sclass GazelleTree {
  L<GazelleTree> children;
  GazelleTree parent;
  double weight = 1, totalWeight;
  S line, lineType;
  S prediction, judgement;
  RuleEngine2_MatchedRule mr;
  bool isSplitNode;
  
  transient GazelleEvalContext ctx;

  *() {}
  *(S *line) {}
  
  toString {
    new LS l;
    if (mr != null)
      for (S s : unnull(mr.remainingConditions))
        l.add("if: " + s);
    addIfNempty(l, prediction);
    if (mr != null)
      l.add(mr.qualitySum() + " / " + formatDouble(mr.relativeQuality(), 2));
    ret line + appendSquareBracketed(joinWithComma(l));
  }
  
  // includes this node
  LS history() {
    new LS l;
    GazelleTree e = this;
    while (e != null) {
      l.add(e.line);
      e = e.parent;
    }
    ret reversed(l);
  }
  
  void add(GazelleTree child) {
    if (children == null) children = new L;
    child.parent = this;
    child.ctx = ctx;
    children.add(child);
  }
}