;; 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 movie_theater) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ())))

;; Contract: number -> number

;; Purpose: computes the profit for a movie 
;; theater given a ticket price
;; Example: if revenue is 600 and the cost is 200 
;; then the profit is 400
(define (profit ticket-price)
  (- (revenue ticket-price)
     (cost ticket-price)))

;; Contract: number -> number

;; Purpose: computes the revenue for a movie 
;; theater given a ticket price
;; Example: if the number of attendees for $5 per ticket
;; is 120 then the revenue is 600.
(define (revenue ticket-price)
  (*  (attendees ticket-price) ticket-price))

;; Contract: number -> number

;; Purpose: computes the cost for a movie 
;; theater to run a movie given a ticket price
;; Examples: if there are 120 attendees then the cost is 184.8
;; Examples: if there are 420 attendees then the cost is 196.8
(define (cost ticket-price)
  (+ 180 
     (* .04 (attendees ticket-price))))

;; Contract: number -> number

;; Purpose: computes the number of movie attendees 
;; given a ticket price

;; examples: 
;; (attendees 5.00) returns 120
;; (attendees 3.00) returns 420
(define (attendees ticket-price)
  (+ 120
     (* (/ 15 .10) (- 5.00 ticket-price))))

;; tests for attendees
(attendees 5.00)
; expected result 
120

;; another way of testing:
(check-expect (attendees 5.00) 120)
(check-expect (attendees 3.00) 420)

;; tests for cost
(check-expect (cost 5.00) 184.8)
(check-expect (cost 3.00) 196.8)

;; tests for revenue:
(check-expect (revenue 5.00) 600)
(check-expect (revenue 3.00) 1260)

;; tests for profit
(check-expect (profit 5.00) 415.2)
(check-expect (profit 3.00) 1063.2)

;; Tasks:
;; exercise 3.1.4: change the program so that the cost is $1.50 
;; per attendee with no fixed cost (write this solution in a 
;; separate file since all the tests will change as well

;; change the program so that there is a limit on the number of
;; attendees: the movie theater can seat at most 400 people.