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{-
A learning tic-tac-toe player in Haskell. It learns the game
by playing against itself repeatedly.
It can play against humans too!
A solution to rubyquiz 11 (http://rubyquiz.com/quiz11.html).
Usage: ./TicTacToe board_size training_time
Copyright 2012 Abhinav Sarkar <abhinav@abhinavsarkar.net>
-}
{-# LANGUAGE BangPatterns, RecordWildCards #-}
module TicTacToe (Move(..), CellState(..), Cell(..), Board(..), Run, Result(..),
Player(..), playMatch, playMatches, RandomPlayer(..),
LearningPlayer, learnedPlayer, playHuman, main)
where
import qualified Data.Map as M
import Control.Monad.State (State, get, put, runState, evalState)
import Data.List (sort, nub, maximumBy)
import Data.List.Split (chunksOf)
import Data.Ord (comparing)
import System.Environment (getArgs)
import System.IO (hSetBuffering, stdin, stdout, BufferMode(..))
import System.Random (Random, StdGen, randomR, newStdGen, split)
import Text.Printf (printf)
-- Randomness setup
type RandomState = State StdGen
getRandomR :: Random a => (a, a) -> RandomState a
getRandomR limits = do
gen <- get
let (val, gen') = randomR limits gen
put gen'
return val
randomChoose :: [a] -> RandomState a
randomChoose list = do
i <- getRandomR (0, length list - 1)
return $ list !! i
toss :: RandomState Bool
toss = randomChoose [True, False]
-- Board setup
data Move = Nought | Cross deriving (Eq, Ord)
data CellState = Filled Move | Empty deriving (Eq, Ord)
data Cell = Cell { cellPos :: Int, cellState :: CellState } deriving (Eq, Ord)
data Board = Board { boardSize :: Int, boardCells :: [Cell] } deriving (Eq, Ord)
type Run = [Board]
data Result = Win | Loss | Draw | Unfinished deriving (Eq, Show)
instance Show Move where
show Nought = "O"
show Cross = "X"
instance Show CellState where
show (Filled move) = show move
show Empty = "~"
instance Show Cell where
show c = show $ cellState c
otherMove :: Move -> Move
otherMove Nought = Cross
otherMove Cross = Nought
otherResult :: Result -> Result
otherResult Draw = Draw
otherResult Loss = Win
otherResult Win = Loss
emptyBoard :: Int -> Board
emptyBoard boardSize =
Board boardSize $ map (flip Cell Empty) [0..(boardSize * boardSize - 1)]
printBoard :: Board -> IO ()
printBoard Board{..} = putStrLn "" >> (mapM_ print . chunksOf boardSize $ boardCells)
makeMove :: Int -> Move -> Board -> Board
makeMove pos move board@Board{..} =
let (l, r) = splitAt pos boardCells
in board { boardCells = l ++ [Cell pos (Filled move)] ++ tail r }
diags :: Board -> [[Cell]]
diags Board{..} =
[map (boardCells !!) . take boardSize . iterate (+ (boardSize + 1)) $ 0,
map (boardCells !!) . take boardSize . iterate (+ (boardSize - 1)) $ (boardSize - 1)]
nextBoards :: Move -> Board -> [(Int, Board)]
nextBoards move board@Board{..} =
map ((\p -> (p, makeMove p move board)) . cellPos)
$ filter (\c -> cellState c == Empty) boardCells
isWin :: Move -> Board -> Bool
isWin move board =
or [any isStrike . chunksOf size . map cellState . boardCells $ board,
any isStrike . chunksOf size . map cellState . boardCells . rotateBoard $ board,
any isStrike . map (map cellState) . diags $ board]
where
size = boardSize board
isStrike = (== replicate size (Filled move))
result :: Move -> Board -> Result
result move board
| isWin move board = Win
| isWin (otherMove move) board = Loss
| Empty `elem` (map cellState . boardCells $ board) = Unfinished
| otherwise = Draw
translateBoard :: [Int] -> Board -> Board
translateBoard idxs board@Board{..} =
board { boardCells =
map (\(i, ri) -> Cell i . cellState $ boardCells !! ri)
$ zip [0..(boardSize * boardSize - 1)] idxs }
rotateBoard, xMirrorBoard, yMirrorBoard :: Board -> Board
rotateBoard board@Board{..} =
translateBoard
(let xs = reverse . chunksOf boardSize $ [0..(boardSize * boardSize - 1)]
in concatMap (\i -> map (!! i ) xs) [0..(boardSize - 1)])
board
xMirrorBoard board@Board{..} =
translateBoard
(concatMap reverse . chunksOf boardSize $ [0..(boardSize * boardSize - 1)]) board
yMirrorBoard board@Board{..} =
translateBoard
(concat . reverse . chunksOf boardSize $ [0..(boardSize * boardSize - 1)]) board
rotateBoardN :: Board -> Int -> Board
rotateBoardN board n = foldl (\b _ -> rotateBoard b) board [1..n]
-- Player setup
class Player a where
playerMove :: a -> Move
play :: a -> Board -> (a, Board)
improvePlayer :: a -> Result -> Run -> a
-- play a match between two players
playMatch :: (Player p1, Player p2) => p1 -> p2 -> Board -> (Result, Run, p1, p2)
playMatch player1 player2 board =
case result (playerMove player1) board of
Unfinished -> let
(player1', board') = play player1 board
in case result (playerMove player1) board' of
Unfinished -> let
(res', run, player2', player1'') = playMatch player2 player1' board'
in (otherResult res', board' : run, player1'', player2')
res -> (res, [], player1', player2)
res -> (res, [], player1, player2)
-- play multiple matches between two players
playMatches :: (Player p1, Player p2) => Int -> Int -> p1 -> p2
-> ([(Result, Run)],p1, p2)
playMatches boardSize times player1 player2 =
foldl (\(matches, p1, p2) _ ->
let
startBoard = emptyBoard boardSize
(res, run, p1', p2') = playMatch p1 p2 startBoard
p1'' = improvePlayer p1' res run
p2'' = improvePlayer p2' (otherResult res) run
in ((res, run) : matches, p1'', p2''))
([], player1, player2) [1..times]
-- RandomPlayer setup
-- play randomly. choose a random move
randomPlay :: Move -> Board -> RandomState Board
randomPlay move board = randomChoose (map snd $ nextBoards move board)
data RandomPlayer = RandomPlayer Move StdGen deriving (Show)
instance Player RandomPlayer where
playerMove (RandomPlayer move _) = move
play (RandomPlayer move gen) board =
let
(board', gen') = runState (randomPlay move board) gen
in (RandomPlayer move gen', board')
improvePlayer player _ _ = player
-- LearningPlayer setup
type Memory = M.Map Board (Int, Int, Int)
-- boards equivalent to this board
eqvBoards :: Board -> [Board]
eqvBoards board = nub . sort $
board : map (rotateBoardN board) [1..3] ++ [xMirrorBoard board, yMirrorBoard board]
data LearningPlayer = LearningPlayer Move Memory StdGen
-- play using the strategy learned till now
learningPlay :: LearningPlayer -> Board -> (LearningPlayer, Board)
learningPlay (LearningPlayer move mem gen) board = let
next = map snd $ nextBoards move board
in case filter (isWin move) next of
(winBoard:_) -> (LearningPlayer move mem gen, winBoard)
[] -> let
otherNext = nextBoards (otherMove move) board
in case filter (isWin (otherMove move) . snd) otherNext of
((pos,_):_) -> (LearningPlayer move mem gen, makeMove pos move board)
[] -> let
scores = map (\b -> (b, boardScore b mem)) next
(board', (w, _, d)) = maximumBy (comparing (calcScore . snd)) scores
in if w /= 0
then (LearningPlayer move mem gen, board')
else let
((rBoard, _), gen') = runState (randomChoose scores) gen
in (LearningPlayer move mem gen', rBoard)
where
boardScore board' mem =
foldl (\score b' -> sumScores score $ M.findWithDefault (0, 0, 0) b' mem)
(0, 0, 0) (eqvBoards board')
sumScores (w, l, d) (w', l', d') = (w + w', l + l', d + d')
calcScore :: (Int, Int, Int) -> Double
calcScore (w, l, d) = fromIntegral w + fromIntegral d * 0.5 - fromIntegral l
-- learn strategy from the run
learnFromRun :: Result -> Run -> Memory -> Memory
learnFromRun res run mem = let
score = incrementScore res (0, 0, 0)
mem' = foldl (\m b -> M.insertWith (\_ -> incrementScore res) b score m)
mem run
in mem'
where
incrementScore res (w, l, d) =
case res of
Win -> (w + 1, l, d)
Loss -> (w, l + 1, d)
Draw -> (w, l, d + 1)
instance Player LearningPlayer where
playerMove (LearningPlayer move _ _) = move
play = learningPlay
improvePlayer (LearningPlayer move mem gen) res run =
LearningPlayer move (learnFromRun res run mem) gen
-- play two LearningPlayers against each other to learn strategy
learnedPlayer :: Int -> Int -> Move -> StdGen -> LearningPlayer
learnedPlayer boardSize times move gen = let
(gen1, gen2) = split gen
p1 = LearningPlayer move M.empty gen1
p2 = LearningPlayer (otherMove move) M.empty gen2
(_, p1', p2') = playMatches boardSize times p1 p2
in p1'
-- Play against human
-- play a player against a human. human enters moves from prompt.
playHuman :: Player p => p -> Board -> IO ()
playHuman player board@Board{..} = do
printBoard board
let boardArea = boardSize * boardSize
case result (playerMove player) board of
Unfinished -> do
putStr $ printf "Move %s? [1-%s] "
(show . otherMove . playerMove $ player) (show boardArea)
pos <- fmap (decr . read) getLine
if pos < 0 || pos > (boardArea - 1)
then do
putStrLn "Invalid Move"
playHuman player board
else
case cellState (boardCells !! pos) of
Filled _ -> do
putStrLn "Invalid Move"
playHuman player board
Empty -> let
board' = makeMove pos Nought board
in case result (playerMove player) board' of
Unfinished -> let
(player', board'') = play player board'
in playHuman player' board''
res -> do
printBoard board'
putStrLn ("Your " ++ show (otherResult res))
res -> putStrLn ("Your " ++ show (otherResult res))
where decr x = x - 1
main :: IO ()
main = do
(boardSize : times : _) <- fmap (map read) getArgs
hSetBuffering stdin LineBuffering
hSetBuffering stdout NoBuffering
gen <- newStdGen
putStrLn "Learning ..."
let !player = learnedPlayer boardSize times Cross gen
putStrLn "Learned"
putStrLn "Tossing for first move"
let t = evalState toss gen
let startBoard = emptyBoard boardSize
if t
then do
putStrLn "You win toss"
playHuman player startBoard
else do
putStrLn "You lose toss"
let (player', board) = play player startBoard
playHuman player' board