sexpToInt :: Sexp -> Maybe Int
sexpToInt (SAtom s) = case B8.readInt s of
  Nothing -> Nothing
  Just (i, rest) -> if B.null rest then Just i else Nothing
sexpToInt :: Sexp -> Maybe Int
sexpToInt (SAtom s) = case B8.readInt s of
  Nothing -> Nothing
  Just (i, rest) -> if B.null rest then Just i else Nothing
sexpToInt (SAtom s) = case B8.readInt s of
  Nothing -> Nothing
  Just (i, rest) -> if B.null rest then Just i else Nothing