(!) :: Sequence a -> Index -> a
(Sequence s) ! i = getElement x
  where
    Split _ x _ = FT.splitTree (Size i <) (Size 0) s
(!) :: Sequence a -> Index -> a
(Sequence s) ! i = getElement x
  where
    Split _ x _ = FT.splitTree (Size i <) (Size 0) s
(Sequence s) ! i = getElement x
  where
    Split _ x _ = FT.splitTree (Size i <) (Size 0) s