title: What does <0> mean with empty struct template?
body: <p>I see a construction like this:</p>
  <pre><code>template&lt;&gt;
  struct AliItemCalc&lt; 0 &gt;
  {
  
  }
  </code></pre>
  <p>What does zero mean?</p>
  <p>EDIT before this there is a definition:</p>
  <pre><code>template &lt;int N&gt;
  struct AliItemCalc
  {
  private:
      static constexpr unsigned a1 = 4096;
      static constexpr unsigned s = AliItemCalc&lt;N-1&gt;::m;
      static constexpr unsigned v = a1 * (s &amp; 0xFFFF);
  
  public:
      static constexpr unsigned m = v;
  };
  </code></pre>