code: public static int subtract(int index0, int index1, int size) {
  		int distance = distanceP(index0, index1, size);
  		if( distance >= size/2+size%2 ) {
  			return distance-size;
  		} else {
  			return distance;
  		}
  	}
docs: Subtracts index1 from index0. positive number if its closer in the positive
  direction or negative if closer in the negative direction.  if equal distance then
  it will return a negative number.
  
  @param index0 element in circular buffer
  @param index1 element in circular buffer
  @param size size of the circular buffer
  @return new index