formatted hs script

src/sudoku-hs/src/Main.hs

@@ -2,15 +2,15 @@
 
 module Main where
 
-import Data.Char (isSpace)
-import Data.List (transpose, minimumBy, delete, dropWhileEnd)
-import Data.Maybe (isNothing, listToMaybe, catMaybes)
 import qualified Data.ByteString.Lazy as BL
-import qualified Data.Vector as V
+import Data.Char (isSpace)
 import qualified Data.Csv as CSV
+import Data.List (delete, dropWhileEnd, minimumBy, transpose)
+import Data.Maybe (catMaybes, isNothing, listToMaybe)
+import Data.Ord (comparing)
+import qualified Data.Vector as V
 import System.Environment (getArgs)
 import Text.Read (readMaybe)
-import Data.Ord (comparing)
 
 type Cell = Maybe Int
 type Grid = [[Cell]]
@@ -18,51 +18,56 @@ type Pos = (Int, Int)
 
 parseCell :: String -> Cell
 parseCell s = readMaybe (trim s)
-  where trim = dropWhileEnd isSpace . dropWhile isSpace
+  where
+    trim = dropWhileEnd isSpace . dropWhile isSpace
 
 readCSV :: FilePath -> IO Grid
 readCSV path = do
-  csvData <- BL.readFile path
-  case CSV.decode CSV.NoHeader csvData of
-    Left err -> error ("CSV parse error: " ++ err)
-    Right v -> return $ map (map (parseCell . trimQuotes) . V.toList) (V.toList v)
-  where trimQuotes = filter (/= '"')
+    csvData <- BL.readFile path
+    case CSV.decode CSV.NoHeader csvData of
+        Left err -> error ("CSV parse error: " ++ err)
+        Right v -> return $ map (map (parseCell . trimQuotes) . V.toList) (V.toList v)
+  where
+    trimQuotes = filter (/= '"')
 
 printGrid :: Grid -> IO ()
 printGrid = putStrLn . unlines . map (unwords . map showCell)
-  where showCell = maybe "." show
+  where
+    showCell = maybe "." show
 
 solve :: Grid -> Maybe Grid
 solve g
-  | isComplete g = Just g
-  | otherwise = case nextCell g of
-      Nothing -> Nothing
-      Just (r, c, opts) ->
-        listToMaybe
-          [ result
-          | n <- opts
-          , let g' = updateGrid g r c (Just n)
-          , Just result <- [solve g']
-          , isComplete result ]
+    | isComplete g = Just g
+    | otherwise = case nextCell g of
+        Nothing -> Nothing
+        Just (r, c, opts) ->
+            listToMaybe
+                [ result
+                | n <- opts
+                , let g' = updateGrid g r c (Just n)
+                , Just result <- [solve g']
+                , isComplete result
+                ]
 
 isComplete :: Grid -> Bool
 isComplete = all (notElem Nothing)
 
 nextCell :: Grid -> Maybe (Int, Int, [Int])
 nextCell g =
-  case filter (not . null . (\(_, _, opts) -> opts)) candidates of
-    [] -> Nothing
-    cs -> Just $ minimumBy (comparing (\(_, _, opts) -> length opts)) cs
+    case filter (not . null . (\(_, _, opts) -> opts)) candidates of
+        [] -> Nothing
+        cs -> Just $ minimumBy (comparing (\(_, _, opts) -> length opts)) cs
   where
     candidates =
-      [ (r, c, validOptions g r c)
-      | (r, row) <- zip [0..] g
-      , (c, cell) <- zip [0..] row
-      , isNothing cell ]
+        [ (r, c, validOptions g r c)
+        | (r, row) <- zip [0 ..] g
+        , (c, cell) <- zip [0 ..] row
+        , isNothing cell
+        ]
 
 validOptions :: Grid -> Int -> Int -> [Int]
 validOptions g r c =
-  foldr delete [1..9] (catMaybes (getRow r g ++ getCol c g ++ getBox r c g))
+    foldr delete [1 .. 9] (catMaybes (getRow r g ++ getCol c g ++ getBox r c g))
 
 getRow :: Int -> Grid -> [Cell]
 getRow r g = g !! r
@@ -72,25 +77,27 @@ getCol c = map (!! c)
 
 getBox :: Int -> Int -> Grid -> [Cell]
 getBox r c g =
-  [ g !! r' !! c'
-  | r' <- [br..br+2], c' <- [bc..bc+2] ]
+    [ g !! r' !! c'
+    | r' <- [br .. br + 2]
+    , c' <- [bc .. bc + 2]
+    ]
   where
     br = r - r `mod` 3
     bc = c - c `mod` 3
 
 updateGrid :: Grid -> Int -> Int -> Cell -> Grid
 updateGrid g r c val =
-  take r g ++
-  [take c (g !! r) ++ [val] ++ drop (c + 1) (g !! r)] ++
-  drop (r + 1) g
+    take r g
+        ++ [take c (g !! r) ++ [val] ++ drop (c + 1) (g !! r)]
+        ++ drop (r + 1) g
 
 main :: IO ()
 main = do
-  args <- getArgs
-  case args of
-    [filePath] -> do
-      grid <- readCSV filePath
-      case solve grid of
-        Nothing -> putStrLn "No complete solution found."
-        Just g  -> printGrid g
-    _ -> putStrLn "Usage: sudoku-solver <sudoku.csv>"
+    args <- getArgs
+    case args of
+        [filePath] -> do
+            grid <- readCSV filePath
+            case solve grid of
+                Nothing -> putStrLn "No complete solution found."
+                Just g -> printGrid g
+        _ -> putStrLn "Usage: sudoku-solver <sudoku.csv>"