title: unresolved external symbol structs
body: <p>error LNK2001: unresolved external symbol "public: static int WrappedVector::_N" (?_N@WrappedVector@@2HA)</p>
  
  <p>header.h</p>
  
  <pre><code>struct WrappedVector
  {
      static int _N;
      double *_x;
  };
  </code></pre>
  
  <p>main.cpp</p>
  
  <pre><code>const int WrappedVector::_N = 3;
  </code></pre>
  
  <p>i don't understand whats wrong</p>