//todo: never to be implemented

//Maybe you should make anyone knows your code's purpose. 

    /* Mark: If there's one thing you learn from this code, it is this...
   Never, ever fly Air France.  Their customer service is absolutely
   the worst.  I've never heard the words "That's not my problem" as 
   many times as I have from their staff -- It should, without doubt
   be their corporate motto if it isn't already.  Don't bother giving 
   them business because you're just a pain in their side and they
   will be sure to let you know the first time you speak to them.

   If you ever want to make me happy just tell me that you, too, will
   never fly Air France again either (in spite of their excellent
   cuisine). 

   Update by oej: The merger with KLM has transferred this
   behaviour to KLM as well. 
   Don't bother giving them business either...

   Only if you want to travel randomly without luggage, you
   might pick either of them.
   */

// Caveat implementor

从《雷神之锤III》的资料中，我在一些随机的帖子中偶然发现了这一点。该文件的完整源代码可以在这里找到。这是一种非常快速的求平方根倒数的方法。至于最好的评论呢?当然，这是一种常见的方法，但考虑到它附着在直线上，它的神奇之处在于它的伟大之处。

float Q_rsqrt( float number )
{
  long i;
  float x2, y;
  const float threehalfs = 1.5F;

  x2 = number * 0.5F;
  y  = number;
  i  = * ( long * ) &y;  // evil floating point bit level hacking
  i  = 0x5f3759df - ( i >> 1 ); // what the fuck?
  y  = * ( float * ) &i;
  y  = y * ( threehalfs - ( x2 * y * y ) ); // 1st iteration
  // y  = y * ( threehalfs - ( x2 * y * y ) ); // 2nd iteration, this can be removed

  #ifndef Q3_VM
  #ifdef __linux__
    assert( !isnan(y) ); // bk010122 - FPE?
  #endif
  #endif
  return y;
}

// StupidCompilerDontInline(SCDI), in the test project where
// allcode was in a single cpp the compiler had inlined nearly
// everything which lead to nice stackoverflow.
// To prevent this the metods are made virtual
#define SCDI virtual