private static void AddToCollectionsIfNotAlreadyExisting(Queue <StackSymbolSequence <S> > stackSymbolQueue, PDA <A, StackSymbolSequence <S> > pda, StackSymbolSequence <S> stackSymbol) { if (!pda.AllStackSymbols.Any(s => s.Equals(stackSymbol))) { pda.AddStackSymbol(stackSymbol); stackSymbolQueue.Enqueue(stackSymbol); } }