static L<File> findAllFiles_noDirs_pred(File dir, O pred) {
  new L<File> l;
  if (isTrue_callF(pred, dir))
    findAllFiles_noDirs_pred_impl(dir, pred, l);
  ret l;
}

svoid findAllFiles_noDirs_pred_impl(File dir, O pred, L<File> l) {
  for (File f : listFiles(dir)) {
    if (!isTrue_callF(pred, f)) continue;
    if (f.isDirectory())
      findAllFiles_noDirs_pred_impl(f, pred, l);
    else
      l.add(f);
  }
}

Began life as a copy of #1003844