Middle three digits: Difference between revisions

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@@ Line 2,452: / Line 2,452: @@
 mid3 n
   | m < 100 = Left "is too small"
-  | even l = Left "has an even number of digits"
+  | even lng = Left "has an even number of digits"
-  | otherwise = Right . take 3 $ drop ((l - 3) `div` 2) s
+  | otherwise = Right . take 3 $ drop ((lng - 3) `div` 2) s
   where
     m = abs n
     s = show m
-    l = length s
+    lng = length s
-showMid3 :: Int -> String
-showMid3 n = show n ++ ": " ++ either id id (mid3 n)
+-- TEST --------------------------------------------------------
 main :: IO ()
-main =
+main = do
+  let xs =
-  mapM_
-    (putStrLn . showMid3)
+        [ 123
-    [ 123
+        , 12345
-    , 12345
+        , 1234567
-    , 1234567
+        , 987654321
-    , 987654321
+        , 10001
-    , 10001
+        , -10001
-    , -10001
+        , -123
-    , -123
+        , -100
-    , -100
+        , 100
-    , 100
+        , -12345
-    , -12345
+        , 1
-    , 1
+        , 2
-    , 2
+        , -1
-    , -1
+        , -10
-    , -10
+        , 2002
-    , 2002
+        , -2002
-    , -2002
+        , 0
-    , 0
+        ]
+      w = maximum $ (length . show) <$> xs
-    ]</lang>
+  (putStrLn . unlines) $
+    (\n ->
+        justifyRight w ' ' (show n) ++
+        " -> " ++ either ((>>= id) . ("(" :) . (: [")"])) id (mid3 n)) <$>
+    xs
+  where
+    justifyRight :: Int -> Char -> String -> String
+    justifyRight n c s = drop (length s) (replicate n c ++ s)</lang>
 Output:
-<pre>123: 123
+<pre>      123 -> 123
-: 234
+-> 234
-1234567: 345
+  1234567 -> 345
-987654321: 654
+987654321 -> 654
-: 000
+-> 000
--10001: 000
+   -10001 -> 000
--123: 123
+     -123 -> 123
--100: 100
+     -100 -> 100
-: 100
+-> 100
--12345: 234
+   -12345 -> 234
-: is too small
+-> (is too small)
-: is too small
+-> (is too small)
--1: is too small
+       -1 -> (is too small)
--10: is too small
+      -10 -> (is too small)
-: has an even number of digits
+-> (has an even number of digits)
--2002: has an even number of digits
+    -2002 -> (has an even number of digits)
-: is too small</pre>
+-> (is too small)</pre>
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