public virtual void TraceIn(string ruleName, int ruleIndex, object inputSymbol)
{
if (TraceDestination == null)
return;
TraceDestination.Write("enter " + ruleName + " " + inputSymbol);
if (state.backtracking > 0)
{
TraceDestination.Write(" backtracking=" + state.backtracking);
}
TraceDestination.WriteLine();
}