static L<S> ai_texts(S a, S b, S c) {
  int position = tripleIndexOf(a, b, c, "$X");
  if (position < 0) fail("bad");
  if (ai_useThoughtSpaces()) {
    AbstractThoughtSpace ts = thoughtSpace();
    L<TripleRef<S>> l = ai_thoughtSpace_query(a, b, c, ts);
    if (empty(l)) ret sharedEmptyList();
    new L<S> out;
    for (TripleRef<S> ref : l) if (ref != null) {
      T3<S> t = ref.triple;
      SS match = simpleMatchTriple_dollarVars(a, b, c, t);
      if (match != null)
        out.add(match.get("$X"));
    }
    ret out;
  }
  
  ret web_texts(ai_search_dollarX(a, b, c));
}