I would say that the actual source code there is extremely ugly. It may be an elegant solution, but there's no way I would want to crawl around in that repo:
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;