internal static IEnumerable <Fiber> CreateChain(Tuple <int, int> range)
{
byte[] min_bytes = System.Text.Encoding.UTF8.GetBytes(new[] { (char)range.Item1 });
byte[] max_bytes = System.Text.Encoding.UTF8.GetBytes(new[] { (char)range.Item2 });
return(min_bytes.SyncZip(max_bytes).Select(it => Fiber.Create(it.Item1, it.Item2)));
}