title: Extract Integer from a datatype
body: <p>I know i can do something like this to get an integer out of a datatype:</p>
  <pre><code>[x | (PhoneNo x) &lt;- [PhoneNo 1234]]
  </code></pre>
  <p>where PhoneNo is defined as:</p>
  <pre><code>data PhoneNo = PhoneNo Integer deriving (Eq, Ord)
  </code></pre>
  <p>However this is better for lists. How can I extract the integer of a single PhoneNo instance?</p>