;name&quot;, expr(something))
  </code></pre>
  <p>I want to know what is the syntaxe of <code>expr</code> ? Is it a regular expression ? I didn't find manual on this.</p>
  <p>Thank you.</p>