Just another update

Task/Digital-root/Haskell/digital-root-1.hs

@@ -1,10 +1,10 @@
-digSum base = f 0 where
-	f a n = let (q,r) = n`divMod`base in
-		if q == 0 then a+r else f (a+r) q
+import Data.List (unfoldr)
 
-digRoot base = f 0 where
-	f p n	| n < base = (p,n)
-		| otherwise = f (p+1) (digSum base n)
+digSum base = sum . unfoldr f where
+        f 0 = Nothing
+	f n = Just (r,q) where (q,r) = n `divMod` base
+
+digRoot base = head . dropWhile ((>= base).snd) . zip [0..] . iterate (digSum base)
 
 main =	do
 	putStrLn "in base 10:"

Task/Digital-root/Haskell/digital-root-2.hs

@@ -1,4 +1,4 @@
-import Data.List (elemIndex)
+import Data.List (elemIndex, unfoldr)
 import Data.Maybe (fromJust)
 import Numeric (readInt, showIntAtBase)
 
@@ -22,17 +22,16 @@ printDigRoot b s = do
 
 -- Convert a base b number to a list of digits, from least to most significant.
 toDigits :: Integral a => a -> a -> [a]
-toDigits b n = toDigits' n 0
-  where toDigits' 0 0 = [0]
-        toDigits' 0 _ = []
-        toDigits' m _ = let (q, r) = m `quotRem` b in r : toDigits' q r
+toDigits b = unfoldr f
+  where f 0 = Nothing
+        f n = Just (r,q) where (q,r) = n `quotRem` b
 
 -- A list of digits, for bases up to 36.
 digits :: String
 digits = ['0'..'9'] ++ ['A'..'Z']
 
 -- Return a number's base b string representation.
-intToStr :: Integral a => a -> a -> String
+intToStr :: (Integral a, Show a) => a -> a -> String
 intToStr b n | b < 2 || b > 36 = error "intToStr: base must be in [2..36]"
              | otherwise = showIntAtBase b (digits !!) n ""