Okay, this is really a newbie question, but here goes. I have a class that
represents a Sudoku grid. Internally, the grid is stored as a vector of vectors
of integers:
(define simple-grid%
(class object%
(super-new)
;b is an internal representation of the grid and is initialized to an empty
grid
(define b(make-vector 9 (make-vector 9 0)))
(define/public (get-cell r c)
(let
([row (vector-ref b (sub1 r))])
(vector-ref row (sub1 c))))
;etc.
I provide methods get-cell to retrieve the contents of a single cell, set-cell!
to (destructively) update the contents of a cell and so forth. In principle, I
could implement equal? by looping all 81 cells and comparing them one by one,
but this seems awkward. It seems like I ought to be able to just check that the
state vectors are equal? but I have no access to b outside the class. In Java,
I'd add a protected method getStateVector that could be called from within a
separate method named equalTo that tells me if a grid object g1 is equivalent
to a g2. Or at least I could do this. I really don't want to expose how the
internal representation of the grid to other classes. Then again, maybe that's
Java thinking in the context of Racket.
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