Initial data commit

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

@@ -0,0 +1,19 @@
+import Data.Bifunctor (bimap)
+import Data.List (unfoldr)
+import Data.Tuple (swap)
+
+digSum :: Int -> Int -> Int
+digSum base = sum . unfoldr f
+  where
+    f 0 = Nothing
+    f n = Just (swap (quotRem n base))
+
+digRoot :: Int -> Int -> (Int, Int)
+digRoot base =
+  head .
+  dropWhile ((>= base) . snd) . iterate (bimap succ (digSum base)) . (,) 0
+
+main :: IO ()
+main = do
+  putStrLn "in base 10:"
+  mapM_ (print . ((,) <*> digRoot 10)) [627615, 39390, 588225, 393900588225]