title: Simple question about tuple of scala
body: <p>I'm new to scala, and what I'm learning is <code>tuple</code>.</p>
  
  <p>I can define a tuple as following, and get the items:</p>
  
  <pre><code>val tuple = ("Mike", 40, "New York")
  println("Name: " + tuple._1)
  println("Age: " + tuple._2)
  println("City: " + tuple._3)
  </code></pre>
  
  <p>My question is:</p>
  
  <ol>
  <li>How to get the length of a tuple?</li>
  <li>Is tuple mutable? Can I modify its items?</li>
  <li>Is there any other useful operation we can do on a tuple?</li>
  </ol>
  
  <p>Thanks in advance!</p>