title: Scala Unit type
body: <p>I use opencsv to parse csv files, and my code is</p>
  
  <pre><code>while( (line = reader.readNext()) != null ) { .... }
  </code></pre>
  
  <p>I got a compiler warning saying:</p>
  
  <pre><code> comparing values of types Unit and Null using `!=' will always yield true
   [warn]     while( (aLine = reader.readNext()) != null ) {
  </code></pre>
  
  <p>How should I do the while loop?</p>