;; 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-intermediate-reader.ss" "lang")((modname week6_w) (read-case-sensitive #t) (teachpacks ((lib "image.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "image.ss" "teachpack" "htdp")))))
;; remove-odds : list-of-numbers -> list-of-numbers
; removes the odd numbers from list
(define (remove-odds l)
  (cond 
    [(empty? l) empty]
    [else 
       (cond
         [(odd? (first l)) (remove-odds (rest l))]
         [else (cons (first l) (remove-odds (rest l)))])]
    ))

; remove-dolls : list-of-symbols -> list-of-symbols
; remove the dolls from list
(define (remove-dolls l)
  (cond 
    [(empty? l) empty]
    [else 
       (cond
         [(symbol=? 'doll (first l)) (remove-dolls (rest l))]
         [else (cons (first l) (remove-dolls (rest l)))])]
    ))

; remove-dolls : list-of-symbols -> list-of-symbols
; remove-odds : list-of-numbers -> list-of-numbers

; filter : (X -> boolean) list-of-X -> list-of-X
; removes all elements meeting criteria p?
(define (myfilter p? l) 
    (cond 
    [(empty? l) empty]
    [else 
       (cond
         [(p? (first l)) (myfilter p? (rest l))]
         [else (cons (first l) (myfilter p? (rest l)))])]
    ))

(define (is-doll x) (symbol=? x 'doll))

(check-expect (remove-odds (list 1 2 3 4 5)) (list 2 4))
(check-expect (remove-dolls (list 'doll 'truck)) 
              (list 'truck))
(check-expect (myfilter odd? (list 1 2 3 4 5)) (list 2 4))
(check-expect (myfilter is-doll (list 'doll 'truck)) 
              (list 'truck))


;(check-expect (remove-dolls (list 'doll 'truck)) 
;              (list 'truck))