static L<S> reTok(L<S> tok) {
  replaceCollection(tok, javaTok(tok));
  ret tok;
}

static L<S> reTok(L<S> tok, int i) {
  ret reTok(tok, i, i+1);
}

static L<S> reTok(L<S> tok, int i, int j) {
  // extend i to an "N" token
  // and j to "C" (so j-1 is an "N" token)
  i = max(i & ~1, 0);
  j = min(l(tok), j | 1);
  if (i >= j) ret tok;
  
  L<S> t = javaTok(joinSubList(tok, i, j));
  replaceListPart(tok, i, j, t);
  
  // fallback to safety
  // reTok(tok);
  
  ret tok;
}

ifclass IntRange
static LS reTok(LS tok, IntRange r) {
  if (r != null) reTok(tok, r.start, r.end);
  ret tok;
}
endif