title: c++ : code explanation for method prototype with const = 0
body: <p>I hava a class declaration with a piece of code that I do not understand :</p>
  
  <pre><code>class Weapon
  {
    public:
      virtual void attack() const = 0;
  };
  </code></pre>
  
  <p>What does the <code>const = 0</code> part means ?</p>