// goes over input only once (doesn't start again at 1 like jreplace_dyn)

static S jreplace_dyn_allowNull(S s, S in, TokReplacer replacer, ITokCondition condition default null) {

  L<S> tok = javaTok(s);

  jreplace_dyn_allowNull(tok, in, replacer, condition);

  ret join(tok);

}

sbool jreplace_dyn_allowNull(LS tok, S in, TokReplacer replacer, ITokCondition condition default null) {

  ret jreplace_dyn_allowNull(tok, in, replacer, condition, false, true);

}

sbool jreplace_dyn_allowNull(LS tok, S in, TokReplacer replacer, ITokCondition condition, bool ignoreCase, bool reTok) {

  LS tokin = javaTok(in);

  jfind_preprocess(tokin);

  S[] toks = toStringArray(codeTokensOnly(tokin));  

  bool anyChange;

  int i = 0;

  for safety to 10000: {

    ping();

    ifdef jreplace_dyn_allowNull_debug

      printVars jreplace_dyn_allowNull_debug(+i, n := l(tok));

    endifdef

    i = findCodeTokens(tok, i, ignoreCase, toks, condition);

    if (i < 0) ret anyChange;

    int start = i, end = i+l(tokin)-2;

    i = end+2;

    S expansion = replacer.get(tok, start, end);

    if (expansion != null) {

      clearAllTokens(tok, start, end); // C to C

      ifdef jreplace_dyn_allowNull_debug

        printVars jreplace_dyn_allowNull_debug(+i, +start, +end, n := l(tok));

      endifdef

      tok.set(start, expansion);

      if (reTok) { // would this ever be false??

        int n = l(tok);

        reTok(tok, start, end);

        i += l(tok)-n; // adjust for replacement

      }

      set anyChange;

    }

  }

  throw fail("woot? 10000! " + quote(in) + " => " + replacer);

}