Exercise 2.27: Modify your deep-reverse procedure of Exercise 2.18 to produce a deep-deep-reverse procedure that takes a list as argument and returns as its value the list with its elements deep-reversed and with all sublists deep-deep-reversed as well. For example,
(define x (list (list 1 2) (list 3 4))) x ((1 2) (3 4)) (deep-reverse x) ((3 4) (1 2)) (deep-deep-reverse x) ((4 3) (2 1))
Please review my code.
(define (deep-deep-reverse lst) (cond ((null? lst) '()) ((list? lst) (append (deep-deep-reverse (cdr lst)) (list (deep-deep-reverse (car lst))))) (else lst)))
I spent an hour doing this, and I am actually extremely surprise on how small this code is in the end. How can I improve this code? Perhaps make it faster?