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Tic-tac-toe in Haskell
import Data.Maybe (isNothing, fromJust)
import Data.List (intercalate)
import Char (toUpper)
import System.IO (hFlush, stdout)
data Move = O | X
deriving (Eq, Show, Enum, Ord)
type Position = (Char, Int)
data BoardMove = BoardMove
{ bMove :: Maybe Move, bPos :: Position }
deriving (Eq, Show)
type Board = [BoardMove]
type InvalidMove = String
bsize = 3
coord = (['A'..], [1..])
empty :: Int -> Board
empty size = do
x <- take size (fst coord)
y <- take size (snd coord)
return $ BoardMove Nothing (x,y)
move :: BoardMove -> Board -> Either InvalidMove Board
move (BoardMove _ (c,r)) [] =
Left $ "Could not make the move to given position " ++ [c] ++ (show r)
move bm@(BoardMove nmov npos) (x:xs)
| findMove x = Right $ bm:xs
| otherwise =
case move bm xs of
Right r -> Right $ x:r
err -> err
where findMove (BoardMove m p) =
p == npos && isNothing m && nmov /= Nothing
win :: BoardMove -> Board -> Bool
win (BoardMove Nothing _) _ = False
win (BoardMove m (c,r)) b = row || col || diag' cb || diag' (reverse cb)
where row = length
(filter (\(BoardMove m2 (_,r2)) ->
m2 == m && r2 == r) b) == bsize
col = length
(filter (\(BoardMove m2 (c2,_)) ->
m2 == m && c2 == c) b) == bsize
diag' xss = all (\(BoardMove m2 _) ->
m2 == m) $ diag xss
cb = chop bsize b
draw :: BoardMove -> Board -> Bool
draw bm b = not (any (isNothing . bMove) b)
&& not (win bm b)
printBoard :: Board -> String
printBoard b = intercalate "\n" $
map (\row-> [(fst . bPos) (row !! 0)] ++ ") | " ++
(intercalate " | "
$ map (\bm-> maybe " " show $ bMove bm) row)
++ " |")
(chop bsize b)
chop :: Int -> [a] -> [[a]]
chop n [] = []
chop n xs = take n xs : chop n (drop n xs)
diag :: [[a]] -> [a]
diag xss = [xss !! n !! n | n <- [0 .. length xss - 1]]
main = do
putStrLn "Starting new game..."
putStrLn "Type 'quit' to exit game"
let newBoard = empty bsize
in do (putStrLn . (\s->"\n"++s++"\n") . printBoard) newBoard
gameloop Nothing newBoard
gameloop prevMove board = do
let currPlayer = maybe X (\(BoardMove mv _) ->
case mv of
Just X -> O
Just O -> X) prevMove
putStr $ "Player '" ++ (show currPlayer) ++ "': "
hFlush stdout
playerMove <- getLine
case (playerMove, (map toUpper playerMove) `elem` allCoord) of
("quit", _) ->
putStrLn "Goodbye!"
(_, False) -> do
putStrLn $ "Possible options: " ++ intercalate ", " allCoord
gameloop prevMove board
otherwise -> do
let pos = (toUpper $ playerMove !! 0,
read [(playerMove !! 1)] :: Int)
currMove = BoardMove (Just currPlayer) pos
currBoard = move currMove board
either putStrLn (putStrLn . (\s->"\n"++s++"\n") . printBoard) currBoard
case currBoard of
Right r -> if win currMove r
then do putStrLn $ "Player '"
++ (show currPlayer) ++"' wins!"
main
else if draw currMove r
then do putStrLn $ "It's a draw!"
main
else gameloop (Just currMove) r
Left err -> gameloop prevMove board
where allCoord = [[x] ++ show y | x <- take bsize (fst coord),
y <- take bsize (snd coord)]
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