C++ 中的 __gcd() 函数探源

 /**
  *  This is a helper function for the rotate algorithm specialized on RAIs.
  *  It returns the greatest common divisor of two integer values.
 */
 template<typename _EuclideanRingElement>
   _EuclideanRingElement
   __gcd(_EuclideanRingElement __m, _EuclideanRingElement __n)
   {
     while (__n != 0)
{
  _EuclideanRingElement __t = __m % __n;
  __m = __n;
  __n = __t;
}
     return __m;
   }