Chess.hs

repeatM :: Monad m => m a -> (a -> m a) -> Int -> m a
repeatM m _ 0
  = m
repeatM m f n
  = repeatM (m >>= f) f (n - 1)

inRange :: (Int, Int) -> Bool
inRange (x, y)
  = x `elem` [0..9] && y `elem` [0..9]

knight :: (Int, Int) -> Int -> [(Int, Int)]
knight start n 
  = repeatM [start] move n
  where
    possibleMoves
      = [ (-1, -2), (-1,  2)
        , ( 1, -2), ( 1,  2)
        , (-2,  1), (-2, -1)
        , ( 2,  1), ( 2, -1)
        ]

    move (x,y)    
      = [(x + dx, y + dy) | (dx, dy) <- possibleMoves, inRange (x + dx, y + dy)]