A-M baby

Task/Middle-three-digits/Haskell/middle-three-digits.hs

@@ -0,0 +1,17 @@
+import Numeric
+
+mid3 :: Integral a => a -> Either String String
+mid3 n |   m < 100 = Left "is too small"
+       |    even l = Left "has an even number of digits"
+       | otherwise = Right . take 3 $ drop ((l-3) `div` 2) s
+  where m = abs n
+        s = showInt m ""
+        l = length s
+
+showMid3 :: Integer -> String
+showMid3 n = show n ++ ": " ++ either id id (mid3 n)
+
+main :: IO ()
+main = mapM_ (putStrLn . showMid3) [
+  123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345,
+  1, 2, -1, -10, 2002, -2002, 0]