@Override
default <U> Tree<Tuple2<T, U>> zipAll(Iterable<U> that, T thisElem, U thatElem) {
Objects.requireNonNull(that, "that is null");
if (isEmpty()) {
return Iterator.ofAll(that).map(elem -> Tuple.of(thisElem, elem)).toTree();
} else {
final java.util.Iterator<U> thatIter = that.iterator();
final Tree<Tuple2<T, U>> tree = ZipAll.apply((Node<T>) this, thatIter, thatElem);
if (thatIter.hasNext()) {
final Iterable<Node<Tuple2<T, U>>> remainder =
Iterator.ofAll(thatIter).map(elem -> Tree.of(Tuple.of(thisElem, elem)));
return new Node<>(tree.getValue(), tree.getChildren().appendAll(remainder));
} else {
return tree;
}
}
}
@SuppressWarnings("unchecked")
static <T, U> Tree<U> apply(
Node<T> node, Function<? super T, ? extends Iterable<? extends U>> mapper) {
final Tree<U> mapped = Tree.ofAll(mapper.apply(node.getValue()));
if (mapped.isEmpty()) {
return Tree.empty();
} else {
final List<Node<U>> children =
(List<Node<U>>)
(Object)
node.getChildren()
.map(child -> FlatMap.apply(child, mapper))
.filter(Tree::isDefined);
return Tree.of(mapped.getValue(), children.prependAll(mapped.getChildren()));
}
}