title: Haskell: Non-exhaustive patterns in function
body: <p>I get non exhaustive patterns exception for the following code</p>
  
  <pre><code>--determine which list is longer
  longer::[a]-&gt;[a]-&gt;Bool
  longer [] [] = False
  longer _ [] = True
  longer (_:[]) (_:[]) = False
  longer (_:xs) (_:ys) = longer xs ys
  </code></pre>
  
  <p>I don't understand what I am doing wrong here.</p>