title: How to write arithmetic expression to evaluate differentiation in haskell
body: <p>I want the user to enter as Diff x^3 and get the answer as 3x^2</p>
  
  <p>How can I write the arithmetic expression for this evaluation?</p>
  
  <p>What is the best way to do this in haskell?</p>
  
  <p>Thank you.</p>