/// <summary>Saves the state to a stream (that is, serializes it).</summary>
 /// <param name="s">the stream</param>
 /// <exception cref="System.IO.IOException">if an I/O error occurs</exception>
 /// <serialData>
 /// The current value is emitted (a
 /// <c>double</c>
 /// ).
 /// </serialData>
 private void WriteObject(ObjectOutputStream s)
 {
     s.DefaultWriteObject();
     s.WriteDouble(Get());
 }