public bool VisitNull(NullDatum d)
{
bw.Write(B_NULL);
return(true);
}
public string VisitNull(NullDatum d)
{
return("#nil");
}
public State VisitNull(State state, NullDatum d) => state;
public SetDatum VisitNull(NullDatum d) => SetDatum.Empty;
