sbool matchDoubleRest(S pat, S s) {

  ret matchDoubleRest(pat, s, null);

}

// matches are as you expect, plus an extra item for half of the rest string

sbool matchDoubleRest(S pat, S s, Matches matches) {

  if (s == null) false;

  ret matchDoubleRest(pat, parse3_cachedInput(s), matches);

}

sbool matchDoubleRest(S pat, LS toks, Matches matches) {

  if (toks == null) false;

  LS tokpat = parse3_cachedPattern(pat);

  int n = toks.size(), nPat = tokpat.size();

  if (n <= nPat || odd((n-nPat)/2)) ret false;

  int nRest = (n-nPat)/4;

  ifdef matchDoubleRest_debug

    print(+nRest);

  endifdef

  S[] m = match2(tokpat, subList(toks, 0, nPat));

  if (m == null) false;

  for (int i = nPat; i < nPat+nRest*2; i += 2)

    if (neqic(toks.get(i), toks.get(i+nRest*2))) {

      ifdef matchDoubleRest_debug

        print("fail at " + i + ": " + toks.get(i) + " / " + toks.get(i+nRest*2));

      endifdef

      ret false;

    }

  if (matches != null) {

    matches.m = new S[m.length+1];

    arraycopy(m, matches.m);

    matches.m[m.length] = joinSubList(toks, nPat, nPat+nRest*2-1); // for Matches.rest()

  }

  true;

}