title: C++ unresolved external symbol, I've already defined functions
body: <p>I've wrote my code nad when I want to build it it says: unresolved external symbol" for some functions, like the destructor:</p>
  
  <p>header file:</p>
  
  <pre><code>template &lt;class T&gt; class Tree
  {
  *not important*
  public:
      ~Tree()
  }
  </code></pre>
  
  <p>cpp file:</p>
  
  <pre><code>template &lt;class T&gt;
  Tree&lt;T&gt;::~Tree()
  {
      if (root != NULL)
      clear(root);
  }
  </code></pre>
  
  <p>I also defined and clear function so thats not the problem..</p>