title: lifting into a data type (Haskell)
body: <pre><code>type PT_Int = Int
  type PT_String = String
  data PolyType = PT_Int Int | PT_String String
  </code></pre>
  
  <p>Given a function f, how do I write a function that lifts it into PolyType? 
  (just trying to understand lifting)</p>