public ParseStackEntry StackAt(int ix)
{
int n = m_stack.Count;
if (m_stkdebug)
Console.WriteLine("StackAt({0}),count {1}",ix,n);
ParseStackEntry pe =(ParseStackEntry)m_stack[ix];
if (pe == null)
return new ParseStackEntry(this,0,m_symbols.Special);
if (pe.m_value is Null)
return new ParseStackEntry(this,pe.m_state,null);
if (m_stkdebug)
Console.WriteLine(pe.m_value.yyname);
return pe;
}