viewR :: Sequence a -> FT.ViewR Sequence a
viewR (Sequence s) = case FT.viewR s of
  FT.EmptyR -> FT.EmptyR
  tree FT.:> (Element a) -> Sequence tree FT.:> a
viewR :: Sequence a -> FT.ViewR Sequence a
viewR (Sequence s) = case FT.viewR s of
  FT.EmptyR -> FT.EmptyR
  tree FT.:> (Element a) -> Sequence tree FT.:> a
viewR (Sequence s) = case FT.viewR s of
  FT.EmptyR -> FT.EmptyR
  tree FT.:> (Element a) -> Sequence tree FT.:> a