static Triple<S> ai_tripelize(S s) {
  S x = "";
  if (endsWith(s, "?")) x = " (?)"; // e.g. for "Al Gore invented the Internet?"
  Triple<S> t = ai_tripelize_impl(dropPunctuationAtEnd(s));
  if (t != null) t.b += x;
  ret t;
}
  
static Triple<S> ai_tripelize_impl(S s) {
  L<S> tok = nlTok(s);
  S a = get(tok, 1);
  if (a == null) null;
  if (ai_questionWord_1(a)) { tok = subList(tok, 2); a = get(tok, 1); }
  if (ai_yesNoQuestionWord_1(a) && neqicOneOf(a, "am", "are", "is")) {
    L<S> tok2 = subList(tok, 2);
    int i = indexOfFirstVerb(tok2);
    S v = get(tok2, i);
    if (v != null) {
      if (eqic(a, "does")) v = verbToThirdPerson(v) + "?";
      else if (eqic(a, "do")) v = v + "?";
      else if (eqic(a, "did")) v = verbToPast(v) + "?";
      else v = a + " " + v + "?";
      ret triple("", v, "");
    }
  }
  if (isVerb(a)) {
    tok = subList(tok, 2);
    //int i = ai_splitTwoNounPhrases(tok);
    int i = ai_endOfNounPhrase(tok);
    ret triple(
      trimJoinSubList(tok, 0, i),
      a + "?",
      trimJoinSubList(tok, i));
  }
  
  int i = ai_endOfNounPhrase(tok);
  int j = indexOfFirstVerb(tok, i);
  ret triple(
    trimJoinSubList(tok, 0, j),
    tok.get(j),
    trimJoinSubList(tok, j+2));
}