static L<PTElement> ai_parseTree_getChildren(AI_BottomUpParser1 parser, L<WeightedProduction> productions, PTElement e) {
  if (e.children == null) {
    e.children = ai_parseTree_makeChildren(parser, productions, e);
    for (PTElement child : unnull(e.children)) child.parent = e;
  }
  ret e.children;
}

static L<PTElement> ai_parseTree_makeChildren(AI_BottomUpParser1 parser, L<WeightedProduction> productions, final PTElement e) {
  if (e instanceof ChooseCategory)
    ret map(((ChooseCategory) e).categories, func(S cat) -> PTElement { new HaveCategory(((ChooseCategory) e).word, cat) });
  if (e instanceof HaveCategory) {
    final HaveCategory h = cast e;
    L<ai_Reconstructed> l = ai_buParser1_reconstructedProductions(parser, productions, h.word, h.category);
    ret map(l, func(ai_Reconstructed r) -> PTElement {
      r.production.b == null
        ? new HaveCategory(r.a, r.production.a, r)
        : new ChoosePart(h.word, r)
    });
  }
  if (e instanceof ChoosePart) {
    ai_Reconstructed r = ((ChoosePart) e).reconstruction;
    ret (L) ll(new HaveCategory(r.a, r.production.a),
      new HaveCategory(r.b, r.production.b));
  }
  null;
}