@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		State other = (State) obj;
		if (left == null) {
			if (other.left != null)
				return false;
		} else if (!left.equals(other.left))
			return false;
		if (symbol == null) {
			if (other.symbol != null)
				return false;
		} else if (!symbol.equals(other.symbol))
			return false;
		return true;
	}