From SICP 2.2.4:
The textbook has already defined a function (right-split ...) as follows:
(define (right-split painter n) (if (= n 0) painter (let ((smaller (right-split painter (- n 1)))) (beside painter (below smaller smaller)))))
and they have indicated that there exists a procedure (up-split ...) which has much the same structure.
Exercise 2.45. Right-split and up-split can be expressed as instances of a general splitting operation. Define a procedure split with the property that evaluating
(define right-split (split beside below)) (define up-split (split below beside))
produces procedures right-split and up-split with the same behaviors as the ones already defined.
I wrote the following function, but I'm not sure the best way to test it. What do you think?
(define (split step1 step2) (define (split-f painter n) (if (= n 0) painter (let ((smaller (split-f painter (- n 1)))) (step2 (step1 smaller smaller))))) split-f) (define right-split (split beside below)) (define up-split (split below beside))