2018-10-01-morning.rkt

2018-10-01-morning.rkt

#lang typed/racket

(define my-list
  (cons 3
        (cons 4 (cons "horse" (cons (cons 16 '())
                                    '())))))

;; determine the length of a list
(define (mylen [l : (Listof Any)]) : Natural
  (match l
    [(cons f r) (add1 (mylen r))]
    ['() 0]))

(require typed/rackunit)
(check-equal? (mylen '()) 0)
(check-equal? (mylen my-list) 4)