nagative or positive

compare.c

//ref: http://stackoverflow.com/questions/33882676/why-intunsigned-intintv
int compare(int x)
{
     return -(int)(
       (unsigned int)( (int) x )  >> ( sizeof(int) * CHAR_BIT - 1 )
     );
}

//equal to
int compare(int x)
{
  return (x < 0) ? -1 :0;
}