static <A> ItIt<ParsedWithTokens<A>> pwt_toTheLeftOf(Iterable<ParsedWithTokens<A>> l, ParsedWithTokens b) {
  ret filterI(iterator(l), p -> {
    //print("ttlo: " + p.iRemaining + " / " + b.iStart);
    ret (p.iRemaining | 1) == (b.iStart | 1);
  });
}