Node buildNode() {
if (head == null) {
throw new IllegalStateException("no SEXPs have been added");
}
head.unsafeSetAttributes(attributesBuilder.build());
return head;
}
public Builder add(SEXP tag, SEXP s) {
if (head == null) {
head = new Node(tag, s, attributesBuilder.build(), Null.INSTANCE);
tail = head;
} else {
Node next = new Node(tag, s, Null.INSTANCE);
tail.nextNode = next;
tail = next;
}
return this;
}