title: Is it possible to represent Set as Tree in Haskell?
body: <p>I'm reading Purely Functional Data Structres and trying to solve exercises they give in haskell.</p>
  
  <p>I've defined <code>Tree</code> in a standard way <code>data Tree a = Empty | Node a (Tree a) (Tree a)</code>
  I'd like to define <code>Set</code> as <code>Tree</code> where nodes are instance of <code>Ord</code>. Is there a way to express this in Haskell? Something like <code>type Set = Tree Ord</code> or I deemed to reimplement tree every time I want express some data structure as tree?</p>