toCounter :: Polymer -> Counter
toCounter polymer = V.create $ do
  !v <- M.replicate 26 0
  for_ polymer $ \p -> do
    let !i = ord p - 65 -- ord 'A'
    M.unsafeModify v succ i
  pure v
toCounter :: Polymer -> Counter
toCounter polymer = V.create $ do
  !v <- M.replicate 26 0
  for_ polymer $ \p -> do
    let !i = ord p - 65 -- ord 'A'
    M.unsafeModify v succ i
  pure v
toCounter polymer = V.create $ do
  !v <- M.replicate 26 0
  for_ polymer $ \p -> do
    let !i = ord p - 65 -- ord 'A'
    M.unsafeModify v succ i
  pure v