Scheme - Retrieving elements from a matrix

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Author

Retrieving elements from a matrix

witt

2005-11-13, 11:12 am

Hello, I'm doing some exercises on scheme programming, and I could use some help with this one.

I'm trying to create a function that takes a 9x9 matrix, and retrieves a list with the linear representation of each 3x3 square contained in the matrix; the order is irrelevant.

I have to use the following code, which returns the first square:

(define topleft-square
(lambda (grid)
(append (first-3 (car grid))
(first-3 (cadr grid))
(first-3 (caddr grid)))))

(define first-3
(lambda (l)
(list (car l) (cadr l) (caddr l))))

I have banged my head around with this, and still couldn't get it to work. A few hints would be really helpful. Thanks;)

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