static boolean find3(S pat, S s) {
  return find3(pat, s, null);
}

static boolean find3(S pat, S s, Matches matches) {
  ret find3(pat, parse3_cachedInput(s), matches);
}
  
static boolean find3(S pat, LS toks, Matches matches) {
  L<S> tokpat = parse3_cachedPattern(pat);
  S[] m = find2(tokpat, toks);
  //print(structure(tokpat) + " on " + structure(toks) + " => " + structure(m));
  if (m == null) false;
  if (matches != null) matches.m = m;
  true;
}