;; 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_m_full) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ())))
; recall: map

; get-addn : number -> (number -> number)
;(define (get-addn n) 
;  (local [(define (addn x) (+ x n))]
;  addn))

;(check-expect (addn 3) 

; add-n-to-all : number list-of-numbers -> list-of-numbers
; adds n to every number in list
(define (add-n-to-all n lon)
  (local [(define (addn x) (+ n x))]
    (map addn lon)
  ))

;(define (add3 x) (+ x 3))

(check-expect (add-n-to-all 5 (list 1 2 3)) (list 6 7 8))
(check-expect (add-n-to-all 0 empty) empty)

; ----------------------- filter -----------------------------

;; remove-odds : list-of-numbers -> list-of-numbers
(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
(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)))])]))

; filter : (X -> boolean) list-of-X -> list-of-X
;(define (filter p? l)
;  (cond
;    [(empty? l) empty]
;    [else (cond
;            [(not (p? (first l))) (filter p? (rest l))]
;            [else (cons (first l) (filter p? (rest l)))])]))

(define (keep-odds lon)
  (filter odd? lon))

(define (remove-dolls-new los)
  (local [(define (not-is-doll s) (not (symbol=? 'doll s)))]
  (filter not-is-doll los)))

(check-expect (remove-dolls-new (list 'doll 'cheese 'person))
              (list 'cheese 'person))
(check-expect (remove-dolls-new (list 'doll 'doll 'person))
              (list 'person))


(check-expect (keep-odds (list 1 2 3 4)) (list 1 3))
(check-expect (keep-odds empty) empty)


; ------------------------foldr--------------------------------
; sum : list-of-numbers -> number
; sums the list of numbers
(define (sum l)
  (cond
    [(empty? l) 0]
    [else (+ (first l) (sum (rest l)))]))

; prod : list-of-numbers -> number
; multiplies the list of numbers
(define (prod l)
  (cond
    [(empty? l) 1]
    [else (* (first l) (prod (rest l)))]))

; foldr : (number number -> number) number list-of-number -> number
;foldr (symbol list-of-symbols -> list-of-symbols) list-of-symbols list-of-symbols -> list-of-symbols

; foldr: (X Y -> Y) Y list-of-X -> Y

;(define (foldr combine base l)
;  (cond
;    [(empty? l) base]
;    [else (combine (first l) (foldr combine base (restl)))]))

(define (sum-new l) (foldr + 0 l))
(define (prod-new l) (foldr * 1 l))

(check-expect (sum-new (list 1 2 3 4)) 10)
(check-expect (sum-new empty) 0)
(check-expect (prod-new (list 1 2 3 4)) 24)
(check-expect (prod-new empty) 1)

; remove-dolls-awesome : list-of-symbols -> list-of-symbols
(define (remove-dolls-awesome l)
  (foldr cons-unless-doll empty l))
; foldr (symbol list-of-symbols -> list-of-symbols) list-of-symbols list-of-symbols -> list-of-symbols

; cons-unless-doll : symbol list-of-symbols -> list-of-symbols
; returns (cons x y) if x not a doll, y otherwise
(define (cons-unless-doll x y)
  (cond [(symbol=? 'doll x) y]
        [else (cons x y)]))

(check-expect (remove-dolls-awesome (list 'doll 'cheese 'person))
              (list 'cheese 'person))
(check-expect (remove-dolls-awesome (list 'doll 'doll 'person))
              (list 'person))