title: Understanding a Scala function from Play framework zentask example
body: <p>This is a function in the zentask example in Application.scala.
  I'm trying to understand it...</p>
  
  <p>What does the f:  => String mean?</p>
  
  <p>What about the chaining of f: => String => Request[AnyContent] => Result</p>
  
  <pre><code>/** 
   * Action for authenticated users.
   */
  def IsAuthenticated(f: =&gt; String =&gt; Request[AnyContent] =&gt; Result) = 
         Security.Authenticated(username, onUnauthorized) { user =&gt;
         Action(request =&gt; f(user)(request))
  }
  </code></pre>