I want to learn more about Haskell and I started with my Sudoku solver

class SudokuClass s where
   initAreas :: s -> s
   createEmptySudoku :: s
   getBoardLength :: s -> Int
   setBoard :: s -> Board -> s

getCellToAreas :: s ->CellToAreas
... other functions with default implementations

I created a Sudoku solver for 9x9 sudoku's.

data Sudoku9x9 = Sudoku9x9 {
   board :: Board,
   areas:: Areas,
   cellToAreas :: CellToAreas
} deriving (Show)

Board, Areas and CellToAreas are of type Map.

After that I create an instance:

instance SudokuClass Sudoku9x9 where
initAreas s = .....

After implementing the 9x9 solver I wanted to create a second instance SudokuTwins, that solves a different kind of sudoku, but uses the same record:

data SudokuTwins = SudokuTwins {
   board :: Board,
   areas:: Areas,
   cellToAreas :: CellToAreas
} deriving (Show)

This is almost a copy of Soduku9x9 (right side of the =)

How can I express the fact that all sudoku solvers use the same recordtype? Can I make a type of the record structure {board:: Board.... } and use it in the constructor function or can I incorperate the recordtype in the class or ......?

Kees