Lab 5

[BertLisser]

Exercise 2. Good but refactoring can be more complete.
In many more places it is possible to replace Constraints by [Position]

type Node = (Sudoku,[Position])
prune :: (Row,Column,Value)
      -> [Position] -> [Position]
constraints :: Sudoku -> [Position]

Why not using

eraseN :: Node -> (Row,Column) -> Node
eraseN n (r,c) = (s, constraints s)

and

Ex. 3

minimal :: Grid -> Bool
minimal g = solutionCount g == 1
            && all (\x -> solutionCount x > 1) (smallerProblems g)

Why not using

eraseN :: Node -> (Row,Column) -> Node
eraseN n (r,c) = (s, constraints s)

and

uniqueSol :: Node -> Bool
uniqueSol node = singleton (solveNs [node]) where
  singleton [] = False
  singleton [x] = True
  singleton (x:y:zs) = False

Exercise 4

doExercise4 :: IO()
doExercise4 = do [r] <- rsolveNs [emptyN]
                 showNode r
                 s <- genProblemEmptyBlocks 20 r
                 print$uniqueSol s  // There are cases that s doesn't have an unique solution
                 showNode s