Printed datatype for Haskell: custom format deep within a data structure

Printed.hs

import Text.Printf
import ComposeLTR

main = do
  print ls
  print lsd
  -- [26,56,114,222,398,628,857,1033,1141,1199,1229,1243]
  -- [26,30,58,108,176,230,229,176,108,58,30,14]

  ln
  print $ map (Printed "%5d") ls
  print $ map (Printed "%5d") lsd
  -- [   26,   56,  114,  222,  398,  628,  857, 1033, 1141, 1199, 1229, 1243]
  -- [   26,   30,   58,  108,  176,  230,  229,  176,  108,   58,   30,   14]

  ln
  print $ map (CShow $ printf "%5d") ls
  print $ map (CShow $ printf "%5d") lsd
  -- [   26,   56,  114,  222,  398,  628,  857, 1033, 1141, 1199, 1229, 1243]
  -- [   26,   30,   58,  108,  176,  230,  229,  176,  108,   58,   30,   14]

data Printed a = Printed String a
instance PrintfArg a => Show (Printed a) where
  show (Printed f a) = printf f a

data CShow a = CShow (a -> String) a
instance Show (CShow a) where
  show (CShow f a) = f a

end = 12

ls :: [Int]
ls = map (\x -> sg 10000 ((x / end - 0.5)) * (3200 - 1945) $> round) [1 .. end]
lsd = zipWith (-) ls (0 : ls)
sg a t = 1 / (1 + a ** (-t))

ln = putStrLn ""

noop :: Monad m => m ()
noop = return ()