static IterableIterator<S> toLines(File f) {
  ret linesFromFile(f);
}

static List<String> toLines(String s) {
  List<String> lines = new ArrayList<String>();
  if (s == null) return lines;
  int start = 0;
  while (true) {
    int i = toLines_nextLineBreak(s, start);
    if (i < 0) {
      if (s.length() > start) lines.add(s.substring(start));
      break;
    }

    lines.add(s.substring(start, i));
    if (s.charAt(i) == '\r' && i+1 < s.length() && s.charAt(i+1) == '\n')
      i += 2;
    else
      ++i;

    start = i;
  }
  return lines;
}

static int toLines_nextLineBreak(String s, int start) {
  int n = s.length();
  for (int i = start; i < n; i++) {
    char c = s.charAt(i);
    if (c == '\r' || c == '\n')
      return i;
  }
  return -1;
}