perturb method

@override num perturb(num position, num deltaPosition)

Returns position if start == position. Returns double.nan otherwise.

Implementation

@override
num perturb(
  num position,
  num deltaPosition,
) {
  deltaPosition = deltaPosition.abs();
  if (overlaps(position - deltaPosition, position + deltaPosition)) {
    return start;
  } else {
    return double.nan;
  }
}