Question

this is the be anwsered in the language scheme and it only

Question 2 (100 marks in total) Write a recursive function (split L) that takes a list L, and returns a new list containing two sublists with the first sublist containing every second element in L and the second list containing the remaining elements not in the first sublist. Here are examples of how split should work: (split 12345678)) ((1 357) (24 68)) (split (cat bird dog horse mouse pig tiger gerbil cow)) ( (cat dog mouse tiger cow) (bird horse pig gerbil)) What should split return if its input is an empty list? Explain why. (100 marks)

Answer 1

Recursive function
;; makes two lists of every element

(define split
  (lambda (L)
    (if (null? L)
        '()
        (list (first L) (second L)))))

;; the first list 
(define first
  (lambda (L)
    (cond ((null? L) '())
          ((null? (cdr L)) L)
          (else (cons (car L)
                      (first (cdr (cdr L))))))))

;; the second list 
(define second
  (lambda (L)
    (cond ((null? L) '())
          ((null? (cdr L)) '())
          (else (cons (car (cdr L))
                      (second (cdr (cdr L))))))))

Q. What should split return if its input is an empty list? Explain why.

A: When input is an empty list it returns (). As in the code above we are checking whether given list is empty or not using condition. If the list is empty we are returning empty list ().