title: Function which Takes a binary tree and prints out its values in order
body: <p>I am currently writing a a function to take a binary tree and print out its values in the right order(in order transversal).The problem i have is i keep getting a non exhaustive pattern error when ever i call the function</p>
  
  <pre><code> --k is the key and d is the value
   -- l is left tree and r is right tree
  treeprint (Node l k d r)      =  treeprint l  ++ show k ++ show d ++ treeprint r 
  treeprint Nil=""
  </code></pre>