title: Wild card matching pattern in Haskell
body: <p>OCaml provides wild card matching pattern when every other case fails:</p>
  
  <pre><code>let imply v = match v with 
           (true,false) -&gt; false
         |   _          -&gt; true;;
  </code></pre>
  
  <p>What's the equivalence in Haskell?</p>