code: @Override
    public boolean addAll(IntSet c)
    {
      modCount++;
      if (c == null || c.isEmpty() || this == c) {
        return false;
      }
  
      ConciseSet other = convert(c);
      if (other.size == 1) {
        return add(other.last);
      }
  
      return replaceWith(performOperation(convert(c), Operator.OR));
    }
docs: {@inheritDoc}