sclass OccTree2 {
  OccTree2 parent;
  E e;
  new L<OccTree2> next;
  int count; // This isn't accurate after replaceWith and stuff
  
  *() {}
  *(E *e) {}
  
  void addScript(L<E> script) {
    OccTree2 node = this;
    ++count;
    for (E c : script)
      (node = node.getOrMakeFollowUp(c)).count++;
  }
  
  OccTree2 getOrMakeFollowUp(E e) {
    OccTree2 node = followUp(e);
    if (node == null)
      next.add(node = newChild(e));
    ret node;
  }
  
  OccTree2 followUp(E e) {
    for (OccTree2 t : next)
      if (eq(t.e, e))
        ret t;
    null;
  }
  
  L<E> followUpKeys() {
    ret collect(next, "e");
  }
  
  OccTree2 newChild(E e) {
    OccTree2 child = new OccTree2(e);
    child.parent = this;
    ret child;
  }
  
  // size including all nodes
  int size() {
    int n = 1;
    for (OccTree2 t : next)
      n += t.size();
    ret n;
  }
  
  L<OccTree2> allLeaves() { new L l; collectLeaves(l); ret l; }
  
  // does not include root node as it has no input line associated
  L<OccTree2> allNodes() { new L l; collectNodes(l); ret l; }
  
  void collectLeaves(L<OccTree2> l) {
    if (isLeaf())
      l.add(this);
    else
      for (OccTree2 t : next)
        t.collectLeaves(l);
  }
  
  void collectNodes(L<OccTree2> l) {
    if (!isRoot())
      l.add(this);
    for (OccTree2 t : next)
      t.collectNodes(l);
  }
  
  bool isRoot() { ret e == null; }
  
  bool isLeaf() {
    ret !isRoot() && isEmpty(next);
  }
  
  int level() {
    int n = 0;
    OccTree2 node = this;
    while (node.parent != null) {
      ++n;
      node = node.parent;
    }
    ret n;
  }
  
  void replaceWith(OccTree2 n) {
    int i = parent.next.indexOf(this);
    parent.next.set(i, n);
    n.parent = parent;
    parent = null;
  }
}