if (0 == range)
if (! range)
nsRangeList::Collapse(nsIDOMNode* aParentNode, PRInt32 aOffset){  nsresult res;  // Delete all of the current ranges  if (!mRangeArray)    return NS_ERROR_FAILURE;  Clear();  nsCOMPtr<nsIDOMRange> range;  res = nsRepository::CreateInstance(kRangeCID, nsnull,                                     kIDOMRangeIID,                                     getter_AddRefs(range));  if (!NS_SUCCEEDED(res))    return res;  if (0 == range)    return NS_ERROR_UNEXPECTED;  res = range->SetEnd(aParentNode, aOffset);  if (!NS_SUCCEEDED(res))    return res;  res = range->SetStart(aParentNode, aOffset);  if (!NS_SUCCEEDED(res))    return res;  setAnchor(aParentNode, aOffset);  setFocus(aParentNode, aOffset);  res = AddItem(range);  if (!NS_SUCCEEDED(res))    return res;  return NS_OK;}