public bool isDistinguishedSymbol(Symbol s)
{
return (s is Nonterminal && s.Sym == DistinguishedSymbol.Sym);
}
public bool isVanishingSymbol(Symbol s)
{
return _vanishingSymbols.Exists(vs => vs.Sym == s.Sym);
}
public bool hasSymbolInRight(Symbol s)
{
return Right.Exists(rr => rr.Sym == s.Sym);
}