I'm making a simple sudoku program that only utilises a 9 x 9 grid. To that end, I have a function to check it is 9 x 9 and also checks to make sure the inputted values are Just Num's.
Here's the closest solution I've come to, I'm thinking the issue is in the pattern match I think (correct me if I'm wrong), this is because it compiles but has the logical error of returning False not True when given a perfectly fine test case. Anyways, here's the code dump :D
type Cell = Maybe Int
type Row = [Cell]
data Sudoku = Sudoku [Row]
deriving ( Show, Eq )
rows :: Sudoku -> [Row]
rows (Sudoku ms) = ms
isSudoku :: Sudoku -> Bool
isSudoku (Sudoku [[cs]]) = length [cs] == 9 && length cs == 9
isSudoku (Sudoku _) = False
Many thanks in advance for any advice given!
[x] as a pattern will only match a singleton list (list with exactly one element in it).
To perform the nested lists check, do
isSudokuList cs = length cs == ... &&
and [length c == ... | c <- cs]
You will have to tweak it to fit your types of course.
You could also define
niner [a,b,c,d,e,f,g,h,i] = True
.......
and use it.