Question

2. Write a scheme function get-even-nums that accepts a list of numbers and returns a new list that contains only the even numbers. (Hint: use reminder function) Sample runs: (get-even-nums ‘(1 2 3 4 5 6 7 8 9)) should return (8 6 4 2). (get-even-nums ‘(1 3 5 7 9)) should return ’( ).

Answer 1

Answer:-

*** The list may not be simple,nested lists can occur and you need to find the even numbers inside those list then we will write this scheme.

(define (evenlist numberlist)
  (cond ((null? numberlist) '())
        ((not (pair? numberlist))
         (if (even? numberlist) (list numberlist) '()))
        (else
         (append (evenlist (car numberlist))
                 (evenlist (cdr numberlist))))))

*** If it is a simple list.

(define (evenlist numberlist)
  (cond
    ((null? numberlist) '())
    (else(not (= 0 (modulo (numberlist) 2))(evenlist(car numberlist))))
    ))