title: "Expected ')' to match this '(' "when adding & to function prototype
body: <p>I'm writing a recursive bst insert function and I recognized that I was modifying a copy of the struct.</p>
  
  <p>So I changed the prototype of the function from this:</p>
  
  <pre><code>void BSTRecursiveInsert(BSTNode* tree, DataObject* elem)
  </code></pre>
  
  <p>to this:</p>
  
  <pre><code>void BSTRecursiveInsert(BSTNode*&amp; tree, DataObject* elem)
  </code></pre>
  
  <p>but I get the compiler error I wrote as question title. What am I missing?</p>