;; 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-lambda-reader.ss" "lang")((modname week6_f) (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")))))

;(define (drop p? l) (filter (negate p?) l))
(define (drop p? l) (filter (lambda (x) (not (p? x))) l))

(define (long-negate p) 
  (local [(define (negated-predicate x)
            (not (p x)))]
    negated-predicate)
  )

(define (negate p) 
  (lambda (x) (not (p x)))
  )

((lambda (x y z) (* x (+ y 3) (sqrt z))) 1 2 4)

(define (mymath x y z) 
  (* x (+ y 3) (sqrt z)))
(mymath 1 2 4)
(define (add3 x) (+ x 3))
(define (add3toeach lon)
  (map (lambda (x) (+ x 3)) lon))

(check-expect (add3toeach (list 1 2 3)) (list 4 5 6))

; adder : number -> (number -> number)
(define adder
  (lambda (x)
    (lambda (y)
      (+ x y))))

; deriv : (number -> number) -> (number -> number)
(define (deriv f)
  (lambda (x)
    (/ (- (f (+ x delta))
          (f (- x delta)))
       (* 2 delta))))

(define delta 0.001)
(define (pow4 n) (* n n n n))
(define 4xcube (deriv pow4))