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