Fast C++ Code Library

I found this code on a Korean site last night. Seems like some very handy stuff (especially for graphics/games - see the Quake 3 reciprocal square root below, mmm...) - although I haven't actually used any of these yet, so use at your own risk.

(It's too big to post up here... FastCodeLibrary.h)

Example:
[PHP]// Fast reciprocal square root (Quake 3 game code)
__inline float 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 f*ck?
y = * (float *) &i;
y = y * (threehalfs - (x2 * y * y)); // 1st iteration

return y;
}[/PHP]