;; 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 f-all-abstract) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f () #f)))
;; sqr-all : LoN -> LoN
;; Square each element of the list
(define (sqr-all lon)
  (f-all sqr lon))

;; double-all : LoN -> LoN
;; Double each element of the list
(define (double-all lon)
  (f-all dbl lon))

;; f-all : (Number -> Number) LoN -> LoN
(define (f-all f lon)
  (cond [(empty? lon) '()]
        [(cons? lon)
         (cons (f (first lon))
               (f-all f (rest lon)))]))

(define (dbl x) (+ x x))