ふぃっしゅ数ver.3の展開

fish3w.hs

type I = Integer
data F3 = S [I] | SS I

instance Show F3 where
  show (S x) = show x
  show (SS x) = show x

sss :: [F3] -> IO I -> IO I
sss [] x             = do
  x' <- x
  appendFile "fish3.txt" ("リストがない  ("++show x'++")\n")
  return x'
sss (S []:ns) x       =
  sss ns x
sss (list@[S [1]]) x        = do
  x' <- x
  let y = 2 * x'
  appendFile "fish3.txt" (show list++"  ("++show x'++") = "++show y++"\n")
  return y
sss (list@(S (1:ns):nss)) x = do
  x' <- x
  appendFile "fish3.txt" (show list++"  ("++show x'++")\n")
  appendFile "fish3.txt" "Xn = "
  fpow (sss (S ns:nss)) x' (return x')
sss (list@(S (n:ns):nss)) x = do
  x' <- x
  appendFile "fish3.txt" (show list++"  ("++show x'++")\n")
  let n'=replicate (fromIntegral x') (n-1)
  sss (S (n'++ns):nss) (return x')
sss (list@(SS 1:nss)) x     = do
  x' <- x
  appendFile "fish3.txt" (show list++"  ("++show x'++")\n")
  sss (S [x']:nss) (return x')
sss (list@(SS n:nss)) x     = do
  x' <- x
  appendFile "fish3.txt" (show list++"  ("++show x'++")\n")
  let n' = replicate (fromIntegral x') (SS (n-1))
  sss (n'++nss) (return x')

fpow :: (a->a) -> I -> (a->a)
fpow f 1 = f
fpow f n = f.fpow f (n-1)

main :: IO I
main = do
  writeFile "fish3.txt" ""
  let l632 = replicate 63 (SS 2)
  sss l632 (return 3)