adjacentCells :: CellMap -> (Int, Int) -> [(Int, Int)]
adjacentCells cells (r, c) = filter (\k -> M.member k cells) possibles
where possibles = [(r, c - 1), (r, c + 1), (r - 1, c), (r + 1, c)]
adjacentCells :: CellMap -> (Int, Int) -> [(Int, Int)]
adjacentCells cells (r, c) = filter (\k -> M.member k cells) possibles
where possibles = [(r, c - 1), (r, c + 1), (r - 1, c), (r + 1, c)]