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NaiveBitBoard.hs
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NaiveBitBoard.hs
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module NaiveBitBoard where
import Data.Bits
import Data.Word
admissible :: (Word64, Word64) -> Word64
admissible brd@(pla, opp) = foldr f 0 [0..63]
where
f pos acc | (pla .|. opp) .&. 1 `shiftL` pos /= 0 = acc
| flipped pos brd == 0 = acc
| otherwise = acc .|. 1 `shiftL` pos
flipped :: Int -> (Word64, Word64) -> Word64
flipped pos (pla, opp) = foldr (.|.) 0 $ map flipped' dirs
where
dirs = [(x, y) | x <- [-1,0,1], y <- [-1,0,1], not (x == 0 && y == 0)]
flipped' (dx, dy) =
let loop acc (x, y) | overflow p' = 0
| check pla p' = acc
| check opp p' = loop (acc .|. place p') p'
| otherwise = 0
where p' = (x+dx, y+dy)
in loop 0 (posx, posy)
posx = pos .&. 7
posy = pos `shiftR` 3
check set p = set .&. place p /= 0
place (x, y) = 1 `shiftL` (x .|. y `shiftL` 3)
overflow (x, y) = x == -1 || x == 8 || y == -1 || y == 8