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> 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()));
}
}