/* doing the real circular magnitude calculation is audibly superior
   to (A+B)/sqrt(2) */
static float dipole_hypot(float a, float b){
  if(a>0.){
    if(b>0.)return sqrt(a*a+b*b);
    if(a>-b)return sqrt(a*a-b*b);
    return -sqrt(b*b-a*a);
  }
  if(b<0.)return -sqrt(a*a+b*b);
  if(-a>b)return -sqrt(a*a-b*b);
  return sqrt(b*b-a*a);
}
static float round_hypot(float a, float b){
  if(a>0.){
    if(b>0.)return sqrt(a*a+b*b);
    if(a>-b)return sqrt(a*a+b*b);
    return -sqrt(b*b+a*a);
  }
  if(b<0.)return -sqrt(a*a+b*b);
  if(-a>b)return -sqrt(a*a+b*b);
  return sqrt(b*b+a*a);
}