#lang racket
;; get-evens1 : listof(number) -> listof(number)
;; Return a list containing the even values from lis
(define (get-evens1 lis)
  (cond ((null? lis) '())
        ((even? (car lis))
              (cons (car lis) (get-evens1 (cdr lis))))
        (else (get-evens1 (cdr lis)))
    ))

;; using let to reduce expression repetition...

;; get-evens : listof(number) -> listof(number)
;; Return a list containing the even values from lis
(define (get-evens lis)
  (cond ((null? lis) '())
        ;; we need to start a new cond inside the
        ;; let block
        (else (let ((n    (car lis))
                    (tail (get-evens (cdr lis))))
                ;; body of let
                (cond ((even? n) (cons n tail))
                      (else tail))
            ))
     ))