;; 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-beginner-reader.ss" "lang")((modname quiz1-practice) (read-case-sensitive #t) (teachpacks ((lib "universe.ss" "teachpack" "2htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "universe.ss" "teachpack" "2htdp")))))
;; Helene Martin, Garfield APCS++ 2010
;; Answers to quiz practice

(define LEAVES-PER-TREE 200000)

;; hours-to-rake number -> number
;; takes in the number of trees and returns the hours to rake
(define (hours-to-rake trees)
  (/ (* trees LEAVES-PER-TREE) 40000))

(check-expect (hours-to-rake 0) 0)
(check-expect (hours-to-rake 1) 5)

;; A employee is a (make-employee string number)
(define-struct employee (name salary))

(define DEREK (make-employee "Derek" 80000))
(define ADAM (make-employee "Adam" 20000))

;; give-raises employee -> employee
;; provides a 10% raise for employees who make less than $60,000
(define (give-raises empl) 
  (cond [(< (employee-salary empl) 60000) (make-employee (employee-name empl)
                                                         (* 1.1 (employee-salary empl)))]
        [else empl]))

(check-expect (give-raises DEREK) DEREK)
(check-expect (give-raises ADAM) (make-employee "Adam" 22000))

;; An address is (make-address string string string number)
(define-struct address (street city state zip))

(define LANE-ADDRESS (make-address "444 Fnord Pl" "Seattle" "WA" 98102))

;; A home-customer is (make-home-customer string address string number)
(define-struct home-customer (name address plan card-num))

(define LANE-UNL (make-home-customer "Lane" LANE-ADDRESS "unlimited" 34454565))
(define LANE-BASIC (make-home-customer "Lane" LANE-ADDRESS "basic" 34454565))

;; An instant-viewer is (make-instant-viewer string number)
(define-struct instant-viewer (e-mail card-num))

(define QUI (make-instant-viewer "qui@qui.com" 23432432))

;; A customer is 
;; - a home-customer
;; - an instant-viewer

;; monthly-cost: customer -> number
;; consumes a video customer and produces the monthly cost for that
;; customer. The cost is $4.95 for home customers on the basic plan,
;; $16.95 for home customers on the unlimited plan, and $9.95 for
;; instant viewers.

(check-expect (monthly-cost LANE-BASIC) 4.95)
(check-expect (monthly-cost LANE-UNL) 16.95)
(check-expect (monthly-cost QUI) 9.95)

(define (monthly-cost a-cust)
  (cond [(home-customer? a-cust) (home-cost a-cust)]
        [(instant-viewer? a-cust) 9.95]))

;; home-cost home-customer -> number
(define (home-cost home-cust)
  (cond [(string=? "basic" (home-customer-plan home-cust)) 4.95]
        [(string=? "unlimited" (home-customer-plan home-cust)) 16.95]))

;; is-cheap? customer -> boolean
;; checks if customer's plan costs $10 or less
(define (is-cheap? customer)
  (<= (monthly-cost customer) 10))

(check-expect (is-cheap? QUI) true)
(check-expect (is-cheap? LANE-UNL) false)