@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;
}
}
}
private static String toLispString(Tree<?> tree) {
final String value = String.valueOf(tree.getValue());
if (tree.isLeaf()) {
return value;
} else {
return String.format(
"(%s %s)", value, tree.getChildren().map(Node::toLispString).mkString(" "));
}
}
static <T> Stream<T> levelOrder(Tree<T> tree) {
Stream<T> result = Stream.empty();
final java.util.Queue<Tree<T>> queue = new java.util.LinkedList<>();
queue.add(tree);
while (!queue.isEmpty()) {
final Tree<T> next = queue.remove();
result = result.prepend(next.getValue());
queue.addAll(next.getChildren().toJavaList());
}
return result.reverse();
}
static <T> Stream<T> inOrder(Tree<T> tree) {
if (tree.isLeaf()) {
return Stream.of(tree.getValue());
} else {
final List<Node<T>> children = tree.getChildren();
return children
.tail()
.foldLeft(Stream.<T>empty(), (acc, child) -> acc.appendAll(inOrder(child)))
.prepend(tree.getValue())
.prependAll(inOrder(children.head()));
}
}
@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()));
}
}
@Override
default Tree<T> clear() {
return Tree.empty();
}
/**
* Returns a Tree containing {@code n} values supplied by a given Supplier {@code s}.
*
* @param <T> Component type of the Tree
* @param n The number of elements in the Tree
* @param s The Supplier computing element values
* @return A Tree of size {@code n}, where each element contains the result supplied by {@code s}.
* @throws NullPointerException if {@code s} is null
*/
static <T> Tree<T> fill(int n, Supplier<? extends T> s) {
Objects.requireNonNull(s, "s is null");
return Collections.fill(n, s, Tree.empty(), Tree::of);
}
/**
* Returns a Tree containing {@code n} values of a given Function {@code f} over a range of
* integer values from 0 to {@code n - 1}.
*
* @param <T> Component type of the Tree
* @param n The number of elements in the Tree
* @param f The Function computing element values
* @return A Tree consisting of elements {@code f(0),f(1), ..., f(n - 1)}
* @throws NullPointerException if {@code f} is null
*/
static <T> Tree<T> tabulate(int n, Function<? super Integer, ? extends T> f) {
Objects.requireNonNull(f, "f is null");
return Collections.tabulate(n, f, Tree.empty(), Tree::of);
}
static <T> Stream<T> postOrder(Tree<T> tree) {
return tree.getChildren()
.foldLeft(Stream.<T>empty(), (acc, child) -> acc.appendAll(postOrder(child)))
.append(tree.getValue());
}
static <T> Stream<T> preOrder(Tree<T> tree) {
return tree.getChildren()
.foldLeft(Stream.of(tree.getValue()), (acc, child) -> acc.appendAll(preOrder(child)));
}