;; The first three lines of this file were inserted by DrRacket. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-beginner-reader.ss" "lang")((modname week2_f_full) (read-case-sensitive #t) (teachpacks ((lib "image.ss" "teachpack" "2htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "image.ss" "teachpack" "2htdp")))))


(define mylistofnumbers (cons 4 (cons 3 empty)))

; a list-of-numbers is either:
; - empty
; - (cons number list-of-numbers)
; template:
;  (cond [(empty? lon) ...]
;        [(cons? lon) ...(first lon) ...(fun-for-lon (rest lon))...])
;  )

; count : list-of-numbers -> number
; returns the number of numbers in a list
(define (count lon) 
  (cond [(empty? lon) 0]
        [(cons? lon) (+ 1 (count (rest lon)))])
  )

(check-expect (count mylistofnumbers) 2)
(check-expect (count (cons 4 (cons 3 (cons 2 (cons 1 empty))))) 4)