Roman numerals/Decode: Difference between revisions

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@@ Line 3,088: / Line 3,088: @@
 Or, in a '''mapAccumR''' version:
 <lang Haskell>import Data.List (mapAccumR)
-import Data.Map.Strict as M
+import qualified Data.Map.Strict as M
 import Data.Maybe (maybe)
 fromRoman :: String -> Maybe Int
 fromRoman cs =
   let go l r
-        | l > r = (-r, l)
+        | l > r = (- r, l)
         | otherwise = (r, l)
-  in traverse (`M.lookup` mapRoman) cs >>=
+   in traverse (`M.lookup` mapRoman) cs
-     (Just . sum . ((:) <$> fst <*> snd) . mapAccumR go 0)
+        >>= ( Just . sum . ((:) <$> fst <*> snd)
+                . mapAccumR go 0
+            )
-mapRoman :: Map Char Int
-mapRoman = M.fromList $ zip "MDCLXVI " [1000, 500, 100, 50, 10, 5, 1, 0]
+mapRoman :: M.Map Char Int
+mapRoman =
--- TEST ---------------------------------------------------
+  M.fromList $
+    zip
+      "MDCLXVI "
+      [ 1000,
+,
+,
+,
+,
+,
+,
+      ]
+--------------------------- TEST -------------------------
 main :: IO ()
 main =
   putStrLn $
-  fTable
+    fTable
-    "Decoding Roman numbers:\n"
+      "Decoding Roman numbers:\n"
-    show
+      show
-    (maybe "Unrecognised character" show)
+      (maybe "Unrecognised character" show)
-    fromRoman
+      fromRoman
+      [ "MDCLXVI",
-    ["MDCLXVI", "MCMXC", "MMVIII", "MMXVI", "MMXVIII", "MMXBIII"]
+        "MCMXC",
+        "MMVIII",
--- FORMATTING ---------------------------------------------
+        "MMXVI",
-fTable :: String -> (a -> String) -> (b -> String) -> (a -> b) -> [a] -> String
+        "MMXVIII",
+        "MMXBIII"
+      ]
+------------------------ FORMATTING ----------------------
+fTable ::
+  String ->
+  (a -> String) ->
+  (b -> String) ->
+  (a -> b) ->
+  [a] ->
+  String
 fTable s xShow fxShow f xs =
+  unlines $
-  let w = maximum (length . xShow <$> xs)
+    s :
-      rjust n c = drop <$> length <*> (replicate n c ++)
-  in unlines $
+    fmap
-     s : fmap (((++) . rjust w ' ' . xShow) <*> ((" -> " ++) . fxShow . f)) xs</lang>
+      ( ((<>) . rjust w ' ' . xShow)
+          <*> ((" -> " <>) . fxShow . f)
+      )
+      xs
+  where
+    rjust n c = drop . length <*> (replicate n c <>)
+    w = maximum (length . xShow <$> xs)</lang>
 {{Out}}
 <pre>Decoding Roman numbers: