title: Haskell Binary Tree Function (map)
body: <p>How can I define a Haskell function which will apply a function to every value in a binary tree? So I know that it is similar to the <code>map</code> function - and that its type would be:</p>
  
  <pre><code>mapT :: (a -&gt; b) -&gt; Tree a -&gt; Tree b
  </code></pre>
  
  <p>But thats about it...</p>