Question

Develop, write and certify a properly recursive procedure reverseDigits to input a positive integer n
and to output the integer formed by reversing the digits of n. Thus (reverseDigits 1234) returns the
integer 4321. Please answer using Dr Racket(R5RS language)

Answer 1

//define the logic first

(define

invert-number-aux (λ (n res)

                  (if (empty? n) res

                      (invert-number-aux

                       (take n (-(length n) 1)) ;new n

                       (append res (list (last n))) ;new res

                       )

                      )))

(define

invert-number (λ (n)

                  (string->number (list->string (invert-number-aux (string->list(number->string n)) '())))

                  ))