static L<Web> ai_filterBadWebs(L<Web> _webs) {
  L<Web> webs = emptyListWithCapacity(_webs);
  int dropped = 0, dropped2 = 0;
  for (Web web : _webs)
    if (web_nodesTooLong(web))
      dropped++;
    else if (!web_tripelizable(web))
      dropped2++;
    else
      webs.add(web);
  if (dropped != 0)
    print("Dropped " + nWeb(dropped) + " with too long nodes");
  if (dropped2 != 0)
    print("Dropped " + n(dropped2, "non-triple"));
  ret webs;
}