title: what c++ inline explicit constructor is good for?
body: <p>i see sometimes this constructor writing with inline explicit.
  for example:</p>
  
  <pre><code>protected : 
      inline explicit Singleton() { 
  
          CCASSERT(Singleton::instance_ == 0, "error Singleton::instance_ == 0."); 
          Singleton::instance_ = static_cast&lt;T*&gt;(this); 
      }
      inline ~Singleton() { 
          Singleton::instance_ = 0; 
      }
  </code></pre>
  
  <p>for what inline explicit is good for ?</p>