;; The first three lines of this file were inserted by DrScheme. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-advanced-reader.ss" "lang")((modname lect05a) (read-case-sensitive #t) (teachpacks ((lib "world.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #t #t none #f ((lib "world.ss" "teachpack" "htdp")))))
; map : (-> (-> alpha beta) (list-of alpha) (list-of beta))
;
(define (mymap f data)
  (cond [(empty? data) empty]
        [(cons? data) (cons (f (first data))
                            (mymap f (rest data))) ]))

(check-expect (mymap sqr empty) empty)
(check-expect (mymap (lambda (x) (+ x 1)) (list 3)) (list 4))
(check-expect (mymap sqr (list 3 4 5)) (list 9 16 25))

(define (add-in-list data)
  (cond [(empty? data) 0]
        [(cons? data) (+ (first data) (add-in-list (rest data)))]))

(define (my-foldl build-answer init-val data)
  (cond [(empty? data) init-val]
        [(cons? data) (build-answer (first data) 
                                    (my-foldl build-answer
                                              init-val
                                              (rest data)))]))